Enantioselective Synthesis of Angularly Substituted 1-Azabicylic Rings: Coupled Dynamic Kinetic Epimerization and Chirality Transfer

Abstract

A new strategy for enantioselective synthesis of azacyclic molecules in which dynamic kinetic equilibration of diastereomeric iminium ions precedes a stereochemistry-determining sigmatropic rearrangement is reported. The method is illustrated by the synthesis in high enantiomeric purity (generally 95–99% ee) of a variety of 1-azabicyclic molecules containing angular allyl or 3-substituted 2-propenyl side chains adjacent to nitrogen and up to three stereogenic centers. In these products, the size of the carbocyclic ring is varied widely (5–12 membered), however useful yields are obtained in forming 1-azabicyclic products containing only fused pyrrolidine and piperidine rings. Chi-rality transfer from substituents at carbons 1 and 2 of the 3-butenylamine fragment of the starting material is investigated, with methyl and phenyl substituents at the allylic position shown to provide exquisite stereocontrol (generally 98–99% chirality transfer). An attractive feature of the method is the ability to carry out the key transformation in the absence of solvent. Illustrated also is the high yielding conversion of four such products to a new family of bicyclic β-amino acids of high enantiomeric purity.

Introduction

1-Azabicyclic rings having an angular substituent adjacent to nitrogen (1, Figure 1) have a variety of potential applications. These ring systems are found in natural products exhibiting potentially useful therapeutic properties such as deoxyharringtonine,¹ and in a few molecules of medicinal chemistry significance, such as 8a-phenyldecahydroquinolines (Figure 1).² One can also readily envisage applications of conformationally constrained β-amino acids of the type depicted in Figure 1 in peptidomimetics or as organocatalysts. Nonetheless, there are remarkably few reports of applications of angularly substituted nitrogen heterocycles 1,³ particularly in light of the presence of other substituted 1-azabicyclic non-aromatic heterocycles in marketed drugs and exploratory drug candidates.⁴ The lack of general methods for the synthesis of heterocycles of type 1, particularly in high enantiomeric purity, could be responsible for their limited use to date.⁵

Figure 1. Angularly Substituted 1-Azabicyclic Ring Systems 1 and Examples of Compounds Containing this Ring System.

We reported earlier a general method for the synthesis of racemic, angularly substituted, 1-azabicylic molecules 1.⁶ The method is illustrated in Scheme 1 for the preparation cis-cyclopentapyrrolidine 4 from aminoketal 2. In this synthesis, a mixture of aminoketal 2, 1 equiv of tri-fluoroacetic acid (TFA) and 2.5 equiv of dimedone is heated for several hours at 120 °C. The tetrasubsti-tuted iminium ion A is formed initially and upon heating undergoes 3,3-sigmatropic equilibration with iminium ion isomer B. The inclusion of dimedone (5,5-dimethylcyclohexane-1,3-dione, 3) selectively traps the less-stable formaldiminium ion isomer B to give presumably adduct C, which upon fragmentation delivers the cis-cyclopentapyrrolidine product 4.⁷ To aid in purification, this product is converted to benzyloxy (Cbz) derivative 5, which was isolated in 86—96% yield. The exomethylene fragment of the iminium ion intermediate eventually emerges as the well known dimedone-formaldehyde adduct 6.

Scheme 1. Methylene Transfer-Driven Cationic 2-Aza-Cope Rearrangement.

During the development of this method, we discovered that when the synthesis of the corresponding cis-octahydroindole 8 was carried out in CD₃OD containing 3 equiv of D₂O, deuterium was incorporated into the angular methine (C3a) and C7 methylene positions of product d₃-8 (Scheme 2).⁶ This deuterium incorporation signified that the initially formed iminium ion D equilibrated with enamonium ion iomers E and F more rapidly than formaldiminium ion intermediate G was trapped to yield cis-octahydroindole product 8.

Scheme 2. Deuterium Incorporation by Iminium/Enamonium Ion Tautomerization.

On the basis of the rapid pre-equilibrium that occurs between iminium ion and enamonium ion intermediates in this synthesis of angularly substituted heterocycles, we postulated that incorporating a nonracemic stereocenter on the homoallylic side chain of an aminoketal precursor such as 9 should result in the [3,3]-sigmatropic rearrangement occurring faster with one C3a epimer to deliver potentially one enantiomer of the azabicyclic product (Scheme 3). For this process to occur with high chirality transfer, the C3a epimers of iminium ion intermediate H must equilibrate rapidly, one epimer must preferentially undergo [3,3]-sigmatropic rearrangement, and dimedone trapping also must occur more rapidly than product iminium ion J equilibrates with its enantiomer.⁸ At the outset, we anticipated that sig-matropic rearrangement via transition state geometry I would be preferred, because bond formation from the convex face and placement of the substituent R in a quasi-equatorial orientation should be favored.

Scheme 3. Potential Synthesis of Enantiomerically Enriched cis-Octahydroindole 8 by Coupled Dynamic Kinetic Epimerization and Chirality Transfer.

In this article, we describe the development of this new strategy into a general method for enan-tioselective synthesis of angularly substituted 1-azabicyclic molecules.⁹ Experiments that illuminate some of the mechanistic details of the cationic 2-aza-Cope rearrangement and other steps in the sequence are discussed also.

Results and Discussion

Synthesis of Aminoketals Containing Enantiomerically Enriched 1-Substituted 3-Butenyl Fragments and Their Conversion to 1-Azabicyclic Products

Our investigations began by preparing five aminoketal precursors 9 that varied in the nature of the homoallylic substituent. The synthesis begins with benzyl 2-oxocyclohexaneacetate (11),¹⁰ which we found most convenient to prepare by fluoride-mediated alkylation of 1-(trimethylsiloxy)cyclohexene (10) with benzyl 2-bromoacetate (Scheme 4).¹¹ Ketalization of 11 catalyzed by scandium triflate yielded dioxolane derivative 12 in 68% overall yield from 10. Cleavage of the benzyl ester by hydrogenolysis, followed by carbodiimide-promoted coupling with (R)-1-substituted-3-butenylamines 13a–e provided amides 14a–e. The enantiomerically enriched (R)-1-substituted-3-butenylamines 13a–e were available in three steps from the corresponding aldehyde and (R)-phenylglycinol by the method of Vilaivan and co-workers.^12,13 Reduction of amide intermediates 14a–e with lithium aluminum hydride delivered aminoketals 9a–e in good overall yields from ketal ester 12.

Scheme 4. Synthesis of Aminoketals 9.

In our initial study, the reaction temperature and the effect of the homoallylic substituent on chirality transfer was examined (Table 1). All reactions were conducted neat by heating mixtures of the aminoketal 9, TFA (1.0 equiv) and dimedone (2.5 equiv). In these small-scale reactions, 0.1 equiv of morpholine was added to ensure that excess TFA was not present, because dimedone is decomposed at elevated temperatures in the presence of this acid. At 120 °C, phenyl-substituted aminoketal 9a was converted to cis-octahydroindole ent-8 in 92% yield with 96% chirality transfer (entry 1).¹⁴ When this reaction was conducted at 100 °C, the rearrangement was significantly slower (entry 2); however, the extent of chirality transfer was not enhanced. No reaction was observed at 80 °C after 1 h (entry 3). The degree of chirality transfer was affected to only a small extent by the incorporation of p-Cl or o-Cl substituents or a p-OMe group in the aryl fragment (entries 4–6). Most notable was the significant decrease in chirality transfer observed when the homoallylic substituent was isopropyl (entry 7). In addition, carrying out the reaction in CD₃OD at 110 °C in a sealed tube (1 equiv of TFA and 2.5 equiv dim-edone) provided ent-8 in 75% yield, however with unsatisfactory (68%) chirality transfer. The absolute configuration of ent-8 was secured by single crystal X-ray analysis of its hydrobromide salt.

Table 1. Enantioselective Synthesis of Octahydroindole 8 from Aminoketals 9a–e.

entry	R	ee (%) 9a	temp (°C)	time(h)	yield (%)	ee (%) ent-8b	chirality transfer (%)
1	Ph (9a)	93	120	5	92	89	96
2	Ph (9a)	93	100	22	84	88	95
3	Ph (9a)	93	80	1	0	—	—
4	4-OMeC6H4(9b)	92	120	5	92	82	89
5	4-ClC6H4(9c)	94	120	5	90	89	95
6	2-ClC6H4(9d)	94	120	5	88	87	93
7	i-Pr (9e)	46	120	22	51	24	52

^aEnantiomeric purity of the homoallylic amine fragment of 9 was determined by enantioselective HPLC.

^bEnantiomeric purity was determined by enantioselective HPLC analysis of the corresponding N-benzoyl derivative.

We briefly investigated the scope of this enantioselective construction of allyl-substituted 1-azabicyclic molecules by examining three additional precursors containing a (R)-1-phenyl-3-butenyl fragment. Aminoacetal substrates 15–17 were prepared by sequences identical (or analogous) to that reported in Scheme 4.¹⁵ As summarized in Scheme 5, cis-hexahydrocyclopenta[b]pyrrole carbamate 18 and cis-octahydrocyclopenta[b]pyridine carbamate 19 were formed in 95% and 80% yield from precursors 15 and 16, respectively, and with 96–97% chirality transfer. In each case, only the cis steroisomer of the product was detected. In contrast, decahydroquinoline carbamate 20 was produced as a nearly 1:1 mixture of cis and trans epimers. These isomers could be separated, and each was shown to have an en-antiomeric purity of 93% ee, corresponding to 97% chirality transfer. The absolute configuration of 18 was determined by single crystal X-ray analysis of the hydrobromide salt of the parent hexahydrocyclo-penta[b]pyrrole;⁹ the absolute configuration for 19 and 20 was assigned in analogy to that of related products 8 and 18.

Scheme 5. Enantioselective Synthesis of Allyl-Substituted Heterocycles 18–20.

Synthesis of 2-Substituted 3-Butenylamines of High Enantiomeric Purity

Although chirality transfer was typically high with substrates having an aryl substituent at the homoallylic position, we entertained the possibility that this selectivity might be even higher with substrates having a substituent at the allylic carbon. We initiated these studies by developing an enantioselective synthesis of (R)-2-phenylbut-2-enylamine. In order to have convenient access to both enantiomers, we chose a route wherein the stereocenter is set by a catalytic enantioselective reaction using a catalyst for which both enantiomers are commercially available (Scheme 6). Using a microwave modification¹⁶ of a method first introduced by Trost,¹⁷ molybdenum-catalyzed enantioselective allylic alkylation of cinnamyl methyl carbonate (21) with dimethyl sodiomalonate gave (S)-pentenoate 23 in high yield and 99% ee. Krapcho decarboxylation of the malonate,¹⁸ followed by saponification of the carboxylic ester delivered (R)-acid 24.¹⁹ Curtius rearrangement of 24 with diphenylphosphoryl azide in t-BuOH, followed by cleavage of the Boc group with trifluoroacetic acid delivered (R)-2-phenylbut-2-enylamine (26) in 83% yield from the precursor acid. This sequence has been demonstrated on multigram scale.

Scheme 6. Synthesis of (R)-2-Phenylbut-2-en-1-amine.

To explore the effect of the 2-butenyl substituent on chirality transfer of reactions of the corresponding aminoacetals, a short synthesis of (S)-2-methylbut-3-en-1-ammonium chloride (29) was developed also (Scheme 7). Enantioselective allylic alkylation of allylbromide 27 (available in one step from (E)-1,4-dibromobut-2-ene)²⁰ with methylmagnesium bromide, catalyzed by 1 mol % CuBr•SMe₂ and 1.2 mol % Taniaphos delivered allylic carbamate 28 in 91% yield and in 95% ee.²¹ Subsequent removal of the tosyl and tert-butoxycarbonyl groups gave the enantiomerically enriched butenylamine hy-drochloride salt 29 in 78% overall yield from allylic bromide 27.

Scheme 7. Synthesis of (S)-2-Methylbut-3-en-1-ammonium Chloride.

Synthesis of Enantiomerically Enriched Aminoacetal Precursors Containing 2-Substituted 3-Butenyl Fragments and Their Conversion to 1-Azabicyclic Products

From homoallylic amine 26 or ammonium salt 29, a variety of aminoacetal precursors were prepared from the corresponding cyclo-alkanone acetal acids by the general method shown in Scheme 4.¹⁵ Our initial studies focused on the reaction of aminoacetal 30 and used the conditions utilized in our earlier studies with the analogous substrate 15 having the phenyl substituent at the homoallylic position. In this way, cis-hexahydrocyclopenta[b]pyrrole carbamate 31 was formed in 89% yield and a remarkable 99% ee, corresponding to complete chirality transfer (eq 1). When the morpholine buffer was omitted, the yield was depressed slightly (80%).

(1)

We next examined whether dimedone was essential to the success of the transformation shown in eq 1 (Table 2). In the absence of dimedone (and morpholine), product 31 was formed in 21% yield (entry 3). On the assumption that 1,3-propanediol was the agent trapping what would be in this case a formaldiminium ion of the 2-aza-Cope rearrangement product, the reaction was carried out in the presence of 3 equiv of this additive. However, the yield of 31 was not improved (entry 4). Methanol was considered also to be a potential trap for the formaldiminium ion intermediate; however, carrying out the reaction in methanol did not result in appreciably higher yields after 24 h at 60 °C (enries 5 and 6). Although we believe that other trapping agents as efficacious as dimedone could likely be found, we decided to explore instead the scope of the efficient, highly enantioselective, reaction shown in eq 1.

Table 2. The Reaction of Aminoacetal 30 with Trifluoroacetic Acid to Form Product 31 in the Presence of Various Additives^a.

entry	additive	temp (°C)	time (h)	yield (%)
1b	dimedone (2.5 equiv)	120	0.5	80
2	dimedone (2.5 equiv), morpholine (0.1 equiv)	120	0.5	89
3c	none	120	0.5	21
4	1,3-propanediol (3 equiv)	120	0.5	21
5	MeOHd	60	24	24
6	5% H2O in MeOHd	60	24	7

^aReactions used a 1:1 molar ratio of rac-30 and trifluoroacetic acid and the indicated additive(s).

^bReactant 30 was prepared from (S)-butenylamine 26 (99% ee).

^cWhen enantioenriched 30 was used, product 31 was formed with >98% chirality transfer.

^dMethanol was the solvent in these reaction; the starting concentration of rac-30 was 0.5 M.

A comparison of phenyl and methyl stereocontrolling groups and results of our initial exploration of this route to functionalized 1-azacyclic ring systems is summarized in Table 3. Angularly substituted cis-hexahydropenta[b]pyrroles 31, cis-octahydroindoles 32, and cis-octahydrocyclopenta[b]pyridines 33 containing a (E)-3-substituted-2-propenyl side chain were obtained in good yields (71-89% yields) and high 95–99% ee (entries 1–6). Chirality transfer was complete, within experimental uncertainty, regardless of the nature of the allylic substituent on the butenyl fragment. Carrying out the synthesis of 31a (87% yield, 99% ee) on gram scale gave the product in comparable yield with no reduction in enantioselectivity, demonstrating the practicality of this method. The high-yield formation of cis-octahydroindole 34a as exclusively a single C7 methyl epimer, indicates that both stereogenic centers of the carbocyclic aminoacetal precursor epimerized by iminium/enamonium tautomerization prior to 2-aza-Cope rearrangement/dimedone trapping. In this case, the methyl-substituted aminoketal provided cis-octahydroindole 34b in slightly diminished diastereoselectivity (9:1 dr) and chirality transfer (96%, entry 8). The absolute configuration of cis-octahydrocyclopenta[b]pyridine 33a was determined by X-ray analysis of the corresponding secondary amine hydrobromide salt,⁹ whereas the absolute configuration of products 31a and 32a was determined by chemical correlation with azacyclic products 18 and 8. Absolute configurations of the other azabicy-clic products reported in Table 3 were assigned by analogy.

Table 3. Enantioslective Synthesis of 1-Azabicyclic Molecules Containing an Angular 3-Phenyl or 3-Methylpropenyl Substituents.

entry	product	R2	yield (%)	ee (%)a	chirality transfer (%)
1		Ph, 31a	89	99	>98
2		Me, 31b	73	95	>98
3		Ph, 32a	82	99	>98
4		Me, 32b	74	95	>98
5		Ph, 33a	89	99	>98
6		Me, 33b	71	95	>98
7		Ph, 34a	81	99	>98
8		Me, 34b	70	91b	96

^aEnantiomeric excess was determined by enantioselective HPLC.

^bThis product was a 9:1 mixture of epimers at the angular methine carbon.

Results of our further investigations of the scope of this chemistry using precursors containing a (R)-2-phenylbutenylamine fragment are summarized in Table 4. At 120 °C, decahydroquinoline 35 was formed as a 1.7:1 mixture of cis and trans stereoisomers (entry 1). Stereoselectivity was increased slightly when the reaction was conducted in methanol at 60 °C (entry 2).²² Both the cis- and trans-decahydroquinoline products were formed in 99% ee. 1-Azabicyclic products containing an (E)-3-phenyl-2-propenyl side chain adjacent to nitrogen can be prepared with various sized rings carbocyclic rings (entries 3–5). The cis steroisomer of the product was strongly favored when the azacyclic ring is five-membered. Extension of this chemistry to the synthesis of 1-azabicyclic molecules in which the azacyclic unit is a medium ring appears problematic. For example, decahydrocyclopenta[b]azocine 38 was formed in only 16% yield after an extended reaction time of 22 h at 120 °C (entry 6). We attribute this low conversion to low efficiency in forming the initial 8-membered-ring iminium ion.

Table 4. Further Scope of the Enantioselective Synthesis of 1-Azabicyclic Molecules Containing an Angular 3-Phenylpropenyl Substituent.

entry	product	temp (°C)	time (h)	dr (cis:trans)a	yield (%)	ee (%)b
1		120	0.5	1.7:1	86	99c
2		60c	20	2:1	72	99d
3		120	0.5	9:1	74	99e
4		60c	20	15.2:1	70	99e
5		120	0.5	>10:1	79	99
6		120	22	>10:1	16f	nd

^aDiastereoselectivities were determined by analysis of the ¹H NMR spectra.

^bEnantiomeric excesswas determined by enantioselective HPLC.

^cReaction carried out in methanol (0.5 M).

^dBoth isomerswere obtained in 99% ee.

^eEnantiomeric excess of the major isomer; the enantiomeric excess of the minor isomer was not determined.

^fEnantiomeric excess was not determined.

As the stereocontrolling step in this construction of 1-azacyclic molecules is an iminium ion [3,3]-sigmatropic rearrangement, the organized six-membered chair transition structure should allow the geometry of a double bond in the starting material to be transformed to a new stereocenter at C1 of the allylic side chain of the product. To examine this possibility, three unsaturated aminoacetal substrates, 39a–c, were prepared from (R)-2-phenyl-3E-alkenylamines having Me, Ph, or cyclohexyl substituents at C4. Exposure of aminoketal 39a, prepared from (R)-2-phenyl-3E-pentenylamine of 87% ee, to trifluoro-acetic acid at 120 °C for 30 min, followed by Cbz protection gave cis-hexahydrocyclopenta[b]pyrrole 40 as a single stereoisomer in 75% yield. The enantiomeric purity (87% ee) of 40 indicated again that chirality transfer was essentially complete. Similar results were obtained in the formation of products 41 and 42, with the exception of their higher enantiomeric purity (99% ee) resulting from the greater dia-stereomeric purity of precursors 39b and 39c.²³ However, the yields of 41 and 42 were diminished, presumably because the larger size of the phenyl and cyclohexyl substituents results in destabilizing steric interactions in the iminium ion [3,3]-sigmatropic rearrangement.

Synthesis of Uncommon β-Amino Acids in High Enantiomeric Purity

β-Amino acids are valuable building blocks in peptide-based drug design, as proteolytic degradation is greatly reduced in vivo, increasing their bioavailability.²⁴ For example, replacing proline with the more rigid analog, oc-tahydroindole-2-carboxylic acid, has been exploited in several bradykinin B₂ antagonists to improve both enzymatic stability and potency.²⁵ Moreover, proline-based catalysts have been shown to be powerful catalysts for a wide variety of transformations²⁶ with recent examples exemplifying 3-pyrrolidinecarboxylic acid catalysts.²⁷ Oxidative cleavage of the angular-allyl side chain of the 1-azabicyclic molecules prepared in the manner reported herein would provide a variety of new, potentially useful, α-amino acids. To demonstrate this potential, we optimized a high-yielding, two-step sequence to achieve this objective. Application of this sequence to prepare four Cbz-protected α-amino acids is reported in Scheme 9.

Scheme 9. Synthesis of Four Representative Cbz-Protected β-Aminoacids.

Mechanistic Discussion

Our current understanding of the high transfer of chirality observed in the azacyclic construction reported in this article is derived in part from our studies of the transformation of aminoketal 30 to cis-hexahydrocyclopenta[b]pyrrole 47. The success of this dynamic kinetic epimerization rearrangement sequence was predicated on iminium/enamonium equilibration occurring faster than the [3,3]-sigmatropic rearrangement step. The rapid tautomerization of iminium ion and enamonium ion intermediates K–M was confirmed to occur more rapidly than the 2-aza-Cope rearrangement when the reaction of aminoketal 30 was carried out in CD₃OD (Scheme 10). As expected, azabicyclic carbamate 31 was isolated with deuterium incorporated in the angular C3a and C6 meth-ylene positions; analysis of this product by electrospray mass spectrometry indicated an 8:4:0:1 ratio of d₃:d₂:d₁:d₀ deuterium incorporation.²⁸

Scheme 10. Deuterium Incorporation in cis-Hexahydrocyclopenta[b]pyrrole 47 via Rapid Iminium/Enamonium Ion Equilibratium.

