Recent Advances in the Denitrogenative Annulation Reactions of 1,2,3-Thiadiazoles

1,2,3-Thiadiazoles exhibit versatile reactivity due to their ability to undergo ring cleavage, forming α-diazothione species through a Dimroth-type equilibrium. Denitrogenation of the α-diazothione, induced by high temperature, irradiation, or strong bases, allows generation of a wide range of reactive intermediates. Since 2016, the transition-metal-catalyzed denitrogenative transannulation of 1,2,3-thiadiazoles has garnered significant attention as a promising approach to constructing diverse heterocyclic scaffolds. This review focuses on the denitrogenative reactions of 1,2,3-thiadiazoles, particularly highlighting the novel rhodium-catalyzed denitrogenative transannulation transformations along with their mechanisms.