Efficient, microwave-mediated synthesis of benzothiazole- and benzimidazole-based heterocycles

Abstract

1-(Benzothiazol-2-yl)-3-(N,N-dimethylamino)-2-(phenylsulfonyl)prop-2-en-1-one (3) and 1-(1-methylbenzimidazol-2-yl)-3-(N,N-dimethylamino)-2-(phenylsulfonyl)prop-2-en-1-one (4) were obtained from the reaction of 1-(benzothiazothiazol-2-yl)-2-phenylsulfonyl-1-ethanone (1) and 1-(1-methyl-1H-benzimidazol-2-yl)-2-(phenylsulfonyl)-1-ethanone (2) with N,N-dimethylformamide dimethyl acetal, respectively. The enaminosulfones 3 and 4 were used as versatile building blocks for the synthesis of novel pyrazolo[1,5-a]pyrimidine and [1,2,4]-triazolo[1,5-a]pyramidine derivatives via their reactions with the appropriate aminopyrazoles and aminotriazole under both microwave and thermal reaction conditions. They have been also utilized as reactive synthons for the construction of novel pyrimido[1,2-a]benzimidazole, pyrido[1,2-a]benzimidazole, pyrimidine, isoxazole and pyrazole heterocycles pendent to benzothiazole and benzimidazole ring systems.