We next probed the reversibility of the aza-Cope rearrangement and methylene transfer steps (Scheme 11). The irreversibility of the methylene transfer step was demonstrated by heating secondary amine 47 with dimedone-formaldehyde adduct 6 (1.25 equiv), trifluoroacetic acid (1 equiv), and mor-pholine (0.1 equiv) at 120 °C in CD₃OD for 48 h. Benzyloxycarbonyl protection of recovered 47 and mass spectrometric analysis showed that deuterium had not been incorporated. In contrast, heating cis-hexahydrocyclopenta[b]pyrrole 47 in CD₃OD at 120 °C for 24 h with paraformaldehyde (3 equiv), tri-fluoroacetic acid (1 equiv) and morpholine (0.1 equiv), followed by the addition of excess dimedone at 120 °C provided, after Cbz protection, carbamate 31 containing extensive deuterium incorporation (d₃:d₂:d₁:d₀ = 36:15:2:1). This latter result establishes that in the absence of dimedone, iminium ion isomers K and N (see Scheme 10) equilibrate under the reaction conditions.

Scheme 11. Probing the Reversibility of the Aza-Cope Rearrangement and Dimedone-Trapping Steps.

To gain additional insight into this chemistry, the reaction of amino acetal ent-48 with 1 equiv of TFA was studied by NMR (Scheme 12). Within 3 min at room temperature, ent-48 was converted to a 1:1 mixture of diastereomeric bicyclic isomers 49 and 50. This mixture was essentially unchanged after 12 h at room temperature. At temperatures above 40 °C, loss of 1,3-propanediol occurred to generate a mixture of products. The major component is iminium ion O (diagnostic ¹³C NMR signal at 221 ppm), with additional products assigned as enamonium ions P and Q (diagnostic vinylic ¹³C NMR signals between 132–123 ppm). This mixture was largely unchanged after heating at 60 °C for 12 h or at 120 °C for 5 min. Addition of excess dimedone to the latter sample and further heating at 130 °C generated ent-51 as the major azacyclic product.

Scheme 12. Intermediates Formed During the Formation of cis-hexahydrocyclopenta[b]pyrrole ent-51.

Based upon the studies reported in Schemes 10–12, we propose the following mechanism (Scheme 13). In the presence of 1 equiv of TFA, an aminoketal such as 30 is transformed at elevated temperatures, by way of enamonium tautomer L, into an equilibrium mixture composed largely of tetrasubstituted iminium ions R and S. In the slow step of the sequence, iminium ion diastereomer S preferentially undergoes [3,3]-sigmatropic rearrangement via favored chair-transition structure T having the phenyl substituent pseudoequatorial to give cis-hexahydrocyclopenta[b]pyrrole formaldiminium ion U. The exquisite chirality transfer observed in the transformations reported herein requires that intermediate U, once formed, does not equilibrate with isomers S and R, because [3,3]-sigmatropic rearrangement of the latter (vide infra) would generate ent-U and erode enantioselectivity. Thus, trapping of intermediate U by dimedone and fragmentation of the dimedone adduct must be irreversible in order to form the 3aS,6aR product 47 in high enantioselectivity.²⁹

Scheme 13. Proposed Mechanism for the Formation of (3aS,6aR)-cis-Hexahydrocyclopenta[b]pyrrole 47 from Amino Acetal 30.

The mechanism proffered in Scheme 13 ascribes the high chirality transfer (>98%) observed in the transformation of 30 to 47 to preferential [3,3]-sigmatropic rearrangement of iminium ion diastere-omers S via transition structure T. As depicted in Figure 2, ent-47 would be the result of [3,3]-sigmatropic rearrangement of diastereomer R from the convex face via boat geometry V.³⁰ The near perfect chirality transfer observed in forming 47 is consistent with transition structure V being at least 3 kcal/mol (more likely 3.5 kcal/mol) higher in energy than chair transition structure T.³¹ In addition to the high enantioselectivity observed in forming cis-hexahydrocyclopenta[b]pyrrole 47, the side chain of 47 is introduced with high E stereoselectivity. Quantitative HPLC analysis calibrated with an authentic sample of the (Z)-3-phenyl-2-propenyl isomer of the Cbz derivative 30³² demonstrated that stereoselec-tivity in forming product 47 having a (E)-3-phenyl-2-propenyl side chain was 150:1. This isomer ratio establishes that chair-transition structure W for [3,3]-sigmatropic rearrangement of iminium ion dia-stereomer R is similarly disfavored (by 3.9 kcal/mol relative to the favored transition structure T).

Figure 2. Higher Energy Pathways Leading to Azacyclic Products ent-47 and 52.

Conclusions and Outlook

In summary, a method of some generality for the enantioselective synthesis of angularly substituted 1-azabicyclic structures having up to three stereocenters is reported. This synthesis illustrates a new strategy for enantioselective synthesis of azacyclic molecules in which dynamic kinetic equilibration of dia-stereomeric iminium ions precedes a stereochemistry determining sigmatropic rearrangement. Critical to the success of this method is the facility of iminium ion/enamonium ion interconversions, and identifying an irreversible step—in this case trapping of the less-stable iminium isomer of a 2-aza-Cope equilibration by reaction with dimedone—to dictate stereoselection.

The method was illustrated by the enantioselective synthesis of a variety of 1-azabicyclic molecules containing angular allyl or 3-substituted 2-propenyl side chains. In these structures, the size of the car-bocyclic ring was varied widely (5–12 membered), however useful yields were obtained in forming bi-cyclic products containing only fused pyrrolidine and piperidine rings. A notable aspect of the method is formation of the structurally rare 1-azacyclic products in high enantiomeric purity (95–99% ee). Also demonstrated is the high yielding conversion of four such products to a new family of bicyclic β-amino acids of high enantiomeric purity, molecules of potential utility for the synthesis of peptidomimetics and scaffolds for medicinal chemistry (Scheme 9). An attractive feature of the method is the ability to carry out the key transformation in the absence of solvent. An unappealing feature of the method as currently practiced is the stoichiometric formation of the dimedone-formaldehyde adduct. The potential to mitigate this drawback by identifying alternate, more attractive, iminium ion trapping steps is suggested by preliminary studies, but to date has not been realized in a high-yielding manner.

Experimental Section

Preparation of Aminoketals Containing a Homoallylic Stereogenic Center

General Procedure A for Oxidative Cleavage of the Chiral Auxiliary

(R)-1-Phenylbut-3-en-1-amine (13a)¹²

Lead acetate (4.50 g, 10.1 mmol) was added to a solution of (2R)-2-phenyl-2-[(1′R)-1′-phenylbut-3′-enylamino]ethanol¹² (2.26 g, 8.45 mmol), CH₂Cl₂ (15 mL), and MeOH (15 mL) at 0 °C. The mixture was stirred at 0 °C for 30 min. Hydroxylamine hydro-chloride (5.87 g, 84.5 mmol) was added and the mixture was stirred at 0 °C for 30 min before concentration in vacuo. The residue was washed with hexanes (50 mL) and suspended in CH₂Cl₂ (50 mL) followed by filtration of the lead precipitate. The filtrate was extracted with 1 N HCl (3 × 30 mL). The combined aqueous layers were washed with Et₂O (30 mL), treated with 10% NaOH until pH 14, and extracted with Et₂O (30 mL). The organic layer was washed with brine (20 mL), dried (MgSO₄), and concentrated in vacuo to afford 13a as a pale yellow oil (890 mg, 6.08 mmol, 72%). Characterization data were consistent with previously reported values.¹² HPLC analysis indicated an enantiomeric excess of 93% [CHIRALCEL OD-H column; flow: 0.5 mL/min; hexanes:i-PrOH:Et₂NH = 900:100:1; λ = 254 nm; major enantiomer t_R = 10.5 min; minor enantiomer t_R = 14.3 min. ${[\alpha ]}_{589}^{23}+42.5,{[\alpha ]}_{577}^{23}+43.2,{[\alpha ]}_{546}^{23}+50.8,{[\alpha ]}_{435}^{23}+85.5(c1.15,{\text{CH}}_2{\text{Cl}}_2)$.

(R)-1-(4-Methoxyphenyl)but-3-en-1-amine (13b)

Following general procedure A, 13b (1.08 g, 6.11 mmol, 74% yield) was obtained as a yellow oil. Characterization data were consistent with previously reported values.¹² HPLC analysis indicated an enantiomeric excess of 92% [CHIRALCEL OD-H column; flow: 0.5 mL/min; hexanes:i-PrOH:Et₂NH = 900:100:1; λ = 254 nm; major enantiomer t_R = 13.1 min; minor enantiomer t_R = 16.8 min]. ${[\alpha ]}_{589}^{23}+31.0,{[\alpha ]}_{577}^{23}+32.2,{[\alpha ]}_{546}^{23}+36.7,{[\alpha ]}_{435}^{23}+66.5(c2.64,{\text{CH}}_2{\text{Cl}}_2)$.

(R)-1-Butyl-3-butenyl-1-(4-chlorophenyl)amine (13c)

Following general procedure A, 13c (1.21 g, 6.70 mmol, 72% yield) was obtained as a colorless oil. Characterization data were consistent previously reported values.¹² HPLC analysis indicated an enantiomeric excess of 94% [CHIRALCEL AD column; flow: 0.5 mL/min; hexanes:i-PrOH:Et₂NH = 950:50:1; λ = 254 nm; major enantiomer t_R = 14.6 min; minor enantiomer t_R = 14.0 min]. ${[\alpha ]}_{589}^{23}+38.1,{[\alpha ]}_{577}^{23}+39.6,{[\alpha ]}_{546}^{23}+44.9,{[\alpha ]}_{435}^{23}+78.5(c2.13,{\text{CH}}_2{\text{Cl}}_2)$.

(R)-1-Butyl-3-butenyl-1-(2-chlorophenyl)amine (13d)

Following general procedure A, 13d (1.10 g, 6.11 mmol, 73% yield) was obtained as a colorless oil. Characterization data were consistent with previously reported values.¹² HPLC analysis indicated an enantiomeric excess of 94% [CHIRALCEL AD column; flow: 0.5 mL/min; hexanes:i-PrOH:Et₂NH = 950:50:1; λ = 254 nm; major enantiomer t_R = 11.9 min; minor enantiomer t_R = 11.4 min]. ${[\alpha ]}_{589}^{23}+72.2,{[\alpha ]}_{577}^{23}+75.4,{[\alpha ]}_{546}^{23}+87.1,{[\alpha ]}_{435}^{23}+155(c1.27,{\text{CH}}_2{\text{Cl}}_2)$.

General Procedure B for the Fluoride-Mediated Alkylation of Enoxysilanes

Benzyl 2-(2-oxocyclohexyl)acetate (11)

To a stirred suspension of TASF (Me) (330 mg, 1.20 mmol) in THF (1.2 mL) at −78 °C was added a solution of 1-cyclohexenyloxytrimethylsilane (200 mg, 1.20 mmol) and benzyl 2-bromoacetate (0.22 mL, 1.4 mmol) in THF (1.8 mL) dropwise via syringe over 5 min. The resulting mixture was stirred at room temperature for 24 h, then diluted with hexanes (25 mL), washed with H₂O (10 mL), dried (MgSO₄), filtered and concentrated in vacuo. Purification of the crude residue by flash chromatography on silica gel (9:1 hexanes:EtOAc) provided 11 as a colorless oil (0.22 g, 0.91 mmol, 77%). ¹H NMR (500 MHz, CDCl₃) δ 7.37–7.30 (m, 5H), 5.18–5.08 (m, 2H), 2.94–2.80 (m, 2H), 2.48–2.32 (m, 2H), 2.26–2.07 (m, 3H), 1.92–1.85 (m, 1H), 1.79–1.58 (m, 2H), 1.44 (qd, J = 12.6, 3.7 Hz, 1H); ¹³C NMR (125 MHz, CDCl₃) δ 210.8, 172.4, 136.0, 128.5, 128.09, 128.05, 66.2, 47.1, 41.8, 34.4, 33.8, 27.7, 25.1; IR (film, cm^-1) 3066, 3035, 2937, 2861, 1733, 1710; Anal. Calcd for C₁₅H₁₈O₃: C, 73.15; H, 7.37. Found: C, 72.89; H, 7.47.

General Procedure C for Ketalization of Cycloalkanones

(1,5-Dioxaspiro[5.5]undec-7-yl)acetic acid benzyl ester (12)

To a solution of ketoester 11 (3.9 g, 16 mmol), 1,3-propanediol (22 mL, 39 mmol), and trimethylorthoformate (8.6 mL, 78 mmol) in ace-tonitrile (160 mL) at 0 °C was added scandium triflate (77 mg, 0.16 mmol). The reaction was maintained at 0 °C for 30 min, then quenched with saturated aqueous NaHCO₃ (∼5 mL) and extracted with Et₂O (3 × 75 mL). The combined organic layers were washed with water (3 × 50 mL) and brine (25 mL), dried (MgSO₄), filtered, concentrated in vacuo and purified on silica gel by flash chromatography (1:9 Et₂O:pentane) to provide 12 (4.2 g, 14 mmol, 88%) as a colorless oil. Characterization data were consistent with previously reported values.6

General Procedure D for Sequential Debenzylation and Amide Bond Formation

2-(1,5-Dioxaspiro[5.5]undec-7-yl)-N-[(1R)-1-phenylbut-3-en-1-yl]acetamide (14a)

Ketal ester 12 (1.82 g, 5.98 mmol), NaHCO₃ (1.82 g, 21.7 mmol), and Pd (OH)₂/C (182 mg, 20 % on carbon, wet) in EtOAc (60 mL) was evacuated and backfilled three times with N₂, then three times with H₂. The mixture was stirred at room temperature under a balloon atmosphere of H₂ for 2.5 h before filtering the solution over Celite, eluting with EtOAc (30 mL). The filtrate was concentrated to give the resulting acid, which was used without further purification.

N-(3-Dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDCI, 1.9 g, 7.2 mmol) was added to a solution of the crude acid, amine 13a (0.88 g, 5.9 mmol), and DMAP (73 mg, 0.60 mmol) in CH₂Cl₂ (13 mL). The solution was maintained at room temperature for 21 h and concentrated in vacuo. The crude residue was purified by flash chromatography (1:3 EtOAc:hexanes) to afford 14a (1.8 g, 5.1 mmol, 86%) as a colorless solid. mp 128–130 °C; ¹H NMR (500 MHz, CDCl₃) δ 7.34–7.22 (m, 5H), 6.30 (app dd, J = 31.7, 8.3 Hz, 1H), 5.70–5.65 (m, 1H), 5.12–5.05 (m, 3H), 4.07–4.05 (m, 1H), 3.92–3.89 (m, 1H), 3.80–3.66 (m, 2 H), 2.81–2.77 (m, 1H), 2.60–2.54 (m, 3H), 2.10–2.00 (m, 1H), 2.00–1.80 (m, 2H), 1.65–1.55 (m, 3H), 1.40–1.05 (m, 5H); ¹³C NMR (125 MHz, CDCl₃) δ 173.1, 142.4, 142.3, 134.44, 134.41, 128.7, 127.3, 126.70, 126.67, 118.2, 118.1, 98.94, 98.92, 59.3, 59.18, 59.17, 52.5, 52.4, 41.0, 40.9, 37.1, 29.2, 28.2, 25.89, 25.85, 25.0, 22.4; IR (thin film, cm^-1) 3290, 1644, 1536, 1447, 1337; HRMS (ESI) m/z: [M + H]⁺ Calcd for C₂₁H₃₀NO₃ 344.2226; Found 344.2237.

2-(1,5-Dioxaspiro[5.5]undec-7-yl)-N-[(1R)-1-(4-methoxyphenyl)but-3-en-1-yl]acetamide (14b)

Following general procedure D, 14b (1.75 g, 4.71 mmol, 88% yield) was obtained as a colorless solid. mp 79–80 °C; ¹H NMR (500 MHz, CDCl₃) δ 7.33–7.23 (m, 2H), 6.81 (app d, J = 7.0 Hz, 2H), 6.30 (app dd, J = 35.0, 7.8 Hz, 1H), 5.77–5.70 (m, 1H), 5.15–5.06 (m, 3H), 3.99 (app ds, J = 11.7, 2.9 Hz, 1H), 3.84 (app dq, J = 15.6, 5.2 Hz, 1H), 3.84 (s, 3H), 3.73-3.71 (m, 1H), 2.74 (app dt, J = 15.1, 5.0 Hz, 1H), 2.51–2.48 (m, 3H), 2.01–1.80 (m, 3H), 1.59–1.52 (m, 3H), 1.47–1.23 (m, 5H); ¹³C NMR (125 MHz, CDCl₃) δ 173.0, 172.9, 158.8, 134.57, 134.55, 134.5, 134.4, 127.81, 127.79, 118.0, 117.9, 114.1, 114.04, 114.02, 98.90, 98.89, 98.88, 98.87, 59.2, 59.1, 55.45, 52.0, 51.88, 40.9, 40.8, 37.01, 36.99, 29.10, 28.14, 5.9, 25.8, 25.0, 22.4; IR (thin film, cm^-1) 3296, 2935, 1638, 1513, 1246; HRMS (ESI) m/z: [M + H]⁺ Calcd for C₂₂H₃₂NO₄ 374.2331; Found: 374.2334.

N-[(1R)-1-(4-Chlorophenyl)but-3-en-1-yl]-2-(1,5-dioxaspiro[5.5]undec-7-yl)acetamide (14c)

Following general procedure D, 14c (1.80 g, 4.76 mmol, 89% yield) was obtained as a colorless solid. mp 135–138 °C; ¹H NMR (500 MHz, CDCl₃) δ 7.27 (app t, J = 8.4 Hz), 7.20 (app t, J = 6.8 Hz, 2H), 6.38 (dd, J = 21.4, 7.6 Hz, 1H), 5.68–5.61 (m, 1H), 5.10–5.02 (m, 3H), 4.04 (app q, J = 11.8, 2.8 Hz, 1H), 3.90 (app q, J = 10.3, 2.5 Hz, 1H), 3.80–3.75 (m, 2H), 2.80 (ddd, J = 19.5, 9.4, 6.8 Hz, 1H), 2.63 (broad s, 1H), 2.50 (t, J = 6.8 Hz, 2H), 2.03–1.84 (m, 3H), 1.72–1.56 (m, 3H), 1.43–1.15 (m, 5H); ¹³C NMR (125 MHz, CDCl₃) δ 173.2, 173.1, 141.1, 141.0, 133.99, 133.96, 133.0, 128.82, 128.80, 128.2, 128.0, 118.6, 118.5, 99.0, 98.9, 59.3, 59.21, 59.19, 52.0, 51.8, 40.8, 37.0, 28.1, 25.9, 22.4; IR (thin film, cm^-1) 3288, 2935, 1638, 1542, 1493; HRMS (ESI) m/z: [M + H]⁺ Calcd for C₂₁H₂₉ClNO₃ 378.1836; Found: 378.1834.

N-[(1R)-1-(2-Chlorophenyl)but-3-en-1-yl]-2-(1,5-dioxaspiro[5.5]undec-7-yl)acetamide (14d)

Following general procedure D, 14d (1.81 g, 4.78 mmol, 91% yield) was obtained as a colorless solid. mp 86–88 °C; ¹H NMR (500 MHz, CDCl₃) δ 7.34 (dt, J = 7.7, 1.5 Hz, 1H), 7.27–7.16 (m, 3H), 6.50 (t, J = 6.5 Hz, 1H), 5.73–5.65 (m, 1H), 5.39 (dtd, J = 13.5, 7.9, 5.5 Hz, 1H), 5.13–5.07 (m, 2H), 4.05 (dtd, J = 18.5, 12.0, 3.0 Hz, 1H), 3.92 (qd, J = 11.5, 2.5 Hz, 1H), 3.83–3.68 (m, 2H), 2.82 (ddd, J = 15.0, 10.0, 5.0 Hz, 1H), 2.63–2.49 (m, 3H), 2.10–2.02 (m, 1H), 2.00–1.84 (m, 2H), 1.66–1.54 (m, 3H), 1.44–1.15 (m, 5H);¹³C NMR (125 MHz, CDCl₃) δ 173.1, 173.0, 139.70, 139.65, 134.21, 134.17, 133.0, 132.9, 130.22, 130.21, 128.4, 128.0, 127.9, 127.0, 126.96, 126.95, 118.4, 118.3, 98.93, 98.92, 98.91, 98.90, 59.23, 59.18, 59.17, 50.6, 50.5, 39.3, 39.2, 36.83, 36.82, 29.14, 29.08, 28.2, 25.9, 25.8, 25.0, 22.4; IR (thin film, cm^-1) 3319, 3070, 1642, 1538, 1478; HRMS (ESI) m/z: [M + Na]⁺ Calcd for C₂₁H₂₈ClNO₃Na 400.1655; Found: 400.1659.

