Hydrogenation of Olefins and Ketones

2 Asymmetric Catalysis with Chiral Ferrocenylphosphine Ligands 

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Chiral ligands for homogeneous hydrogenation of olefins and ketones... 

As in asymmetric hydrogenation of olefins and ketones, chiral diphosphine-Rh or -Ir complexes have frequently been used as catalysts [ 1,162,335]. Recently, a chiral titanocene catalyst... 

Thus, according to Sabatier the hydrogenations of olefins and ketones are the same type of reaction, while according to the multiplet classification these two reactions are of different types, and indeed, the two reaction types require two different catalysts. Naturally, in the application of a given classification the thermodynamic nature of the reactions should be taken into account as well as their structural aspects. This classification and thermodynamic requirements do not yet deal with the kinetics of processes. The latter is involved in the principles of structural and energetic correspondence of the multiplet theory. 

Avidin is a glycoprotein and consists of four identical subunits. Avidin shows a very strong affinity to biotin with a of approximately 10 M (Fig. Ic). The affinity of avidin for biotin can be utilized to introduce metal complexes into the avidin cavity by a covalent bond with biotin. In fact, hybrids of avidin and biotin conjugated with Rh diphosphine and Ru diamine moieties have been shown to allow asymmetric hydrogenations of olefin and ketone substrates [8,25,26]. 

Rhodium and ruthenium complexes of 2,2 -bis(diphenylphosphino)-l,l -binaphthyl (BINAP) have frequently been used as catalysts for enantioselective hydrogenation of olefins and ketones." "" From consideration of the literature on this subject, it was proposed that the presence of a mono-oxidized BINAP in an organometallic catalyst could have interesting consequences." Accordingly, Rh(BINAP)(CO)Cl was prepared, and upon reaction with O2, (BINAP(0))Rh(CO)Cl was formed. These compounds were authenticated by X-ray crystallography, and IR and NMR spectroscopies. The kinetics of this reaction were monitored by solution (chloroform was the solvent) IR spectroscopy. In the absence of added CO, the oxygenated compound was formed in about 50% yield. BINAP(0)2 and CO2 are also produced. Plots of obs (from loss of reactant) versus [O2] at various temperatures yielded... 

Asymmetric catalytic reduction reactions represent one of the most efficient and convenient methods to prepare a wide range of enantiomerically pure compounds (i.e. a-amino acids can be prepared from a-enamides, alcohols from ketones and amines from oximes or imines). The chirality transfer can be accomplished by different types of chiral catalysts metallic catalysts are very efficient for the hydrogenation of olefins, some ketones and oximes, while nonmetallic catalysts provide a complementary method for ketone and oxime hydrogenation. 

Historically, since the Wilkinson catalyst [RhCKPPhjj] proved to be active for hydrosilylation of ketones with hydrosilanes in the early 1970s, the asymmetric version has been examined by using many optically active phosphorus ligands, which were mainly developed for the asymmetric hydrogenation of olefins. Many ketones were cataly tically reduced in high yields with moderate enantioselectiv-ities. As representative milestones, the first trial with (-l-)-DIOP (LI Fig. 1) and... 

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