Oxidation of 3-acetyl-5-methylthio-2-phenyl-2,3-dihydro-1,3,4-thiadiazole with m-chloroperbenzoic acid and nucleophilic substitution of the oxidation product, 3-acetyl-5-methylsulphinyl-2-phenyl-2,3-dihydro-1,3,4-thiadiazole. X-Ray molecular structure of (2S*)-3-acetyl-5-[(R*)-methylsulphinyl]-2-phenyl-2,3-dihydro-1,3,4-thiadiazole and of (1R*,2S*)-3-acetyl-5-[(S*)-methylsulphinyl]-2-phenyl-2,3-dihydro-1,3,4-thiadiazole 1-oxide

Abstract

3-Acetyl-5-methylthio-2-phenyl-2,3-dihydro-1,3,4-thiadiazole (1) was oxidized to 3-acetyl-5-methyl-sulphonyl-2-phenyl-2,3-dihydro-1,3,4-thiadiazole 1-oxide (9) with m-chloroperbenzoic acid by way of diastereoisomeric mixtures of 3-acetyl-5-methylsulphinyl-2-phenyl-2,3-dihydro-1,3,4-thiadiazoles (7a) and (7b) and 3-acetyl-5-methylsulphinyl-2-phenyl-2,3-dihydro-1,3,4-thiadiazole 1-oxides (8a) and (8b). The relative stereochemistry of compounds (7a) and (8b) was established by X-ray crystallographic analysis. 5-Substituted 3-acetyl-2-phenyl-2,3-dihydro-1,3,4-thiadiazoles were synthesized by substitution of the methylsulphinyl groups of compounds (7a) and (7b) with several nucleophiles.