2-(1,5-Dioxaspiro[5.5]undec-7-yl)-N-[(1R)-1-isopropylbut-3-en-1-yl]-acetamide (14e)

Following general procedure D, 14e (747 mg, 2.40 mmol, 68% yield) was obtained as a colorless solid from (R)-2-methylhex-5-en-3-amine (51% ee).³³ mp 88–92 °C; ¹H NMR (500 MHz, CDCl₃) δ 5.80–5.73 (m, 2H), 5.07–5.03 (m, 2H), 4.06 (tt, J = 12.0, 3.0 Hz, 1H), 3.95–3.84 (m, 2H), 3.83–3.77 (m, 2H), 2.80 (dt, J = 14.5, 3.0 Hz, 1H), 2.61 (br s, 1H), 2.26 (dt, J = 15.0, 5.0 Hz, 1H), 2.15–2.10 (m, 2H), 1.93 (ddd, J = 14.6, 7.5, 2.8 Hz, 2H), 1.78–1.71 (m, 2H), 1.69–1.63 (m, 1H), 1.62–1.55 (m, 2H), 1.43–1.18 (m, 5H), 0.90 (ddd, J = 14.5, 6.8, 2.2 Hz, 6H); ¹³C NMR (125 MHz, CDCl₃) δ 173.41, 173.38, 135.4, 117.24, 117.21, 99.0, 98.9, 59.3, 59.22, 59.19, 53.4, 53.3, 37.12, 37.09, 37.0, 31.5, 31.4, 29.1, 29.0, 28.3, 28.2, 25.9, 25.0, 22.5, 19.48, 19.46, 18.1; IR (thin film, cm^-1) 3294, 2941, 1654, 1538, 1108; HRMS (ESI) m/z: [M + Na]⁺ Calcd for C₁₈H₃₁NO₃Na 332.2202; found: 332.2210.

General Procedure E for Reduction of an Amide with Lithium Aluminum Hydride

(1R)-N-[2-(1,5-Dioxaspiro[5.5]undec-7-yl)ethyl]-1-(4-methoxyphenyl)but-3-en-1-amine (9b)

Under an atmosphere of dry N₂, LiAlH₄ (1.64 g, 43.1 mmol) was added to a solution of 14b (1.61 g, 4.31 mmol) and Et₂O (110 mL) at 0 °C. The suspension was stirred at room temperature for 22 h. After cooling to 0 °C, water (3 mL), 10% NaOH (3 mL), and water (3 mL) were slowly added sequentially and the mixture was stirred at room temperature for 0.5 h. After filtration, the filtrate was dried (MgSO₄) and concentrated in vacuo. The crude residue was purified by flash chromatography (100:1 EtOAc:Et₃N) to afford 9b as a colorless oil (1.31 g, 3.66 mmol, 85%). ¹H NMR (500 MHz, CDCl₃) δ 7.23 (dd, J = 8.7, 3.9 Hz, 2H), 6.86 (d, J = 8.7 Hz, 2H), 5.71 (ddt, J = 17.4, 10.0, 7.2 Hz, 1H), 5.09–5.01 (m, 2H), 4.01 (td, J = 11.5, 2.5 Hz, 1H), 3.88 (td, J = 11.5, 3.0 Hz, 1H), 3.81–3.73 (m, 5H), 3.62 (q, J = 6.6 Hz, 1H), 2.53–2.42 (m, 2H), 2.40–2.34 (m, 3H), 1.99–1.84 (m, 2H), 1.54–1.47 (m, 5H), 1.43–1.15 (m, 7H); ¹³C NMR (125 MHz, CDCl₃) δ 158.68, 158.67, 136.5, 136.0, 128.41, 128.38, 117.40, 117.36, 113.80, 113.79, 99.17, 99.16, 62.4, 62.2, 59.13, 59.12, 59.07, 59.06, 55.42, 55.41, 46.9, 46.4, 43.29, 43.25, 28.8, 28.44, 28.35, 28.0, 27.8, 25.9, 22.48, 22.46; IR (thin film, cm^-1) 2933, 2860, 1511, 1245, 1106; HRMS (ESI) m/z: [M + H]⁺ Calcd for C₂₂H₃₄NO₃ 360.2539; Found: 360.2536.

(1R)-N-[2-(1,5-Dioxaspiro[5.5]undec-7-yl)ethyl]-1-phenylbut-3-en-1-amine (9a)

Following general procedure E, 9a (1.56 g, 1.62 mmol, 97% yield) was obtained as a pale yellow oil; changes from the standard procedure include the use of THF (70 mL) and Et₂O (30 mL) as the solvent mixture (to assist in the solubility of the amide). ¹H NMR (500 MHz, CDCl₃) δ 7.32–7.31 (m, 4H), 7.26–7.21 (m, 1H),5.76–5.608 (m, 1H), 5.10–5.02 (m, 2H), 4.01 (td, J = 11.5, 3.0 Hz, 1H), 3.88 (td, J = 11.0, 2.5 Hz, 1H), 3.80–3.74 (m, 2H), 3.66 (q, J = 6.2 Hz, 1H), 2.54–2.45 (m, 2H), 2.44–2.36 (m, 3H), 2.00–1.84 (m, 2H), 1.63–1.47 (m, 7H), 1.44–1.16 (m, 7H); ¹³C NMR (125 MHz, CDCl₃) δ 144.4, 135.9, 128.42, 128.41, 128.39, 128.38, 127.44, 127.43, 127.42, 127.39, 127.38, 127.01, 126.99, 117.53, 117.49, 99.14, 99.13, 63.0, 62.8, 59.12, 59.11, 59.05, 59.0, 47.0, 46.4, 43.3, 43.2, 28.8, 28.5, 28.4, 28.3, 28.0, 27.8, 25.8, 22.5, 22.4; IR (thin film, cm^-1) 2931, 2860, 1453, 1245, 1108; HRMS (ESI) m/z: [M + H]⁺ Calcd for C₂₁H₃₂NO₂ 330.2433; Found: 330.2426.

(1R)-1-(4-Chlorophenyl)-N-[2-(1,5-dioxaspiro[5.5]undec-7-yl)ethyl]but-3-en-1-amine (9c)

Following general procedure E, 9c (1.50 g, 4.13 mmol, 98% yield) was obtained as a colorless oil; changes from the standard procedure include the use of THF (16 mL) as the solvent mixture (to assist in the solubility of the amide). ¹H NMR (500 MHz, CDCl₃) δ 7.32–7.24 (m, 4H), 5.69 (ddt, J = 10.5, 7.5 Hz, 1H), 5.08–5.02 (m, 2H), 4.01 (tt, J = 11.0, 2.0 Hz, 1H), 3.88 (td, J = 11.5, 3.0 Hz, 1H), 3.77–3.75 (m, 2H), 3.64 (q, J = 6.5 Hz, 1H), 2.50–2.45 (m, 2H), 2.38–2.33 (m, 3H), 1.99–1.84 (m, 2H), 1.55–1.46 (m, 5H), 1.42–1.15 (m, 7H); ¹³C NMR (125 MHz, CDCl₃) δ 143.0, 142.9, 135.34, 135.33, 132.47, 132.45, 128.81, 128.80, 128.79, 128.78, 128.77, 128.75, 128.74, 128.73, 128.72, 128.52, 128.50, 117.9, 117.8, 99.08, 99.07, 99.06, 62.36, 62.35, 62.19, 62.18, 62.17, 59.10, 59.09, 59.03, 59.01, 47.0, 46.4, 43.21, 43.19, 30.5, 28.8, 28.4, 28.3, 28.2, 28.1, 27.8, 25.8, 24.5, 22.42, 22.40; IR (thin film, cm^-1) 2933, 2860, 1490, 1245, 1108; HRMS (ESI) m/z: [M + Na]⁺ Calcd for C₂₁H₃₀ClNO₂Na 386.1863; Found: 386.1860.

(1R)-1-(2-Chlorophenyl)-N-[2-(1,5-dioxaspiro[5.5]undec-7-yl)ethyl]but-3-en-1-amine (9d)

Following general procedure E, 9d (1.35 g, 3.69 mmol, 83% yield) was obtained as a colorless oil; changes from the standard procedure include the use of THF (16 mL) as a solvent (to assist in the solubility of the amide) and the purification of 9d on silica gel by flash chromatography (100:100:1 hex-anes:EtOAc:Et₃N). ¹H NMR (500 MHz, CDCl₃) δ 7.55 (ddd, J = 7.8, 4.2, 1.7 Hz, 1H), 7.34 (dt, J = 7.9, 0.9 Hz, 1H), 7.27 (tt, J = 7.5, 1.5 Hz, 1H), 7.17 (td, J = 7.4, 1.7 Hz, 1H), 5.83–5.75 (m, 1H), 5.14–5.06 (m, 2H), 4.25 (ddd, J = 12.5, 8.0, 5.0 Hz, 1H), 4.06–4.00 (m, 1H), 3.90 (tt, J = 11.0, 3.0 Hz, 1H), 3.82–3.76 (m, 2H), 2.55–2.48 (m, 3H), 2.44–2.36 (m, 1H), 2.30 (dt, J = 14.0, 8.0 Hz, 1H), 2.03–1.95 (m, 1H), 1.94–1.86 (m, 1H), 1.57–1.53 (m, 4H), 1.42 (dq, J = 13.0, 2.5 Hz, 1H), 1.38–1.28 (m, 2H), 1.27–1.17 (m, 4H); ¹³C NMR (125 MHz, CDCl₃) δ 141.39, 141.36, 135.43, 135.42, 133.8, 133.7, 129.58, 129.56, 128.32, 128.25, 127.86, 127.85, 127.1, 127.0, 117.9, 117.8, 99.13, 99.12, 59.13, 59.11, 59.05, 59.0, 58.4, 58.2, 46.8, 46.4, 41.5, 41.4, 31.8, 31.1, 28.8, 28.5, 28.4, 28.3, 28.0, 27.8, 25.83, 25.82, 24.5, 22.8, 22.5, 22.4, 14.3; IR (thin film, cm^-1) 2933, 2860, 1461, 1441, 1108; HRMS (ESI) m/z: [M + H]⁺ Calcd for C₂₁H₃₁ClNO₂ 364.2043; Found: 364.2043.

(1R)-N-[2-(1,5-Dioxaspiro[5.5]undec-7-yl)ethyl]-1-isopropylbut-3-en-1-amine (9e)

Following general procedure E, 9e (488 mg, 1.65 mmol, 85% yield) was obtained as a pale yellow oi. ¹H NMR (500 MHz, CDCl₃) δ 5.80 (ddt, J = 17.0, 10.0, 7.5 Hz, 1H), 5.10–04 (m, 2H), 4.03 (td, J = 11.0, 3.0 Hz, 1H), 3.90 (td, J = 11.5, 3.0 Hz, 1H), 3.82–3.79 (m, 2H), 2.68–2.62 (m, 1H), 2.55–2.45 (m, 2H), 2.37–2.33 (m, 1H), 2.23–2.18 (m, 1H), 2.08–2.01 (m, 1H), 1.99–1.87 (m, 2H), 1.84–1.77 (m, 1H), 1.66–1.53 (m, 6H), 1.45–1.21 (m, 8H), 0.91–0.88 (m, 6H); ¹³C NMR (125 MHz, CDCl₃) δ 137.2, 116.7, 99.19, 99.18, 62.92, 62.91, 62.89, 59.10, 59.09, 59.03, 47.1, 47.0, 42.8, 35.34, 35.31, 30.2, 30.1, 28.9, 28.8, 28.42, 28.36, 27.9, 25.9, 24.4, 22.47, 22.46, 19.0, 18.9, 18.19, 18.17; IR (thin film, cm^-1) 2935, 2863, 1465, 1445, 1109; HRMS (ESI) m/z: [M + H]⁺ Calcd for C₁₈H₃₄NO₂ 296.2590; Found: 296.2585.

Representative Procedure for the Synthesis of Octahydroindole ent-8 from Aminoacetals 9

(3aR,7aS)-7a-Allyloctahydro-1H-indole (ent-8)

A stirring mixture of 9a (0.20 g, 0.62 mmol), TFA (47 μ L, 0.62 mmol), and morpholine (5.4 μL, 0.062 mmol) was heated at 120 °C. Dimedone (0.22 g, 1.5 mmol) was added and the solution was maintained at 120 °C for 5 h. After cooling to room temperature, the reaction mixture was dissolved in Et₂O (10 mL). The mixture was extracted with 1 N HCl (2 × 10 mL), and the combined aqueous layers were washed with Et₂O (30 mL), treated with 10% NaOH until pH 14, and extracted with Et₂O (30 mL). The organic layer was washed with brine (20 mL), dried (MgSO₄), filtered, and concentrated in vacuo to afford ent-8 as yellow oil (94 mg, 0.57 mmol, 92%). ${[\alpha ]}_{589}^{23}+18.2,{[\alpha ]}_{577}^{23}+16.2,{[\alpha ]}_{546}^{23}+19.2,(c0.450,{\text{CH}}_2{\text{Cl}}_2)$; HPLC analysis of the derived benzoyl protected amine S1 indicated an enantiomeric excess of 88% (see below). ¹H NMR (500 MHz, CDCl₃) δ 5.87-5.79 (m, 1H), 5.09-5.02 (m, 2H), 3.03-2.91 (m, 2H), 2.25 (ddt, J = 13.9, 8.0, 1.2 Hz, 1H), 2.11 (ddt, J = 15.1, 7.0, 6.3 Hz, 1H), 1.89-1.82 (m, 1H), 1.76-1.63 (m, 3H), 1.57-1.50 (m, 1H), 1.48-1.27 (m, 7H); ¹³C NMR (125 MHz, CDCl₃) δ 135.0, 117.8, 61.9, 42.8, 42.5, 42.3, 31.4, 29.8, 26.8, 22.5, 22.1; IR (thin film, cm^-1) 3300, 2923, 1667, 1407; HRMS (ESI) m/z: [M + H]⁺ Calcd for C₁₁H₂₀N 166.1596; Found: 166.1594.

7a-Allyl-1-benzoyloctahydro-1H-indole (S1)

Benzoyl chloride (37 mg, 0.26 mmol) was added to a solution of ent-8 (31 mg, 0.19 mmol), Et₃N (40 mg, 0.40 mmol) and CH₂Cl₂ (0.5 mL) at room temperature. The solution was maintained at room temperature for 1 h. After the addition of Et₂O (10 mL), the organic layer was washed with water (5 mL), 1N HCl (5 mL), 10% NaOH (5 mL) and brine (5 mL). The organic layer was dried (MgSO₄), filtered, and concentrated in vacuo. The crude residue was purified by flash chromatography (1:10 EtOAc:hexanes) to afford the title compound as a colorless solid (44 mg, 0.17 mmol, 87%). HPLC analysis indicated an enantiomeric excess of 89% [CHIRALCEL AD column; flow: 1.0 mL/min; 96.5% n-hexane/3.5% i-PrOH; λ = 220 nm; major enantiomer t_R = 28.3 min; minor enantiomer t_R = 25.5 min minor enantiomer t_R=25.5 min]. mp 46-47 °C; ${[\alpha ]}_{589}^{23}+76.8,{[\alpha ]}_{577}^{23}+79.5,{[\alpha ]}_{546}^{23}+90.8,{[\alpha ]}_{435}^{23}+171(c1.04,{\text{CH}}_2{\text{Cl}}_2)$. . ¹H NMR (500 MHz, CDCl₃) δ 7.41–7.35 (m, 5H), 5.91–5.83 (m, 1H), 5.16–5.13 (m, 2H), 3.33–3.30 (m, 2H), 3.25 (dd, J = 13.9, 6.5 Hz, 1H), 2.60–2.53 (m, 2H), 2.28–2.23 (m, 1H), 1.91–1.83 (m, 1H), 1.77 (td, J = 13.1, 4.1 Hz, 1H), 1.71–1.56 (m, 4H), 1.50–1.30 (m, 3H); ¹³C NMR (125 MHz, CDCl₃) δ 170.0, 139.0, 134.7, 129.4, 128.4, 126.6, 118.3, 65.5, 50.7, 39.7, 37.5, 32.8, 27.3, 25.2, 22.8, 21.5; IR (thin film, cm^-1) 1630, 1403, 1218, 1189, 1138; HRMS (ESI) m/z: [M + Na]⁺ Calcd for C₁₈H₂₃NONa 292.1677; Found: 292.1680.

Synthesis and Characterization of Aminoketals 15–17 and Their Precursors

Benzyl 2-(2-oxocyclopentyl)acetate (S2)

Following general procedure B, S2 (2.3 g, 9.9 mmol, 78%) was obtained as a colorless oil. This product was purified on silica gel by flash chromatography (19:1 hexanes:EtOAc to 9:1 hexanes:EtOAc). Characterization data were consistent with previously reported values.³⁴

Benzyl 2-(6,10-dioxaspiro[4.5]decan-1-yl)acetate (S3)

Following general procedure C, S3 (5.8 g, 20 mmol, 96%) was obtained as a colorless oil. ¹H NMR (500 MHz, CDCl₃) δ 7.37-7.28 (m, 5H), 5.14 (d, J = 12.4 Hz, 1H), 5.08 (d, J = 12.4 Hz, 1H), 3.90–3.77 (m, 4H), 2.71 (dd, J = 15.0, 3.8 Hz, 1H), 2.38–2.25 (m, 2H), 2.11 (ddd, J = 13.1, 8.7, 6.9 Hz, 1H), 1.96–1.86 (m, 2H), 1.82 (ddd, J = 13.1, 9.4, 6.1 Hz, 1H), 1.71–1.62 (m, 2H), 1.39–1.31 (m, 2H); ¹³C NMR (125 MHz, CDCl₃) δ 173.5, 136.3, 128.4, 128.1, 128.0, 108.1, 65.9, 62.1, 60.6, 45.1, 33.8, 29.9, 28.6, 25.8, 20.8; IR (thin film, cm^-1) 2958, 2867, 1733; HRMS (ES) m/z: [M + Na]⁺ Calcd for C₁₇H₂₂O₄Na 313.1416; Found: 313.1420.

2-(6,10-Dioxaspiro[4.5]dec-1-yl)-N-[(1R)-1-phenylbut-3-en-1-yl]acetamide (S4)

Following general procedure D, S4 (1.5 g, 4.5 mmol, 89%) was obtained as a colorless oil. ¹H NMR (500 MHz, CDCl₃) δ 7.33–7.23 (m, 5H), 7.07 (br s, 0.5H), 6.90 (br s, 0.5H), 5.74–5.66 (m, 1H), 5.11–5.01 (m, 3H), 3.94–3.78 (m, 4H), 3.75–3.71 (m, 1H), 2.69 (ddd, J = 15.7, 7.8, 3.6 Hz, 1H), 2.62–2.52 (m, 2H), 2.29–2.03 (m, 3H), 1.96–1.81 (m, 3H), 1.75–1.57 (m, 3H), 1.39–1.24 (m, 2H); ¹³C NMR (125 MHz, CDCl₃) δ 172.5, 142.3, 142.1, 134.5, 128.64, 128.63, 127.4, 127.3, 126.9, 126.73, 126.70, 126.69, 117.90, 117.89, 108.2, 108.1, 62.4, 62.3, 60.7, 60.6, 52.9, 52.7, 46.2, 46.1, 41.0, 40.7, 36.2, 36.1, 30.7, 30.54, 30.53, 30.2, 30.0, 25.9, 25.7, 21.5, 21.3; IR (thin film, cm^-1) 3292, 1638, 1542, 1152; HRMS (ESI) m/z: [M + Na]⁺ Calcd for C₂₀H₂₇NO₃Na 352.1889; Found: 352.1894.

N-[2-(6,10-Dioxaspiro[4.5]dec-1-yl)-ethyl]-(1R)-1-phenylbut-3-en-1-amine (S5)

Following general procedure E, S5 (1.15 g, 3.67 mmol, 93%) was obtained as a colorless oil. ¹H NMR (500 MHz, CDCl₃) δ 7.27–7.22 (m, 4H), 7.19–7.16 (m, 1H), 5.67 (ddt, J = 16.9, 9.4, 7.5 Hz, 1H), 5.04–4.97 (m, 2H), 3.85–3.75 (m, 4H), 3.62 (t, J = 6.9, 1H), 2.50–2.34 (m, 4H), 2.10–1.99 (m, 1H), 1.90–1.49 (m, 8H), 1.39–1.27 (m, 2H), 1.24–1.13 (m, 1H); ¹³C NMR (125 MHz, CDCl₃) δ 144.44, 144.38, 135.8, 128.36, 128.35, 127.41, 127.40, 127.0, 126.9, 117.4, 108.83, 108.81, 62.83, 62.75, 62.19, 62.17, 60.7, 46.9, 46.8, 46.6, 46.5, 43.21, 43.20, 30.7, 29.4, 29.22, 29.17, 29.1, 26.07, 26.05, 21.28, 21.25; IR (thin film, cm^-1) 2954, 2861, 1453, 1246, 1108; HRMS (ESI) m/z: [M + H]⁺ Calcd for C₂₀H₃₀NO₂ 316.2277; Found: 316.2282.

