Reactivity of 1,2,3-triazoles towards sulfonyl chlorides. A novel approach to 1-and 2-sulfonyl-4-azolyl-1,2,3-triazoles

The reactions of N-unsubstituted triazoles with sulfonyl chlorides afforded mixtures of regioisomeric 1- and 2-sulfonyl-1,2,3-triazoles. In some cases, pure regioisomers were obtained by crystallization of mixtures of isomers. 1,2,3-Triazoles bearing thiadiazole, isoxazole and benzene rings react with mesyl chloride and tosyl chloride to form mainly 1-substituted 1,2,3-triazoles. Coriversely, reactions of triazoles 1a,b and oxadiazolyi triazole 1h with more bulky 1-(2,4-dimethylphenyl)sulfonyl chloride affords mainly 2-substitued products. Oxadiazole 1b furnishes an equal mixture of the regioisomeric products 3 and 4 as a result of the reaction with mesyl and tosyl chlorides. Higher temperatures increase the ratio of isomers in favor of the 2-substituted triazole. The ratio of isomers depends on both the nature of the azolyl ring and on the size of the substituent in the sulfonyl chloride. Based on the results of experimental and theoretical data, 1-substituted and 2-substituted 1,2,3-triazoles can be considered as the kinetic and thermodynamic products. (C) 2015 Elsevier Ltd. All rights reserved.