Facile Construction of Quinoline-2-carboxylate Esters through Aerobic Oxidation of Alkyl 4-Anilinocrotonates Induced by a Radical Cation Salt.

A facile construction of quinoline-2-carboxylate esters through an aerobic oxidation of alkyl 4-anilinocrotonates is described. In the presence of dioxygen, sp3 C-H bonds in 4-anilinocrotonates can easily be oxidized by using a catalytic amount of a radical cation salt, providing a radical intermediate. After further oxidation and domino cyclization, the desired quinoline derivatives were afforded in high yields. This reaction provides a new way to construct the pharmaceutically relevant quinoline skeleton, avoiding harsh reaction conditions and tedious starting material synthesis.