Three-Component Synthesis of Tetrahydroquinolines

Significance

Reported is a mild CAN-catalyzed reaction between anilines and two equivalents of vinyl ethers affording 2-methyl-1,2,3,4-tetrahydroquinolines 1 (cis) and 2 (trans) in good to excellent yields with commonly 9:1 cis/trans diastereoselectivity. Isomers 1 were dehydrogenatively aromatized to yield 2-methylquinoline derivatives 3 accompanied, in some cases, by the corresponding 4-ethers 4. Further studies to optimize formation of derivatives 4 were not reported. The overall process is similar to a stepwise Povarov reaction whose mechanism is discussed (O. Jiménez, G. de la Rosa, R. Lavilla Angew. Chem. Int. Ed. 2005, 44, 6521-6525).