2-Benzoyl-4-phenyl-1,2,5-thiadiazol-3(2H)-one 1,1-Dioxide

3,5-Diphenyl-4H-1,2,6-thiadiazin-4-one treated with meta-chloroperoxybenzoic acid undergoes an oxidative ring contraction to give 2-benzoyl-4-phenyl-1,2,5-thiadiazol-3(2H)-one 1,1-dioxide in a 29% yield, the structure of which is supported by single-crystal X-ray diffraction analysis and the available spectroscopic data.