Asymmetric conjugate addition of alkylzirconium reagents to α,ß-unsaturated lactones.

The asymmetric synthesis of ß-substituted lactones by catalytic asymmetric conjugate addition of alkyl groups to α,ß-unsaturated lactones is reported. The method uses alkylzirconium nucleophiles prepared in situ from alkenes and the Schwartz reagent. Enantioselective additions to 6- and 7-membered lactones proceed at rt, tolerate a wide variety of functional groups, and are readily scalable. The method was used in a formal asymmetric synthesis of mitsugashiwalactone.

Rhodium-catalyzed asymmetric synthesis of silicon-stereogenic dibenzooxasilines via enantioselective transmetalation.

A rhodium-catalyzed asymmetric synthesis of silicon-stereogenic dibenzooxasilines has been developed. High enantioselectivities have been achieved by employing (S,S)-Me-Duphos as the ligand through "enantioselective transmetalation".