Direct access to 1-aryl-5-amino-1,2,4-triazoles and [1,2,4]triazolo[1,5-a]pyridines by two new single-step reactions from 1,3,4-thiadiazol-2-amines

Two new single-step reactions allowing the construction of two heterocyclic motifs are reported. Both processes involve 5-substituted 1,3,4-thiadiazol-2-amines as starting materials. Reaction with 1-fluoro-2-nitrobenzenes in presence of Hünigʹs base permitted the convenient synthesis of various 3-substituted 1-aryl-5-amino-1,2,4-triazoles. Reaction with 2-chloro-3-nitropyridines and 2-chloro-5-nitropyridines in similar conditions readily gave access to a number of [1,2,4]triazolo[1,5-a]pyridines. In absence of base, adducts composed by one aromatic unit and two thiadiazole units were formed. This observation and previous work by Anders and co-workers led to the suggestion of plausible mechanisms for these reactions.