Umpolung of o-phenylenediamines by conversion into isobenzimidazole. An expedient approach to heterocycles with nucleophilic substituents

Abstract

Isobenzimidazole-2-spirocyclohexane(1)can be made to react with nitrogen, oxygen, sulphur, and carbon nucleophiles to give mono-and di-substitied derivatives. On reductive ring-opening the correspondingly substituted o-phenylenediamine is obtained. The scope of this synthetic principle has been studied and the reaction used to prepare various heterocycles with substituents that are difficult to introduce by conventional methods. Selenadiazole or its 4-chloro and 4,5-dichloro derivatives were found to be unsuitable alternatives to (1).