INFLUENCE OF DIFFERENT TYPES OF AMPHIPHILES ON THE RHODIUM(I) COMPLEX-CATALYZED ASYMMETRIC HYDROGENATION OF (Z)-METHYL-ALPHA-ACETAMIDOCINNAMATE IN AQUEOUS-MEDIUM

The homogeneous asymmetric hydrogenation of (Z)-methyl-alpha-acetamido cinnamate catalyzed by the system Rh(COD)2!BF4 + 1.1 BPPM could be ef fected in water as medium in the presence of micelle-forming amphiphil es. Both activity and enantioselectivity were enhanced significantly a nd have been compared with results obtained in methanol as solvent. Th e effect was found with nonionic, zwitterionic and anionic surfactants and depends on the critical micelle concentration. Cationic surfactan ts like hexadecylalkyl ammonium salts act according to the anion as in hibitor (e.g. bromide), or promotor (e.g. hydrogensulfate). The princi ple of enhancing activity and stereoselectivity in complex-catalyzed h ydrogenation due to micelles seems to be a phenomenon of general impor tance.