N-(4-Bromophenyl)-2-(2-thienyl)acetamide

The thienyl ring in the title compound, C12H10BrNOS, is disordered over two diagonally opposite positions, the major component having a site-occupancy factor of 0.660 (5). The molecule is twisted as evidenced by the dihedral angles of 70.0 (4) and 70.5 (6)° formed between the benzene ring and the two orientations of the disordered thiophene ring. Linear supramolecular chains along the a axis are found in the crystal structure through the agency of N—H⋯O hydrogen bonding.

The thienyl ring in the title compound, C 12 H 10 BrNOS, is disordered over two diagonally opposite positions, the major component having a site-occupancy factor of 0.660 (5). The molecule is twisted as evidenced by the dihedral angles of 70.0 (4) and 70.5 (6) formed between the benzene ring and the two orientations of the disordered thiophene ring. Linear supramolecular chains along the a axis are found in the crystal structure through the agency of N-HÁ Á ÁO hydrogen bonding.
The use of the EPSRC X-ray crystallographic service at the University of Southampton, England and the valuable assistance of the staff there is gratefully acknowledged. JLW acknowledges support from CAPES (Brazil).

Comment
The various uses, for example, as dyestuffs, flavour agents, drugs, and inhibitors, have been well documented for 2-substituted thiophenes related to the title compound (Campaigne, 1984). Thiophenes are present in many natural and synthetic products that have a wide range of pharmacological activities (Kleemann et al., 2006). The in vitro antimycobacterial activities of a series of N-(aryl)-2-thiophen-2-ylacetamide derivatives were recently investigated and encouraging activities were detected for some of these (Lourenço et al., 2007). The search for new drugs having antibacterial activity against Mycobacterium tuberculosis is a vital task due to the increase of multi-drug resistant tuberculosis (MDR-TB) and AIDS cases worldwide, and the increasing resistance to the currently used main line drugs such as isoniazid and rifampin (http://www.who.int/tdr/diseases/tb/default.htm). Recently, we reported the structure of N-(2,6-dimethylphenyl)-2-(thiophen-2-yl)acetamide (Ferreira et al., 2009) and as a continuation of these studies, the title thiophene derivative, (I), is described.
The molecular structure of (I), Fig. 1, is twisted as seen in the values of the C6-N1-C7-C8 and S1-C1-C5-C6 torsion angles of 35.0 (5) and 88.4 (4) °, respectively; the S1'-C1-C5-C6 torsion angle for the minor component of the disordered thiophene ring is -89.9 (5) °. The dihedral angle formed between the thiophene and benzene rings is 70.0 (4) °; the equivalent angle involving the minor component of the thiophene ring is 70.5 (6) °. The anti-conformation of the amide group allows for the formation of linear supramolecular chains along the a axis via N-H···O hydrogen bonding, Fig. 2 and Table 1.

Experimental
A solution of 4-bromoaniline (2 mmol) and 2-thienylacetyl chloride (2 mmol) in tetrahydrofuran (20 ml) was stirred for 2 h at room temperature, water (30 ml) added and the mixture was extracted with ethyl acetate (2 x 20 ml). The combined organic layers were washed with saturated aqueous NaHCO 3 and brine, dried over MgSO 4 , filtered, and rotary evaporated to give the crude product, (yield 96%), which was recrystallized from EtOH; m.pt.

Refinement
The C-bound H atoms were geometrically placed (C-H = 0.95-0.99 Å) and refined as riding with U iso (H) = 1.2U eq (C).
The N-H atom was located in a difference map and refined with the distance restraint N-H = 0.88±0.01 and with U iso (H) = 1.2U eq (N). The thienyl ring was disordered with two diagonally opposed positions resolved for the S1 and C4 atoms (the anisotropic displacement parameters for the two components of the C4 atom were constrained to be equal). The major component had a site occupancy factor = 0.660 (5).