Visible-Light-Induced Decarboxylative Annulation of α,β-Unsaturated Acids with Amines and α-Keto Acids for 2,4-Diarylquinoline Synthesis

An efficient and sustainable approach for the synthesis of 2,4-diarylquinolines has been developed via a visible-light-promoted metal-free three-component decarboxylative annulation pathway. This one-pot protocol combines readily available feed-stock alpha,beta-unsaturated acids, aromatic amines, and alpha-keto acids in a cascade manner to access substituted quinolines under eco-benign conditions. Moreover, mechanistic insights suggest initial C-C cross coupling followed by decarboxylative 6 pi electrocyclic annulation to afford the desired products. The broad substrates scope and excellent functional group tolerance make this protocol more attractive and synthetically applicable toward the construction of complex N-heterocycles.