From N ‐Substituted Thioamides to Symmetrical and Unsymmetrical 3,4,5‐Trisubstituted 4 H ‐1,2,4‐Triazoles: Synthesis and Characterisation of New Chelating Ligands

An improved protocol for the synthesis of N ‐substituted pyridine‐2‐thiocarboxamides under the conditions of the Willgerodt−Kindler reaction, employing a catalytic amount of sodium sulfide nonahydrate, has been developed. Following this protocol, eight thioamides carrying aromatic or aliphatic N ‐substituents have been prepared in good to excellent yields. Condensation of these thioamides or their S ‐alkylated congeners with hydrazides in refluxing 1‐butanol has afforded eight unfused 3,4,5‐trisubstituted 4 H ‐1,2,4‐triazoles in good yields, including four examples of the otherwise not easily obtainable 4‐alkyl‐3,5‐diaryl‐4 H ‐1,2,4‐triazoles. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)