Benzyl 3-(2-oxocyclopentyl)propanoate (S6)

Ketone S6 was prepared using an adaptation of the procedure of Cotarco and co-workers.³⁵ A stirring solution of cyclopentanone (19 mL, 0.21 mol), 4-methoxyphenol (0.17 g, 1.4 mmol), cyclohexylamine (1.7 mL, 15 mmol) and acetic acid (0.15 mL, 2.5 mmol) was heated to 80 °C for 10 min, then warmed to 130 °C over 30 min. Benzyl acrylate (16 mL, 0.11 mol) was added via syringe pump at a rate of 6.8 mL/h. Upon complete addition, the reaction was cooled to 25 °C and the residue was purified directly on silica gel by flash chromatography (1:9-1:4 EtOAc:hexanes) to provide S6 (13 g, 52 mmol, 47%) as a colorless oil. ¹H NMR (500 MHz, CDCl₃) δ 7.40-7.31 (m, 5H), 5.15 (s, 2H), 2.55-2.45 (m, 2H), 2.31 (dd, J = 18.8, 8.6 Hz, 1H), 2.23-2.17 (m, 1H), 2.16-2.07 (m, 3H), 2.05-1.97 (m, 1H), 1.82-1.73 (m, 1H), 1.73-1.63 (m, 1H), 1.56-1.46 (m, 1H); ¹³C NMR (125 MHz, CDCl₃) δ 219.9, 172.7, 135.8, 128.3, 128.1, 128.0, 65.9, 47.9, 37.7, 31.9, 29.2, 24.6, 20.3; IR (thin film, cm^-1) 2960, 2877, 1733; Anal. Calcd for C₁₅H₁₈O₃: C, 73.15; H, 7.37. Found: C, 73.26; H, 7.40; HRMS (ES) m/z: [M + Na]⁺ Calcd for C₁₅H₁₈O₃Na 269.1154; Found: 269.1144.

Benzyl 3-(6,10-dioxaspiro[4.5]decan-1-yl)propanoate (S7)

Following general procedure C, S7 (4.6 g, 16 mmol, 56%) was obtained as a colorless oil. ¹H NMR (500 MHz, CDCl₃) δ 7.38–7.27 (m, 5H), 5.14–5.08 (m, 2H), 3.90–3.79 (m, 4H), 2.54–2.42 (m, 2H), 2.09 (dt, J = 13.3, 8.5 Hz, 1H), 1.90–2.01 (m, 2H), 1.87–1.74 (m, 3H), 1.70–1.53 (m, 3H) 1.37–1.24 (m, 2H); ¹³C NMR (125 MHz, CDCl₃) δ 173.7, 136.2, 128.3, 128.2, 128.0, 108.3, 65.8, 61.9, 60.4, 47.9, 32.8, 30.5, 28.7, 25.7, 23.7, 20.9; IR (thin film, cm^-1) 2956, 2865, 1733; Anal. Calcd for C₁₈H₂₄O₄: C, 71.03; H, 7.95. Found: C, 71.12; H, 7.94; HRMS (ES) m/z: [M + Na]⁺ Calcd for C₁₈H₂₄O₄Na 327.1572; Found: 327.1564.

3-(6,10-Dioxaspiro[4.5]dec-1-yl)-N-[(1R)-1-phenylbut-3-en-1-yl]propionamide (S8)

Following general procedure D, S8 (1.66 g, 4.85 mmol, 97%) was obtained as a colorless oil. ¹H NMR (500 MHz, CDCl₃) δ 7.30–7.22 (m, 5H), 6.41 (app br d, J = 20.8 Hz, 1H), 5.71–5.63 (m, 1H), 5.08–5.05 (m, 3H), 3.87–3.80 (m, 4H), 2.53–2.51 (m, 2H), 2.48–2.41 (m, 1H), 2.29–2.22 (m, 1H), 2.18–2.10 (m, 1H), 2.02–1.74 (m, 5H), 1.69–1.49 (m, 3H), 1.41–1.36 (m, 1H), 1.31–1.19 (m, 1H); ¹³C NMR (125 MHz, CDCl₃) δ 173.19, 173.16, 142.3, 142.2, 134.5, 134.4, 128.74, 128.69, 128.6, 127.4, 127.33, 127.27, 126.8, 126.7, 126.6, 118.2, 118.03, 118.00, 109.0, 108.9, 62.39, 62.36, 62.1, 60.5, 52.6, 52.4, 47.5, 47.4, 40.9, 35.3, 34.3, 31.0, 30.9, 29.6, 29.5, 26.2, 25.0, 21.34, 21.25; IR (thin film, cm^-1) 3288, 2956, 1638, 1542, 1248; HRMS (ESI) m/z: [M + Na]⁺ Calcd for C₂₁H₂₉NO₃Na 366.2045; Found: 366.2037.

N-[3-(6,10-Dioxaspiro[4.5]dec-1-yl)-propyl]-(1R)-1-phenylbut-3-en-1-amine (16)

Following general procedure E, 16 (1.27 g, 3.84 mmol, 88%) was obtained as a colorless oil. ¹H NMR (500 MHz, CDCl₃) δ 7.30–7.27 (m, 4H), 7.21–7.18 (m, 1H), 5.72–5.64 (m, 1H), 5.06–4.99 (m, 2H), 3.87–3.79 (m, 4H), 3.62 (t, J = 6.9 Hz, 1H), 2.43–2.36 (m, 4H), 2.06–2.00 (m, 1H), 1.95–1.88 (m, 1H), 1.84–1.68 (m, 6H), 1.34 (dq, J = 7.9, 2.6 Hz, 1H), 1.26–1.19 (m, 1H), 1.17–1.08 (m, 1H); ¹³C NMR (125 MHz, CDCl₃) δ 144.31, 144.26, 135.8, 128.4, 127.39, 127.37, 127.0, 117.5, 108.9, 62.9, 62.8, 62.11, 62.10, 60.8, 48.9, 48.8, 48.4, 48.3, 43.2, 43.1, 30.71, 30.68, 29.1, 29.02, 28.99, 28.9, 26.34, 26.27, 26.1, 21.12, 21.09; IR (thin film, cm^-1) 2952, 2860, 1453, 1246, 1109; HRMS (ESI) m/z: [M + H]⁺ Calcd for C₂₁H₃₂NO₂ 330.2433; Found: 330.2433.

Benzyl 3-(2-oxocyclohexyl)propanoate (S9)

Ketone S9 was prepared using an adaptation of the procedure of Cotarco and co-workers.³⁵ A stirring solution of cyclohexanone (24 mL, 0.21 μmol), 4-methoxyphenol (0.17 g, 1.4 mmol), cyclohexylamine (1.7 mL, 15 mmol) and acetic acid (0.15 mL, 2.5 mmol) was heated to 80 °C for 10 min, then warmed to 130 °C over 30 min. Benzyl acrylate (16 mL, 0.11 mol) was added via syringe pump at a rate of 6.8 mL/h. Upon complete addition, the reaction was cooled to 25 °C and the residue was purified directly on silica gel by flash chromatography (1:9–1:4 EtOAc:hexanes) to provide S9 (23 g, 87 mmol, 83%) as a colorless oil. ¹H NMR (500 MHz, CDCl₃) δ 7.32–7.24 (m, 5H), 5.06 (s, 2H), 2.45–2.1 (m, 5H), 2.09–1.95 (m, 3H), 1.83–1.74 (m, 1H), 1.64–1.49 (m, 3H), 1.31 (dq, J = 8.9, 3.7 Hz, 1H); ¹³C NMR (125 MHz, CDCl₃) δ 211.0, 173.0, 135.8, 128.2, 128.0, 127.9, 65.8, 49.3, 41.8, 33.8, 31.5, 27.7, 24.8, 24.5; IR (thin film, cm⁻¹) 2935, 2861, 1733, 1708; Anal. Calcd for C₁₆H₂₀O₃: C, 73.82; H, 7.72. Found: C, 73.88; H, 7.72; HRMS (ES) m/z: [M + Na]⁺ Calcd for C₁₆H₂₀O₃Na 283.1310; Found: 283.1297.

Benzyl 3-(1,5-dioxaspiro[5.5]undecan-7-yl)propanoate (S10)

Following general procedure C, S10 (4.1 g, 13 mmol, 78%) was obtained as a colorless oil; changes from the standard procedure include the exposure of this substrate to reaction conditions at 25 °C for 3 h. ¹H NMR (500 MHz, CDCl₃) δ 7.36–7.27 (m, 5H), 5.08 (s, 2H), 3.98 (app td, J = 11.5, 2.7 Hz, 1H), 3.85 (app td, J = 11.3, 2.7 Hz, 1H), 3.77–3.72 (m, 2H), 2.49–2.40 (m, 1H), 2.39–2.30 (m, 1H), 2.22–2.13 (m, 1H), 1.93–1.83 (m, 1H), 1.62–1.46 (m, 6H), 1.41–1.26 (m, 3H), 1.25–1.12 (m, 2H); ¹³C NMR (125 MHz, CDCl₃) δ 174.0, 136.2, 128.4, 128.1, 128.0, 98.9, 65.9, 58.8, 58.7, 44.0, 32.9, 28.0, 27.3, 25.5, 24.2, 23.4, 22.2; IR (thin film, cm^-1) 2935, 2861, 1735; Anal. Calcd for C₁₉H₂₆O₄: C, 71.67; H, 8.23. Found: C, 71.62; H, 8.39.

3-(1,5-Dioxaspiro[5.5]undec-7-yl)-N-[(1R)-1-phenylbut-3-en-1-yl]propionamide (S11)

Following general procedure D, S11 (1.45 g, 4.03 mmol, 99%) was obtained as a colorless oil. ¹H NMR (500 MHz, CDCl₃) δ 7.34–7.24 (m, 5H), 6.51 (app t, J = 9.4 Hz, 1H), 5.76–5.67 (m, 1H), 5.17–5.08 (m, 3H), 4.07 (tdd, J = 11.9, 5.9, 3.0 Hz, 1H), 3.92 (td, J = 11.7, 2.8 Hz, 1H), 3.82–3.73 (m, 2H), 2.62–2.59 (m, 1H), 2.57–2.52 (m, 2H), 2.44–2.38 (m, 1H), 2.25–2.14 (m, 2H), 2.02–1.90 (m, 1H), 1.66–1.50 (m, 4H), 1.44–1.11 (m, 7H); ¹³C NMR (125 MHz, CDCl₃) δ172.8, 172.7, 142.4, 142.3, 134.7, 134.5, 128.7, 128.6, 127.4, 127.3, 126.8, 126.7, 118.0, 99.53, 99.52, 59.19, 59.17, 59.1, 52.51, 52.45, 41.0, 40.8, 35.3, 35.2, 28.4, 28.1, 28.0, 25.9, 24.3, 24.2, 22.44, 22.4; IR (thin film, cm^-1) 3305, 2935, 1640, 1541, 1448; HRMS (ESI) m/z: [M + H]⁺ Calcd for C₂₂H₃₂NO₃ 358.2382; Found: 358.2390.

N-[3-(1,5-Dioxaspiro[5.5]undec-7-yl)-propyl]-(1R)-1-phenylbut-3-en-1-amine (17)

Following general procedure E, 17 (1.17 g, 3.41 mmol, 89%) was obtained as a colorless oil. ¹H NMR (500 MHz, CDCl₃) δ 7.34–7.31 (m, 4H), 7.25–7.22 (m, 1H), 5.76–5.67 (m, 1H), 5.10–5.03 (m, 2H), 4.01 (td, J = 11.4, 3.1 Hz, 1H), 3.88 (td, J = 10.5, 2.7 Hz, 1H), 3.79–3.75 (m, 2H), 3.65 (t, J = 6.8 Hz, 1H), 2.49–2.41 (m, 5H), 1.91–1.83 (m, 1H), 1.78–1.70 (m, 1H), 1.66–1.62 (m, 1H), 1.57–1.46 (m, 4H), 1.44–1.30 (m, 3H), 1.27–1.20 (m, 3H), 1.14–1.06 (m, 1H); ¹³C NMR (125 MHz, CDCl₃) δ 144.2, 135.8, 128.5, 127.43, 127.40, 127.1, 117.6, 99.3, 62.8, 62.7, 59.10, 59.09, 59.0, 48.3, 48.1, 43.1, 28.7, 28.4, 28.34, 28.29, 27.33, 27.25, 25.8, 25.2, 25.1, 24.3, 22.5; IR (thin film, cm^-1) 2933, 2860, 1453, 1244, 1107; HRMS (ESI) m/z: [M + H]⁺ Calcd for C₂₂H₃₄NO₂ 344.2590; Found: 344.2581.

General Procedure F for 2-Aza-Cope Rearrangement and Cbz Protection to Yield 1-Azabicyclic Products ent-8 and 18–20

Preparation of (3aR, 6aS)-benzyl 6a-allylhexahydrocyclopenta[b]pyrrole-1(2H)-carboxylate (18)

A stirring mixture of 15 (228 mg, 0.722 mmol), TFA (56.0 μL, 0.722 mmol) and morpholine (6.30 μL, 0.0722 mmol) was heated to 120 °C. Dimedone (253 mg, 1.81 mmol) was added and the solution was maintained at 120 °C for 2 h. After cooling to room temperature, the reaction mixture was dissolved in CHCl₃ (5 mL). A saturated aqueous solution of Na₂CO₃ (2.4 mL), water (2.4 mL) and benzyl chloroformate (310 μL, 2.17 mmol) was added and the biphasic solution was stirred at room temperature for 18 h. The aqueous layer was extracted with CH₂Cl₂ (3 × 10 mL) and the combined organic layer was dried (Na₂SO₄), filtered, and concentrated in vacuo. The crude residue was purified by flash chromatography (1:20 EtOAc:hexanes) to afford 18 as a colorless oil (196 mg, 95%). HPLC analysis indicated an enantiomeric excess of 92% [CHIRALCEL OJ column; flow: 1.0 mL/min; 96% n-hexane/4% i-PrOH; λ = 220 nm; major enantiomer t_R = 6.7 min; minor enantiomer t_R = 8.5 min]. ${[\alpha ]}_{589}^{23}-11.4,{[\alpha ]}_{577}^{23}-11.0,{[\alpha ]}_{546}^{23}-12.2,{[\alpha ]}_{435}^{23}-18.5(c1.99,{\text{CH}}_2{\text{Cl}}_2)$. ¹H NMR (500 MHz, DMSO-d₆, 388 K) δ 7.36 (app d, J = 4.5 Hz, 4H), 7.32–7.28 (m, 1H), 5.79–5.71 (m, 1H), 5.13–5.00 (m, 2H), 3.53–3.42 (m, 2H), 2.81–2.77 (m, 2H), 2.50–2.44 (m, 1H), 2.37 (dd, J = 18.8, 7.5 Hz, 1H), 2.16 (dt, J = 12.3, 6.3 Hz, 1H), 1.93 (dq, J = 12.6, 8.1 Hz, 1H), 1.87–1.80 (m, 1H), 1.72–1.65 (m, 1H), 1.64–1.51 (m, 3H), 1.45–1.38 (m, 1H); ¹³C NMR (125 MHz, DMSO-d₆, 388 K) δ 152.6, 136.7, 134.2, 127.4, 126.7, 126.6, 116.4, 73.1, 64.9, 47.3, 47.0, 40.5, 40.0, 39.8, 39.7, 39.5, 39.3, 39.2, 39.0, 37.3, 31.1, 27.8, 24.0; IR (thin film, cm^-1) 2946, 1696, 1405, 1355; HRMS (ESI) m/z: [M + Na]⁺ Calcd for C₁₈H₂₃NO₂Na 308.1626; Found: 308.1622.

(3aR, 7aS)-Benzyl 7a-allyloctahydro-1H-indole-carboxylate (Cbz-ent-8)

Following general procedure F, (164 mg, 0.549 mmol, 85%) was obtained as a colorless oil; changes from the standard procedure include heating 9a at 120 °C for 5 h and purification by flash chromatography on silica gel (20:1 hexanes:Et₂O). HPLC analysis indicated an enantiomeric excess of 89% [CHIRALCEL OJ column; flow: 1.0 mL/min; 96% n-hexane/4% i-PrOH; λ = 220 nm; major enantiomer t_R = 7.8 min; minor enantiomer t_R = 11.6 min]. ${[\alpha ]}_{589}^{23}-11.4,{[\alpha ]}_{577}^{23}-11.0,{[\alpha ]}_{546}^{23}-12.2,{[\alpha ]}_{435}^{23}-18.5(c1.99,{\text{CH}}_2{\text{Cl}}_2)$. ¹H NMR (500 MHz, DMSO-d₆, 398 K) δ 7.36–7.28 (m, 5H), 5.78–5.70 (m, 1H), 5.12–5.00 (m, 4H), 3.62–3.57 (m, 1H), 3.34–3.29 (m, 1H), 2.72 (dd, J = 15.0, 7.1 Hz, 1H), 2.50–2.44 (m, 1H), 2.14–2.09 (m, 1H), 1.94–1.60 (m, 5H), 1.51–1.28 (m, 5H); ¹³C NMR (125 MHz, DMSO-d₆, 398 K) δ 152.9, 136.8, 133.8, 127.4, 126.6, 126.5, 116.3, 64.7, 63.1, 45.4, 39.0, 38.8, 31.3, 25.4, 24.8, 20.7, 20.4; IR (thin film, cm^-1) 2927, 1696, 1401, 1337; HRMS (ESI) m/z: [M + Na]⁺ Calcd for C₁₉H₂₅NO₂Na 322.1783; Found: 322.1777.

(4aR, 7aS)-Benzyl 7a-allyloctahydro-1 H-cyclopenta[b]pyridine-1-carboxylate (19)

Following general procedure F, 19 (155 mg, 0.517 mmol, 80%) was obtained as a colorless oil; changes from the standard procedure include heating at 120 °C for 5 h and purification of the product by silica gel column chromatography (10:1 hexanes:Et₂O). HPLC analysis indicated an enantiomeric excess of 91% [CHIRALCEL OJ column; flow: 1.0 mL/min; 96% n-hexane/4% i-PrOH; λ = 220 nm; major enantiomer t_R = 7.3 min]. ${[\alpha ]}_{589}^{23}+63.8,{[\alpha ]}_{577}^{23}+64.8,{[\alpha ]}_{546}^{23}+72.9,{[\alpha ]}_{435}^{23}+124(c0.79,{\text{CH}}_2{\text{Cl}}_2)$. . ¹H NMR (500 MHz, DMSO-d₆, 298 K) δ 7.38–7.29 (m, 5H), 5.80 (ddt, J = 16.7, 10.4, 7.5 Hz, 1H), 5.08–4.96 (m, 4H), 3.81 (ddd, J = 13.4, 6.4, 3.3 Hz, 1H), 2.96 (ddd, J = 13.4, 11.2, 5.0 Hz, 1H), 2.61 (dd, J = 13.8, 7.4 Hz, 1H), 2.26 (dd, J = 13.8, 7.6 Hz, 1H), 2.20–2.14 (m, 1H), 2.04–1.97 (m, 2H), 1.78–1.71 (m, 1H), 1.67–1.34 (m, 7H); ¹³C NMR (125 MHz, DMSO-d₆, 298 K) δ 155.3, 137.1, 134.7, 128.3, 127.6, 127.5, 117.5, 66.6, 65.7, 41.7, 40.9, 40.1, 37.5, 28.7, 24.0, 21.1, 20.7; IR (thin film, cm^-1) 2948, 1702, 1410, 1218; HRMS (ESI) m/z: [M + Na]⁺ Calcd for C₁₉H₂₅NO₂Na 322.1783; Found: 322.1778.

