Palladium-Catalyzed Enantioselective Synthesis of Silacyles

Significance

Reported is the synthesis of chiral organosilacycles 2 via the palladium-catalyzed ring expansion of silacyclobutanes 1. Optimization demonstrated the importance of highly hindered BINOL-derived phosphoramidite ligands 4 to prevent competing formation of 3. Investigation of the substrate scope demonstrated that meta and para substitution of the aryl ring attached to silicon (R^²) is well tolerated, but ortho substitution leads to lower selectivities and yields. Alkyne substitution (R^¹) is well tolerated. Further elaboration of this scaffold is also demonstrated by the derivatization of 5 to afford both the hydroboration product 6 and the reduced silacycles 7 and 8 whilst retaining the high enantioselectivity garnered from the ring opening.