Synthesis of 1,2,4-Triazoles via Oxidative Heterocyclization: Selective C-N Bond Over C-S Bond Formation.
The higher propensity of C-N over C-S bond forming ability was demonstrated, through formal C-H functionalization during the construction of 4,5-disubstituted 1,2,4-triazole-3-thiones from arylidenearylthiosemicarbazides catalyzed by Cu(II). However, steric factors imparted by the o-disubstituted substrates tend to change the reaction path giving thiodiazole as the major or an exclusive product. Upon prolonging the reaction time, the in situ generated thiones are transformed to 4,5-disubstituted 1,2,4-triazoles via a desulfurization process. Two classes of heterocycles viz. 4,5-disubstituted 1,2,4-triazole-3-thiones and 4,5-disubstituted 1,2,4-triazoles can be synthesized from arylidenearylthiosemicarbazides by simply adjusting the reaction time. Desulfurization of 1,2,4-triazole-3-thiones is assisted by thiophilic Cu to provide 1,2,4-triazoles with concomitant formation of CuS and polynuclear sulfur anions as confirmed from scanning electron microscope and energy dispersive X-ray spectroscopy measurements. A one-pot synthesis of an antimicrobial compound has been successfully achieved following this strategy.
Department of Chemistry, Indian Institute of Technology Guwahati , Guwahati 781039, India.
Anupal
A
Gogoi
Department of Chemistry, Indian Institute of Technology Guwahati , Guwahati 781039, India.
Srimanta
S
Guin
Department of Chemistry, Indian Institute of Technology Guwahati , Guwahati 781039, India.
Suresh
S
Rajamanickam
Department of Chemistry, Indian Institute of Technology Guwahati , Guwahati 781039, India.
Saroj Kumar
SK
Rout
Department of Chemistry, Indian Institute of Technology Guwahati , Guwahati 781039, India.
Bhisma K
BK
Patel