(4aR, 8aS)-Benzyl 8a-allyloctahydroquinoline-1(2H)-carboxylate (cis-20) and (4aR, 8aR)-benzyl 8a-allyloctahydroquinoline-1(2H)-carboxylate (trans-20)

Octahydroquinoline cis-20 was isolated as a colorless oil (80 mg, 0.25 mmol, 41%) and trans-20 was isolated as a colorless oil (66 mg, 0.21 mmol, 34%). Changes from the standard procedure include heating at 120 °C for 5 h and separation of the products by flash chromatography on silica gel (20:1 hexanes:Et₂O). cis-20: HPLC analysis indicated an enantiomeric excess of 93% [CHIRALCEL OJ column; flow: 1.0 mL/min; 96% n-hexane/4% i-PrOH; λ = 220 nm; major enantiomer t_R = 6.2 min; minor enantiomer t_R = 7.9 min]. ${[\alpha ]}_{589}^{23}+50.1,{[\alpha ]}_{577}^{23}+53.2,{[\alpha ]}_{546}^{23}+60.4,{[\alpha ]}_{435}^{23}+104(c1.05,{\text{CH}}_2{\text{Cl}}_2)$. ¹H NMR (500 MHz, DMSO-d₆, 348 K) δ 7.39-7.28 (m, 5H), 5.76 (ddt, J = 17.5, 10.0, 7.3 Hz, 1H), 5.07–5.00 (m, 4H), 3.79 (dt, J = 13.2, 4.7 Hz, 1H), 3.26–3.20 (m, 1H), 2.68 (dt, J = 7.3, 1.2 Hz, 1H), 2.33 (ddd, J = 12.7, 8.3, 3.8 Hz, 1H), 1.83–1.64 (m, 4H), 1.60–1.48 (m, 5H), 1.46–1.27 (m, 3H); ¹³C NMR (125 MHz, DMSO-d₆, 348 K) δ 154.9, 136.9, 133.8, 127.8, 127.1, 127.0, 116.9, 65.3, 60.1, 40.8, 38.3, 35.7, 32.2, 27.3, 23.1, 21.9, 21.7, 20.6; IR (thin film, cm^-1) 2934, 1697, 1398, 1261; HRMS (ESI) m/z: [M + Na]⁺ Calcd for C₂₀H₂₇NO₂Na 336.1939; Found: 336.1938. trans-20: HPLC analysis indicated an enantiomeric excess of 93% [CHIRALCEL OJ column; flow: 1.0 mL/min; 96% n-hexane/4% i-PrOH; λ = 220 nm; major enantiomer t_R = 6.5 min; minor enantiomer t_R = 8.0 min]. ${[\alpha ]}_{589}^{23}+20.3,{[\alpha ]}_{577}^{23}+20.5,{[\alpha ]}_{546}^{23}+22.7,{[\alpha ]}_{435}^{23}+35.7(c1.17,{\text{CH}}_2{\text{Cl}}_2)$. ¹H NMR (500 MHz, DMSO-d₆) δ 7.37–7.28 (m, 5H), 5.69 (ddt, J = 17.2, 10.1, 7.2 Hz, 1H), 5.10 (d, J = 17.1 Hz, 1H), 5.00–4.93 (m, 3H), 3.97 (dt, J = 14.0, 4.4 Hz, 1H), 3.08 (ddd, J = 14.3, 11.4, 3.0 Hz, 1H), 2.88 (br d, J = 13.1 Hz, 1H), 2.64 (dd, J = 15.0, 7.6 Hz, 1H), 2.40 (dd, J = 14.8, 6.9 Hz, 1H), 1.64–1.52 (m, 5H), 1.51–1.30 (m, 5H), 1.29–1.18 (m, 2H); ¹³C NMR (125 MHz, DMSO-d₆, 298 K) δ 155.1, 137.3, 134.0, 128.3, 127.6, 127.4, 117.2, 65.5, 62.5, 45.2, 41.2, 35.0, 30.7, 29.6, 26.6, 25.3, 24.8, 22.7; IR (thin film, cm^-1) 2930, 1702, 1391, 1160; HRMS (ESI) m/z: [M + Na]⁺ Calcd for C₂₀H₂₇NO₂Na 336.1939; Found: 336.1947.

Preparation and Characterization of Aminoketals Employed in the Transformations Reported in Table 3

The direct precursors of 1-azabicyclic products 31a and 34a have been reported previously.⁹

N-((S)-2-Methylbut-3-en-1-yl)-2-(6,10-dioxaspiro[4.5]decan-1-yl)acetamide) (S12)

Following general procedure D, S12 (63 mg, 0.24 mmol, 85%) was obtained as a colorless solid; changes to the general procedure involve adding Et₃N (42 μL) to the amide-coupling step. ¹H NMR (500 MHz, CDCl₃) δ 6.35 (broad s, 1H), 5.72–5.69 (m, 1H), 5.08–5.03 (m, 2H), 3.94–3.87 (m, 4H), 3.32–3.29 (m, 1H), 3.09–3.08 (m, 1H), 2.62 (dd, J = 15.6, 7.0 Hz, 1H), 2.38–2.31 (m, 1H), 2.28–2.21 (m, 1H), 2.14–2.07 (m, 2H), 2.02–1.85 (m, 3H), 1.70–1.65 (m, 2H), 1.42–1.25 (m, 2H), 1.03 (d, J = 6.8 Hz, 3H); ¹³C NMR (125 MHz) δ 173.3, 141.83, 141.78, 115.1, 115.0, 108.3, 62.4, 60.8, 60.8, 46.19, 46.15, 44.67, 44.65, 38.2, 38.1, 36.2, 30.6, 29.85, 28.82, 26.06, 26.05, 21.3, 17.79, 17.75; IR (thin film, cm^-1) 3304, 3079, 2962, 1735, 1103; HRMS (ESI) m/z: [M + H]⁺ Calcd for C₁₅H₂₆NO₃ 268.1913; Found: 268.1915.

(2S)-N-(2-(6,10-dioxaspiro[4.5]decan-1-yl)ethyl)-2-methylbut-3-en-1-amine (S13)

Following general procedure E, S13 (28 mg, 0.11 mmol, 46%) was obtained as a colorless oil. ¹H NMR (500 MHz, CDCl₃) δ 5.70–5.63 (m, 1H), 5.07–4.99 (m, 2H), 3.93–3.84 (m, 4H), 2.72–2.61 (m, 2H), 2.56–2.46 (m, 2H), 2.39–2.33 (m, 1H), 2.11 (dddd, J = 7.7, 7.7, 7.7, 7.7 Hz, 1H), 2.02–1.97 (m, 1H), 1.87–1.79 (m, 3H), 1.68-1.57 (m, 3H), 1.43–1.25 (m, 4H), 1.00 (d, J = 6.7 Hz, 3H); ¹³C NMR (125 MHz) δ 143.0, 114.6, 114.5, 108.9, 62.2, 60.79, 55.77, 55.76, 49.1, 48.9, 47.1, 47.0, 38.5, 38.4, 30.70, 30.66, 29.4, 29.3, 29.2, 26.2, 21.3, 18.50, 18.46; IR (thin film, cm^-1) 3315, 3075, 2955, 1111; HRMS (ESI) m/z: [M + H]⁺ Calcd for C₁₅H₂₈NO₂ 254.2120; Found: 254.2127.

N-((R)-2-phenylbut-3-enyl)-2-(1,5-dioxaspiro[5.5]undecan-7-yl)acetamide (S14)

Following general procedure D, S14 (307 mg, 0.893 mmol, 55%) was obtained as a colorless oil. ¹H NMR (500 MHz, CDCl₃) δ 7.32 (t, J = 7.5 Hz, 2H), 7.25–7.21 (m, 3H), 6.00–5.93 (m, 2H), 5.15–5.09 (m, 2H), 3.98 (t, J = 11.7 Hz, 1H), 3.86 (t, J = 11.7 Hz, 1H), 3.74–3.58 (m, 3H), 3.55–3.44 (m, 2H), 2.72 (d, J = 14.6 Hz, 1H), 2.59 (d, J = 11.7 Hz, 1H), 1.95 (broad s, 1H), 1.89–1.75 (m, 2H), 1.57 (app d, J = 9.9 Hz, 3H), 1.39–1.22 (m, 4H), 1.12 (m, 1H); ¹³C NMR (125 MHz, CDCl₃) δ 173.9, 173.8, 141.54, 141.46, 139.3, 128.9, 128.03, 127.99, 127.0, 116.4, 116.3, 98.8, 98.7, 59.13, 59.10, 49.7, 49.6, 43.7, 43.6, 36.9, 36.8, 29.1, 28.9, 28.1, 25.8, 25.0, 22.4; IR (thin film, cm^-1) 3301, 2933, 1644, 1108; HRMS (ESI) m/z: [M + Na]⁺ Calcd for C₂₁H₂₉NO₃Na 366.2045; Found: 366.2051.

(2R)-N-(2-(1,5-dioxaspiro[5.5]undecan-7-yl)ethyl)-2-phenylbut-3-en-1-amine (S15)

Following general procedure E, S15 (228 mg, 0.692 mmol, 80%) was obtained as a light yellow oil. ¹H NMR (500 MHz, CDCl₃) δ 7.32 (t, J = 7.9 Hz, 2H), 7.24–7.21 (m, 3H), 6.01–5.94 (m, 1H), 5.15–5.10 (m, 2H), 4.01 (tt, J = 11.4, 3.2 Hz, 1H), 3.88 (t, J = 10.1 Hz, 1H), 3.78–3.76 (m, 2H), 3.55 (q, J = 7.6 Hz, 1H), 2.95–2.87 (m, 2H), 2.72–2.65 (m, 1H), 2.62–2.55 (m, 1H), 2.46 (app broad s, 1H), 1.99–1.86 (m, 2H), 1.59–1.52 (m, 3H), 1.45–1.22 (m, 8H); ¹³C NMR (125 MHz, CDCl₃) δ 142.7, 140.40, 140.37, 128.9, 128.8, 127.94, 127.92, 126.77, 126.75, 116.0, 115.9, 99.2, 59.14, 59.08, 54.7, 54.6, 50.1, 48.92, 48.86, 28.6, 28.3, 28.1, 25.8, 24.5, 22.5; IR (thin film, cm^-1) 3319, 3080, 2933, 1108; HRMS (ESI) m/z: [M + H]⁺ Calcd for C₂₁H₃₂NO₂ 330.2433; Found: 330.2437.

N-((S)-2-Methylbut-3-en-1-yl)-2-(1,5-dioxaspiro[5.5]undecan-7-yl)acetamide (S16)

Following general procedure D, S16 (83 mg, 0.29 mmol, 80%) was obtained as a colorless solid; changes to the general procedure involve the addition of Et₃N (56.0 μL) to the amide coupling step. ¹H NMR (500 MHz, CDCl₃) δ 5.92 (broad s, 1H), 5.71–5.64 (m, 1H), 5.07–5.05 (m, 2H), 4.05 (app dt, J = 11.8, 2.8 Hz, 1H), 3.93 (app dt, J = 11.8, 2.8 Hz, 1H), 3.80–3.78 (m, 2H), 3.35–3.27 (m, 1H), 3.07–2.98 (m, 1H), 2.76 (dd, J = 14.3, 4.6 Hz, 1H), 2.61 (broad d, J = 12.9 Hz, 1H), 2.35–2.29 (m, 1H), 2.04–1.95 (m, 1H), 1.94–1.87 (m, 2H), 1.65–1.58 (m, 3H), 1.41–1.18 (m, 5H), 1.01 (d, J = 6.9 Hz, 3H); ¹³C NMR (125 MHz, CDCl₃) δ 173.80, 173.79, 141.84, 141.82, 115.14, 115.09, 98.8, 59.20, 59.15, 44.51, 44.48, 38.34, 38.26, 36.9, 36.8, 29.03, 28.98, 28.2, 25.8, 25.0, 22.4, 17.8, 17.7; IR (thin film, cm^-1) 3079, 2933, 1643; HRMS (ESI) m/z: [M + Na]⁺ Calcd for C₁₆H₂₇NO₃Na 304.1889; Found: 304.1881.

2S)-N-(2-(1,5-Dioxaspiro[5.5]undecan-7-yl)ethyl)-2-methylbut-3-en-1-amine (S17)

Following the general procedure, S17 (24 mg, 0.095 mmol, 74%) was obtained as a colorless oil. ¹H NMR (500 MHz, CDCl₃) δ 5.65–5.61 (m, 1H), 5.06–4.98 (m, 2H), 4.01 (app dt, J = 11.5, 2.8 Hz, 1H), 3.88 (app dt, J = 11.2, 2.1 Hz, 1H), 3.78–3.76 (m, 2H), 2.66–2.29 (m, 1H), 2.57–2.43 (m, 4H), 2.36–2.33 (m, 1H), 1.96–1.88 (m, 2H), 1.60–1.55 (m, 4H), 1.42–1.24 (m, 7H), 0.99 (d, J = 6.7 Hz, 3H); ¹³C NMR (125 MHz, CDCl₃) δ 143.0, 114.6, 114.5, 99.2, 59.2, 59.1, 55.83, 55.76, 49.2, 49.0, 38.5, 38.4, 28.7, 28.6, 28.4, 28.3, 28.1, 25.8, 24.4, 22.5, 18.53, 18.48; IR (thin film, cm^-1) 2933, 2862, 1446; HRMS (ESI) m/z: [M + H]⁺ Calcd for C₁₆H₃₀NO₂ 268.2277; Found: 268.2271.

N-((R)-2-Phenylbut-3-enyl)-3-(6,10-dioxaspiro[4.5]decan-1-yl)propanamide (S18)

Following general procedure D, S18 (408 mg, 1.19 mmol, 73%) was obtained as a colorless oil. ¹H NMR (500 MHz, CDCl₃) δ 7.32 (t, J = 7.5 Hz, 2H), 7.24–7.21 (m, 3H), 5.99–5.92 (m, 2H), 5.14–5.09 (m, 2H), 3.88 (tt, J = 11.7, 2.4 Hz, 1H), 3.83–3.78 (m, 2H), 3.77–3.72 (m, 1H), 3.70–3.61 (m, 1H), 3.54–3.46 (m, 2H), 2.41–2.35 (m, 1H), 2.24–2.17 (m, 1H), 2.14–2.08 (m, 1H), 1.98–1.87 (m, 1H), 1.85–1.66 (m, 4H), 1.64–1.52 (m, 3H), 1.34 (dt, J = 13.2, 2.4 Hz, 1H), 1.29–1.19 (m, 1H); ¹³C NMR (125 MHz, CDCl₃) δ 173.98, 173.97, 141.5, 139.34, 139.28, 128.84, 128.82, 128.02, 127.98, 127.0, 116.33, 116.31, 108.8, 62.31, 62.28, 60.5, 49.62, 49.57, 47.5, 43.5, 35.2, 30.81, 30.77, 29.55, 29.54, 26.1, 25.1, 21.29, 21.27; IR (thin film, cm^-1) 3299, 3083, 2958, 1646; HRMS (ESI) m/z: [M + Na]⁺ Calcd for C₂₁H₂₉NO₃Na 366.2045; Found: 366.2044.

(2R)-N-(3-(6,10-Dioxaspiro[4.5]decan-1-yl)propyl)-2-phenylbut-3-en-1-amine (S19)

Following general procedure E, S19 (330 mg, 1.00 mmol, 88% yield) was obtained as light yellow oil. ¹H NMR (500 MHz, CDCl₃) δ 7.32 (t, J = 7.6 Hz, 2H), 7.24–7.21 (m, 3H), 6.01–5.94 (m, 1H), 5.15–5.11 (m, 2H), 3.93–3.82 (m, 4H), 3.55 (q, J = 7.4 Hz, 1H), 2.90 (d, J = 7.4 Hz, 2H), 2.68–2.59 (m, 2H), 2.11–2.05 (m, 1H), 2.03–1.93 (m, 1H), 1.89–1.37 (m, 9H), 1.30–1.12 (m, 3H); ¹³C NMR (125 MHz, CDCl₃) δ 142.6, 140.3, 128.9, 127.9, 126.8, 116.1, 109.0, 62.2, 60.8, 54.5, 50.3, 50.1, 48.9, 30.7, 29.0, 28.9, 26.3, 26.2, 21.2; IR (thin film, cm^-1) 3332, 3081, 2863, 1148, 1109; HRMS (ESI) m/z: [M + H]⁺ Calcd for C₂₁H₃₂O₂N 330.2433; Found: 330.2429.

N-((S)-2-Methylbut-3-en-1-yl)-3-(6,10-dioxaspiro[4.5]decan-1-yl)propanamide (S20)

Following general procedure D, S20 (59 mg, 0.21 mmol, 72%) was obtained as a colorless solid; changes in the procedure include the addition of Et₃N (45 μL) to the amide-coupling step. ¹H NMR (500 MHz, CDCl₃) δ 5.95 (broad s, 1H), 5.73–5.66 (m, 1H), 5.08–5.03 (m, 2H), 3.95–3.87 (m, 4H), 3.32 (ddd, J = 12.7, 6.0, 6.0 Hz, 1H), 3.08–3.03 (m, 1H), 2.41–2.39 (m, 1H), 2.31–2.29 (m, 1H), 2.26–2.22 (m, 1H), 2.18–2.12 (m, 1H), 2.02–2.00 (m, 1H), 1.90–1.81 (m, 3H), 1.78–1.76 (m, 1H), 1.66–1.60 (m, 3H), 1.39 (d, J = 13.3 Hz, 1H), 1.31–1.27 (m, 1H), 1.02 (d, J = 6.8 Hz, 3H); ¹³C NMR (125 MHz, CDCl₃) δ 173.9, 141.8, 141.7, 115.1, 115.0, 108.9, 62.3, 60.5, 47.72, 47.71, 44.5, 44.4, 38.2, 38.1, 35.4, 30.9, 30.8, 29.50, 29.46, 26.1, 25.1, 25.0, 21.29, 21.27, 17.72, 17.68; IR (thin film, cm^-1) 3298, 3080, 2960, 1644; HRMS (ESI) m/z: [M + Na]⁺ Calcd for C₁₆H₂₇NO₃Na 304.1889; Found: 304.1882.

(2S)-N-(3-(6,10-Dioxaspiro[4.5]decan-1-yl)propyl)-2-methylbut-3-en-1-amine (S21)

Following general procedure E, S21 (26 mg, 0.097 mmol, 46%) was obtained as a colorless oil. ¹H NMR (500 MHz, CDCl₃) δ 5.69–5.62 (m, 1H), 5.11–5.00 (m, 2H), 3.93–3.85 (m, 4H), 2.62–2.52 (m, 3H), 2.49–2.45 (m, 1H), 2.38–2.35 (m, 1H), 2.11–2.05 (m, 1H), 1.98–1.96 (m, 1H), 1.89–1.78 (m, 3H), 1.65–1.51 (m, 5H), 1.39 (d, J = 14.7 Hz, 1H), 1.32–1.12 (m, 2H), 1.00 (d, J = 6.7 Hz, 3H), 0.89–0.88 (m, 1H); ¹³C NMR (125 MHz, CDCl₃) δ 142.8, 114.69, 114.68, 108.9, 62.1, 60.6, 55.50, 55.49, 60.4, 48.87, 48.85, 38.3, 36.8, 30.6, 30.4, 29.8, 28.9, 28.8, 28.6, 26.2, 26.1, 24.9, 23.7, 21.1, 18.5, 18.4, 17.8; IR (thin film, cm^-1) 3076, 2955, 2863; HRMS (ESI) m/z: [M + H]⁺ Calcd for C₁₆H₃₀NO₂ 268.2277; Found: 268.2271.

2-(11-Methyl-1,5-dioxaspiro[5.5]undecan-7-yl)-N-((S)-2-methylbut-3-en-1-yl)acetamide (S22)

Following general procedure D, S22 (31 mg, 0.11 mmol, 70%) was obtained as a colorless solid; changes to the general procedure include addition Et₃N (23 μL) to the amide coupling step. ¹H NMR (500 MHz, CDCl₃) δ 5.85 (broad d, J = 26.6 Hz, 1H), 5.69–5.66 (m, 1H), 5.07–5.04 (m, 2H), 3.95–3.80 (m, 4H), 3.34–3.29 (m, 1H), 3.04–3.01 (m, 1H), 2.78–2.58 (m, 1H), 2.50–2.44 (m, 1H), 2.35–2.29 (m, 1H), 2.19–2.10 (m, 1H), 2.03 (dd, J = 14.3, 4.6 Hz, 1H), 1.98–1.90 (m, 1H), 1.85–1.81 (m, 1H), 1.67–1.52 (m, 2H), 1.52–1.42 (m, 1H), 1.39–1.32 (m, 3H), 1.02 (d, J = 6.6 Hz, 3H), 0.96 (d, J = 7.0 Hz, 3H); ¹³C NMR (125 MHz, CDCl₃) δ 172.0, 141.7, 141.6, 115.24, 115.16, 58.7, 58.6, 48.13, 48.11, 45.6, 44.50, 44.46, 44.4, 38.31, 38.30, 38.24, 38.19, 37.4, 37.12, 37.11, 36.8, 35.58, 35.56, 25.51, 25.48, 19.7, 17.69, 17.65, 14.6, 13.7; IR (thin film, cm^-1) 3296, 3078, 2963, 1640; HRMS (ESI) m/z: [M + Na]⁺ Calcd for C₁₇H₂₉NO₃Na 318.2045;, Found: 318.2047.

(2S)-2-Methyl-N-(2-(11-methyl-1,5-dioxaspiro[5.5]undecan-7-yl)ethyl)but-3-en-1-amine (S23)

Following general procedure E, S23 (42 mg, 0.15 mmol, 48%) was obtained as a colorless oil. ¹H NMR (500 MHz, CDCl₃) δ 5.71–5.63 (m, 1H), 5.08–5.00 (m, 2H), 3.84 (broad s, 4H), 2.71–2.63 (m, 1H), 2.60–2.45 (m, 3H), 2.39–2.34 (m, 1H), 1.90–1.51 (m, 7H), 1.44–1.36 (m, 5H), 1.01 (d, J = 6.6 Hz, 3H), 0.93 (d, J = 6.8 Hz, 3H); ¹³C NMR (125 MHz, CDCl₃) δ 143.0, 114.61, 114.56, 100.7, 58.7, 58.5, 55.74, 55.67, 49.1, 48.9, 38.5, 38.4, 25.6, 19.7, 18.5, 18.4, 13.9; IR (thin film, cm^-1) 3076, 2931, 2861; HRMS (ESI) m/z: [M + H]⁺ Calcd for C₁₇H₃₂NO₂ 282.2433; Found: 282.2428.

