Iodine/TBAB-promoted oxidative cyclization: an efficient approach to thiadiazoles.

A rapid and efficient method for synthesizing 2-amino-1,3,4-thiadiazoles and 1,2,3-thiadiazoles via the oxidative cyclization of N-tosylhydrazones obtained from aromatic aldehydes and acetophenones has been developed. The reaction uses potassium thiocyanate or elemental sulphur as its sulphur source, with tetrabutylammonium bromide (TBAB) as a promoter in molecular iodine and a DMSO solvent system. This approach produces moderate to high yields across a wide range of substrates and proceeds smoothly within 5-15 minutes. Avoiding the use of column chromatography improves the environmental sustainability, scalability, and practicality of the synthetic protocol. This TBAB-assisted approach delivers more effectiveness and more applicability than traditional catalyst-free methods, providing a useful framework for thiadiazole synthesis that is highly useful for heterocyclic and medicinal chemistry.