Enantioselective Arylation of Tetrasubstituted Enamines: Access to Enantioenriched Indolenine and 1H-Indole Derivatives

Palladium-catalyzed
intramolecular enantioselective β-arylation
of tetrasubstituted endocyclic and exocyclic enamines is
developed. A range of optically active medium-ring fused indolenines
or 3,3′-spiroindolenines were achieved in enantiomeric ratios
up to 98:2 with Cs2CO3 or K3PO4 as the base in the presence of chiral PHOX ligands. The use
of Ag3PO4 as a base led to enantioenriched 1H-indoles
in good enantiomeric ratios (up to 89:11) with (S)-DIFLUORPHOS as a chiral ligand, which proceeded via a possible
domino enamine-isomerization/β-arylation sequence.