Cyclohexane-1,3-diyl bis(N-phenylcarbamate)

The asymmetric unit of the title compound, C20H22N2O4, comprises two crystallographically independent molecules (A and B) with slightly different geometries. The dihedral angle between the two terminal phenyl rings is 61.7 (1)° in molecule A and 29.6 (1)° in B. The cyclohexane rings adopt chair conformations. In the crystal packing, intermolecular N—H⋯O hydrogen bonds interconnect adjacent molecules into a ladder-like structure along the c axis incorporating R 2 2(20) ring motifs. The crystal packing is further stabilized by weak intermolecular C—H⋯π interactions.

The asymmetric unit of the title compound, C 20 H 22 N 2 O 4 , comprises two crystallographically independent molecules (A and B) with slightly different geometries. The dihedral angle between the two terminal phenyl rings is 61.7 (1) in molecule A and 29.6 (1) in B. The cyclohexane rings adopt chair conformations. In the crystal packing, intermolecular N-HÁ Á ÁO hydrogen bonds interconnect adjacent molecules into a ladder-like structure along the c axis incorporating R 2 2 (20) ring motifs. The crystal packing is further stabilized by weak intermolecular C-HÁ Á Á interactions.

Comment
Carbamates are a well-known class of organic compounds. They can be prepared by nickel-catalyzed coupling of CO 2 and amines (Niu et al., 2007), by stirring of alcohols including steroids as well as primary and secondary alcohols, polyols, phenols with sodium cyanate and trifluoroacetic acid (Loev & Kormendy, 1963), by carbonylation of aromatic nitro compounds (Lapidus et al., 1987), by the reaction of isocyanates with alcohols in presence of Lewis acid (Ibuka et al., 1985) and by the reaction of an amine and an alcohol with phosgene. Phytosterol, β-sitosterol, stigmasterol, cholesterol, cyclohexanol and α-terpineol react with phenyl isocyanate to give carbamates (Banerjee et al., 1978;Graia et al., 2009;Ghalib et al., 2010).
In the present work, the title compound has been synthesized by the reaction of cyclohexane-1,3-diol with phenylisocyanate in the presence of catalytic amount of HCl in chloroform solvent.
The asymmetric unit of the title compound comprises of two crystallographically independent molecules, designated A and B (Fig. 1). The orientation of the C1-C6 phenyl ring with respect to the rest of the molecule is different in A and B, as shown in the superposition of the non-H atoms of molecules A and B (Fig. 2) using XP in SHELXTL (Sheldrick, 2008); the r.m.s. deviation is 0.474 Å.

Experimental
A mixture of cyclohexane-1,3-diol (1.005 ml) and phenyl isocyanate (2.174 ml) in a 1:2 molar ratio was stirred in chloroform for 30 minutes in the presence of catalytic amount of HCl. The reaction mixture was dried with rota vapor at low pressure and then crystallized in a 1:1 mixture of chloroform and alcohol to afford colourless needle-like single crystals (yield: 2.60 g, m.p. 489.2 K). The melting point was taken using a Thermo Fisher digital melting point apparatus of IA9000 series and is uncorrected supplementary materials sup-2 Refinement N-bound H atoms were located in a difference Fourier map and allowed refined freely [range of N-H = 0.83 (2)-0.92 (3) Å]. The remaining H atoms were placed in their calculated positions, with C-H = 0.93-0.98 Å, and refined using a riding model, with U iso (H) = 1.2U eq (C). Fig. 1. The asymmetric unit of the title compound, showing 50% probability displacement ellipsoids for non-H atoms and the atom-numbering scheme.

Special details
Experimental. The crystal was placed in the cold stream of an Oxford Cryosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1)K.
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2sigma(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.