In the presence of a catalytic amount of diphenylboryl triflate, aldehydes smoothly react with (S)-1-phenyl-1-trimethylsilyloxyethane and allyltrimethylsilane to afford the chiral homoallyl ethers in good yields with high stereoselectivities.
Synthesis and Lewis acid properties of a ferrocene-based planar-chiral borenium cation
作者:Jiawei Chen、Roger A. Lalancette、Frieder Jäkle
DOI:10.1039/c3cc41556b
日期:——
The first planar chiral ferrocenylborenium species (pR)-3+ is obtained in the enantiopure form by halide abstraction from the corresponding chloroborane adduct (pR)-2 using Krossing's salt. Competition experiments suggest that the Lewis acidity of (pR)-3+ is higher than that of B(C6F5)3 towards anions and slightly lower towards neutral Lewis bases. The ferrocenylborenium species (pR)-3+ is examined as a catalyst for the stereoselective hydrosilylation of ketones.
Cationic Carboxylato Complexes of Dirhodium(II) with Oxo Thioethers: Catalysts for Silane Alcoholysis under Homogeneous and Liquid-Liquid Biphasic Conditions
A set of cationic dirhodium(II) complexes with oxo thioethers was prepared and employed as catalysts for the silane alcoholysis reaction. The complexes were found to be highly active under homogeneous conditions, both in the absence and in the presence of a solvent, including coordinating solvents such as N,N-dimethylformamide; the catalysts could be conveniently employed in concentrations as low as
Hidden Enantioselective Hydrogenation of N-Silyl Enamines and Silyl Enol Ethers in Net C═N and C═O Hydrosilylations Catalyzed by Ru–S Complexes with One Monodentate Chiral Phosphine Ligand
作者:Susanne Bähr、Martin Oestreich
DOI:10.1021/acs.organomet.7b00030
日期:2017.2.27
Ruthenium thiolate complexes with one chiral monodentate phosphine ligand are applied to enantioselective hydrosilylation of enolizable 'mines and ketones. The structural features of the catalyst exclude the presence of more than one phosphine ligand at the ruthenium center in the enantioselectivity-determining step. The enantiomeric excesses obtained in these reduction reactions ate moderate (up to 66% ee), but the stereochemical outcome enables an experimental analysis of the reaction pathways operative in this catalysis. A two-step sequence consisting of successive N-Si/O Si dehydrogenative coupling and enamine/enol ether hydrogenation is, the prevailing mechanisin Of action. Both steps involve cooperative bond activation at the Ru-S bond of the coordinatively unsaturated ruthenium complex: Si-H bond activation in the dehydrogenative coupling and heterolytic H-H splitting in the hydrogenation. Previously documented side reactions such as deprotonation/protonation equilibria as well as competing direct C=N or C=O hydrogenation have been excluded.