Immobilization of rhodium complexes in aqueous HBF4. The enantioselective hydrogenation of prochiral olefins with RhNBD>5+

Article abstract of DOI:10.1016/0022-328X(90)85477-G

The complex <-RhNBD>⁵⁺ is active for the enantioselective hydrogenation of cinnamic acid derivatives at low pH in aqueous solutions of the noncoordinating acid HBF4.Analytical data are consistent with protonation occuring exclusively at the dimethylamino groups and not at the metal.Enantiomeric excesses of 67 to 97percent are obtained for the hydrogenation of Z-(4-OMe, 3-OAcC6H3CH=C(NHC(O)Me)-COOH in aqueous HBF4 at 14 bar H2.The use of aqueous acidic solutions allows for the convenient workup of the product and recycling of the catalyst.