A New Strategy for the Synthesis of Diverse Benzo[a]carbazoles via Divergent Catalytic Michael Reaction

A new type of divergent tandem Michael addition of α,α-dicyanomethylidenecarbazoles with β-nitrostyrenes, afforded multifunctional benzo[a]carbazoles [BCs] and benzodihydro[a]carbazoles [BDHCs] in good yields. In addition, the direct multicomponent transformation of α,α-dicyanomethylidenecarbazoles, acenaphthenequinone and malononitrile results in the formation of an unreported imino and amino functionalized spiro[acenaphthylene-8',4-benzo[a]carbazole] hybrids via amine-controlled divergent reactions. The spiro products also were obtained in good yields. The structures of the synthesized cycloadducts were confirmed by elemental analysis, spectral data (FT-IR, ¹H, ¹³C NMR and HRMS) and by single crystal X-ray diffraction studies. The application of this divergent tandem Michael addition protocol is beneficial from the view point of diversity-oriented one-pot synthesis of benzo[a]carbazole derivatives from simple starting materials.