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Enantioselective homogeneous catalytic hydrogenation

Fig. 17.77. Enantioselective homogeneous catalytic hydrogenations of two stereoiso-meric -(acylamino)acrylic acids to one and the same R-amino acid. - The mechanism of the hydrogenation of these acids is exemplified by their Z-isomer Figure 17.78. Fig. 17.77. Enantioselective homogeneous catalytic hydrogenations of two stereoiso-meric -(acylamino)acrylic acids to one and the same R-amino acid. - The mechanism of the hydrogenation of these acids is exemplified by their Z-isomer Figure 17.78.
Enantioselective homogeneous catalytic hydrogenations of an a-(acylamino)acrylic acid to an R-amino acid. [Pg.603]

This chapter aims to provide an overview of the current state of the art in homogeneous catalytic hydrogenation of C=0 and C=N bonds. Diastereoselec-tive or enantioselective processes are discussed elsewhere. The chapter is divided into sections detailing the hydrogenation of aldehydes, the hydrogenation of ketones, domino-hydroformylation-reduction, reductive amination, domino hydroformylation-reductive amination, and ester, acid and anhydride hydrogenation. [Pg.413]

Asymmetric reduction with very high enantioselectivity has also been achieved with achiral reducing agents and optically active catalysts. Two approaches are represented by (1) homogeneous catalytic hydrogenation with the catalyst 2,2 -bis(diphenylphosphino)-1,1 -binaphthyl-ruthenium acetate, BINAP Ru(OAc)2, which reduces... [Pg.1800]

The process of homogeneous catalytic hydrogenation can be made enantioselective by establishing a chiral environment at the catalytic metal center. Most of the successful cases of enantioselective hydrogenation involve reactants having a potential... [Pg.189]

Recent work by several research groups has shown that supercritical fluids can be superior to other solvents for several chemical processes. For example, DeSimone has demonstrated the ability of supercritical CO2 to replace Freons in the free radical polymerization of fluorinatkl acrylate monomers. 34) Noyori has shown that significant rate enhancements can be achieved in supercritical carbon dioxide relative to other solvents for the homogeneous catalytic hydrogenation of carbon dioxide to either formic acid or its derivatives in the presence of triethylamine or triethylamine/methanol respectively, (equation 1). (55-57) As discussed below, we have recently demonstrated that improved enantioselectivities can be achieved in supercritical carbon dioxide for the catalytic asymmetric hydrogenation of several enamides. 5 8)... [Pg.133]

The synthesis of cationic rhodium complexes constitutes another important contribution of the late 1960s. The preparation of cationic complexes of formula [Rh(diene)(PR3)2]+ was reported by several laboratories in the period 1968-1970 [17, 18]. Osborn and coworkers made the important discovery that these complexes, when treated with molecular hydrogen, yield [RhH2(PR3)2(S)2]+ (S = sol-vent). These rhodium(III) complexes function as homogeneous hydrogenation catalysts under mild conditions for the reduction of alkenes, dienes, alkynes, and ketones [17, 19]. Related complexes with chiral diphosphines have been very important in modern enantioselective catalytic hydrogenations (see Section 1.1.6). [Pg.10]

As recently recognized by the Nobel Chemistry award committee, the conceptualization, development, and commercial application of enantioselective, homogeneous hydrogenation of alkenes represents a landmark achievement in modem chemistry. Further elaboration of asymmetric hydrogenation catalysts by Noyori, Burk, and others has created a robust and technologically important set of catalytic asymmetric synthetic techniques. As frequently occurs in science, these new technologies have spawned new areas of fundamental research. Soon after the development of... [Pg.107]

Selectivity could be of different type—chemoselectivity, regioselectivity, enantioselectivity, etc. Reactions 1.11-1.13 are representative examples of such selectivities taken from homogeneous catalytic processes. In all these reactions, the possibility of forming more than one product exists. In reaction 1.11 a mixture of normal and isobutyraldehyde rather than propane, the hydrogenation product from propylene, is formed. This is an example of chemoselectivity. Furthermore, under optimal conditions normal butyraldehyde may be obtained with more than 95% selectivity. This is an example of regioselectivity. Similarly, in reaction 1.12 the alkene rather than the alcohol functionality of allyl... [Pg.5]

Polymer-supported chiral catalysts have likewise been prepared in order to obtain access to reusable systems (cf. Section 3.1.1, especially Section 3.1.1.3). For example, copolymerized functionalized BINAP [160, 161] could be applied in the enantioselective hydrogenation of olefinic substrates (up to 94 % ee). Similarly, the copolymerization of vinyl-BINAPHOS with styrene derivatives led to a heterogenized auxiliary which made it possible to hydroformylate styrene and vinyl acetate (Rh catalysis) with selectivities and enantioselectivities close to those provided by the parent homogeneous catalytic system [162]. [Pg.1026]

As a result, the majority of contributions to the present edition have had to be either updated or completely replaced by new articles. This applies to the sections mentioned above, but also to the rapidly growing area of enantioselective synthesis (Sections 3.3.1 and 3.2.6), the catalytic hydrogenation of sulfur- and nitrogen-containing compounds in raw oils (Section 3.2.13), the Pauson-Khand reaction (Section 3.3.7), and a number of industrially relevant topics covered under Applied Homogeneous Catalysis in Part 2. New aspects of organometallic catalysis have emerged from the chemistry of renewable resources (Section 3.3.9) and the chemistry around the multi-talented catalyst methyltrioxorhenium (Section 3.3.13). [Pg.1460]


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Enantioselectivity homogeneous hydrogenation

Enantioselectivity hydrogenation

Homogeneous Hydrogenated

Homogeneous catalytic hydrogenation

Hydrogen enantioselective

Hydrogen enantioselectivity

Hydrogen homogeneous

Hydrogenation enantioselective

Hydrogenation homogenous

Hydrogenation, catalytic enantioselective

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