Radical cation salts induced domino reaction of anilines with enol ethers: Synthesis of 1,2,3,4-tetrahydroquinoline derivatives

A domino reaction of anilines with cyclic and acyclic enol ethers induced by catalytic amounts of TBPA+ (5 mol%) was investigated and a series of 2,4-disubstituted-1,2,3,4-tetrahydroquinolines were synthesized. Different from cyclic enol ethers, when acyclic enol ethers were used in the reaction, they serve as surrogates of acetaldehyde, producing a series of 2-methyl-4-anilino-1,2,3,4-tetrahydroquinolines. A single electron transfer mechanism was proposed to rationalize the products formation.