Construction of Fused Tetrahydroquinolines by Catalytic Hydride-Transfer-Initiated Tandem Functionalization of Quinolines.

Herein, we present a new annulation reaction of quinolinium salts with indoles and paraformaldehyde, which enables syn -diastereoselective construction of a vast range of fused tetrahydroquinolines via ruthenium-catalyzed hydride-transfer-initiated tandem functionalization of the quinoline skeleton. The developed transformation proceeds with mild reaction conditions, good substrate and functional group compatibility, readily available feedstocks, and operational simplicity.