(2R)-N-[5-(4-Chlorophenyl)-1,3,4-thiadiazol-2-yl]-2-(cinnamoylamino)propanamide

In the title compound, C20H17ClN4O2S, the dihedral angle between the two benzene rings is 65.9 (1)°; the corresponding angle between the 4-chlorophenyl and thiadiazole rings is 3.4 (8)°. The conformations of the N—H and C=O bonds are anti with respect to each other. The enone groups show a trans configuration. The structure displays intermolecular N—H⋯O, C—H⋯N, C—H⋯S and C—H⋯O hydrogen bonding.

In the title compound, C 20 H 17 ClN 4 O 2 S, the dihedral angle between the two benzene rings is 65.9 (1) ; the corresponding angle between the 4-chlorophenyl and thiadiazole rings is 3.4 (8) . The conformations of the N-H and C O bonds are anti with respect to each other. The enone groups show a trans configuration. The structure displays intermolecular N-HÁ Á ÁO, C-HÁ Á ÁN, C-HÁ Á ÁS and C-HÁ Á ÁO hydrogen bonding.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: GW2052).

Comment
In our previous work, 1,3,4-thiadiazole scaffold compounds and their biological activity have been studied (Tu et al., 2008). In view of the importance of these organic materials, the title compound ( Fig. 1) was synthesized (Foroumadi et al., 1999;Levy & Palmer 1942;Song et al., 1992) and its crystal structure is reported here. The structure of title compound, C 20 H 17 ClN 4 O 2 S, has orthorhombic (P2 1 2 1 2 1 ) symmetry. The dihedral angles between the p-cholobenzene and thiadiazol rings is 3.4 (8) °, the corresponding values between the two benzene rings are measured to 65.9 (1)°. The conformations of the N-H and C=O bonds are anti with respect to each other. The enone groups are trans configurated. Bond lengths and angles are in normal ranges and comparable to those in related structures (Gowda et al., 2008;Fun et al., 2008;Thiruvalluvar et al., 2008). In the crystal structure, molecules are linked through intermolecular hydrogen bonds forming a three-dimensional network (Table 1, Figure 2).
Experimental N,N-Dicyclohexylcarbodiimide (5.7 mmol) was added to a cooled solution of N-cinnamoyl-D-alanine (5.6 mmol) and Nhydroxysuccinimide (5.6 mmol) in freshly distillation dioxane (30 ml). The reaction mixture was stirred overnight at room temperature. The insoluble material was filtered off and washed with cold dioxane. 2-Amino-5-(4-choloxyphenyl)-1,3,4thiadiazole (5.5 mmol) was added to the filtrate and the reaction mixture was stirred for 48 hr at room temperature. The solvent was removed under reduced pressure. The residual was dissolved in EtOAc and the insoluble material was filtered off. The filtrate was washed successively with saturated Na 2 CO 3 solution(20 ml, x 3), water(20 ml, x 1), 0.1 M HCl(20 ml, x 3) and water(20 ml, x 1). The organic layer evaporated in vacuo, the residual was recrystallized from methanol. Colorless block-shaped single crystals of the title compound suitable for X-ray diffraction analysis precipitated after several days.

Refinement
H atoms were positioned geometrically and refined using a riding model using SHELXL97 default values (U ĩso (H) = 1.2 U eq (C) for CH and CH 2 groups and U ĩso (H) = 1.5 U eq (C) for CH 3 ). Refinement with all data (Friedel opposites not merged) led to an unsuitably large error of the Flack parameter. The final refinement was therefore performed with a data set with merged Friedel pairs, hence the calculated Flack parameter is meaningless. The absolute configuration is nevertheless undoubtly as described since enantiomerically pure starting compounds were used and the reaction conditions are not condidered to lead to racemization or inversion.   Symmetry codes: (i) x+1/2, −y+1/2, −z; (ii) x−1/2, −y+1/2, −z; (iii) x+1, y, z; (iv) x−1/2, −y+3/2, −z.