N-[1-(5-Acetamido-3-acetyl-2-methyl-2,3-dihydro-1,3,4-thiadiazol-2-yl)-2-phenylethyl]acetamide

In the title compound, C17H22N4O3S, the dihedral angle between the planes of the thiadiazole and phenyl rings is 63.47 (7)°. The dihedral angle between the thiadiazole ring and the acetamide side chain is 7.72 (9)°. Molecules related by a 21 screw axis along the a axis are linked by intermolecular N—H⋯O hydrogen bonds generating a supramolecular chain.

In the title compound, C 17 H 22 N 4 O 3 S, the dihedral angle between the planes of the thiadiazole and phenyl rings is 63.47 (7) . The dihedral angle between the thiadiazole ring and the acetamide side chain is 7.72 (9) . Molecules related by a 2 1 screw axis along the a axis are linked by intermolecular N-HÁ Á ÁO hydrogen bonds generating a supramolecular chain.
Thiadiazole derivatives are known to exhibit high antibacterial activity against Staphylococcus aureus (Tehranchaian et al., 2005).
In the title compound (I), the thiadiazole ring adopts an mild envelop conformation with atom C11 at the flap position. C11 deviates from the mean planes through the other four atoms by 0.085 Å.
The molecular structure of (I) is shown in Fig 1. and selected geometric parameters are listed in Table 1. The bond lengths for C-S, C=N and N-N are within normal ranges (Allen et al., 1987). All the bondlengths and angles in (I) are as expected (Table 1). The dihedral angle between 1,3,4 thiadiazole ring and the phenyl ring is 63.47°. The dihedral angle between thiadiazole ring and the acetamide side chain(N4/C16/O3/C17) is 7.72°.
The molecules related by 2 1 screw along a axis (Fig 2)are linked by intermolecular N-H.·O hydrogen bond (Table 1) generating a supramolecular chain.

Experimental
A mixture of powdered thiosemicarbazone (3.0 mmol, acetic hydride(0.5 ml) and pyridine(2.5 ml) was taken in a round bottom flask and heated on a water bath for 3hrs. The reaction mixture was evaporated under reduced pressure and diluted in methanol. The viscous liquid obtained was allowed to stand overnight. The colour less precipitate formed was seperated by filteration and crystalized in methanol.

Refinement
All the hydrogen atoms were geometrically fixed and allowed to ride on their parent atoms with C-H = 0.86 − 0.97 Å, and U iso = 1.5 eq (C) for methyl H atoms and 1.2U eq (C) for other H atoms.
supplementary materials sup-2 Figures Fig. 1. The molecuar structure and labelling scheme for (I) with displacement ellipsoids for non-H atoms are drawn at the 30% probability level.  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 S1 0.04506 (