Skip to main content
NCBI home page
ACS AuthorChoice logoLink to ACS AuthorChoice
. 2022 Nov 29;87(24):16902–16906. doi: 10.1021/acs.joc.2c02217

Carbene Routes to Cyclopropatetrahedrane

Murray G Rosenberg §, Udo H Brinker †,§,*
PMCID: PMC9764353  PMID: 36446051

Abstract

graphic file with name jo2c02217_0007.jpg

The formation of cyclopropatetrahedrane (tetracyclo[2.1.0.01,3.02,4]pentane) via four different carbene reactions is computed using the (U)CCSD(T)(full)/cc-pVTZ//(U)ωB97X-D/cc-pVTZ + 1.3686(EZPVE) theoretical model. Intrinsic reaction coordinate plots confirm that each carbene is directly linked to cyclopropatetrahedrane via a unique cyclopropanation step. Each elementary step is assessed according to the structure and energy of its transition state.

This report assesses four carbene reactions that ostensibly could form cyclopropatetrahedrane (1;1Figure 1a),2,3 a cyclopropane-fused derivative of tetrahedrane (2; Figure 1b).4−7 To date, 1 and 2 remain hypothetical constructs, although derivatives of 2(4) as well as pristine 3 and 4 (Figure 1c,d)8,9 have been prepared (cf. Table S1 in Supporting Information). Nevertheless, earlier computations suggest that 1 will be kinetically stable because (1) it occupies a deep energy minimum on the C5H4 hypersurface and (2) none of its 21 vibrational normal modes falls below ν̅ = 443 cm–1.2,3 Forming 1 will be challenging because (1) its computed strain energy (ΔstrainH° = 157 kcal/mol)2a is phenomenal and (2) the bridging CH2–group of 1 establishes a bond that connects two inverted C atoms (i.e., each C atom has four bonds pointing in the same direction;10−12Figure 1a; cf. Figures S2 and S3 in Supporting Information). Also, the long C1–C4 bond (r = 1.664 Å)2a of 1 is electron-depleted, weak, and prone to breakage when compared with typical aliphatic C–C bonds. Routes to 1 have been proposed, such as via a 2,4-dihalotricyclo[1.1.1.01,3]pentane synthon (5; Scheme 1).4,5 However, carbene routes to 1 have never been investigated.

Figure 1.

Figure 1

Open in a new tab

Cyclopropatetrahedrane (1) is a cyclopropane-fused derivative of tetrahedrane (2), which itself is one of the Platonic-solid-like hydrocarbons that also include cubane (3) and dodecahedrane (4).

Scheme 1. A Proposed Retrosynthesis of Cyclopropatetrahedrane (1).

Scheme 1

Open in a new tab

Carbene reaction intermediates are uncharged, electron-deficient, and highly energetic.13−27 They are prized for their ability to form a wide variety of cyclopropanes, which can be done in two ways. The divalent C atom (:C<) can (1) insert into a homovicinal C–H bond (e.g., carbene 6 → 2) or (2) add to a C–C double bond (e.g., carbene 7 → 2) (Scheme 2).28 These two signature reactions are useful when building polycycloalkanes. Thus, an examination of carbene routes to highly strained 1 is warranted.

Scheme 2. Types of Intramolecular Carbene Cyclopropanations.

Scheme 2

Open in a new tab

Four routes to 1 via four different hypothetical carbene reaction intermediates (Scheme 3) were evaluated using the (U)CCSD(T)(full)/cc-pVTZ//(U)ωB97X-D/cc-pVTZ + 1.3686(EZPVE) theoretical model (see Computational Methods). Paths a–c depict homovicinal C–H bond insertion reactions within carbenes 8–10, respectively, and path d depicts a C–C double bond addition reaction within carbene 11. The structures in Scheme 3 are drawn in a uniform manner to emphasize the new bonds being formed (cf. Figure 2): (1) path a, Cα–Cβ; (2) path b, Cγ–Cγ; (3) path c, Cβ–Cγ; and (4) path d, Cα–Cβ and Cβ–Cβ. Each elementary step is characterized in terms of its transition state (TS) structure, activation energy (Ea), and net energy change (ΔE) (Table 1). Intrinsic reaction coordinate (IRC) plots (Figure 3a–d) and videos (see Supporting Information) are also provided to demonstrate that each carbene is directly linked to 1.

