(2E)-4-(4-Bromophenyl)-2-{2-[(1E)-cyclopentylidene]hydrazin-1-ylidene}-3-phenyl-2,3-dihydro-1,3-thiazole

In the title compound, C20H18BrN3S, the cyclopentane ring adopts a half-chair conformation. The 4-bromophenyl and phenyl rings make dihedral angles of 34.6 (1) and 68.52 (6)°, respectively, with the dihydrothiazole ring. In the crystal, the molecules pack in sheets approximately parallel to (101) which are formed by weak C—H⋯Br interactions

In the title compound, C 20 H 18 BrN 3 S, the cyclopentane ring adopts a half-chair conformation. The 4-bromophenyl and phenyl rings make dihedral angles of 34.6 (1) and 68.52 (6) , respectively, with the dihydrothiazole ring. In the crystal, the molecules pack in sheets approximately parallel to (101) which are formed by weak C-HÁ Á ÁBr interactions

Comment
The anti-microbial activities of substituted thiazoles are well established because they possess the (S-C=N) toxophoric unit (Mahajan et al., 2008). Thiazoles were reported to possess anti-cancer (Abbs et al., 2008), anti-tubercular (Chowki et al., 2008), anti-inflammatory (Karabasanagouda et al., 2008), analgesic (Basavaraja et al., 2008) anthelmintic (Bhusari et al., 2000) and diuretic (Basawaraj et al., 2005) activities. Based on these facts and as part of our on-going study we herein report the synthesis and crystal structure of the title compound.
In the crystal, the molecules of (I) pack in sheets approximately parallel to (101) which are formed by weak C-H···Br interactions ( Table 1, Fig. 2).

Experimental
A mixture of 1 mmol (233 mg) of cyclopentan-1-one N-phenylthiosemicarbazone and 1 mmol (278 mg) of 2-bromo-1-(4bromophenyl)ethanone in 30 ml e thanol was stirred and refluxed at 350 K. The reaction was monitored by TLC until completion. On cooling, a solid yellow product precipitated which was filtered off and recrystallized from ethanol to furnish yellow crystals, suitable for X-ray diffraction.

Refinement
H-atoms were placed in calculated positions (C-H = 0.95 -0.99 Å) and included as riding contributions with isotropic displacement parameters 1.2 times those of the attached carbon atoms. At the conclusion of refinement with all atoms at unit occupancy, the largest difference peak appeared in the vicinity of Br1. Refinement of this as a second component of a disorder of Br1 led to improvement in the results and a more realistic value for U(iso) for Br1. The geometry associated with the minor component (Br1A) suggests that there is a small amount of "whole molecule" disorder but since the refined occupancy of Br1A is only 0.02, there is not enough information from the final difference map to reliably position the remainder of the minor component.  The title compound with 50% probability displacement ellipsoids for non-hydrogen atoms.

Figure 2
Packing viewed down the b axis with the C-H···Br interactions shown as dotted lines.

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 > σ(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 Rfactors based on ALL data will be even larger. H-atoms were placed in calculated positions (C-H = 0.95 -0.99 Å) and included as riding contributions with isotropic displacement parameters 1.2 times those of the attached carbon atoms. At the conclusion of refinement with all atoms at unit occupancy, the largest difference peak appeared in the vicinity of Br1. Refinement of this as a second component of a disorder of Br1 led to improvement in the results and a more realistic value for U(iso) for Br1. The geometry associated with the minor component (Br1A) suggests that there is a small amount of "whole molecule" disorder but since the refined occupancy of Br1A is only 0.02, there is not enough information from the final difference map to reliably position the remainder of the minor component.

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