Hydrogenation, asymmetric catalysis

As mentioned in Sect. 2.2, phosphine oxides are air-stable compounds, making their use in the field of asymmetric catalysis convenient. Moreover, they present electronic properties very different from the corresponding free phosphines and thus may be employed in different types of enantioselective reactions, m-Chloroperbenzoic acid (m-CPBA) has been showed to be a powerful reagent for the stereospecific oxidation of enantiomerically pure P-chirogenic phos-phine-boranes [98], affording R,R)-97 from Ad-BisP 6 (Scheme 18) [99]. The synthesis of R,R)-98 and (S,S)-99, which possess a f-Bu substituent, differs from the precedent in that deboranation precedes oxidation with hydrogen peroxide to yield the corresponding enantiomerically pure diphosphine oxides (Scheme 18) [99]. 

Brown JB (1999) Hydrogenation of functionalised carbon-carbon double bonds. In Jacobsen EN, Pfaltz A, Yamamoto H (eds) Comprehensive asymmetric catalysis, vol 1. Springer, Berhn Heidelberg New York, chap 5.1 Noyori R, Takaya H (1990) Acc Chem Res 23 345... 

R. Noyori and T. Ohkuma, Asymmetric Catalysis by Architectural and Functional Molecular Engineering Practical Chemo- and Stereoselective Hydrogenation of Ketones , Angew. Chem. Int. Ed. Engl, 2001, 40, 40. 

The hydrogenation of a cinnamate was also investigated as a first step to determine kinetics and finally to come to a quantitative determination of kinetic models and parameters in asymmetric catalysis [64]. The enantiomeric excess of enantioselective catalytic hydrogenations is known to be dependent on pressure, chiral additives and mixing. Such dependences are often due to kinetics, demanding appropriate studies. 

Ohkuma, T. and Noyori, R. (2004) Hydrogenation of carbonyl groups, in Comprehensive Asymmetric Catalysis, Supplement I (eds. E.N. Jacobsen, A. Pfaltz and H. Yamamoto), Springer, Berlin, pp. 1-41. 

Noyori, R. and Okhuma, T. (2001) Asymmetric catalysis by architectural and functional molecular engineering practical chemo- and stereoselective hydrogenation of ketones. Angewandte Chemie-International Edition, 40 (1), 40-73. 

Annual Volume 71 contains 30 checked and edited experimental procedures that illustrate important new synthetic methods or describe the preparation of particularly useful chemicals. This compilation begins with procedures exemplifying three important methods for preparing enantiomerically pure substances by asymmetric catalysis. The preparation of (R)-(-)-METHYL 3-HYDROXYBUTANOATE details the convenient preparation of a BINAP-ruthenium catalyst that is broadly useful for the asymmetric reduction of p-ketoesters. Catalysis of the carbonyl ene reaction by a chiral Lewis acid, in this case a binapthol-derived titanium catalyst, is illustrated in the preparation of METHYL (2R)-2-HYDROXY-4-PHENYL-4-PENTENOATE. The enantiomerically pure diamines, (1 R,2R)-(+)- AND (1S,2S)-(-)-1,2-DIPHENYL-1,2-ETHYLENEDIAMINE, are useful for a variety of asymmetric transformations hydrogenations, Michael additions, osmylations, epoxidations, allylations, aldol condensations and Diels-Alder reactions. Promotion of the Diels-Alder reaction with a diaminoalane derived from the (S,S)-diamine is demonstrated in the synthesis of (1S,endo)-3-(BICYCLO[2.2.1]HEPT-5-EN-2-YLCARBONYL)-2-OXAZOLIDINONE. 

Asymmetric catalysis by chiral rhodium complexes in both hydrogenation and hydrosilation have been found. Kagan (42) recently reported that the chiral phosphine rhodium complex [(—)-DIOPRhCl]2 gave the most efficient asymmetric syntheses observed to date. This complex is ... 

Asymmetry in metal-alkene coordination plays a critical role in asymmetric catalysis, with implications far beyond the scope of the present treatment. An instructive example is provided by catalytic asymmetric hydrogenation of enamides,... 

The enantioselective hydrogenation of prochiral substances bearing an activated group, such as an ester, an acid or an amide, is often an important step in the industrial synthesis of fine and pharmaceutical products. In addition to the hydrogenation of /5-ketoesters into optically pure products with Raney nickel modified by tartaric acid [117], the asymmetric reduction of a-ketoesters on heterogeneous platinum catalysts modified by cinchona alkaloids (cinchonidine and cinchonine) was reported for the first time by Orito and coworkers [118-121]. Asymmetric catalysis on solid surfaces remains a very important research area for a better mechanistic understanding of the interaction between the substrate, the modifier and the catalyst [122-125], although excellent results in terms of enantiomeric excesses (up to 97%) have been obtained in the reduction of ethyl pyruvate under optimum reaction conditions with these Pt/cinchona systems [126-128],... 

Knowles, W. S. Asymmetric hydrogenations — The Monsanto L-Dopa process. In Blaser, H.-U., Schmidt, E. (Eds.), Asymmetric Catalysis on Industrial Scale. Wiley-VCH, Weinheim, 2004, p. 23. 

Bisphosphinamidites which are supported by an axially chiral framework are another important class of ligands. Although reported as early as 1980 [50], no reports on the use of binaphthyl-based bisphosphinamidite in asymmetric catalysis were published during the decade thereafter. As described above, the selectivity and substrate generality in these early attempts were very limited in scope. In 1998, we unveiled that by partially hydrogenating BINAM to H8-BINAM and... 

Chaloner, P.A., Esteruelas, M.A., Joo, F., Oro, L.A., Homogeneous Hydrogenation, Kluwer, Dordrecht, 1994 Noyori, R., Asymmetric Catalysis in Organic Synthesis (especially Chapter 2), John Wiley Sons, Inc., New York, 1994 Ojima, I. (Ed.), Catalytic Asymmetric Synthesis,... 

One of the first applications of the then newly developed Ru-binap catalysts for a,/ -unsaturated acids was an alternative process to produce (S)-naproxen. (S)-Naproxen is a large-scale anti-inflammatory drug and is actually produced via the resolution of a racemate. For some time it was considered to be one of the most attractive goals for asymmetric catalysis. Indeed, several catalytic syntheses have been developed for the synthesis of (S)-naproxen intermediates in recent years (for a summary see [14]). The best results for the hydrogenation route were obtained by Takasago [69] (Fig. 37.15), who recently reported that a Ru-H8-binap catalyst achieved even higher activities (TON 5000, TOF 600 h 1 at 15 °C, 50 bar) [16]. 

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