Scheme 3. Four Carbene Routes to Cyclopropatetrahedrane (1).

Scheme 3

Open in a new tab

Figure 2.

Figure 2

Open in a new tab

C2v-symmetric cyclopropatetrahedrane (1) comprises (a) one 2°-C atom (α), (b) two 4°-C atoms (β), and (c) two 3°-C atoms (γ). (ORTEP structure shows 50% ellipsoids.)

Table 1. Computed Data for Carbene Isomerizations to 1a,b.

Carbene IRC path ν̅ TS (cm–1) Ea (kcal/mol) ΔE (kcal/mol)
8 a 1164i 15.8 –50.2
9 b 915i 14.2 –24.5
10 c 961i 3.5 –29.2
11 d 329i 27.8 10.0
Open in a new tab
a

Cf. Scheme 3.

b

CCSD(T)(full)/cc-pVTZ//ωB97X-D/cc-pVTZ + 1.3686(EZPVE) theoretical model.

Figure 3.

Figure 3

Open in a new tab

Four IRCs were computed using the CCSD(T)/cc-pVTZ//ωB97X-D/cc-pVTZ theoretical model. Routes (a)–(c) depict homovicinal C–H bond insertion reactions within carbenes 8–10, respectively, while route (d) depicts a C–C double bond addition reaction within carbene 11.

Path a involves the hypothetical carbene (tetrahedryl)carbene (8).29 A homovicinal C–H bond insertion reaction via TSa was confirmed by its one, and only one, imaginary frequency (Table 1, path a), by animating the corresponding vibration, and by plotting the IRC, which links 8 directly to 1 (i.e., 8 → TSa → 1; Figure 3a (blue)).

An intriguing aspect of the carbene itself was found. Its computed singlet–triplet energy gap (ΔES–T)30 of −6.7 kcal/mol, corrected for the experimental ΔES–T of CH2 (eq 1; see Supporting Information),31 indicates that alkylcarbene 8 has a singlet ground state, and decidedly so. Hyperconjugation32−35 between the C1′–C4′ “banana” bond and the vacant p orbital of the carbene’s divalent C atom is a contributing factor (cf. Figure S1 in Supporting Information). The :CH-group of the lowest energy conformation of 8 is bent 41 deg toward the C1′–C4′ bond in comparison to the ·C·H-group of triplet (tetrahedryl)carbene (i.e., 38) (Scheme 3, path a) even though this deformation causes the C1′ atom’s four bonds to point in one direction (i.e., C1′ is an inverted C atom; cf. Figure S2 in Supporting Information). The distorted geometry of 8 may assist the formation of TSa since a triangular array comprising the C1, C1′, and C4′ atoms is already established (Figure 3a (blue)). Thus, the high ΔH⧧ may be more prohibitive than ΔS⧧ for the homovicinal C–H bond insertion reaction 8 → 1.

graphic file with name jo2c02217_m001.jpg 1

Path b involves the hypothetical carbene tricyclo[1.1.1.01,3]pent-2-ylidene (9). A homovicinal C–H bond insertion reaction via TSb was confirmed by its one, and only one, imaginary frequency (Table 1, path b), by animating the corresponding vibration, and by plotting the IRC, which links 9 directly to 1 (i.e., 9 → TSb → 1; Figure 3b (green)).

