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 α,β-unsaturated acids, aromatic amines, and α-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 6π 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.