Asymmetric Synthesis of 2,2-Disubstituted Dihydroquinolines via Rhodium-Catalyzed Dearomative Arylation and Alkenylation of 2-Substituted Quinolinium Salts

A synthetic protocol for the construction of chiral 2,2-disubstituted dihydroquinolines via rhodium-catalyzed asymmetric dearomative arylation and alkenylation of 2-substituted quinolinium salts has been disclosed. 2-Substituted quinolinium triflates and bromide preferred to undergo asymmetric arylation with arylboronic acids, and 2-substituted quinolinium tetrafluoroborate favored to carry out asymmetric alkenylation with alkenylboronic acids, providing a series of chiral 2,2-disubstituted dihydroquinolines with high yields and enantioselectivities. The key for this dearomative reaction stands in the counteranions of 2-substituted quinolinium salts, which guarantee the reactivities and stereoselectivities at the same time.