Path c involves the hypothetical carbene trans-tricyclo[2.1.0.01,3]pent-2-ylidene (10). A homovicinal C–H bond insertion reaction via TSc was confirmed by its one, and only one, imaginary frequency (Table 1, path c), by animating the corresponding vibration, and by plotting the IRC, which links 10 directly to 1 (i.e., 10 → TSc → 1; Figure 3c (yellow)).

Path d involves the hypothetical carbene 4-methylenebicyclo[1.1.0]but-2-ylidene (11). A cycloaddition reaction via TSd was confirmed by its one, and only one, imaginary frequency (Table 1, path d), by animating the corresponding vibration, and by plotting the IRC, which links 11 directly to 1 (i.e., 11 → TSd → 1; Figure 3d (red)). However, in contrast to those of the homovicinal C–H bond insertion reactions (Table 1, paths a–c), the net ΔE computed for this elementary step is positive. This indicates a thermodynamic preference for a cycloreversion of 1 (i.e., 1 → 11). However, 1 → 11 is computed to have a high ΔH‡ (18.1 kcal/mol; see Supporting Information). Of course, this enthalpy barrier is not insurmountable even in a frozen Ar matrix (T = ca. 10 K) under photolytic conditions.36

Computational chemistry was used to assess the viability of forming cyclopropatetrahedrane (1) via four different carbene reactions. The hypothesis appears to be valid because a TS was found for each of the elementary steps (i.e., Scheme 3, paths a–d). Furthermore, the respective IRC plots (Figure 3a–d) reveal a direct link between each carbene and 1. The IRCs and ZPVE-corrected single-point energies show that the homovicinal C–H bond insertion reactions via H atom transfer are exothermic but the C–C double bond addition reaction is endothermic. The formation of 1 via a homovicinal C–H bond insertion within trans-tricyclo[2.1.0.01,3]pent-2-ylidene (10) requires an Ea of just 3.5 kcal/mol. The bent posture adopted by the electron-seeking :CH-group of (tetrahedryl)carbene (8) is akin to a house plant that is bent toward a sunlit window; each “stalk” bends to obtain what it needs. In contrast, stabilizing hyperconjugation is precluded in triplet (tetrahedryl)carbene (38) because of its half-occupied p orbital. Thus, the triplet carbene is strictly Cs-symmetric.

Computational Methods

Quantum chemical calculations were performed on 1, carbenes 8–11, transition states TSa–TSd, and intrinsic reaction coordinate (IRC) paths a–d using the Spartan’20 (v. 1.1.4) computer program.37 Restricted SCF wave functions of molecular equilibrium geometries and transition states were computed using a (100,434) DFT integration grid, the RSH-GGA functional ωB97X-D,38 and Dunning’s cc-pVTZ basis set. Unrestricted SCF wave functions were computed for triplet-state carbenes. Normal-mode vibrational analyses were performed at the level of geometry optimization. The harmonic frequencies were used to obtain temperature-independent zero-point vibrational energy (EZPVE)39 and temperature-dependent thermal vibrational energy (ΔvibH) values. Each reaction TS had one, and only one, imaginary frequency, ν̅ TS. Its vibration was animated to verify that the motions conformed to the elementary step. An IRC was computed to ensure that the carbene followed a direct route to 1. Single-point energy (E) values were computed using the CCSD(T)(full) coupled-cluster theory method and Dunning’s cc-pVTZ basis set. All EZPVE values were scaled by z = 1.368640 before being added to E (T = 0 K; p = 0 atm). Relative energy values (ΔrelE) are specified with regard to 1 ((ΔrelE = [0]). Conversion of E values to enthalpy (HT) values was done according to eq S1 (see Supporting Information; computational standard state: T = 298.15 K; p = 1 atm; cf. Table S2). All ΔvibH values were scaled by H = 0.95640 before being added to the ZPVE-corrected E values. The increase in kinetic energy, due to translations (3(1/2)RT) and rotations (3(1/2)RT), for each nonlinear molecule was then added. Finally, RT (i.e., “pV work” needed to expand 1 mol of ideal gas to V = 24.465 L at T = 298.15 K and p = 1 atm) was added to obtain HT (eq S1).

