Ethyl 4-(3-bromo-2-thienyl)-2-oxo-6-phenylcyclohex-3-ene-1-carboxylate

The title compound, C19H17BrO3S, crystallizes with two molecules in the asymmetric unit. The methyl group of one molecule is disordered approximately equally over two positions. The dihedral angles between the thiophene and phenyl groups are 68.5 (2) and 67.5 (2)° in the two molecules.

The title compound, C 19 H 17 BrO 3 S, crystallizes with two molecules in the asymmetric unit. The methyl group of one molecule is disordered approximately equally over two positions. The dihedral angles between the thiophene and phenyl groups are 68.5 (2) and 67.5 (2) in the two molecules.

Experimental
The Swedish research council (VR) is acknowledged for providing funding for the single-crystal diffractometer.
of biological activities (Dimmock et al., 1999). An important feature of chalcones and their heteroanalogs is the ability to act as activated unsaturated systems in conjugated addition reactions of carbanions in the presence of basic catalysts (House, 1972). This type of reaction may be exploited with the goal of obtaining highly functionalized cyclohexene derivatives (Tabba et al., 1995). In view of the importance of these derivatives and continuing our efforts in this field (Fischer et al., 2007a;2007b), a new derivative, the title compound, (I), has been prepared and its crystal structure is reported in this paper.
The structure of (I) contains two molecules in an asymmetric unit (Figs. 1 and 2). A methyl C-atom of methoxy group in the molecule 1, presented in Fig. 1 is disordered over two sites C19 and C19'. The geometry in the two molecules is unexceptional. The crystal packing is stabilized by van der Waals forces. The dihedral angles between the thiophene groups and phenyl groups in the two molecules are 68.5 (2) and 67.5 (2)°.

Refinement
Hydrogen atoms were placed at calculated positions with C-H distances: 0.95, 0.98 and 0.99 Å for aromatic, methyl and methylene groups, respectively, and were included in the refinements in riding mode with U iso = 1.2 and 1.5 time U eq of the carrier atoms for non-methyl and methyl groups, respectively. A methyl C-atom of methoxy group in molecule 1 was disordered over two positions C19 and C19' with site occupation factors of 0.513 (6) and 0.487 (6), respectively. Fig. 1. The structure of molecule 1 in the asymmetric unit; displacement ellipsoids have been plotted at the 50% probability level. Only one of the conformational isomers is shown.

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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.