DIASTEREOSELECTIVE C-C BOND FORMATION BY CARBENE INSERTIONS INTO PT-CH3 BONDS

The platinum complexes [PtX(CH3)(S,S-diop)] (X = Cl, Br, I) react quantitatively with N2CHCO2R (R = Et, R-menthyl) in polar solvents (CD3CN, DMSO) to give [PtX{CH(CH3)CO2R}(S,S-diop)] as a 2:1 (R = Et) or 4:1 (R = R-menthyl) mixture of diastereomers. The major diastereomer when X = Cl and R = Et is readily separated, and its crystal structure reveals that the configuration about the a-carbon is R; this complex is configurationally stable in solution for at least 12 days. In less polar solvents (CDCl3, C6D6), reaction of N2CHCO2-Et with [PtX(CH3)(S,S-diop)] (X = Br, I) give the products of carbene insertion into the Pt-X as well as Pt-C bonds.