2-Acetamidocinnamic acid, formation

Asymmetric hydrogen transfer from EtOH, /-PrOH or triethylammonium formate to Z-a-acetamidocinnamic acid Z-3.32 (R = Ph, Z = COMe, R = H) or to itaconic acid 7.7 (R = H) is highly enantioselective when the catalyst is a binap-Ru complex [873, 1333] (Figure 7.14). The relationship between the absolute configuration of the saturated add and the binap ligand is the same as in the catalytic hydrogenation. However, hydrogen transfer to other a,P-unsaturated acids, such as the precursor of naproxen (7.15), is less enantioselective [1333],... 

Formation of a a-alkylrhodium by insertion of an alkene into a Rh—H bond is a key step in homogeneous asymmetric hydrogenation of alkenes by Rh(I) catalysts. Such intermediates are characterized using multinuclear NMR both in hydrogenation of (Z)-a-acetamidocinnamate by [Rh(Ph2 PCH2 CHj PPhj)] and in the asymmetric hydrogenation of a-benzamidocinnamic acid or its methyl ester by (R,R)-l,2-bis(o-methoxy-phenylphenylphosphino)ethane complexes of Rh(I) . 

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