Carbazoles and its annulated derivatives have gained widespread attention in recent years which results to their extensive biological, pharmaceutical and industrial applications. Recently, extensive efforts have been exerted to access diverse carbazoles and benzocarbazoles due to their potential anticancer, antitumor, anti-estrogenic, anti-inflammatory, and antifungal activity. Moreover, molecules bearing carbazole skeleton have been widely utilized in material science, organic light-emitting diodes, fluorescent sensors, and dye-sensitized solar cells due to its unique optical properties, high luminescent efficiency, and wide band gap.
Owing to the usefulness and importance of carbazole derivatives, a number of methods for their syntheses have been developed. Despite of this, there is no report on an efficient and robust strategy to construct complex π-extended carbazole via a one-pot domino reaction using cheap and commercially available feedstock. Moreover, the effective functionalization of a versatile cyano substituent on the polyannulated carbazoles has not yet been reported. This transformation involves a sequential Michael addition/intramolecular nucleophilic addition of an enol to a nitro group/reduction of an −NO2 to −NH group/ intramolecular Baeyer−Villiger oxidation/carboxylic acid and HCN elimination/6π-electrocyclization/oxidation as supported by density functional theory (DFT) calculations. As an application, the synthesized compounds exhibited excellent fluorescence-sensing ability to detect Cu2+ ions. Herein, we describe the efficient synthesis of π-extended carbazole derivatives via copper-catalyzed domino [5+3+1] annulation strategy (Scheme 1).