The reactivity of Oxone towards 4,6-di(cycloamino)-1,3-phenylenediamines: synthesis of spirocyclic oxetane ring-fused imidazobenzimidazoles

Spirocyclic oxetane ring-fused imidazo[4,5-f]benzimidazole and imidazo[5,4-f]benzimidazole are reported. Oxone-mediated ring-closures to give imidazobenzimidazoles require acid and the functionalization of the 4,6-di(cycloamino)-1,3-phenylenediamine to the anilides. This is in contrast to benzimidazole forming oxidative cyclizations, which use 2-(cycloamino)anilines and require no acid. New evidence for N-oxide and nitroso-intermediates in respective imidazobenzimidazole and benzimidazole forming reactions is provided.