Ruthenium complexes, Noyori catalytic

Review. Noyori has reviewed homogeneous asymmetric catalysis, particularly by complexes of (R)- and (S)-BINAP with ruthenium. He suggests possible reasons for the high efficiency of Ru-BINAP complexes in catalytic hydrogenation (40 references). 

More recently Noyori developed asymmetric hydrogenation of simple ketones with BlNAP/diamine-ruthenium complexes.In this system the catalytic process contrasted with the conventional mechanism of asymmetric hydrogenation of unsaturated bonds which requires metal-substrate 7t-complexation. In fact with BlNAP/diamine-ruthenium neither the ketone substrate nor the alcohol product interacted with the metallic centre during the catalytic cycle. The enantiofaces of the prochiral ketones were differentiated on the molecular surface of the coordinatively saturated RuH intermediate. 

KRs based on the oxidation of a chiral secondary alcohol to a prochiral ketone has been of considerable interest as the later can be usually recycled into the racemic starting material by simple hydride reduction [2d, 55]. The first broadly applicable method for this purpose was reported by Noyori et al. [56], under catalytic hydride transfer conditions similar to those employed for the asymmetric hydrogenation of ketones. For example, excellent results (s>50) have been reported for the KR of benzyhc alcohols by using a chiral diamine-ruthenium complex in the... 

The present interest in asymmetric catalysis was demonstrated by awarding Nobel prizes to three winners W. S. Knowles (USA) for elaboration of rhodium complex catalysts effective in asymmetric synthesis of anti-Parkinson medicine, R. Noyori (Japan) for elaboration of a new catalytic system based on chiral ruthenium-phosphine complex catalysts that are very effective in hydrogenation reactions, and B. Sharpless (USA) for elaboration of epoxidation and other reactions under the action of chiral titanium complexes. 

Ligand-metal bifunctional catalysis provides an efficient method for the hydrogenation of various unsaturated organic compounds. Shvo-type [83-85] Ru-H/OH and Noyori-type [3-7] Ru-H/NH catalysts have demonstrated bifimctionality with excellent chemo- and enantioselectivities in transfer hydrogenations and hydrogenations of alkenes, aldehydes, ketones, and imines. Based on the isoelectronic analogy of H-Ru-CO and H-Re-NO units, it was anticipated that rhenium nitrosyl-based bifunctional complexes could exhibit catalytic activities comparable to the ruthenium carbonyl ones (Scheme 29) [86]. 

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