Benzothiazine containing thiosemicarbazides are important synthetic intermediates for synthesis of triazole and oxadiazole derivatives

Bhikan J. Khairnar and Bhata R

Abstract

A series of novel 3-methyl-7-substituted-4H-1,4-benzothiazine-2-carbohydrazide (3a-e) and corresponding thiosemicarbazide (4a-q) have been synthesized from 2-amino-5-substituted-thiophenol (1a-e) through the synthesis of 2-carboethoxy-3-methyl-7-substituted-1,4-benzothiazine (2a-e). The 1,4-benzothiazine thiosemicarbazides i.e. 2- [(3-methyl-7-substituted-4H-1,4-benzothiazin-2-yl) carbonyl]-N-arylhydrazine carbothiamide (4a-q) when cyclised with 2N sodium hydroxide via intramolecular dehydrative cyclisation gave benzothiazonyl-1,2,4-triazoles; and the thiosemicarbazide when cyclized with iodine via intramolecular cyclisation gave benzothiazonyl 1,2,4-oxadiazoles in high yields.