Acknowledgments

Dedicated to the memory of University of Florida Distinguished Chemistry Professor Dr. William (Bill) M. Jones (1930–2022), with the appreciation of his contributions to the advancement of carbene chemistry.

Data Availability Statement

The data underlying this study are available in the published article and its online Supporting Information.

Supporting Information Available

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.joc.2c02217.

  • Computational methods, Cartesian coordinates, ORTEP structures, energies/enthalpies, and geometric proof of inverted C atoms (PDF)

  • Energy results (XLSX)

  • IRC data (XLSX)

  • Inverted carbon atom data (XLSX)

  • IRC data and video (wB97X-D_cc-pVTZ.IRC_path a_(Tricyclo[1_1_0_0(2,4)but-1-yl)carbene_(8)) MOV)

  • IRC data and video (wB97X-D_cc-pVTZ.IRC_path b_Tricyclo[1_1_1_0(1,3)]pent-2-ylidene_(9)) (MOV)

  • IRC data and video (wB97X-D_cc-pVTZ.IRC_path c_Tricyclo[2_1_0_0(1,3)]pent-2-ylidene_(10)) (MOV)

  • IRC data and video (wB97X-D_cc-pVTZ.IRC_path d_4-Methylenebicyclo[1_1_0]but-2-ylidene_(11)) (MOV)

The authors declare no competing financial interest.

Supplementary Material

jo2c02217_si_001.pdf (926KB, pdf)
jo2c02217_si_002.xlsx (19.8KB, xlsx)
jo2c02217_si_003.xlsx (1.4MB, xlsx)
jo2c02217_si_004.xlsx (19.1KB, xlsx)
jo2c02217_si_005.mov (7.7MB, mov)
jo2c02217_si_006.mov (8.1MB, mov)
jo2c02217_si_007.mov (7.6MB, mov)
jo2c02217_si_008.mov (7.9MB, mov)

