2H-benzimidazoles (isobenzimidazoles). Part 2. Synthesis and reactions of 5-azido-2H-benzimidazole-2-spirocyclohexane

Abstract

A practicable synthesis of the title compound from 5-phenylsulphonyl-2H-benzimidazole and sodium azide is described. The 5-azido-2H-benzimidazole undergoes photolysis in the presence of various secondary aliphatic amines to give the corresponding 4-amino-5-dialkylamino-2H-benzimidazoles. By contrast thermal decomposition of the azide with exclusion of light led, in the presence of secondary amines, to 5-amino-6-dialkylamino-2H-benzimidazoles, but with thiols the corresponding 5-amino-4-thio-2H-benzimidazoles were obtained. A mechanism to account for the formation of these derivatives is proposed and conversions of some of the products into other heterocycles are described. Selective ¹³C-{¹H} n.O.e. difference spectroscopy was applied for a structural assignment.