Synthesis of 5-amino-3-(het)aryl-1H-1,2,4-triazoles via Cyclization of(het)aroylaminoguanidines in Aqueous Medium

The effective and clean procedure for the preparation of 5-amino-3-(het)aryl-1,2,4-triazoles (3a-c) via cyclization of (het)aroylaminoguanidines (2a-c) in water was reported. Two tautomeric forms, namely 5-amino-3-(het)aryl-1,2,4-triazoles (A) and 3-amino-5-(het)aryl-1,2,4-triazoles (B) were found to exist in tautomeric equilibrium. Form A was a predominant tautomer in DMSO solution (KT = 9-33).