On Features of Halocyclization of 4‐Allyl‐5‐substituted‐2,4‐dihydro‐3H‐1,2,4‐triazol‐3‐thiones and Synthesis of New Derivatives of 1,2,3‐Triazoles

Abstract A study was carried out on the regioselectivity of the electrophilic halocyclization of 4‐allyl‐5‐substituted‐2,4‐dihydro‐3 H ‐1,2,4‐triazol‐3‐thiones by the action of bromine and iodine. It was revealed which factors influence the structure of the reaction products. 6‐(Bromomethyl)‐3‐substituted‐5,6‐dihydrothiazolo[2,3‐ c ]‐[1,2,4]triazoles have been shown to be good starting materials for the synthesis of polyheterocyclic systems containing a 1,2,3‐triazole ring. In contrast, 6‐iodo‐3‐substituted‐6,7‐dihydro‐5 H ‐[1,2,4]triazolo[3,4‐ b ][1,3]thiazines do not undergo azidation. Due to the dehydrohalogenation reaction, a double bond is formed.