Copper(II)-Catalyzed Sequential C,N-Difunctionalization of 1,4-Naphthoquinone for the Synthesis of Benzo[f]indole-4,9-diones under Base-Free Condition

An efficient synthesis of benzo[f]indole-4,9-diones has been achieved by copper(II)-catalyzed naphthoquinone sequential C,N-difunctionalization reactions with β-enaminones. New C-C and C-N bonds are easily formed in the reaction course. Copper(II) salt plays a dual role as Lewis acid and oxidative catalyst, and O2 acts as the terminal oxidant. The advantage of this reaction is the high atom economy with broad substrate scope and excellent yields. The reaction can be scaled up to using at least grams of substrates.