Recent Developments in the Synthesis of 1,2,5-Thiadiazoles and 2,1,3-Benzothiadiazoles

The fast-growing interest in 1,2,5-thiadiazoles and their fused analogues including 2,1,3-benzothiadiazoles in recent years as important compounds in materials science and biomedicine has led to great progress in the synthesis of these heterocyclic systems. In this short review, the development of known procedures together with novel reactions is covered. New starting materials, unknown and unexpected transformations for the construction of the thiadiazole ring are emphasized. 1 Introduction 2 Synthesis of Monocyclic 1,2,5-Thiadiazoles 2.1 From 1,2-Diamines, vic-Dioximes and Related Compounds 2.2 From Alkyl Aryl (Hetaryl) Ketoximes and Tetrasulfur Tetranitride 2.3 By Condensation Reactions 2.4 From Other Heterocycles 3 Synthesis of Fused 1,2,5-Thiadiazoles 3.1 From ortho-Phenylenediamines and Related Compounds 3.2 From ortho-Aminonitroso and ortho-Aminonitro Derivatives 3.3 By Condensation Reactions 3.4 By Chalcogen Exchange in 1,2,5-Oxa- and 1,2,5-Selenadiazoles 3.5 Miscellaneous Methods 4 Conclusions