Diastereoselective, multicomponent access to trans-2-aryl-4-arylamino-1,2,3,4-tetrahydroquinolines via an AA′BC sequential four-component reaction and their application to 2-arylquinoline synthesis

The CAN-catalyzed reaction between 3,5-disubstituted anilines, vinyl ethers and aromatic aldehydes leads to trans-2-aryl-4-arylaminotetrahydroquinolines, in an AA′BC sequential multicomponent transformation related to the Povarov reaction that was also extended to the use of a second aniline as the C-4 substituent. The unusual trans stereochemistry was explained by stabilization of the corresponding intermediate by intramolecular hydrogen bonding. The presence of the 4-anilino substituent allowed adapting the method to the synthesis of 4-unsubstituted 2-arylquinolines, by treatment of the crude product from the MCR with FeCl₃ in methanol.