Further insight in the minor/major concept using hydrogen pressure effect in asymmetric hydrogenation

The catalytic system prepared from [Rh(COD)2]BF4 and (R,R)-Me-BPE provides a spectacular detrimental hydrogen pressure effect on ee from 94% down to 56% in the hydrogenation of methylacrylate, whereas it has a strong beneficial effect on the hydrogenation of E-emap (from 42% up to 72%). The kinetic parameters have been determined for both systems and have helped to identify the most enantioselective controlling steps (MECS). Accordingly, further explanations for the structure-ee and hydrogen pressure relationship are proposed.

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► Spectacular opposite hydrogen pressure effects on ee for one catalyst Rh/(R,R)-Me-BPE.
► Major-minor vs. key-and-lock principles domination depends on hydrogen pressure.
► Relation between hydrogen pressure effects on ee and substrate structure is discussed.
► Full set of kinetic constants provided for 2 catalytic systems.