References

  1. Tetracyclo[2.1.0.01,3.02,4]pentane.
  2. a Veis L.; Čársky P.; Pittner J.; Michl J. Coupled Cluster Study of Polycyclopentanes: Structure and Properties of C5H2n, n = 0–4. Collect. Czech. Chem. Commun. 2008, 73, 1525–1551. 10.1135/cccc20081525. [DOI] [Google Scholar]; b Levin M. D.; Kaszynski P.; Michl J. Bicyclo[1.1.1]pentanes, [n]Staffanes, [1.1.1]Propellanes, and Tricyclo[2.1.0.02,5]pentanes. Chem. Rev. 2000, 100, 169–234. 10.1021/cr990094z. [DOI] [PubMed] [Google Scholar]; c Balaji V.; Michl J. New Strained Organic Molecules: Theory Guides Experiment. Pure Appl. Chem. 1988, 60, 189–194. 10.1351/pac198860020189. [DOI] [Google Scholar]; d Ekholm M.; Nevalainen V. Automatic Evaluation of Stabilities of Bridged and/or Fused Ring Compounds. Zero-Bridged Rings of Size 3–6. Finn. Chem. Lett. 1989, 16, 107–112. [Google Scholar]
  3. a Lewars E.Personal Computers in Computational Chemistry. In Mathematical Physics in Theoretical Chemistry; Blinder S. M., House J. M., Eds.; Developments in Physical and Theoretical Chemistry, House J. M., Ed.; Elsevier: Amsterdam, 2019; Chapter 7, pp 219–260. [Google Scholar]; b Lewars E. G.Modeling Marvels: Computational Anticipation of Novel Molecules ;Springer: Dordrecht, The Netherlands, 2008; Chapter 13, pp 227–256 (cf. pp 235–237, 243–251). [Google Scholar]
  4. a Maier G. Tetrahedrane and Cyclobutadiene. Angew. Chem., Int. Ed. Engl. 1988, 27, 309–332. 10.1002/anie.198803093. [DOI] [Google Scholar]; b Balci M.; McKee M. L.; Schleyer P. v. R. Theoretical Study of Tetramethyl- and Tetra-tert-butyl-Substituted Cyclobutadiene and Tetrahedrane. J. Phys. Chem. A 2000, 104, 1246–1255. 10.1021/jp9922054. [DOI] [Google Scholar]; c Nemirowski A.; Reisenauer H. P.; Schreiner P. R. Tetrahedrane—Dossier of an Unknown. Chem.—Eur. J. 2006, 12, 7411–7420. 10.1002/chem.200600451. [DOI] [PubMed] [Google Scholar]; d Schulman J. M.; Venanzi T. J. A Theoretical Study of the Tetrahedrane Molecule. J. Am. Chem. Soc. 1974, 96, 4739–4746. 10.1021/ja00822a002. [DOI] [Google Scholar]; e Dodziuk H.(CH)2n Cage Structures, ‘in’-‘out’ Isomerism in Perhydrogenated Fullerenes and Planar Cyclohexane Rings. In Strained Hydrocarbons: Beyond the van’t Hoff and Le Bel Hypothesis ;Dodziuk H., Ed.; Wiley-VCH: Weinheim, Germany, 2009; Chapter 2.4, pp 59–69. [Google Scholar]; f Hopf H.Classics in Hydrocarbon Chemistry: Syntheses, Concepts, Perspectives ;Wiley-VCH: Weinheim, Germany, 2000. [Google Scholar]
  5. a Wiberg K. B. Bent Bonds in Organic Compounds. Acc. Chem. Res. 1996, 29, 229–234. 10.1021/ar950207a. [DOI] [Google Scholar]; b Wiberg K. B.; Bader R. F. W.; Lau C. D. H. Theoretical Analysis of Hydrocarbon Properties. 1. Bonds, Structures, Charge Concentrations, and Charge Relaxations. J. Am. Chem. Soc. 1987, 109, 985–1001. 10.1021/ja00238a004. [DOI] [Google Scholar]; c Wiberg K. B. The Concept of Strain in Organic Chemistry. Angew. Chem., Int. Ed. Engl. 1986, 25, 312–322. 10.1002/anie.198603121. [DOI] [Google Scholar]; d de Meijere A. Bonding Properties of Cyclopropane and Their Chemical Consequences. Angew. Chem., Int. Ed. Engl. 1979, 18, 809–886. 10.1002/anie.197908093. [DOI] [Google Scholar]