Preparation and Characterization Data of 1-Azabicyclic Products Reported in Table 3

Characterization data for azabicyclic compounds 31a, 32a, 33a, and 34a have been described.⁹

General Procedure G for the 2-Aza-Cope Rearrangement and Subsequent Cbz Protection to Provide Products Reported in Tables 3 and 4

(3aS,6aR)-Benzyl 6a-((E)-but-2-en-1-yl)hexahydrocyclopenta[b]pyrrole-1(2H)-carboxylate (31b)

A mixture of aminoketal S13 (28 mg, 0.12 mmol), morpholine (1 μL, 0.011 mmol), TFA (13 μL, 0.11 mmol), and dimedone (29 mg, 0.28 mmol) was stirred at 120 °C in a sealed 1-dram vial using an aluminum heating block. After 30 min, the reaction vessel was cooled in an ice bath for approximately 1 min. The reaction mixture was allowed to warm to room temperature, dissolved in CHCl₃ (1 mL) and transferred to a larger reaction vessel. To this flask was added saturated aqueous Na₂CO₃ (0.5 mL), H₂O (0.5 mL), and benzyl chloroformate (57 μL, 0.34 mmol). The reaction was vigorously stirred at room temperature for 24 h, then extracted with CH₂Cl₂ (3 × 5 mL). The combined organic extracts were dried (MgSO₄), filtered, and concentrated in vacuo. The crude residue was purified on silica gel (1:19 EtOAc:hexanes) to provide 24 mg (0.081 mmol, 73%) of 31b as a colorless oil. HPLC analysis indicated an enantiomeric excess of 95% [CHIRALCEL AD column; flow: 1 mL/min; 98% n-hexane/2% i-PrOH; λ = 210 nm; major enantiomer t_R = 11.25 min; minor enantiomer t_R = 13.89 min]. ${[\alpha ]}_{577}^{23}-7.88,{[\alpha ]}_{546}^{23}-6.81,{[\alpha ]}_{435}^{23}-14.0(c0.45,{\text{CH}}_2{\text{Cl}}_2)$. ¹H NMR (500 MHz, DMSO-d₆, 393K) δ 7.36–7.28 (m, 5H), 5.46–5.32 (m, 2H), 5.11 (d, J = 12.7 Hz, 1H), 5.06 (d, J = 12.7 Hz, 1H), 3.52–3.46 (m, 1H), 3.43–3.39 (m, 1H), 2.69 (dd, J = 12.1, 6.3 Hz, 1H), 2.43 (dddd, J = 8.6, 8.6, 5.3, 5.3 Hz, 1H), 2.27 (dd, J = 15.8, 8.4 Hz, 1H), 2.15–2.11 (m, 1H), 1.93–1.86 (m, 1H), 1.81 (dddd, J = 15.4, 7.3, 7.3, 7.3 Hz, 1H), 1.72–1.45 (m, 4H), 1.62 (d, J = 5.8 Hz, 3H), 1.43–1.37 (m, 1H); ¹³C NMR (125 MHz, DMSO-d₆, 393K) δ 152.8, 136.9, 127.5, 126.8, 126.70, 126.67, 125.8, 125.0, 73.4, 64.9, 47.3, 47.1, 37.3, 31.2, 27.8, 24.1, 16.7; IR (thin film, cm^-1) 2948, 1699; HRMS (ESI) m/z: [M + H]⁺ Calcd for C₁₉H₂₆NO₂ 300.1964; Found: 300.1960.

(3aS,7aR)-Benzyl 7a-((E)-but-2-en-1-yl)octahydro-1H-indole-1-carboxylate) (32b)

Following general procedure G, 32b (25 mg, 0.078 mmol, 75%) was obtained as a colorless oil. HPLC analysis indicated an enantiomeric excess of 95% [CHIRALCEL AD column; flow: 1.0 mL/min; 98% n-hexane/2% i-PrOH; λ = 210 nm; major enantiomer t_R = 13.47 min; minor enantiomer t_R = 17.22 min]. ${[\alpha ]}_{589}^{23}-47.2,{[\alpha ]}_{577}^{23}-48.0,{[\alpha ]}_{546}^{23}-54.7,{[\alpha ]}_{435}^{23}-94.3(c0.43,{\text{CH}}_2{\text{Cl}}_2)$. ¹H NMR (500 MHz, DMSO-d₆, 393K) δ 7.38–7.27 (m, 5H), 5.41–5.37 (m, 1H), 5.30–5.29 (m, 1H), 5.07 (d, J = 12.7 Hz, 1H), 5.01 (d, J = 12.2 Hz, 1H), 3.56–3.52 (m, 1H), 3.24 (app dd, J = 16.3, 7.9 Hz, 1H), 2.43 (dd, J = 16.2, 6.0 Hz, 1H), 2.33 (dd, J = 13.6, 7.8 Hz, 1H), 2.06–2.02 (m, 1H), 1.89–1.64 (m, 4H), 1.58 (d, J = 5.6 Hz, 3H), 1.46–1.26 (m, 6H); ¹³C NMR (125 MHz, DMSO-d₆, 393K) δ 152.9, 137.0, 127.6, 126.8, 126.7, 126.3, 124.9, 64.8, 63.3, 45.5, 40.1, 37.4, 31.5, 25.4, 24.8, 21.0, 20.6, 16.8; IR (thin film, cm^-1) 3029, 2928, 2857, 1701; HRMS (ESI) m/z: [M + Na]⁺ Calcd for C₂₀H₂₇NO₂Na 336.1939; Found: 336.1934.

(4aS,7aR)-Benzyl 7a-((E)-but-2-en-1-yl)octahydro-1H-cyclopenta[b]pyridine-1-carboxylate (33b)

Following general procedure G, 33b (42 mg, 0.13 mmol, 71%) was obtained as a colorless oil. HPLC analysis indicated an enantiomeric excess of 95% [CHIRALCEL OJ column; flow: 0.5 mL/min; 99.9% n-hexane/0.1% i-PrOH; λ = 210 nm; major enantiomer t_R = 44.40 min; minor enantiomer t_R = 5.46 min (for the opposite enantiomer as shown above)]. ${[\alpha ]}_{589}^{23}-13.0,{[\alpha ]}_{577}^{23}-13.8,{[\alpha ]}_{546}^{23}-14.9,{[\alpha ]}_{435}^{23}-28.8(c0.36,{\text{CH}}_2{\text{Cl}}_2)$. ¹H NMR (500 MHz, CDCl₃) δ 7.35–7.31 (m, 5H), 5.46–5.38 (m, 2H), 5.15 (d, J = 12.4 Hz, 1H), 3.96 (d, J = 12.6 Hz, 1H), 3.96 (app dd, J = 13.4, 5.7 Hz, 1H), 2.97 (app dt, J = 13.2, 4.8 Hz, 1H), 2.62 (dd, J = 12.7, 4.4 Hz, 1H), 2.19–2.12 (m, 3H), 2.10–2.08 (m, 1H), 1.77–1.67 (m, 3H), 1.64 (d, J = 4.9 Hz, 3H), 1.57–1.42 (m, 5H); ¹³C NMR (125 MHz, CDCl₃) δ 156.6, 137.3, 128.53, 128.52, 128.49, 128.2, 128.0, 127.9, 127.1, 67.6, 66.7, 42.3, 41.4, 39.5, 38.3, 29.5, 24.7, 21.8, 21.4, 18.2; IR (thin film, cm^-1) 3031, 2922, 2851, 1745; HRMS (ESI) m/z: [M + Na]⁺ Calcd for C₂₀H₂₇NO₂Na 336.1939; Found: 336.1931.

(3aS,7R,7aS)-Benzyl 7a-((E)-but-2-en-1-yl)-7-methyloctahydro-1H-indole-1-carboxylate (34b)

Following general procedure G, 34b (12 mg, 0.035 mmol, 70%) was obtained as a colorless oil. HPLC analysis indicated an enantiomeric excess of 91% [CHIRALCEL AD column; flow: 1.0 mL/min; 98% n-hexane/2% i-PrOH; λ = 210 nm; major enantiomer t_R = 9.02 min; minor enantiomer t_R = 20.11 min (for the opposite enantiomer as shown above)]. ${[\alpha ]}_{589}^{23}-34.3,{[\alpha ]}_{577}^{23}-39.4,{[\alpha ]}_{546}^{23}-44.8,{[\alpha ]}_{435}^{23}-78.3(c0.87,{\text{CH}}_2{\text{Cl}}_2)$; data is for the opposite enantiomer as shown above). ¹H NMR (500 MHz, DMSO-d₆, 393K) δ 7.42–7.34 (m, 5H), 5.49–5.47 (m, 1H), 5.23–5.19 (m, 1H), 5.13 (d, J = 12.1 Hz, 1H), 5.07 (d, J = 12.6 Hz, 1H), 3.54–3.51 (m, 1H), 3.40–3.33 (m, 1H), 3.26–3.22 (m, 1H), 2.21–2.14 (m, 2H), 1.98–1.90 (m, 2H), 1.71–1.42 (m, 7H), 1.61 (d, J = 23.9 Hz, 3H), 1.00 (broad s, 3H); ¹³C NMR (125 MHz, DMSO-d₆, 393K) δ 154.4, 128.7, 128.5, 128.2, 128.1, 127.8, 127.64, 127.55, 125.7, 67.4, 65.7, 46.4, 37.1, 31.8, 29.9, 24.9, 24.7, 24.4, 20.2, 17.8, 17.1; IR (thin film, cm^-1) 3028, 2826, 2885, 1704; HRMS (ESI) m/z: [M + Na]⁺ Calcd for C₂₁H₂₉NO₂Na 350.2096; Found: 350.2098.

Synthesis and Characterization Data of 1-Azabicyclics Reported in Table 4 and Their Precursors

N-((R)-2-phenylbut-3-enyl)-3-(1,5-dioxaspiro[5.5]undecan-7-yl)propanamide (S24)

Following general procedure D, S24 (496 mg, 1.39 mmol, 86%) was obtained as a colorless oil. ¹H NMR (500 MHz, CDCl₃) δ 7.32 (t, J = 7.5 Hz, 2H), 7.27–7.21 (m, 3H), 6.00–5.93 (m, 2H), 5.15–5.10 (m, 2H), 4.03–3.97 (m, 1H), 3.88 (tt, J = 11.7, 3.1 Hz, 1H), 3.77–3.60 (m, 3H), 3.53–3.46 (m, 2H), 2.54 (app d, J = 12.7 Hz, 1H), 2.35–2.28 (m, 1H), 2.15–2.02 (m, 2H), 1.96–1.83 (m, 1H), 1.59–1.53 (m, 3H), 1.39–1.07 (m, 7H); ¹³C NMR (125 MHz, CDCl₃) δ 173.65, 173.63, 141.54, 141.52, 139.29, 139.25, 128.9, 128.8, 128.01, 127.97, 126.99, 126.98, 116.41, 116.37, 99.3, 59.15, 59.13, 59.0, 49.6, 49.5, 44.7, 43.7, 35.4, 35.3, 28.2, 28.0, 25.8, 24.8, 24.43, 24.41, 22.4; IR (thin film, cm^-1) 3299, 3083, 2861, 1644; HRMS (ESI) m/z: (M + Na]⁺ Calcd for C₂₂H₃₁NO₃Na 380.2202; Found: 380.2200.

(2R)-N-(3-(1,5-dioxaspiro[5.5]undecan-7-yl)propyl)-2-phenylbut-3-en-1-amine (S25)

Following general procedure E, S25 (229 mg, 0.667 mmol, 49%) was obtained as a light yellow oil. ¹H NMR (500 MHz, CDCl₃) δ 7.32 (t, J = 7.6 Hz, 2H), 7.23–7.22 (m, 3H), 5.99–5.93 (m, 1H), 5.14–5.11 (m, 2H), 4.02 (t, J = 11.2 Hz, 1H), 3.89 (dt, J = 11.3, 2.3 Hz, 1H), 3.78 (app broad s, 2H), 3.54 (q, J = 7.5 Hz, 1H), 2.90 (d, J = 7.4 Hz, 2H), 2.64–2.60 (m, 2H), 2.45 (broad d, J = 8.8 Hz, 1H), 1.90–1.10 (m, 15H); ¹³C NMR (125 MHz, CDCl₃) δ 142.6, 140.3, 128.8, 128.0, 127.9, 126.8, 116.0, 99.3, 59.1, 59.0, 54.5, 50.3, 50.1, 28.5, 28.3, 27.3, 25.8, 25.2, 24.4, 22.5; IR (thin film, cm^-1) 3315, 3081, 2933; HRMS (ESI) m/z: [M + H]⁺ Calcd for C₂₂H₃₄NO₂ 344.2589; Found: 344.2583. Characterization data for azabicyclic compound 35 has been described.⁹

Benzyl 2-(2-oxocyclododecyl)acetate (S26)

Following general procedure B, S26 (825 mg, 2.50 mmol, 64%) was obtained as a colorless solid. mp 64–65 °C; ¹H NMR (500 MHz, CDCl₃) δ 7.38–7.31 (m, 5H), 5.13–5.06 (m, 2H), 3.18–3.13 (m, 1H), 2.96–2.87 (m, 2H), 2.32 (dd, J = 16.7, 5.2 Hz, 1H), 2.25 (ddd, J = 17.7, 5.8, 3.6 Hz, 1H), 2.04–1.98 (m, 1H), 1.89–1.83 (m, 1H), 1.60–1.53 (m, 1H), 1.42–1.17 (m, 14H), 1.08–1.06 (m, 1H); ¹³C NMR (125 MHz, CDCl₃) δ 212.4, 172.7, 136.1, 128.8, 128.43, 128.40, 66.6, 47.3, 37.6, 34.3, 28.6, 26.3, 24.1, 23.3, 22.7, 22.4, 21.8, 21.2; IR (thin film, cm^-1) 3033, 2931, 2864, 1735, 1709, 1164; HRMS (ES) m/z: [M + Na]⁺ Calcd for C₂₁H₃₀O₃Na 353.2093; Found: 353.2084.

(1,5-Dioxa-spiro[5.11]heptadec-7-yl)-acetic acid benzyl ester (S27)

Following general procedure C, ketal S27 was obtained as a colorless oil (430 mg, 1.10 mmol, 91%). This product was purified by flash chromatography on silica gel (100:0 to 98:2 to 95:5 hexanes:EtOAc). ¹H NMR (500 MHz, CDCl₃) δ 7.40–7.29 (m, 5H), 5.15–5.08 (m, 2H), 4.00 (t, J = 11.5 Hz, 1H), 3.78–3.73 (m, 2H), 3.53 (dd, J = 11.0, 4.1 Hz, 1H), 2.82 (dd, J = 15.3, 8.7 Hz, 1H), 2.43 (t, J = 8.7 Hz, 1H), 2.30–2.23 (m, 1H), 2.10 (dd, J = 15.3, 2.4 Hz, 1H), 1.98–1.90 (m, 1H), 1.61–1.22 (m, 19H), 1.11–1.06 (m, 1H); ¹³C NMR (125 MHz, CDCl₃) δ 174.7, 136.9, 128.5, 128.3, 128.0, 102.4, 65.8, 59.6, 59.5, 39.1, 34.4, 26.43, 26.37, 25.8, 25.4, 24.6, 23.6, 22.9, 22.7, 22.4, 22.2, 19.3; IR (thin film, cm^-1) 3063, 2931, 2862, 1736, 1248, 1142; HRMS (ES) m/z: [M + Na]⁺ Calcd for C₂₄H₃₆O₄Na 411.2511; Found: 411.2515.

N-((R)-2-Phenylbut-3-enyl)-2-(1,5-dioxaspiro[5.11]heptadecan-7-yl)acetamide (S28)

Following general procedure D, S28 (171 mg, 0.400 mmol, 71%) was obtained as an amorphous colorless solid. ¹H NMR (500 MHz, CDCl₃) δ 7.32 (t, J = 7.9 Hz, 2H), 7.23–7.21 (m, 3H), 6.31 (d, J = 18.8 Hz, 1H), 5.96 (dddd, J = 17.2, 9.9, 6.9, 2.5 Hz, 1H), 5.14–5.07 (m, 2H), 3.99 (t, J = 12.1 Hz, 1H), 3.80–3.69 (m, 3H), 3.64–3.42 (m, 4H), 2.78 (dt, J = 15.1, 5.8 Hz, 1H), 2.25 (ddd, J = 14.8, 11.7, 7.5 Hz, 1H), 2.06 (t, J = 7.7 Hz, 1H), 1.93 (ddd, J = 15.3, 7.6, 2.6 Hz, 1H), 1.88–1.77 (m, 2H), 1.56–1.20 (m, 17H), 1.09–1.04 (m, 1H); ¹³C NMR (125 MHz, CDCl₃) δ 174.9, 174.8, 141.64, 141.58, 139.6, 139.5, 128.87, 128.85, 128.03, 127.99, 126.9, 116.2, 116.1, 102.9, 59.64, 59.58, 59.3, 49.6, 49.4, 43.5, 43.4, 39.5, 39.4, 37.5, 37.4, 27.2, 27.1, 26.4, 26.3, 25.5, 24.5, 23.6, 22.74, 22.65, 22.47, 22.45, 22.1, 19.3; IR (thin film, cm^-1) 3323, 2931, 2863, 1647, 1140, 1117, 1089; HRMS (ESI) m/z: [M + Na]⁺ Calcd for C₂₇H₄₁NO₃Na 450.2984; Found: 450.2972.

(2R)-N-(2-(1,5-Dioxaspiro[5.11]heptadecan-7-yl)ethyl)-2-phenylbut-3-en-1-amine (S29)

Following general procedure E, S29 (81 mg, 0.20 mmol, 58%) was obtained as a colorless oil. ¹H NMR (500 MHz, CDCl₃) δ 7.32 (t, J = 7.5 Hz, 2H), 7.25–7.20 (m, 3H), 6.01–5.95 (m, 1H), 5.14–5.10 (m, 2H), 4.02 (t, J = 11.9 Hz, 1H), 3.84 (q, J = 11.4 Hz, 1H), 3.77–3.69 (m, 2H), 3.57 (q, J = 7.3 Hz, 1H), 2.92 (d, J = 7.3 Hz, 2H), 2.72–2.69 (m, 2H), 2.32–2.26 (m, 1H), 2.07–1.93 (m, 2H), 1.56–1.23 (m, 22H), 1.12–1.08 (m, 1H); ¹³C NMR (125 MHz, CDCl₃) δ 142.77, 142.75, 140.52, 140.48, 128.8, 127.94, 127.90, 126.7, 115.9, 115.8, 103.31, 103.27, 59.5, 59.4, 54.6, 50.3, 50.2, 50.1, 39.9, 39.8, 29.93, 29.91, 27.1, 27.0, 26.6, 26.4, 25.6, 25.11, 25.09, 24.0, 23.14, 23.10, 23.0, 22.6, 22.3, 19.5; IR (thin film, cm^-1) 3327, 3026, 2929, 2861, 1467, 1245, 1112; HRMS (ESI) m/z: [M + H]⁺ Calcd for C₂₇H₄₄O₂N 414.3372; Found: 414.3362.

(3aS,13aR)-Benzyl 13a-((Z)-3-phenylallyl)tetradecahydro-1H-cyclododeca[b]pyrrole-1-carboxylate (36)

Following general procedure E, 36 (41 mg, 89 μmol, 74%) was obtained as a colorless amorphous solid (9:1 mixture of diastereomers by ¹H NMR). The major diastereomer was partially purified by preparatory TLC (9:1 hexanes/EtOAc) for characterization. HPLC analysis indicated an en-antiomeric excess of 99% [CHIRALCEL OD column; flow: 1.0 mL/min; 99.5% n-hexane/0.5% i-PrOH; λ = 254 nm; major enantiomer t_R = 19.16 min; minor enantiomer t_R = 27.21 min]. ¹H NMR (500 MHz, DMSO-d₆, 393 K) δ 7.32–7.25 (m, 9H), 7.19–7.18 (m, 1H), 6.28 (d, J = 15.4 Hz, 1H), 6.15–6.11 (m, 1H), 5.12 (d, J = 12.6 Hz, 1H), 5.03 (d, J = 12.6 Hz, 1H), 3.51 (t, J = 9.8 Hz, 1H), 3.30–3.24 (m, 1H), 2.82–2.68 (m, 2H), 2.32 (dd, J = 14.0, 7.4 Hz, 1H), 2.26–2.22 (m, 1H), 2.09–2.07 (m, 1H), 1.90 (td, J = 12.8, 7.1 Hz, 1H), 1.69 (t, J = 11.8 Hz, 1H), 1.51–1.27 (m, 18H); ¹³C NMR (125 MHz, DMSO, 393 K) δ 137.2, 131.1, 127.9, 127.7, 127.1, 126.3, 125.2, 67.2, 65.0, 46.7, 26.3, 25.9, 25.1, 23.5, 21.59, 21.56, 21.4, 21.1, 17.9; IR (thin film, cm^-1) 3027, 2925, 2852, 1702, 1459, 1402; HRMS (ESI) m/z: [M + Na]⁺ Calcd for C₃₁H₄₁NO₂Na 482.3035; Found: 482.3034. The ring fusion geometry was assigned by ¹H NOE analysis as depicted in the drawing below.

