Highly Regio- and Enantioselective Catalytic 1,6-Conjugate Addition of Grignard Reagents to Cyclic Dienones

The catalytic asymmetric conjugate additions of alkyl Grignard reagents to cyclic dienones were achieved using an (R)-Sunphos ligand L6. Chiral 2-styryl chromanone and its analogues were produced in high to excellent yields, excellent regioselectivities, and excellent enantioselectivities (82-99% ee's) with a broad substrate scope. This study expands the asymmetric 1,6-conjugate addition of Grignard reagents from linear dienones to more challenging cyclic dienones, and gram-scale reactions further demonstrate the practical applicability of this protocol.