  6. Wiberg K. B.Strained Hydrocarbons: Structures, Stability, and Reactivity. In Reactive Intermediate Chemistry; Moss R. A., Platz M. S., Jones M. Jr., Eds.; Wiley-Interscience: Hoboken, NJ, 2004; Part 1, Chapter 15, pp 717–740. [Google Scholar]
  7. Karton A.; Schreiner P. R.; Martin J. M. L. Heats of Formation of Platonic Hydrocarbon Cages by Means of High-Level Thermochemical Procedures. J. Comput. Chem. 2016, 37, 49–58. 10.1002/jcc.23963. [DOI] [PubMed] [Google Scholar]
  8. a Eaton P. E.; Cole T. W. Cubane. J. Am. Chem. Soc. 1964, 86, 3157–3158. 10.1021/ja01069a041. [DOI] [Google Scholar]; b Paquette L. A.; Ternansky R. J.; Balogh D. W.; Kentgen G. Total Synthesis of Dodecahedrane. J. Am. Chem. Soc. 1983, 105, 5446–5450. 10.1021/ja00354a043. [DOI] [Google Scholar]
  9. Hoffmann R. How Should Chemists Think?. Sci. Am. 1993, 268 (2), 66–73. 10.1038/scientificamerican0293-66.8446882 [DOI] [Google Scholar]
  10. Greenberg A.; Liebman J. F.. Strained Organic Molecules ;Academic: New York, 1978; Chapter 6.B, pp 343–369. [Google Scholar]
  11. a Mieusset J.-L.; Brinker U. H. On the Existence of Uncharged Molecules with a Pyramidally Coordinated Carbon: The Cases of Pentacyclo[4.3.0.02,9.03,8.07,9]non-4-ene and Heptacyclo[7.6.0.01,5.05,15.06,14.010,14.010,15]pentadecane. J. Org. Chem. 2005, 70, 10572–10575. 10.1021/jo051847m. [DOI] [PubMed] [Google Scholar]; b Mlinarić-Majerski K.Molecules with Inverted Carbon Atoms. In Strained Hydrocarbons: Beyond the van’t Hoff and Le Bel Hypothesis; Dodziuk H., Ed.; Wiley-VCH: Weinheim, Germany, 2009; Chapter 2.1, pp 33–43. [Google Scholar]
  12. Wu W.; Gu J.; Song J.; Shaik S.; Hiberty P. C. The Inverted Bond in [1.1.1]Propellane Is a Charge-Shift Bond. Angew. Chem., Int. Ed. 2009, 48, 1407–1410. 10.1002/anie.200804965. [DOI] [PubMed] [Google Scholar]
  13. Skell P. S.; Woodworth R. C. Structure of Carbene, CH2. J. Am. Chem. Soc. 1956, 78, 4496–4497. 10.1021/ja01598a087. [DOI] [Google Scholar]
  14. Hine J.Divalent Carbon; Ronald: New York, 1964. [Google Scholar]
  15. Kirmse W.Carbene Chemistry, 2nd ed.; Academic: New York, 1971. [Google Scholar]
  16. Hoffmann R.; Zeiss G. D.; Van Dine G. W. The Electronic Structure of Methylenes. J. Am. Chem. Soc. 1968, 90, 1485–1499. 10.1021/ja01008a017. [DOI] [Google Scholar]
  17. a Carbenes:Jones M. Jr., Moss R. A., Eds.; Reactive Intermediates in Organic Chemistry, Olah G. A., Ed.; Wiley-Interscience: New York, 1973. [Google Scholar]; b Carbenes:Moss R. A., Jones M. Jr., Eds.; Reactive Intermediates in Organic Chemistry, Olah G. A., Ed.; Wiley-Interscience: New York, 1975. [Google Scholar]
  18. Jones M. Jr. Carbenes. Sci. Am. 1976, 234 (2), 101–113. 10.1038/scientificamerican0276-101. [DOI] [Google Scholar]
  19. Wentrup C.Reactive Molecules: The Neutral Reactive Intermediates in Organic Chemistry; Wiley: New York, 1984; Chapter 4, pp 162–264. [Google Scholar]
  20. Carbene (Carbenoide): Regitz M., Ed. Methoden der Organischen Chemie (Houben–Weyl); Thieme: Stuttgart, 1989; Vol. E19b. (Ger.). [Google Scholar]
