Asymmetric Three-Component Coupling Reaction of Alkyne, Enone, and Aldehyde Catalyzed by Chiral Phebox Ruthenium Catalysts

Catalytic asymmetric three-component coupling reactions of terminal alkynes, α,β-unsaturated ketones, and aldehydes were studied. The chiral ruthenium complexes containing bis­(oxa­zolinyl)­phenyl ligands were found to serve as efficient catalysts for a tandem reaction based on conjugate addition of terminal alkynes to α,β-unsaturated ketones and subsequent aldol reaction with aldehydes, giving β-hydroxyketone derivatives containing α-propargyl groups in high yields with moderate to good enantioselectivities. This method can produce various functional molecules from commercially available substrates in a one-pot procedure. The absolute configuration of the major product was determined by X-ray analysis. The control experiments suggested that a ruthenium enolate species generated in situ by conjugate addition could be involved as an intermediate for the aldol coupling with an aldehyde.