Synthesis and alkylation of 5-(3-chlorobenzo[b]thien-2-yl)-4H-1,2,4-triazole-3-thiol under classical and microwave conditions. AM1 semiemperical calculations for investigating the regioselectivity of alkylation

✍ Scribed by E. S. H. El Ashry; A. A. Kassem; H. Abdel-Hamid; F. F. Louis; S. H. A. N. Khattab; M. R. Aouad

• Publisher: Journal of Heterocyclic Chemistry
• Year: 2006
• Tongue: English
• Weight: 469 KB
• Volume: 43
• Category: Article
• ISSN: 0022-152X
• DOI: 10.1002/jhet.5570430602

✦ Synopsis

Abstract

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Under microwave irradiation (MWI), 5‐(3‐chlorobenzo[b]thien‐2‐yl)‐4__H__‐1,2,4‐triazole‐3‐thiol (3) was synthesized in a good yield by intramolecular cyclization of the carbonyl thiosemicarbazide 2. A regioselective S‐alkylation of 3 with benzyl chloride or allyl bromide has been achieved by using triethylamine as a base, while other different basic conditions led to a mixture of bis(alkylated) derivatives N^4^, S‐ and S, N^2^‐, under both of classical and MWI conditions. The relative stabilities, charge densities, dipole moments and electronic energies of reactants, transition states and intermediates were calculated by the AM1 method and used for investigating the regioselectivity.