  21. Jones W. M.; Brinker U. H.. Some Pericyclic Reactions of Carbenes. In Pericyclic Reactions; Marchand A. P., Lehr R. E., Eds.; Academic: New York, 1977; pp 109–198. [Google Scholar]
  22. Kinetics and Spectroscopy of Carbenes and Biradicals; Platz M. S., Ed.; Plenum: New York, 1990. [Google Scholar]
  23. a Advances in Carbene Chemistry; Brinker U. H., Ed.; JAI: Greenwich, CT, 1994; Vol. 1. [Google Scholar]; b Advances in Carbene Chemistry; Brinker U. H., Ed.; JAI: Stamford, CT, 1998; Vol. 2. [Google Scholar]; c Advances in Carbene Chemistry ;Brinker U. H., Ed.; Elsevier: Amsterdam, 2001; Vol. 3. [Google Scholar]
  24. Carbene Chemistry: From Fleeting Intermediates to Powerful Reagents; Bertrand G., Ed.; Dekker: New York, 2002. [Google Scholar]
  25. Jones M. Jr.; Moss R. A.. Singlet Carbenes. In Reactive Intermediate Chemistry; Moss R. A., Platz M. S., Jones M. Jr., Eds.; Wiley-Interscience: Hoboken, NJ, 2004; Part 1, Chapter 7, pp 273–328. [Google Scholar]
  26. Contemporary Carbene Chemistry ;Moss R. A., Doyle M. P., Eds. Wiley Series of Reactive Intermediates in Chemistry and Biology; Rokita S. E., Ed.; Wiley: Hoboken, NJ, 2014. [Google Scholar]
  27. Bachrach S. M.Computational Organic Chemistry, 2nd ed.; Wiley: Hoboken, NJ, 2014; Chapter 5, pp 297–372. [Google Scholar]
  28. Scott L. T.; Jones M. Jr. Rearrangements and Interconversions of Compounds of the Formula (CH)n. Chem. Rev. 1972, 72, 181–202. 10.1021/cr60276a004. [DOI] [Google Scholar]
  29. (Tricyclo[1.1.0.02,4]but-1-yl)methylene.
  30. Tomioka H.Triplet Carbenes. In Reactive Intermediate Chemistry; Moss R. A., Platz M. S., Jones M. Jr., Eds.; Wiley-Interscience: Hoboken, NJ, 2004; Part 1, Chapter 9, pp 375–461. [Google Scholar]
  31. a Jensen P.; Bunker P. R. The Potential Surface and Stretching Frequencies of X̃3B1 Methylene (CH2) Determined from Experiment Using the Morse Oscillator-Rigid Bender Internal Dynamics Hamiltonian. J. Chem. Phys. 1988, 89, 1327–1332. 10.1063/1.455184. [DOI] [Google Scholar]; b Gaspar P. P.; Hammond G. S.. Spin States in Carbene Chemistry. In Carbenes; Moss R. A., Jones M. Jr., Eds.; Wiley: New York, 1975; Vol. 2, Chapter 6, pp 207–362. [Google Scholar]
  32. a Wu J. I-C.; Schleyer P. v. R. Hyperconjugation in Hydrocarbons: Not Just a “Mild Sort of Conjugation”. Pure Appl. Chem. 2013, 85, 921–940. 10.1351/PAC-CON-13-01-03. [DOI] [Google Scholar]; b Alabugin I. V.; dos Passos Gomes G.; Abdo M. A. Hyperconjugation. WIREs Comput. Mol. Sci. 2019, 9, e1389 10.1002/wcms.1389. [DOI] [Google Scholar]
  33. a Gronert S.; Keeffe J. R.; More O’Ferrall R. A.. Carbene Stability. In Contemporary Carbene Chemistry; Moss R. A., Doyle M. P., Eds.; Wiley Series of Reactive Intermediates in Chemistry and Biology; Rokita S. E., Ed.; Wiley: Hoboken, NJ, 2014; Part 1, Chapter 1, pp 3–39. [Google Scholar]; b Rod A. R.; Vessally E. Alkyl Substituted Effects on Carbenes: DFT ab initio Calculations. Asian J. Chem. 2007, 19, 1709–1713. [Google Scholar]; c Stracener L. L.; Halter R. J.; McMahon R. J.; Castro C.; Karney W. L. Singlet–Triplet Energy Separation of Cyclobutylidene. J. Org. Chem. 2000, 65, 199–204. 10.1021/jo9914925. [DOI] [PubMed] [Google Scholar]; d Sulzbach H. M.; Platz M. S.; Schaefer H. F. III; Hadad C. M. Hydrogen Migration vs Carbon Migration in Dialkylcarbenes. A Study of the Preferred Product in the Carbene Rearrangements of Ethylmethylcarbene, Cyclobutylidene, 2-Norbornylidene, and 2-Bicyclo[2.1.1]hexylidene. J. Am. Chem. Soc. 1997, 119, 5682–5689. 10.1021/ja970181d. [DOI] [Google Scholar]
