Microwave Assisted Synthesis of Biologically Active 4-Hydroxy-7v-(Phenylcarbonyl)-2h-1,2-Benzothiazine-3-Carbohydrazide 1,1-Dioxide Derivatives

Abstract

Microwave assisted synthesis of a series of 4-hydroxy-N'-(phenylcarbonyl)-2H-1,2-benzothiazine-3-carbohydrazide 1,1-dioxides from sodium saccharin is reported. Sodium o-benzosulfimide was N-alkylated with ethyl chloroacetate followed by base catalyzed ring expansion to six membered 1,2-benzothiazine through Gabriel-Coleman type rearrangement yielding ethyl 4-hydroxy-2H-1,2-benzothiazine-3-carboxylate 1,1-dioxide. It was later condensed with a series of benzohydrazides synthesized from various carboxylic acids to get the title compounds. All the synthesized compounds were subjected to preliminary evaluation for their biological activity against series of Gram positive, Gram negative bacteria and fungi. Some of the compounds showed marked activity against the selected microorganisms.