Just a little bit: The 1/FeCl2 complex was activated in the presence of Zn and exhibited catalytic activity for the hydrosilanereduction of ketones to give the S‐configured alcohol. In contrast, the mixed‐catalyst system of 1 and Fe(OAc)2 provides the R enantiomer. This approach provides both enantiomers from a single chiral source by the addition of a small amount of Zn.
system based on manganese pentacarbonyl bromide, as metal precursor, and ethylenediamine as ligand. The reaction proceeds in high yield at 80 °C, in 3 h, with 0.5 mol% of catalyst. In the presence of chiral (1R,2R)-N,N′-dimethyl-1,2-diphenylethane-1,2-diamine, as the ligand, sterically hindered alcohols were produced with enantiomeric excess up to 90%.
A series of commercially available chiral amino-phosphines, in combination with Mn(CO)5Br, has been evaluated for the asymmetricreduction of ketones, using isopropanol as hydrogen source. With the most selective ligand, the corresponding manganese complex was synthesized and fully characterized. A series of ketones (20 examples) was hydrogenated in the presence of 0.5 mol% of the manganese pre-catalyst
achiral electron-rich mono-phosphine ligand, catalyzes efficient asymmetric hydrogenation of a wide range of aryl ketones, affording chiral alcohols with high yields and moderate to excellent enantioselectivities (29 examples, up to 93% ee). Notably, the achiral mono-phosphine ligand shows a remarkable effect on the enantioselectivity of the reaction.
For the catalytic enantioselective borohydride reduction, the theoretical simulation of various axial groups in Co complex catalysts predicted that the Co–carbene complexes could be employed as efficient catalysts. The newly designed complexes generated from the Co complex and methyl diazoacetate made it possible to catalyze the enantioselective borohydride reduction in a halogen-free solvent.