syn-Dispiro­[1,3-dioxolane-2,17′-penta­cyclo­[12.2.1.16,9.02,13.05,10]octa­decane-18′,2′′-[1,3]dioxolane]-7′,15′-diene

Rulla M Kachlan; Macey C Ruble; Jacob C Timmerman; Markus Etzkorn; Daniel S Jones

doi:10.1107/S1600536810041565

. 2010 Oct 20;66(Pt 11):o2880. doi: 10.1107/S1600536810041565

syn-Dispiro[1,3-dioxolane-2,17′-pentacyclo[12.2.1.1^6,9.0^2,13.0^5,10]octadecane-18′,2′′-[1,3]dioxolane]-7′,15′-diene

Rulla M Kachlan ^a, Macey C Ruble ^a, Jacob C Timmerman ^a, Markus Etzkorn ^a,^*, Daniel S Jones ^a,^*

PMCID: PMC3009060 PMID: 21589061

Abstract

The title compound, C₂₂H₂₈O₄, is composed of a central octadecane ring and two spiro[bicyclo[2.2.1]hept[2]ene-7,2′-[1,3]dioxolane] units. This polycycle has pseudo twofold symmetry and the central cyclooctane ring has a distorted boat configuration.

Related literature

For related structures, see: Garcia et al. (1991a ▶,b ▶); Tenbusch et al. (2010 ▶). For the chemistry of syn-bisquinoxalines, see: Chou et al. (2005 ▶); Etzkorn et al. (2010 ▶).

Experimental

Crystal data

C₂₂H₂₈O₄
M _r = 356.44
Monoclinic,
a = 11.4167 (11) Å
b = 6.7354 (7) Å
c = 24.185 (2) Å
β = 103.521 (9)°
V = 1808.2 (3) Å³
Z = 4
Cu Kα radiation
μ = 0.71 mm⁻¹
T = 295 K
0.35 × 0.20 × 0.20 mm

Data collection

Enraf–Nonius CAD-4 diffractometer
8422 measured reflections
3248 independent reflections
2693 reflections with I > 2σ(I)
R _int = 0.045
3 standard reflections every 79 reflections intensity decay: 2%

Refinement

R[F ² > 2σ(F ²)] = 0.039
wR(F ²) = 0.106
S = 1.05
3248 reflections
236 parameters
H-atom parameters constrained
Δρ_max = 0.24 e Å⁻³
Δρ_min = −0.19 e Å⁻³

Data collection: CAD-4 EXPRESS (Enraf–Nonius, 1994 ▶); cell refinement: CAD-4 EXPRESS; data reduction: XCAD4 (Harms & Wocadlo, 1995 ▶); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997 ▶) and Mercury (Macrae, et al., 2006 ▶); software used to prepare material for publication: WinGX (Farrugia, 1999 ▶).

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536810041565/su2208sup1.cif

e-66-o2880-sup1.cif^{(23.7KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536810041565/su2208Isup2.hkl

e-66-o2880-Isup2.hkl^{(156.1KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Acknowledgments

This work was supported in part by funds provided by the University of North Carolina at Charlotte. Support for Research Experience for Undergraduates (REU) participant RMK was provided by the National Science Foundation, award number CHE-0851797. Many helpful discussions with T. Blake Monroe are gratefully acknowledged.

