Hydrogenation mechanism of enantioselective

The mechanism of enantioselective hydrogenation by rhodium complexes has been reviewed on several occasions, including a recent detailed publication by the present author [14]. In addition, much of the contemporary work by Gridnev and Imamoto has been reviewed, as described below. Consequently, details of the older studies will be cited only briefly to provide the necessary context, after which the post-1998 developments will be discussed in detail. For a mature field, it is surprising how much new and significant information has been reported during the past five years. 

The mechanism of enantioselective hydrogenation on nickel catalysts modified with optically active compounds was suggested for the first time by Balandin s group They proposed that the reaction proceeded through an intermediate complex involving catalyst metal atom, (Ni), modifier molecule, (M), and substrate molecule, (S) Ni-M-S. Similar models were proposed later by Yasumori et al and Izumi and Tai... 

According to the generally accepted mechanism of enantioselective hydrogenation by Rh complexes, co-ordination of the substrate to the solvated Rh complex to form the bidentate catalyst-substrate complex, outlined in Fig. 2.5, was invoked. 

Scheme 7.3 Mechanism of enantioselective hydrogenation of imines by (R,R)-(EBTHI)TiF2/ PhSiH3 catalytic system...

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