Tandem regioselective 1,5-electrocyclizations of bis-nitrilimines—a new convenient synthesis of 1,2,4-triazolo[3,4-b][1,3,4]thiadiazoles

Abstract

Starting from bis(substituted methylene)carbonothioic dihydrazides, two series of 1,2,4-triazolo[3,4-b][1,3,4]thiadiazole derivatives were synthesized via their oxidative cyclization. The mechanism and regioselectivity of the reactions studied were discussed. The structures of the compounds prepared were elucidated on the basis of their analyses, spectral data, alternative synthesis, and comparison with authentic samples of their isomers.

Keywords:

• Hydrazones
• 1,5-Electrocyclization
• Nitrilimines
• Heterocycles