Asymmetric 1,4-Addition of Arylboroxines to β,β-Disubstituted α,β-Unsaturated Ketones

Significance

Catalytic asymmetric 1,4-addition of organometallic reagents to β,β-disubstituted α,β-unsaturated compounds is a powerful method for constructing all-carbon quaternary stereocenters. The authors previously reported a rhodium-catalyzed asymmetric 1,4-addition of sodium tetraarylborates to β,β-disubstituted α,β-enones 1 in the presence of the chiral diene ligand (R)-L (J. Am. Chem. Soc. 2009, 131, 13588). To overcome the limitation of using tetraarylborates as nucleophiles, the authors herein report the use of a chiral tetrafluorobenzobarrelene ligand [(R,R)-Ph-tfb*] for the asymmetric 1,4-addition of more readily available arylboroxines. Excellent yields and enantioselectivities were achieved with a variety of aryl groups.