Synthesis and Crystal Structure Determination of 3-Phenyl-2-(2-phenylhydrazino)-4H-1-benzothiopyran-4-one

A new type of substituted benzothiopyranone, 3-phenyl-2-(2-phenylhydrazino)-4 H -1-benzothiopyran-4-one, has been prepared by the condensation-acid cyclization of polylithiated phenylacetic acid phenylhydrazide with lithiated methyl thiosalicylate. Absorption spectra, especially 13 C NMR, provided good indication of its structure, which was conclusively established with X-ray crystal structure analysis. In comparison to the few benzothiopyran X-ray reports documented, the benzothiopyranone ring of the molecule was found to be essentially planar, with the 3-phenyl ring nearly perpendicular to the benzothiopyranone fused-ring system. Crystals of C 21 H 16 N 2 OS are orthorhombic, P 2 1 2 1 2 1 , a = 10.140(4) Å, b = 10.432(4) Å, c = 16.228(7) Å, Z = 4, V = 1717(1) Å 3 , R 1 = 0.0267 and wR 2 = 0.0725 for reflections with I > 2σ( I ). The molecular packing in the crystal is the result of N–H···O hydrogen bonding. Graphical Abstract X-ray crystal analysis confirmed the structure of 3-phenyl-2-(2-phenylhydrazino)-4 H -1-benzothiopyran-4-one prepared by the condensation–cyclization of polylithiated phenylacetic acid phenylhydrazide with lithiated methyl thiosalicylate.