Di-tert-butyl N,N′-(octa­hydro­penta­lene-2,5-di­yl)dicarbamate

Amol M Kendhale; Rajesh G Gonnade; Gangadhar J Sanjayan

doi:10.1107/S1600536808014876

. 2008 May 24;64(Pt 6):o1149. doi: 10.1107/S1600536808014876

Di-tert-butyl N,N′-(octahydropentalene-2,5-diyl)dicarbamate

Amol M Kendhale ^a, Rajesh G Gonnade ^b,^*, Gangadhar J Sanjayan ^a

PMCID: PMC2961559 PMID: 21202657

Abstract

In the molecule of the title compound, C₁₈H₃₂N₂O₄, the central bicyclo[3.3.0]octane (octahydropentalene) has a rigid ring junction. Both rings of the bicyclo[3.3.0]octane unit adopt an envelope conformation, and the flexible tert-butylcarbamoyl side chains each have an extended conformation. Such a constrained bicyclo[3.3.0]octane aliphatic template is of interest with respect to the design of novel self-assembling motifs. Molecules related by c-glide symmetry are linked via intermolecular N—H⋯O hydrogen bonds, forming a two-dimensional layer structure. Neighboring layers are weakly associated along the a axis due to the close approach of the tert-butylcarbamoyl groups (2.55 Å).

Related literature

For related literature, see: Bertz et al. (1982 ▶); Kendhale et al. (2008 ▶); Yates et al. (1960 ▶); Yeo et al. (2006 ▶).

Experimental

Crystal data

C₁₈H₃₂N₂O₄
M _r = 340.46
Monoclinic,
a = 33.161 (17) Å
b = 6.060 (3) Å
c = 9.926 (5) Å
β = 95.594 (9)°
V = 1985.2 (18) Å³
Z = 4
Mo Kα radiation
μ = 0.08 mm⁻¹
T = 297 (2) K
0.64 × 0.13 × 0.08 mm

Data collection

Bruker SMART APEX diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2003 ▶) T _min = 0.951, T _max = 0.994
9395 measured reflections
3479 independent reflections
2863 reflections with I > 2σ(I)
R _int = 0.026

Refinement

R[F ² > 2σ(F ²)] = 0.056
wR(F ²) = 0.133
S = 1.08
3479 reflections
271 parameters
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.17 e Å⁻³
Δρ_min = −0.14 e Å⁻³

Data collection: SMART (Bruker, 2003 ▶); cell refinement: SAINT (Bruker, 2003 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: ORTEP-3 (Farrugia, 1997 ▶); software used to prepare material for publication: SHELXTL (Sheldrick, 2008 ▶).

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536808014876/wk2086sup1.cif

e-64-o1149-sup1.cif^{(21.5KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536808014876/wk2086Isup2.hkl

e-64-o1149-Isup2.hkl^{(170.6KB, hkl)}

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

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N2—H2⋯O3ⁱ	0.86	2.11	2.954 (3)	167
N1—H1⋯O1ⁱⁱ	0.86	2.19	3.022 (3)	162

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Symmetry codes: (i) Inline graphic ; (ii) .

Acknowledgments

AMK is the recipient of a Senior Research Fellowship from the Council of Scientific and Industrial Research (CSIR), New Delhi, India.

supplementary crystallographic information

Comment

The skeleton of bicyclo[3.3.0]octane is interesting because it has a rigid ring junction as well as conformationally flexible side groups (Bertz et al., 1982; Yates et al., 1960). Depending on the substituents, it can adopt one of three different conformations in a given circumstance (Yeo et al., 2006). In the context of our interest in extending the applicability of bicyclo[3.3.0]octane as a self-assembling motif (Kendhale et al., 2008), the title compound (I) has been synthesized and here we report its crystal structure.

The two five-membered rings of the bicyclo[3.3.0]octane subunit adopt an exo/endo envelope conformation, while the flexible tert-Butylcarbamoyl group takes an extended conformation (Fig. 1).

In the crystal, molecules related by c-glide symmetry are linked via intermolecular N—H···O hydrogen bonds (Table 1) forming a layered arrangement (Fig.2). These layers are weakly associated along the a axis due to the close approach of the bulkier tert-butylcarbamoy group (2.55 Å).

Experimental

Tetramethylbicyclo[3.3.0]octane-3,7-dione-2,4,6,8-tetracarboxylate, bicyclo[3.3.0]octane-3,7-dione and 2, 5-dihydroxy-bicyclo[3.3.0]octane were prepared according to the literature procedure (Bertz et al., 1982; Yeo et al., 2006). The 2, 5-dihydroxy-bicyclo[3.3.0]octane (3.86 g, 27.183 mmol) was treated with methanesulfonyl chloride (6.31 ml, 9.34 g, 81.549 mmol) and triethyl amine (11.36 ml, 8.25 g, 81.549 mmol) in DCM (50 ml) at room temperature for 12 h to obtain 2,5-dimethanesulfonyloxy bicyclo[3.3.0]octane. Nucleophilic displacement of 2,5-dimethanesulfonyloxy bicyclo[3.3.0]octane (6 g, 20.134 mmol) by sodium azide (13.08 g, 201.34 mmol) in DMF (40 ml) at 343 K for 24 h, delivered 2,5-diazido-bicyclo[3.3.0]octane. The 2,5-diazido-bicyclo[3.3.0]octane (0.5 g, 2.6041 mmol) was hydrogenated in the presence of Pd/c-methanol (20 ml) system, and in situ protection with tert-Butyl Dicarbonate (Boc)2O, (1.7 g, 7.812 mmol), afforded the required 5-tert-Butoxycarbonylamino-octahydro-pentalen-2-yl)-carbamic acid tert-butyl ester (0.61 g, 69%). Colourless needles suitable for X-ray diffraction were obtained by slow evaporation of a solution in methanol-ethyl acetate (1:4) mixture at room temperature.