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

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Abstract
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 4H‐1,2,4‐triazoles in good yields, including four examples of the otherwise not easily obtainable 4‐alkyl‐3,5‐diaryl‐4H‐1,2,4‐triazoles. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)