Copper-Catalyzed Cascade Synthesis of 2-Aryl-3-cyanobenzofuran and Dibenzo[b,f]oxepine-10-carbonitrile Derivatives

The copper-catalyzed reaction of aryl aldehydes with 2-iodobenzylcyanides afforded 2-aryl-3-cyanobenzofurans in isolated yields of up to 74% in a cascade manner, which involves Knoevenagel condensation, aryl hydroxylation, oxa-Michael addition, and aromatization reactions. Conversely, 2-halo benzaldehydes as reacting partners with 2-iodobenzylcyanide regioselectively furnished dibenzo[b,f]oxepine-10-carbonitrile derivatives up to 85% isolated yields via tandem Knoevenagel condensation, aryl hydroxylation, and Ullmann coupling reactions.