Constructions of tetrahydro-γ-carboline skeletons via intramolecular oxidative carbon-carbon bond formation of enamines.

The synthetically and biologically important 4-methyl and 4-methoxy tetrahydro-γ-carboline compounds were readily synthesized in high yields from an aryl amine and a 5-amino-3-oxopentanoate derivative through a series of reactions of enamination, oxidative annulation, deprotection/lactamization and the final reduction reaction of the carbonyl group. The underpinning strategy involves the oxidative C(sp(2))-C(sp(2)) bond formation realized by either Pd(OAc)2/Cu(OAc)2 or a hypervalent iodine reagent.