(2R,3R)-3-(2-Chlorophenyl)-N-phenyloxirane-2-carboxamide

In the title compound, C15H12ClNO2, the two benzene rings adopt a syn configuration with respect to the epoxy ring; the dihedral angles between the epoxy ring and the two benzene rings are 59.71 (16) and 67.58 (15)°. There is a weak intramolecular N—H⋯O bond, which may help to establish the conformation. In the crystal, the molecules are linked into a chain parallel to the b axis through intermolecular N—H⋯O hydrogen bonds.

In the title compound, C 15 H 12 ClNO 2 , the two benzene rings adopt a syn configuration with respect to the epoxy ring; the dihedral angles between the epoxy ring and the two benzene rings are 59.71 (16) and 67.58 (15) . There is a weak intramolecular N-HÁ Á ÁO bond, which may help to establish the conformation. In the crystal, the molecules are linked into a chain parallel to the b axis through intermolecular N-HÁ Á ÁO hydrogen bonds.

Comment
Optically active epoxides are highly useful intermediates as building blocks for the synthesis of biologically active compounds. They can be further transformed to key intermediates of several pharmaceutical products (Flisak et al. 1993;Porter & Skidmore, 2000;Watanabe et al. 1998;Shing et al., 2006). Various effective systems have been developed over the years for the preparation of chiral epoxides. The Darzens reaction, has proven to be one of the most powerful approaches (Zhu & Espenson,1995). We report herein the crystal structure of the title compound.
There is a weak intramolecular N-H···O bond which might induce the observed conformation. The molecules are linked into a chain parallel to the b axis through intermolecular N-H···O hydrogen bonds (Table 1, Fig. 2).
Experimental 2-chloro-N-phenylacetamide (0.17 g, 1.0 mmol) and potassium hydroxide (0.112 g, 2.0 mmol) were dissolved in acetonitrile (4 ml). To the solution was added 2-chlorophenylaldehyde (0.14 g, 1.0 mmol) at 298 K, the solution was stirred for 2 h and removal of solvent under reduced pressure, the residue was purified through column chromatography. Colourless single crystals of (I) were obtained by recrystallization from an ethanol solution.

Refinement
All H atoms attached to C atoms and N atom were fixed geometrically and treated as riding with C-H = 0.93 Å and N-H = 0.86 Å with U iso (H) = 1.2U eq (C or N) Figures   Fig. 1. The molecular structure of (I) with the atom labeling scheme. Ellipsoids are drawn at the 30% probability level. H atoms are represented as small spheres of arbitrary radii. Intramolecular hydrogen bond is shown as dashed line.

Special details
Experimental. Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.

CrysAlisPro (Oxford Diffraction, 2009)
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 > σ(F 2 ) is used only for calculating Rfactors(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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq C1 0.4506 (5