Benzyl 2-(2-oxocycloheptyl)acetate (S30)

Keto ester S30 was prepared using an adapted procedure from Cotarco and co-workers.³⁵ A 250 mL round bottom flask with stir bar fitted with a Dean Stark trap was charged with cycloheptanone (11 mL, 89 mmol), pyrrolidine (6.4 g, 89 mmol), and benzene (60 mL) and heated to reflux. After 20 h, the reaction was concentrated in vacuo at 55 °C for 1 h. The resultant red oil was dissolved in benzene (45 mL) and 2-bromobenzylacetate (8.0 mL, 12 mmol) was added and the reaction was heated to reflux. After 24 h, the reaction was allowed to cool to 22 °C, concentrated in vacuo, taken up in MeOH (30 mL) and water (6 mL), heated to reflux for 2 h, allowed to cool to 22 °C, and partitioned between Et₂O (400 mL) and 1 M HCl (200 mL). The organic layer was washed with 1 M HCl (2 × 100 mL), saturated aqueous sodium bicarbonate (1 × 50 mL) and brine (1 × 15 mL), dried (MgSO₄), filtered, concentrated in vacuo and the residue was purified by flash chroma-tography on silica gel (2:25–3:25 EtOAc:hexanes) to give S30 (6.3 g, 24 mmol, 45%) as a colorless oil. ¹H NMR (500 MHz, CDCl₃) δ 7.36–7.27 (m, 5H), 5.12–5.05 (m, 2H), 3.10 (dddd, J = 10.9, 8.5, 5.7, 2.9 Hz, 1H), 2.87 (dd, J = 16.8, 8.4 Hz, 1H), 2.59 (dt, J = 16.3, 7.8 Hz, 1H), 2.50–2.38 (m, 1H), 2.33 (dd, J = 16.8, 5.7 Hz, 1H), 1.92–1.76 (m, 3H), 1.76–1.63 (m, 2H), 1.57–1.47 (m, 1H), 1.40–1.22 (m, 2H); ¹³C NMR (125 MHz, CDCl₃) δ 213.8, 172.2, 135.8, 128.4, 128.02, 127.98, 66.1, 47.2, 43.2, 36.5, 31.0, 29.1, 28.8, 23.3; IR (thin film, cm^-1) 2925, 2854, 1733, 1702; Anal. Calcd for C₁₆H₂₀O₃: C, 73.82; H, 7.72. Found: C, 73.49; H, 7.73.

Benzyl 2-(1,5-dioxaspiro[5.6]dodecan-7-yl)acetate (S31)

Following general procedure C, S31 (5.2 g, 16 mmol) was isolated as a colorless oil in 84% yield; changes from the general procedure include the exposure of the substrate to the reaction conditions for 2 h. ¹H NMR (500 MHz, CDCl₃) δ 7.37–7.25 (m, 5H), 5.15 (d, J = 12.4 Hz, 1H), 5.07 (d, J = 12.4 Hz, 1H), 3.94 (td, J = 11.9, 2.9 Hz, 1H), 3.81 (td, J = 11.7, 2.4 Hz, 1H), 3.73–3.67 (m, 2H), 2.92–2.84 (m, 1H), 2.27–2.18 (m, 2H), 2.09 (ddd, J = 14.8, 9.6, 2.2 Hz, 1H), 1.96–1.80 (m, 2H), 1.76–1.63 (m, 2H), 1.58–1.35 (m, 6H), 1.28 (dt, J = 10.9, 2.2 Hz, 1H); ¹³C NMR (125 MHz, CDCl₃) δ 173.8, 136.2, 128.1, 127.9, 127.7, 101.2, 65.5, 59.04, 58.96, 45.8, 35.8, 29.4, 28.0, 27.8, 26.6, 25.3, 20.3; IR (thin film, cm^-1) 2931, 2863, 1733; Anal. Calcd for C₁₉H₂₆O₄: C, 71.67; H, 8.23. Found: C, 71.45; H, 8.34.

N-((R)-2-Phenylbut-3-enyl)-2-(1,5-dioxaspiro[5.6]dodecan-7-yl)acetamide (S32)

Following general procedure D, S32 (369 mg, 1.03 mmol, 66%) was obtained as a colorless oil. ¹H NMR (500 MHz, CDCl₃) δ 7.32 (t, J = 7.4 Hz, 2H), 7.25–7.21 (m, 3H), 6.00–5.93 (m, 1H), 5.83 (app broad d, J = 5.3 Hz, 1H), 5.15–5.10 (m, 2H), 3.96 (t, J = 11.7 Hz, 1H), 3.82 (t, J = 11.6 Hz, 1H), 3.76–3.59 (m, 3H), 3.56–3.45 (m, 2H), 2.66 (dd, J = 14.6, 4.0 Hz, 1H), 2.10–2.04 (m, 2H), 2.01–1.95 (m, 2H), 1.91–1.76 (m, 2H), 1.70–1.61 (m, 2H), 1.52–1.32 (m, 6H); ¹³C NMR (125 MHz, CDCl₃) δ 173.90, 173.87, 141.50, 141.46, 139.3, 128.9, 128.0, 127.0, 116.39, 116.36, 102.1, 59.5, 59.43, 59.41, 49.7, 49.6, 46.43, 46.38, 43.7, 43.6, 38.14, 38.09, 29.79, 29.77, 28.4, 28.1, 28.0, 27.1, 25.6, 20.6; IR (thin film, cm^-1) 3296, 3080, 2928, 1643; HRMS (ESI) m/z: [M + Na]⁺ Calcd for C₂₂H₃₁NO₃Na 380.2202; Found: 380.2201.

(2R)-N-(2-(1,5-dioxaspiro[5.6]dodecan-7-yl)ethyl)-2-phenylbut-3-en-1-amine (S33)

Following general procedure E, S33 (225 mg, 0.655 mmol, 70%) was obtained as a colorless oil. ¹H NMR (500 MHz, CDCl₃) δ 7.32 (t, J = 7.5 Hz, 2H), 7.24–7.21 (m, 3H), 6.02–5.95 (m, 1H), 5.15–5.11 (m, 2H), 3.97 (tt, J = 11.3, 2.9 Hz, 1H) 3.86 (t, J = 11.0 Hz, 1H), 3.81–3.74 (m, 2H), 3.56 (q, J = 7.5 Hz, 1H), 2.97–2.88 (m, 2H), 2.71 (tt, J = 10.1, 4.8 Hz, 1H), 2.64–2.57 (m, 1H), 2.25–2.18 (m, 1H), 1.97–1.84 (m, 2H), 1.77–1.72 (m, 4H), 1.61–1.26 (m, 9H); ¹³C NMR (125 MHz, CDCl₃) δ 142.7, 140.4, 128.84, 128.82, 127.94, 127.92, 126.8, 126.7, 116.0, 115.9, 102.6, 59.5, 59.4, 54.73, 54.71, 50.2, 49.11, 49.08, 46.23, 46.19, 30.51, 30.49, 30.3, 28.74, 28.72, 27.20, 27.17, 27.0, 26.9, 25.7, 20.9; IR (thin film, cm-) 3027, 2929, 2861, 2809, 1454, 1108; HRMS (ESI) m/z: [M + H]⁺ Calcd for C₂₂H₃₄O₂N 344.2590; Found: 344.2581.

Characterization data for azabicyclic compound 37 has been described previously.⁹

Benzyl 5-(2-oxocyclopentyl)pentanoate (S34)

Following general procedure B, S34 (385 mg, 1.40 mmol, 55%) was obtained as a colorless oil after flash chromatography on silica gel (19:1 hex-anes:EtOAc to 9:1 hexanes:EtOAc to 4:1 hexanes:EtOAc). H NMR (500 MHz, CDCl₃) δ 7.37-7.32 (m, 5H), 5.12 (s, 2H), 2.37 (t, J = 7.4 Hz, 2H), 2.29 (dd, J = 18.7, 8.4 Hz, 1H), 2.22–2.16 (m, 1H), 2.13–2.05 (m, 1H), 2.02–1.96 (m, 2H), 1.80–1.74 (m, 2H), 1.71–1.61 (m, 2H), 1.48 (qd, J = 10.8, 6.7 Hz, 1H), 1.37 (app quintet, J = 7.9 Hz, 2H), 1.26 (dq, J = 16.1, 8.4 Hz, 1H); ¹³C NMR (125 MHz, CDCl₃) δ 221.5, 173.6, 136.3, 128.7, 128.37, 128.36, 66.3, 49.1, 38.3, 34.3, 29.7, 29.4, 27.2, 25.0, 20.9; IR (thin film, cm^-1) 3033, 2940, 2860, 1735, 1158; HRMS (ES) m/z: [M + Na]⁺ Calcd for C₁₇H₂₂O₃Na 297.1467; Found: 297.1467.

5-(6,10-Dioxa-spiro[4.5]dec-1-yl)-pentanoic acid benzyl ester (S35)

Following general procedure C, ketal S35 was obtained as a colorless oil (622 mg, 1.87 mmol, 64%). ¹H NMR (500 MHz, CDCl₃) δ 7.39–7.32 (m, 5H), 5.12 (s, 2H), 3.93–3.82 (m, 4H), 2.38 (t, J = 7.6 Hz, 2H), 2.09–2.05 (m, 1H), 2.05–1.88 (m, 1H), 1.86–1.76 (m, 3H), 1.70–1.59 (m, 5H), 1.41–1.19 (m, 5H); ¹³C NMR (125 MHz, CDCl₃) δ 174.0, 136.4, 128.7, 128.4, 128.3, 109.0, 66.2, 62.0, 60.8, 48.9, 34.6, 30.7, 29.0, 28.2, 28.1, 26.2, 25.6, 21.2; IR (thin film, cm^-1) 3066, 3034, 2950, 1737, 1151, 1106; HRMS (ES) m/z: [M + Na]⁺ Calcd for C₂₀H₂₈O₄Na 355.1885; Found: 355.1884.

N-((R)-2-phenylbut-3-enyl)-5-(6,10-dioxaspiro[4.5]decan-1-yl)pentanamide (S36)

Following general procedure D, S36 (242 mg, 0.651 mmol, 72%) as a colorless oil. ¹H NMR (500 MHz, CDCl₃) δ 7.31 (t, J = 7.5 Hz, 2H), 7.23–7.18 (m, 3H), 5.98–5.91 (m, 1H), 5.54 (broad s, 1H), 5.14–5.09 (m, 2H), 3.90–3.82 (m, 4H), 3.59–3.58 (m, 1H), 3.51–3.48 (m, 2H), 2.11–2.03 (m, 3H), 1.97–1.93 (m, 1H), 1.85–1.73 (m, 3H), 1.64–1.54 (m, 5H), 1.38–1.14 (m, 5H); ¹³C NMR (125 MHz, CDCl₃) δ 173.3, 141.3, 139.0, 128.8, 127.9, 127.0, 116.5, 108.9, 62.0, 60.7, 49.5, 48.8, 43.6, 36.9, 30.6, 28.9, 28.13, 28.09, 26.2, 26.1, 21.0; IR (thin film, cm^-1) 3295, 3078, 2944, 1645; HRMS (ESI) m/z: [M + Na]⁺ Calcd for C₂₃H₃₃O₃NNa 394.2358; Found: 394.2365.

N-((R)-2-phenylbut-3-enyl)-5-(6,10-dioxaspiro[4.5]decan-1-yl)pentan-1-amine (S37)

Following general procedure E, S37 (146 mg, 0.408 mmol, 66%) was obtained as a light-yellow oil. ¹H NMR (500 MHz, CDCl₃) δ 7.32 (t, J = 7.4 Hz, 2H), 7.23–7.18 (m, 3H), 6.00–5.93 (m, 1H), 5.14–5.11 (m, 2H), 3.92–3.85 (m, 5H), 3.54 (q, J = 6.9 Hz, 1H), 2.89 (d, J = 7.4 Hz, 2H), 2.60 (t, J = 7.2 Hz, 2H), 2.10–0.90 (m, 17H); ¹³C NMR (125 MHz, CDCl₃) δ 142.5, 140.3, 128.8, 127.8, 126.8, 116.0, 109.1, 62.1, 60.8, 54.6, 50.1, 49.9, 48.9, 30.7, 30.1, 28.9, 28.5, 28.4, 27.9, 26.2, 21.1; IR (thin film, cm^-1) 2930, 2858, 1453, 1149, 1111; HRMS (ESI) m/z: [M + H]⁺ Calcd for C₂₃H₃₆NO₂ 358.2746; Found: 358.2741.

Preparation and Characterization Data for 1-Azabicyclic Reported in Scheme 8 and Their Aminoketal Precursors

Scheme 8. Enantioselective Synthesis of cis-exahydrocyclopenta[b]pyrrole Carbamates Having Chiral Allylic Side Chains.

(R,E)-tert-Butyl 2-phenylpent-3-enylcarbamate (S38)

Diphenylphosphoryl azide (0.33 mL, 1.5 mmol) was added dropwise via syringe to a solution of (R,E)-3-phenylhex-4-enoic acid³⁶ (0.29 g, 1.5 mmol) and Et₃N (0.21 mL, 1.5 mmol) in t-BuOH (2.2 mL) at room temperature. The resulting solution was heated at 85 °C for 48 h, cooled to room temperature, diluted with EtOAc (50 mL), and washed sequentially with H₂O (10 mL), saturated aqueous NaHCO₃ (10 mL), and brine (10 mL). The organic layer was dried (MgSO₄), filtered, and concentrated in vacuo. Purification of the crude residue by flash chromatography on silica gel (19:1 hexanes: EtOAc to 9:1 hexanes:EtOAc) gave S38 (0.31 g, 1.2 mmol, 77%) as a colorless solid (mp 47–48 °C). HPLC analysis indicated an enantiomeric excess of 84%. The product was recrystallized with n-hexane/i-PrOH to an enantiomeric excess of 87% [CHIRALCEL OD-H column; flow: 1.0 mL/min; 99.7% n-hexane/0.3% i-PrOH; λ = 220 nm; major enantiomer t_R = 44.75 min; minor enantiomer t_R = 55.41 min]. ${[\alpha ]}_{589}^{24}-17.7,{[\alpha ]}_{577}^{24}-19.6,{[\alpha ]}_{546}^{23}-24.0,{[\alpha ]}_{435}^{23}-45.6(c=1.0,{\text{CH}}_2{\text{Cl}}_2)$; ¹H NMR (500 MHz, CDCl₃) δ 7.33 (t, J = 7.4 Hz, 2H), 7.25–7.20 (m, 3H), 5.58–5.55 (m, 2H), 4.50 (broad s, 1H), 3.42–3.36 (m, 3H), 1.70 (d, J = 4.5 Hz, 3H), 1.43 (s, 9H); ¹³C NMR (125 MHz, CDCl₃) δ 156.0, 142.3, 131.9, 128.9, 127.9, 127.4, 126.9, 79.4, 49.2, 45.5, 28.6, 18.3; IR (thin film, cm^-1) 3357, 2975, 2931, 1702, 1506, 1171; HRMS (ESI) m/z: [M + Na]⁺ Calcd for C₁₆H₂₃NO₂Na 284.1626; Found: 284.1628.

(R,E)-2-Phenylpent-3-en-1-amine (S39)

To a solution of N-Boc amine S38 (180 mg, 0.690 mmol) in CH₂Cl₂ (3.4 mL) was added TFA (0.530 mL, 6.90 mmol) dropwise via syringe at 0 °C. The resulting solution was stirred at room temperature for 1.5 h and quenched with 10% aqueous NaOH at 0 °C until a pH of 14 was reached. The mixture was allowed to warm to room temperature and extracted with Et₂O (3 × 15 mL). The organic layers were combined, dried (MgSO₄), filtered and concentrated in vacuo to provide S39 (140 mg) as a yellow oil that was used in subsequent reactions without further purification.

N-((R,E)-2-Phenylpent-3-enyl)-2-(6,10-dioxaspiro[4.5]decan-1-yl)acetamide (S40)

Following general procedure D, S40 (35 mg, 0.10 mmol, 16%) was obtained as a colorless oil. ¹H NMR (500 MHz, CDCl₃) δ 7.32 (t, J = 7.9 Hz, 2H), 7.24–7.21 (m, 3H), 6.26 (broad s, 1H), 5.57–5.54 (m, 2H), 3.87–3.75 (m, 4H), 3.63–3.44 (m, 3H), 2.56 (dd, J = 14.9, 6.6 Hz, 1H), 2.20–2.08 (m, 1H), 2.08–2.04 (m, 2H), 1.87–1.80 (m, 3H), 1.69 (d, J = 5.2 Hz, 3H), 1.65–1.62 (m, 1H), 1.33–1.26 (m, 3H); ¹³C NMR (125 MHz, CDCl₃) δ 173.25, 173.23, 142.5, 142.4, 132.19, 132.16, 131.9, 128.9, 128.8, 127.93, 127.88, 127.2, 127.1, 127.0, 126.8, 108.3, 108.2, 62.30, 62.28, 60.74, 60.71, 48.8, 48.7, 46.03, 45.98, 44.23, 44.17, 36.05, 36.04, 30.47, 30.46, 29.6, 29.5, 26.0, 25.99, 21.2, 18.3; IR (thin film, cm^-1) 3299, 2961, 2932, 2867, 1642, 1544; HRMS (ESI) m/z: [M + Na]⁺ Calcd for C₂₁H₂₉NO₃Na 366.2045; Found: 366.2044.

(2R,E)-N-(2-(6,10-Dioxaspiro[4.5]decan-1-yl)ethyl)-2-phenylpent-3-en-1-amine (39a)

Following general procedure E, 39a (33 mg, 0.10 mmol, 98%) was obtained as a light-brown oil. ¹H NMR (500 MHz, CDCl₃) δ 7.31 (t, J = 7.7 Hz, 2H), 7.23–7.19 (m, 3H), 5.58–5.55 (m, 2H), 3.92–3.82 (m, 4H), 3.49 (q, J = 7.2 Hz, 1H), 2.88–2.85 (m, 2H), 2.69–2.64 (m, 2H), 2.10–2.06 (m, 1H), 2.00–1.91 (m, 1H), 1.84–1.74 (m, 5H), 1.69–1.62 (m, 8H), 1.40–1.36 (m, 2H), 1.31–1.26 (m, 2H); ¹³C NMR (125 MHz, CDCl₃) δ 143.59, 143.55, 133.2, 133.1, 128.77, 128.75, 127.81, 127.79, 126.8, 126.7, 126.56, 126.55, 108.9, 62.2, 60.8, 55.2, 49.3, 48.9, 47.1, 30.6, 30.5, 29.9, 29.3, 29.1, 26.1, 21.3, 18.3; IR (thin film, cm^-1) 3305, 3206, 2954, 2861, 1451, 1149, 1110; HRMS (ESI) m/z: [M + H]⁺ Calcd for C₂₁H₃₂NO₂ 330.2433; Found: 330.2423.

(3aS,6aS)-Benzyl 6a-((R,E)-4-phenylbut-3-en-2-yl)hexahydrocyclopenta[b]pyrrole-1(2H)-carboxylate (40)

Following general procedure G, 40 (28 mg, 0.075 mmol, 75%) was obtained as a colorless oil. HPLC analysis indicated an enantiomeric excess of 87% [CHIRALCEL OD-H column; flow: 1.0 mL/min; 99.8% n-hexane/0.2% i-PrOH; λ = 254 nm; major enantiomer t_R = 43.90 min; minor enantiomer t_R = 40.20 min]. ¹H NMR (500 MHz, CDCl₃) δ 7.38–7.29 (m, 9H), 7.20 (t, J = 7.3 Hz, 1H), 6.43 (d, J = 15.8 Hz, 1H), 6.17 (dd, J = 15.8, 8.5 Hz, 1H), 5.14–5.09 (m, 2H), 3.60–3.47 (m, 2H), 3.34 (m, 1H), 2.67–2.50 (m, 1H), 2.14–2.10 (m, 1H), 2.00–1.92 (m, 2H), 1.76–1.72 (m, 1H), 1.60–1.55 (m, 2H), 1.50–1.38 (m, 2H), 0.88 (d, J = 7.3 Hz, 3H); ¹³C NMR (125 MHz, CDCl₃) δ 152.7, 137.0, 136.8, 132.4, 129.8, 127.7, 127.6, 126.9, 126.6, 126.2, 125.3, 76.6, 65.0, 47.3, 44.1, 41.4, 36.7, 32.3, 28.6, 24.3, 15.2; IR (thin film, cm^-1) 3027, 2955, 2868, 1698, 1402; HRMS (ESI) m/z: [M + Na]⁺ Calcd for C₂₅H₂₉NO₂Na 398.2096; Found: 398.2097.

(R,E)-tert-Butyl (2,4-diphenylbut-3-en-1yl)carbamate (S41)

To a solution of the catalyst HG-II³⁷ (13 mg, 0.02 mmol) in CH₂Cl₂ (1.3 mL) was added homoallylamine 25 (0.10 g, 0.40 mmol) and styrene (0.16 mL, 1.2 mmol). The green solution was heated to reflux for 12 h. After 12 h, the solution was cooled to room temperature and concentrated under reduced pressure to a brown solid. The crude material was purified by silica gel chromatography (100% hexanes to 4:1 hexanes:Et₂O) to yield S41 as a colorless solid (92 mg, 0.28 mmol, 70%). mp 80–81 °C; ${[\alpha ]}_{22}^{589}-6.35,{[\alpha ]}_{22}^{577}-7.12,{[\alpha ]}_{22}^{546}-8.15,{[\alpha ]}_{22}^{435}-7.48(c1.3,{\text{CH}}_2{\text{Cl}}_2)$; ¹H NMR (500 MHz, CDCl₃) δ 7.34–7.21 (m, 10H), 6.49 (d, J = 15.9 Hz, 1H), 6.34 (dd, J = 15.9, 7.8 Hz, 1H), 4.57 (broad s, 1H), 3.69–3.68 (m, 1H), 3.57–3.56 (m, 1H), 3.52–3.48 (m, 1H), 1.43 (s, 9H); ¹³C NMR (125 MHz) δ 156.1, 141.7, 137.2, 131.7, 130.8, 129.0, 128.7, 128.0, 127.6, 127.1, 126.5, 79.5, 49.5, 45.5, 28.6; IR (thin film, cm^-1) 3430, 3358, 3060, 2979, 1710; HRMS (ESI) m/z: [M + Na]⁺ Calcd for C₂₁H₂₅O₂NNa 346.1783; Found: 346.1793.