  34. a Rosenberg M. G.; Brinker U. H. Tricyclo[2.1.0.02,5]pent-3-ylidene: Stereoelectronic Control of Bridge-Flapping within a Nonclassical Nucleophilic Carbene. J. Org. Chem. 2021, 86, 878–891. 10.1021/acs.joc.0c02414. [DOI] [PMC free article] [PubMed] [Google Scholar]; b Rosenberg M. G.; Brinker U. H. Diastereoselective Carbenes: Stereoelectronic Control of Bent Singlet trans-2’-Substituted Cyclobutylcarbenes. Tetrahedron Lett. 2018, 59, 645–649. 10.1016/j.tetlet.2018.01.006. [DOI] [Google Scholar]; c Knoll W.; Kaneno D.; Bobek M. M.; Brecker L.; Rosenberg M. G.; Tomoda S.; Brinker U. H. Intra- and Intermolecular Reaction Selectivities of γ-Substituted Adamantanylidenes. J. Org. Chem. 2012, 77, 1340–1360. 10.1021/jo202132c. [DOI] [PubMed] [Google Scholar]; d Kaneno D.; Tomoda S. Origin of Facial Diastereoselection. Evidence for Negative Role of Antiperiplanar Hyperconjugation Effects in the Transition State of Carbene Insertion. Org. Lett. 2003, 5, 2947–2949. 10.1021/ol035073c. [DOI] [PubMed] [Google Scholar]
  35. Rosenberg M. G.; Brinker U. H. Bent Singlet Cyclobutylcarbene: Computed Geometry, Properties, and Product Selectivity of a Nonclassical Carbene. J. Org. Chem. 2019, 84, 11873–11884. 10.1021/acs.joc.9b01732. [DOI] [PubMed] [Google Scholar]
  36. Bally T.Matrix Isolation. In Reactive Intermediate Chemistry; Moss R. A., Platz M. S., Jones M. Jr., Eds.; Wiley-Interscience: Hoboken, NJ, 2004; Part 2, Chapter 17, pp 797–845. [Google Scholar]
  37. Spartan’20, version 1.1.4; Wavefunction, Inc.: Irvine, CA, 2022.
  38. Chai J.-D.; Head-Gordon M. Long-Range Corrected Hybrid Density Functionals with Damped Atom–Atom Dispersion Corrections. Phys. Chem. Chem. Phys. 2008, 10, 6615–6620. 10.1039/b810189b. [DOI] [PubMed] [Google Scholar]
  39. Csonka G. I.; Ruzsinszky A.; Perdew J. P. Estimation, Computation, and Experimental Correction of Molecular Zero-Point Vibrational Energies. J. Phys. Chem. A 2005, 109, 6779–6789. 10.1021/jp0519464. [DOI] [PubMed] [Google Scholar]
  40. Computational Chemistry Comparison and Benchmark DataBase. National Institute of Standards and Technology. http://cccbdb.nist.gov/introx.asp (accessed 2022-08-22).

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

jo2c02217_si_001.pdf (926KB, pdf)
jo2c02217_si_002.xlsx (19.8KB, xlsx)
jo2c02217_si_003.xlsx (1.4MB, xlsx)
jo2c02217_si_004.xlsx (19.1KB, xlsx)
jo2c02217_si_005.mov (7.7MB, mov)
jo2c02217_si_006.mov (8.1MB, mov)
jo2c02217_si_007.mov (7.6MB, mov)
jo2c02217_si_008.mov (7.9MB, mov)

Data Availability Statement

The data underlying this study are available in the published article and its online Supporting Information.

Articles from The Journal of Organic Chemistry are provided here courtesy of American Chemical Society

RESOURCES