supplementary crystallographic information

Comment

The title compound is of interest as a non-chlorinated tether unit for syn-bisquinoxaline molecular tweezers. The non-chlorinated compounds are anticipated to display higher solubility in common organic solvents, thus facilitating the quantitative investigation of host–guest chemistry in solution. The title polycyclic molecule, 3, presented here was obtained by a twofold Diels-Alder reaction of cyclooctadiene and a cyclopentadieneone derivative, 1, followed by subsequent dehalogenation (Fig. 1). Larger molecular frameworks that incorporate scaffold 2a can be found in syn-bisquinoxalines that have previously been investigated for their luminescent properties (Chou et al., 2005) and for their behavior as molecular tweezers (Etzkorn et al., 2010). Compound 3 stems from the chlorinated derivative 2a, which was separated from its anti-isomer 2bvia repeated recrystallization from diethyl ether, i.e., the ether solution becomes more enriched in syn-isomer 2a. To improve the solubility of any molecular framework that is derived from scaffold 2a, we reduced the latter with sodium metal in ethanol and liquid ammonia to furnish 3 in good yield. The fully dechlorinated compound 3 did indeed show improved solubility in common organic solvents and, upon further functionalization to tweezer scaffolds, is expected to improve overall solubility.

The title molecule, 3, has pseudo 2-fold symmetry. The central cyclooctane has a distorted boat configuration (Fig. 2). The dioxalane ring (O1,C13,O2,C20,C19) has an envelope configuration with atom O2 at the flap, while ring (O3,C18,O4,C22,C21) has a half-chair configuration being twised about bond O4-C22.

A literature search revealed three related crystal structures. The first (Garcia et al., 1991a) is similar to 3, but has the anti-orientation and an open ketal structure on each of the bridgehead carbon atoms. The second (Tenbusch et al., 2010) is an octachloro derivative with the anti-orientation. The third (Garcia et al., 1991b) is an octachloro syn-structure with an open ketal arrangement on each of the bridgehead carbon atoms; this structure assumes the same distorted boat configuration as does compound 3.

Experimental

The synthesis of the title compound, 3, is described in Fig. 1. A mixture of cycloocatdiene (3 g, 29 mmol) and spiroketal (1) (15 g, 57 mmol) was refluxed in toluene (3 ml) for three hours. The off-white paste was filtered, washed with methylene chloride (75 ml), dried, and washed again with cold methanol (15 ml) to remove traces of the mono-Diels-Alder adduct. The remaining colorless solid (14.5 g, 83%) was composed of a mixture of 2a and 2 b in a 1:4 ratio, respectively. After repeated recrystallization from diethyl ether, the pure syn-isomer 2a was obtained as colorless platelets (3.7 g, 21%).

A solution of 2a (1 g, 1.58 mmol) and THF (20 ml) was added to a mixture of liquid ammonia (250 ml) and ethanol (1.5 ml). Pieces of sodium metal (0.8 g, 29.6 mmol) were slowly added over two hours; the reaction mixture was then stirred for an additional hour. The reaction was quenched with solid ammonium chloride, and the ammonia was allowed to evaporate. The residue was taken up in water (75 ml) and the aqueous phase was extracted with methylene chloride (4 x 50 ml) to yield 3 as light-brown crystals (0.490 g). Purification of 3 by column chromatography (cyclohexane: ethyl acetate [4:1], R_f= 0.11) afforded colorless crystals (0.439 g, 78%); Mp.>568 K. IR (KBr): ~ν = 2955, 2856 (CH₂), 1649 (C═C), 1473 (CH₂ bend), 1303, 1290 (C—O—C), 1243, 1224, 1084, 1046, 819, 725 cm^-1; ¹H NMR (CDCl₃; 300 MHz):δ = 6.18 (m, 4H, H-7',-8',-15',-16'), 3.98–3.90 (m, 4H, H-4,-4"), 3.85–3.76 (m, 4H, H-5,-5"), 2.86–2.72 (m, 4H, H-2',-5',-10'-13'), 2.46–2.4 (m, 4H, H-1',-6',-9',-13'); ¹³C NMR (CDCl₃; 75.6 MHz):δ = 133.7 (C-7',-8',-15',-16'), 124.8 (C-17',-18'), 64.8 (C-4,-4"), 64.1 (C-5,-5"), 53.6 (C-2',-5',-10',-13'), 37.4 (C-1',-6', -9',-14'), 25.3 (C-3',-4',-11',-10').