Synthetic applications of C,C-bis(iminophosphoranes): Preparation of [5+5] rigid bicyclic guanidines and 1,3,6-benzothiadiazepino[3,2-a] benzimidazole derivatives

Article abstract of DOI:10.1016/S0040-4020(01)89618-6

Aza Wittig-type reaction of bis(iminophosphorane)1, derived from bis(2-aminophenyl)amine with two equivalents of isocyanate directly provided benzimidazo[1,2,a]benzimidazole derivatives 2. However, the reaction with one equivalent of isocyanate or carbon disulfide afforded C-aryl iminophosphoranes 3 or 6, respectively, derived from the 1-phenylbenzimidazole ring, which underwent cyclization by the action of one equivalent of isocyanate to give the [5+5] rigid bicyclic guanidines 2 or 1,3,6-benzothiadiazepino[3,2-a] benzimidazole 8.