K₂CO₃-Catalyzed Dual C–C-Coupled Cyclization to 3-Amino-4-benzoylbiphenyls and In Situ I₂-Catalyzed C–N Bond Forming Annulation: A Metal-Free Synthesis of Arylacridones

Abstract

Unprecedented metal-free cyclization catalysis reactions are developed in a highly regioselective fashion to synthesize 3-amino-4-benzoyl biphenyls and arylacridones with high atom economy. Catalytic K2CO3 is utilized as the only reagent for the unusual rapid dual C–C-coupled cyclization between β-keto enamines and cinnamaldehydes to furnish the functionalized biphenyls. Its C(sp2)–H functionalized C–N bond-forming cyclization was performed in situ using molecular I2 as a catalyst to furnish valuable arylacridones. Plausible mechanisms for the new cyclization reactions are predicted by conducting various control experiments and ESI-MS analyses.