A novel route to 1-benzyl-1,2,4-triazole derivatives through disproportionation of isothiosemicarbazones

✍ Scribed by Chiji Yamazaki; Mariko Ohno

• Publisher: Journal of Heterocyclic Chemistry
• Year: 1997
• Tongue: English
• Weight: 320 KB
• Volume: 34
• Category: Article
• ISSN: 0022-152X
• DOI: 10.1002/jhet.5570340305

✦ Synopsis

Abstract

Aromatic isothiosemicarbazones 1–4 underwent disproportionation at elevated temperature in the presence of a thiol or a thiol‐releasing substance to give 1‐arylmethylene‐3‐alkylthio‐5‐aryl‐1__H__‐1,2,4‐triazole derivatives 6–9 in moderate yields. An isothiosemicarbazone of aliphatic aldehyde with no α‐hydrogen did not give rise to the corresponding disproportionation under the similar conditions. Cross reaction occurred between two different isothiosemicarbazones but the cross compound could be isolated only in a poor yield. Any inert solvent markedly inhibited the disproportionation reaction even only with a slight dilution. A tentative reaction mechanism, in which it might involve a potential nitrene‐sulfonium ion pair as a key step, is presented.