A new strategy for the synthesis of diverse benzo[a]carbazoles via a divergent catalytic Michael reaction

Abstract

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 unreported imino and amino functionalized spiro[acenaphthylene-8′,4-benzo[a]carbazole] hybrids via amine-controlled divergent reactions. The spiro products were also 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 viewpoint of the diversity-oriented one-pot synthesis of benzo[a]carbazole derivatives from simple starting materials.