Asymmetric hydrogenation olefin route

P is an optically active tertiary phosphine, likely will resemble the RhCl(PPh3)3 system (23). However, even in this exhaustively studied system, both hydride and/or unsaturate routes are feasible (23, 24) by varying conditions, the choice of route could affect stereoselectivity. Most asymmetric hydrogenations have used prochiral olefinic acid substrates, and these systems have not been thoroughly studied even with nonchiral catalysts. 

There is no doubt that catalytic asymmetric synthesis has a significant advantage over the traditional diastereomeric resolution technology. However, it is important to note that for the asymmetric hydrogenation technology to be commercially useful, a low-cost route to the precursor olefins is just as crucial. The electrocarboxylation of methyl aryl ketone and the dehydration of the substituted lactic acids in Figures 5 and 6 are highly efficient. Excellent yields of the desired products can be achieved in each reaction. These processes are currently under active development. However, since the subjects of electrochemistry and catalytic dehydration are beyond the scope of this article, these reactions will be published later in a separate paper. 

Optically active aldehydes are important precursors for biologically active compounds, and much effort has been applied to their asymmetric synthesis. Asymmetric hydroformylation has attracted much attention as a potential route to enantiomerically pure aldehyde because this method starts from inexpensive olefins and synthesis gas (CO/H2). Although rhodium-catalyzed hydrogenation has been one of the most important applications of homogeneous catalysis in industry, rhodium-mediated hydroformylation has also been extensively studied as a route to aldehydes. 

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