Asymmetric hydrogenation,

Asymmetric Hydrogenation. Asymmetric hydrogenation with good enantio-selectivity of unfunctionalized prochiral alkenes is difficult to achieve.144 145 Chiral rhodium complexes, which are excellent catalysts in the hydrogenation of activated multiple bonds (first, in the synthesis of a-amino acids by the reduction of ol-N-acylamino-a-acrylic acids), give products only with low optical yields.144 146-149 The best results ( 60% ee) were achieved in the reduction of a-ethylstyrene by a rhodium catalyst with a diphosphinite ligand.150 Metallocene complexes of titanium,151-155 zirconium,155-157 and lanthanides158 were used in recent studies to reduce the disubstituted C—C double bond with medium enantioselectivity. 

Keywords Asymmetric hydrogenation, Asymmetric transfer hydrogenation, BINAP, Chiral alcohols, Chiral amines, Homogeneous catalysts, Simple ketones... 

Reactions with 1,1,1 -trifluoro-2-(acetyloxy)-2-propene provide the first example of a vinyl acetate with a fully saturated substituent geminal to the heteroatom to be hydrogenated asymmetrically with high efficiency (eq 4). ... 

Enzymatic hydrogenations generate optically pure isomers attempts to initiate such processes are made on metal-catalyzed hydrogenations. Asymmetric hydrogenation can fill the need for asymmetric compounds of which only one enantiomorph is active, e.g., amino acids such as L-lysine, 1 (indispensable in animal feeds), L-phenylalanine, 2 (a sweet peptide component), L-dopa 3 (a drug for Parkinsonism), are required in the L-form for human or animal consumption. Consequently, most of the examples investigated are related to the asymmetric hydrogenation of acrylic acid or cinnamic acid derivatives. 

Progress in catalytic asymmetric hydrogenation (asymmetric hydrogenation of N- and O-heterocycles, heterocycles as chiral ligands in catalysts 01MI132. 

Alkylrhodiums form from the reaction of Rh hydrides and alkenes. This reaction is important in hydrogenation, asymmetric hydrogenation, alkene isomerization and hydroformylation and other catalytic processes. The regiochemistry seen in this reaction is the subject of theoretical study that rationalizes the formation of the less substituted (T-alkyrhodium intermediate on electronic grounds Several Rh complexes form stable ff-alkylrhodiums on reaction of Rh hydrides with fluorinated alkenes (see Table 8) . 

HYDROGENATION, ASYMMETRIC (-)-and (+)-2,3-0-IsopropyIidene-2,3-dihydroxy-l,4-bis(diphenyIphosphine)butane. Neomenthyldiphenylphosphine. HYDROGENATION CATALYSTS frthap/o-AlIyltris(trimethylphosphite)cobalt(I). Lindlar catalyst. Palladium catalysts. Palladium(II) chloride. Rhodium-on-carbon. Tris(triphenylphosphine)chlotorhodium. Tris(triphenylphosphine)ruthenium dl-chloride. Urushibara catalysts. 

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