(R,E)-2,4-Diphenylbut-3-en-1-amine (S42)

To a solution of Boc-amide S41 (89 mg, 0.28 mmol) in CH₂Cl₂ (1.3 mL) at 0 °C was added TFA (0.21 mL, 2.8 mmol) dropwise over 3 min. The resulting clear and colorless solution was warmed to room temperature and maintained for 1.5 h. The reaction was quenched by the addition of 10% aqueous solution of NaOH until the solution is basic (pH >10 analyzed by pH paper) at 0 °C. The solution was allowed to warm to room temperature and extracted with Et₂O (3 × 50 mL). The organic layers were combined, dried with MgSO₄, filtered and concentrated to provide the amine S42 as a slightly yellow oil (61 mg, 0.28 mmol). This amine was used without further purification. ${[\alpha ]}_{22}^{589}+6.24,{[\alpha ]}_{22}^{577}+6.61,{[\alpha ]}_{22}^{546}+8.33,{[\alpha ]}_{22}^{435}+22.2(c1.9,{\text{CH}}_2{\text{Cl}}_2)$; ¹H NMR (500 MHz, CDCl₃) δ 7.39–7.20 (m, 10H), 6.51 (d, J = 15.7 Hz, 1H), 6.25 (dd, J = 15.7, 8.1 Hz, 1H), 3.59 (broad d, J = 7.2 Hz, 1H), 3.47 (broad s, 2H), 3.10 (broad s, 2H); ¹³C NMR (125 MHz) δ 141.1 136.9, 132.3, 130.1, 129.2, 128.8, 127.9, 127.8, 127.4, 126.5, 50.9, 46.0; IR (thin film, cm^-1) 3357, 3290, 2929; HRMS (ESI) m/z: [M + H]⁺ Calcd for C₁₆H₁₈N 224.1439; Found: 224.1445.

N-((R,E)-2,4-Diphenylbut-3-en-1-yl)-2-(6,10-dioxaspiro[4.5]decan-1yl)acetamide (S43)

Following general procedure D, S43 (45 mg, 0.11 mmol, 65%) was obtained as a colorless solid. ¹H NMR (500 MHz, CDCl₃) δ 7.39–7.20 (m, 10H), 6.47 (dd, J = 12.7, 4.5 Hz, 1H), 6.36–6.31 (m, 1H), 3.85–3.54 (m, 7H), 2.58 (dd, J = 14.4, 6.8 Hz, 1H), 2.21–2.13 (m, 1H), 2.11–2.00 (m, 2H), 1.91–1.71 (m, 3H), 1.65–1.54 (m, 3H), 1.29–1.22 (m, 2H); ¹³C NMR (125 MHz) δ 173.38, 173.36, 141.9, 141.7, 137.3, 137.2, 131.4, 131.0, 129.0, 128.72, 128.71, 128.1, 128.0, 127.63, 127.60, 127.1, 126.4, 108.2, 62.3, 60.7, 49.04, 49.01, 46.09, 46.05, 44.2, 44.1, 36.08, 36.05, 30.52, 30.45, 30.4, 29.9, 29.7, 29.6, 26.0, 21.2, 21.2; IR (thin film, cm^-1) 3330, 3059, 2960, 2866, 1721; HRMS (ESI) m/z: [M + Na]⁺ Calcd for C₂₆H₃₁NO₃Na 428.2202; Found: 428.2203.

(2R,E)-N-(2-(6,10-Dioxaspiro[4.5]decan-1yl)ethyl)-2,4-diphenylbut-3-en-1-amine (39b)

Following general procedure E, 39b (204 mg, 0.520 mmol, 81% yield) was obtained as a light-yellow oil. ¹H NMR (500 MHz, CDCl₃) δ 7.46—7.26 (m, 10H), 6.55 (dd, J = 15.9, 4.0 Hz, 1H), 6.42 (dd, J = 15.9, 8.0 Hz, 1H), 3.97–3.76 (m, 5H), 3.08 (d, J = 7.4 Hz, 2H), 2.78–2.68 (m, 2H), 2.18–2.12 (m, 1H), 2.02–2.00 (m, 1H), 1.94–1.83 (m, 3H), 1.7–1.65 (m, 3H), 1.50–1.22 (m, 4H); C NMR (125 MHz) δ 142.71, 142.67, 137.42, 137.39, 132.1, 132.0, 131.14, 131.07, 128.89, 128.88, 128.7, 128.65, 128.59, 128.4, 128.3, 127.96, 127.94, 127.7, 127.44, 127.43, 126.8, 126.84, 126.82, 126.4, 126.3, 108.8, 62.7, 62.2, 62.1, 60.8, 54.9, 49.41, 49.39, 48.84, 48.82, 46.97, 46.96, 30.53, 30.50, 29.23, 29.21, 29.0, 26.0, 21.2; IR (thin film, cm^-1) 3654, 3025, 2951, 1147; HRMS (ESI) m/z: [M + H]⁺ Calcd for C₂₆H₃₄NO₂ 392.2590; Found: 392.2585.

(3aS, 6aS)-Benzyl 6a-((1S, E)-1,3-diphenylallyl)hexahydrocyclopenta[b]pyrrole-1(2H)-carboxylate (41)

Following general procedure G, 41 (6 mg, 14 μmol, 65% yield) was obtained as a light colorless oil. HPLC analysis indicated an enantiomeric excess of 99% [CHIRALCEL AD column; flow: 1.0 mL/min; 98% n-hexane/2% i-PrOH; λ = 254 nm; major enantiomer t_R = 29.97 min; minor en-antiomer t_R = 23.72 min]. ${[\alpha ]}_{22}^{589}-66.0,{[\alpha ]}_{22}^{577}-69.9,{[\alpha ]}_{22}^{546}-79.7,{[\alpha ]}_{22}^{435}-148.6(c1.2,{\text{CH}}_2{\text{Cl}}_2)$. ¹H NMR (500 MHz, DMSO-d₆, 393K) δ 7.50–7.40 (m, 6H), 7.35–7.30 (m, 3H), 7.24–7.15 (m, 6H), 6.73 (dd, J = 15.6, 9.9 Hz, 1H), 6.48 (d, J = 15.5 Hz, 1H), 5.22 (d, J = 12.6, 1H), 5.12 (broad d, J = 13.4 Hz, 1H), 4.50 (broad d, J = 12.8 Hz, 1H), 3.30 (ddd, J = 10.5, 8.0, 8.0 Hz, 1H), 3.02-2.97 (m, 1H), 2.69 (ddd, J = 10.7, 8.8, 4.7 Hz, 1H), 2.24 (broad s, 1H), 2.04 (ddd, J = 14.3, 7.3, 7.3 Hz, 1H), 1.90–1.84 (m, 1H), 1.60–1.46 (m, 2H), 1.42–1.37 (m, 1H), 1.31–1.28 (m, 1H), 1.18–1.12 (m, 1H); ¹³C NMR (125 MHz, DMSO-d₆, 393K) δ 152.7, 141.4, 136.82, 136.78, 131.9, 129.5, 127.9, 127.8, 127.6, 127.1, 127.0, 126.9, 126.5, 125.6, 125.5, 77.5, 65.1, 51.6, 46.6, 43.9, 37.1, 32.6, 27.6, 24.3; IR (thin film, cm^-1) 3028, 2951, 1699, 1132; HRMS (ESI) m/z: [M + Na]⁺ Calcd for C₃₀H₃₁NO₂Na 460.2252; Found: 460.2243.

(R,E)-tert-Butyl (4-cyclohexyl-2-phenylbut-3-en-1-yl)carbamate (S44)

To a stirring solution of HG-II³⁷ (23 mg, 0.036 mmol) in CH₂Cl₂ (1.2 mL) was added homoallylic carbamate 25 (0.090 g, 0.36 mmol) and vinylcyclohexane (0.25 mL, 1.8 mmol). The green solution was heated to reflux for 12 h. After 22 h, the solution was cooled to room temperature and concentrated under reduced pressure to a brown solid. The crude material was purified by flash chromatography on silica gel (100% hexanes to 9:1 hexanes:Et₂O) to yield S44 as a colorless solid (49 mg, 0.15 mmol, 41%) that was a 9:1 mixture of E:Z double-bond isomers. mp 83–84 °C.¹H NMR (600 MHz, CDCl₃) δ 7.33–7.31 (m, 2H), 7.24–7.20 (m, 3H), 5.54–5.48 (m, 2H), 5.44–5.39 (m, 0.18 H), 3.41 (broad s, 1H), 3.37–3.32 (m, 2H), 3.22–3.18 (m, 0.11H), 1.97-1.93 (m, 1H), 1.74–1.69 (m, 5H), 1.65-1.63 (1.3H), 1.43 (s, 10.5 H), 1.29–1.22 (m, 2.4 H), 1.18–1.10 (m, 3.3 H); ¹³C NMR (125 MHz, CDCl₃) δ 156.0, 142.5, 138.8, 128.8, 128.0, 127.90, 127.88, 127.8, 127.6, 126.8, 79.3, 49.0, 45.7, 40.9, 33.2, 28.6, 26.2; IR (thin film, cm^-1) 3438, 3363, 2975, 1704, 1601, 1171; HRMS (ESI) m/z: [M + Na]⁺ Calcd for C₂₁H₃₁NO₂Na 352.2252; Found: 352.2254.

(R,E)-4-Cyclohexyl-2-phenylbut-3-en-1-amine (S45)

To a solution of Boc-amide S44 (49 mg, 0.15 mmol) in CH₂Cl₂ (0.68 mL) at 0 °C was added TFA (0.12 mL, 1.5 mmol) dropwise over 3 minutes. The resulting clear and colorless solution was warmed to room temperature and maintained for 1.5 h. The reaction was quenched by the addition of 10% aqueous solution of NaOH until the solution is basic (pH >10 analyzed by pH paper) at 0 °C. The solution was warmed to room temperature and ex-tracted with Et₂O (3 × 50 mL). The organic layers were combined, dried with MgSO₄, filtered and con-centrated to provide the amine as a colorless oil. The crude material could be used without further puri-fication or purified to obtain an analytically pure sample (>98% E olefin isomer) by flash chromatog- raphy on silica gel (99:1 Et₂O:Et₃N) to yield S45 as a colorless oil (25 mg, 0.11 mmol. 73%). ${[\alpha ]}_{23}^{589}-25.1,{[\alpha ]}_{23}^{577}-27.0,{[\alpha ]}_{23}^{546}-30.7,{[\alpha ]}_{23}^{435}-56.4(c1.3,{\text{CH}}_2{\text{Cl}}_2)$; ¹H NMR (500 MHz, CDCl₃) δ 7.34–23 23 23 7.16 (m, 5H), 5.52–5.51 (m, 2H), 3.23–3.19 (m, 1H), 2.95–2.87 (m, 2H), 2.00–1.92 (m, 1H), 1.73–1.63 (m, 5H), 1.47 (broad s, 1H), 1.28–1.07 (m, 6H); ¹³C NMR (125 MHz) δ 143.3, 138.7, 128.7, 128.6, 127.9, 126.5, 53.0, 47.7, 40.9, 33.4, 33.3, 26.3, 26.2, 25.1; IR (thin film, cm-) 3366, 3284, 3026, 2920, 2850, 1074, 1029; HRMS (ESI) m/z: [M + H]⁺ Calcd for C₁₆H₂₄N 230.1909; Found: 230.1909.

N-((R,E)-4-cyclohexyl-2-phenylbut-3-en-1-yl)-2-(6,10-dioxaspiro[4.5]decan-1-yl)acetamide (S46)

Following general procedure D, S46 (27 mg, 0.065 mmol, 64% yield) was obtained as a colorless oil. ¹H NMR (500 MHz, CDCl₃) δ 7.38–7.35 (m, 2H), 7.28–7.25 (m, 3H), 6.23 (broad d, J = 17.1 Hz, 1H), 5.55 (s, 1H), 5.54 (dd, J = 3.0, 1.2 Hz, 1H), 3.93–3.76 (m, 4H), 3.71–3.60 (m, 1H), 3.56–3.41 (m, 2H), 2.60 (dd, J = 15.1, 6.7 Hz, 1H), 2.67–2.20 (m, 1H), 2.13–2.07 (m, 2H), 2.10–1.90 (m, 1H), 1.91–1.58 (m, 12H), 1.41–1.05 (m, 5H); ¹³C NMR (125 MHz) δ 173.24, 173.21, 142.6, 142.5, 138.6, 138.5, 128.8, 128.3, 128.0, 127.9, 126.8, 108.3, 108.2, 62.30, 62.27, 60.73, 60.70, 48.7, 48.6, 46.1, 45.9, 44.33, 44.26, 40.9, 36.1, 33.21, 33.17, 30.51, 30.47, 29.9, 29.6, 29.5, 26.3, 26.2, 26.01, 25.99, 21.2; IR (thin film, cm^-1) 3296, 3061, 2920, 1644; HRMS(ESI) m/z: [M + Na]⁺ Calcd for C₂₆H₃₇NO₃Na 434.2671; Found: 434.2680.

(2R,E)-N-(2-(6,10-Dioxaspiro[4.5]decan-1-yl)ethyl)-4-cyclohexyl-2-phenylbut-3-en-1-amine (39c)

Following general procedure E, 39c (18 mg, 0.045 mmol, 67% yield) was obtained as a color-less oil. ¹H NMR (500 MHz, CDCl₃) δ 7.31–7.29 (m, 2H), 7.23–7.20 (m, 3H), 5.51–5.50 (m, 2H), 3.89–3.84 (m, 4H), 3.51–3.45 (m, 1H), 2.89–2.83 (m, 2H), 2.69–2.67 (m, 2H), 2.11–2.06 (m, 1H), 2.00–1.90 (m, 2H), 1.82–1.55 (m, 11H), 1.44–1.04 (m, 9H); ¹³C NMR (125 MHz) δ 138.4, 129.1, 128.7, 128.7, 127.8, 126.51, 126.49, 108.90, 108.88, 62.23, 62.22, 60.79, 60.77, 55.3, 55.2, 49.0, 48.82, 48.76, 47.0, 46.9, 41.0, 40.9, 33.33, 33.30, 33.24, 33.23, 30.7, 30.6, 29.31, 29.25, 29.0, 26.4, 26.27, 26.26, 26.15, 21.24, 21.23; IR (thin film, cm^-1) 3430, 3313, 3052, 2923, 1264; HRMS (ESI) m/z: [M + H]⁺ Calcd for C₂₆H₄₀NO₂ 398.3059; Found: 398.3053.

(3aS,6aS)-Benzyl 6a-((R,E)-1-cyclohexyl-3-phenylallyl)hexahydrocyclopenta[b]pyrrole-1(2H)-carboxylate (42)

Following general procedure G, 42 (31 mg, 0.071 mmol, 49%) was obtained as a colorless oil. HPLC analysis indicated an enantiomeric excess of 99% [CHIRALCEL AD column; flow: 0.5 mL/min; 98% n-hexane/2% i-PrOH; λ = 254 nm; major enantiomer t_R = 28.77 min; minor en-antiomer t_R = 32.53 min]. ${[\alpha ]}_{23}^{589}+41.9,{[\alpha ]}_{23}^{577}+42.1,{[\alpha ]}_{23}^{546}+49.7,{[\alpha ]}_{23}^{435}+92.1(c=0.34,{\text{CH}}_2{\text{Cl}}_2)$; ¹H NMR (500 MHz, DMSO-d₆, 393K) δ 7.42–7.35 (m, 6H), 7.32–7.29 (m, 3H), 7.22–7.19 (m, 1H), 6.34 (d, J = 15.8 Hz, 1H), 6.14 (dd, J = 15.7, 10.6, 1H), 5.15 (d, J = 12.7 Hz, 1H), 5.06 (d, J = 12.6 Hz, 1H), 3.62–3.51 (m, 1H), 2.97 (d, J = 9.5 Hz, 1H), 2.09 (broad s, 1H), 2.00 (dddd, J = 12.9, 8.5, 8.5, 8.5 Hz, 1H), 1.85 (dddd, J = 7.7, 7.7, 7.7, 7.7 Hz, 1H), 1.771.73 (m, 2H), 1.69–1.66 (m, 1H), 1.63–1.39 (m, 8H), 1.31–1.29 (m, 1H), 1.23–1.14 (m, 3H), 1.11–1.01 (m, 3H); C NMR (125 MHz, DMSO-d₆, 393K) δ 152.7, 137.0, 136.9, 132.0, 129.4, 127.8, 127.6, 126.9, 126.8, 126.2, 125.4, 76.7, 65.0, 53.3, 47.3, 44.6, 37.9, 33.03, 32.99, 29.4, 28.4, 25.9, 25.7, 25.3, 23.8; IR (thin film, cm^-1) 3028, 2925, 2851, 1699; HRMS (ESI) m/z: [M + Na]⁺ Calcd for C₃₀H₃₇NO₂Na 466.2722; Found: 466.2714.

The synthesis and characterization of amino acids 43–45 have been reported previously.⁹

(S)-2-((3aS,6aS)-1-((Benzyloxy)carbonyl)octahydrocyclopenta[b]pyrrol-6a-yl)-2-cyclohexylacetic acid (46)

Ozone was bubbled through a solution of 42 (12 mg, 25 μmol) in MeOH (1.7 mL) at −78 °C for approximately 30 seconds until a persistent blue color was observed. The solu-tion was purged with O₂ until colorless, quenched with dimethyl sulfide (81 μL, 1.1 mmol), and warmed to room temperature. After 24 h, the reaction mixture was concentrated in vacuo, dissolved in MeCN (1.8 mL) and H₂O (0.17 mL), and cooled to 0 °C. Sodium chlorite (23 mg, 0.25 mmol) was added to the solution and the reaction mixture was warmed to room temperature. After stirring for 24 h, the reaction mixture was concentrated in vacuo, diluted with brine (5 mL), and extracted with EtOAc (3 × 5 mL). The combined organic extracts were dried (MgSO₄), filtered, and concentrated. Purification of the crude residue by flash chromatography on silica gel (100:100:1 hexanes:Et₂O:AcOH) provided 46 (10 mg, 25 μmol, 99% yield) as a colorless oil. ${[\alpha ]}_{23}^{589}-2.90,{[\alpha ]}_{23}^{577}-3.46,{[\alpha ]}_{23}^{546}+1.24,{[\alpha ]}_{23}^{435}+1.88(c0.31,{\text{CH}}_2{\text{Cl}}_2)$; ¹H NMR (500 MHz, DMSO-d₆, 393K) δ 11.56 (broad s, 1H), 7.36 (broad s, 4H), 7.30 (broad s, 1H), 5.16 (d, J = 1.8 Hz, 1H), 5.06 (broad m, 1H), 3.53–3.41 (broad m, 2H), 3.27 (broad s, 1H), 2.09–2.03 (broad m, 1H), 1.92–1.84 (broad m, 2H), 1.73–1.38 (broad m, 11H), 1.32–0.86 (broad m, 6H); ¹³C NMR (125 MHz, DMSO-d₆, 393K) δ 174.6, 152.6, 137.5, 128.4, 128.3, 128.0, 127.6, 127.1, 75.7, 65.2, 53.0, 47.0, 43.4, 38.5, 36.6, 33.5, 32.7, 30.9, 29.4, 26.3, 26.1, 25.8, 25.0; IR (thin film, cm^-1) 2921, 2851, 1214; HRMS (ESI) m/z: [M + Na]⁺ Calcd for C₂₃H₃₁NO₄Na 408.2151; Found: 408.2153.

2,2,2-trifluoro-1l3-ethan-1-one, 6a-(3-hydroxypropoxy)-1-((S)-2-methylbut-3-en-1- yl)octahydrocyclopenta[b]pyrrol-1-ium salt (diastereomers 49 and 50)

¹H NMR (500 MHz, DMSO-d₆) δ 8.38–8.29 (br d, 2H), 5.73–5.66 (m, 1H), 5.13–5.05 (m, 2H), 3.85–3.74 (m, 4H), 2.98–2.84 (m, 1H), 2.84–2.83 (m, 2H), 2.52–2.48 (m, 1H), 2.11–2.06 (m, 2H), 1.81–1.69 (m, 5H), 1.55–1.50 (m, 3H), 1.34 (d, J = 2.4 Hz, 1H), 1.18–1.16 (m, 1H), 0.98 (d, J = 7.0 Hz, 3H); ¹³C NMR (125 MHz, DMSO-d_6, contains a mixture of diastereomers, signals observed are reported): δ 258.4, 158.2, 139.8, 139.8, 139.8, 116.2, 116.2, 107.7, 107.6, 61.5, 59.9, 51.5, 46.58, 46.55, 45.97, 45.96, 34.8, 29.9, 28.4, 25.5, 24.7, 24.7, 24.6, 20.72, 20.71, 14.5.