Stereochemistry at carbon upon protonolysis of a late transition metal-alkyl bond: A reaction of relevance to catalytic enantioselective hydrogenation of olefins

Reaction of [Ru((R)-BINAP)(H)(MeCN)_n (acetone)_3-n](BF₄) (where n = 0-3) (2) with 1 equiv of the olefin substrate methyl α-acetamidoacrylate (MAA) in acetone at room temperature immediately generated a mixture (72:28) of two diastereomers of the complex [Ru((R)-BINAP)(MeCN)(MAA(H))](BF₄)(3). The olefin-hydride insertion reaction between 2 and MAA to generate 3 was regioselective, with transfer of the hydride to the β-olefinic carbon and transfer of ruthenium to the α-carbon in both diastereomers of 3. The two diastereomers of 3 differ by the absolute configuration at the α-carbon of MAA(H) ((S_cα)-3 and (R_cα)-3). The absolute configuration of the major ((S_cα)-3) diastereomer was determined by X-ray diffraction in conjunction with NMR spectroscopic data. Protonolysis of the ruthenium-carbon bond in 3 and in the methyl α-acetamidocinnamate (MAC) analog ([Ru((R)-BINAP)(MeCN)((S)-MAC(H))](BF₄)((S_cα)-4)) by addition of 2 equiv HBF₄·Et₂O in CH₂ Cl₂ at room temperature was not stereospecific and did not occur with β-hydride elimination from the methyl or benzyl groups.