Reactions of tetrasulfur tetranitride with aryl dibromomethyl ketones: one-pot synthesis of 3-aroylformamido-4-aryl-1,2,5-thiadiazoles and their reactions

Abstract

Heating of dibromomethyl aryl ketones with tetrasulfur tetranitride (S₄N₄) at 115 °C without a solvent gave 3-aroylformamido-4-aryl-1,2-5-thiadiazoles 8 as major products (12–71%) and 3,5-diaroyl-1,2,4-thiadiazoles 2 as minor products in certain cases. The structures of compounds 8 were determined based on the X-ray analysis of 3-benzoylformamido-4-phenyl-1,2,5-thiadiazole 8a and comparison with an authentic sample of comound 8a, as well as all the spectroscopic and analytical data of compounds 8. Oxidation of compounds 8 with m-chloroperbenzoic acid in chloroform at room temperature gave compounds 2(0–66%), whereas reduction of compounds 8 with sodium boranuide in a mixture of chloroform–ethanol at room temperature gave 3-amino-4-aryl-1,2,5-thiadiazoles 10(71–93%). Treatment of 3-(3-nitrobenzoylformamido)-4-(3-nitrophenyl)-1,2,5-thiadiazole 8d with either sodium hydroxide in aqueous p-dioxane at reflux or sodium hydride in chloroform at room temperature gave 3-amino-4-(3-nitrophenyl)-1,2,5-thiadiazole 10d in 56 and 80% yield, respectively.