Radical Promoted Synthesis of Furoquinolines via Anomalous Dakin‐Type Reaction

Abstract A radical promoted approach for the selective synthesis of furo[3,2‐ b ]quinolines and benzylidene‐1,3‐dihydrofuro[3,4‐ b ]quinolines have been achieved from 2‐alkynyl quinoline‐3‐carbaldehydes by fine‐tuning of base and oxidant in good yields. In the presence of an oxidant, the reaction afforded the 5‐endo‐dig cyclized furoquinolines by decarbonylative intramolecular cyclization via a Dakin‐type reaction; however, in the absence of oxidant, 5‐exo‐dig cyclized products were obtained selectively through reductive intramolecular cyclization. The formation of furoquinolines was further supported by X‐ray crystallographic studies. The proposed mechanism was well supported by the control experiments. magnified image