Ketone hydrogenation, asymmetric catalysis

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. 

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. 

Only partial solutions have been provided thus far to many of the most important transformations amenable to asymmetric catalysis. For example, no generally effective methods exist yet for enantioselective epoxidation or aziridination of terminal olefins, or for hydroxylation of C-H bonds of any type. Despite the enormous advances in asymmetric hydrogenation catalysis, highly enantioselective reduction of dialkyl ketones remains elusive [9]. And as far as asymmetric C-C bond-forming reactions are concerned, the list of successful systems is certainly shorter than the list of reactions waiting to be developed. 

Asymmetric catalysis by low-valent transition-metal complexes has enormous potential for organic chemistry, but many of its present limitations must be overcome before this can be realized. With existing ligands, hydrogenation of enamides and certain unsaturated carboxylic acids is optically efficient, as is the hydrogenation of ct-amino ketones(58),... 

The asymmetric hydrogenation of prochiral ketones is often an important step in the industrial synthesis of fine and pharmaceutical products. Several noble metal nanoparticles have been investigated for asymmetric catalysis of prochiral substrates but platinum colloids have been the most widely studied and relevant enantiomeric excesses have been reported (>95%). Nevertheless, the enantioselec-tive hydrogenation of ethyl pyruvate catalyzed by PVP-stabilized rhodium nanocluster modified by cinchonidine and quinine was reported by Li and coworkers (Scheme 11.7) [68]. 

Felfoldi, K., Balazsik, K., Bartok, M. (2003) Heterogeneous asymmetric catalysis. Part 32. High enantioselectivities in the hydrogenation of activated ketones on cinchona alkaloid modified Platinum-alumina catalysts, J. Mo/. Catal. A. Chem. 202, 163-170. 

Most reactions involving asymmetric catalysis are based around the conversion of a planar sp carbon atom into a tetrahedral sp carbon atom. This category of reactions includes asymmetric hydrogenation of alkenes and ketones, as well as the addition of other reagents to these groups as identified in Figure 1.1. 

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