Noyori defined

Noyori and coworkers reported well-defined ruthenium(II) catalyst systems of the type RuH( 76-arene)(NH2CHPhCHPhNTs) for the asymmetric transfer hydrogenation of ketones and imines [94]. These also act via an outer-sphere hydride transfer mechanism shown in Scheme 3.12. The hydride transfer from ruthenium and proton transfer from the amino group to the C=0 bond of a ketone or C=N bond of an imine produces the alcohol or amine product, respectively. The amido complex that is produced is unreactive to H2 (except at high pressures), but readily reacts with iPrOH or formate to regenerate the hydride catalyst. 

Noyori (4) has recently disclosed the mechanistically intriguing condensation of enolsilanes and acetals, which is catalyzed by tri-methylsilyl triflate (69) (eq. [61]). The results of a set of representative condensations between stereochemically defined enolates and... 

In reactions exhibiting a (+)-NLE, some authors have quantified the magnitude of the amplification by comparing the ee of the product obtained with that expected if there were a linear correlation between catalyst and product ees. However, as previously mentioned, the ratio of ees gives a less informative index of amplification than when compared with ers. Thus we propose to define routinely the size of an amplification (the amplification index /) as the ratio of the enantiomeric ratio (er) of the product experimentally observed to the er of the product expected for a linear relationship. This amplification index / has been plotted against eeai)X in the case of the diethylzinc addition to benzaldehyde catalyzed by (-)-DAIB 2, as described by Noyori et al. (Scheme 8, top). Here the maximum amplification (with I = 32) occurs when DAIB has an eeaux of approximately 20%. Expressing the amplification in terms of the ratio of ees,... 

In 2005, M. Wills and coworkers reported the synthesis of a Ru(II) tethered version of Noyori s catalysts 3.28 (Figure 3.10). These complexes have a rigid stmcture and are stereochemically well defined moreover they are very active catalysts for asymmetric hydrogenation of ketones. 

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