A new approach for convenient one-pot synthesis of 5-(1-oxidopyridyl)- and 5-(1-oxidoquinolyl)-2-alkylsulphonyl-1,3,4-thiadiazoles

Abstract

Acetylation of pyridine-4-carbaldehyde methylthio(thiocarbonyl)hydrazone (1a) with acetic anhydride gave 4-acetyl-2-methylthio-5-(4-pyridyl)-4,5-dihydro-1,3,4-thiadiazole (2). Oxidation of compound (2) with 30% hydrogen peroxide in acetic acid furnished 2-methylsulphonyl-5-(1-oxido-4-pyridyl),-1,3,4-thiadiazole (3a). 2-Alkylsulphonyl-1,3,4-thiadiazoles (3a–h) having 1-oxido-2-pyridyl, 1-oxido-3-3-pyridyl, 1-oxido-4-pyridyl, 1-oxido-2-quinolyl, and 1-oxido-4-quinolyl groups at the 5-position were obtained in good yields from the corresponding pyridine-(1a–f) and quinoline-carbaldehyde (1g) and (1h) alkylthio(thiocarbonyl)hydrazones by a one-pot synthesis. A reaction pathway from compound (2) to compound (3a) is also described.