Triple role of boronic acid as a catalyst in the alkylation of quinoline to functionalized tetrahydroquinoline.

The triple role of arylboronic acid as a catalyst in the alkylation of quinoline to -substituted tetrahydroquinoline with a diaryl motif at the C6-position has been developed. This reaction involves the tandem reduction of quinoline to tetrahydroquinoline, followed by reductive -alkylation with aldehyde to form -alkylated tetrahydroquinoline and subsequent regioselective alkylation at the C6-position using -quinone methides (-QMs) in a one-pot operation. The methodology is compatible with a wide variety of functional groups and is also useful in the late-stage functionalization of pharmaceuticals. The mechanistic study demonstrates the existence of organoboron catalysts as both Lewis acids and hydrogen-bond donors.