Synthesis of pyrrolo[3′,2′:4,5][1,3]diazepino[2,1,7-cd]pyrrolizine derivatives from dicyanovinylene-bis(meso-aryl)dipyrrin

Abstract

Pyrrolo[3′,2′:4,5][1,3]diazepino[2,1,7-cd]pyrrolizine derivatives 2 and 3 were synthesized from dicyanovinylene-bis(meso-aryl)dipyrrin in the presence of either BF₃·OEt₂ or InBr₃, where 2 was readily oxidized in aerobic conditions to be 3. It was understood that the fully elongated π-conjugation of 3 is achieved via the conformation of 2. Crystal structures of 2 and 3 were elucidated by X-ray diffraction analysis. Furthermore, two redox states, 3_ox and 3_red were observed in the chemical redox processes.