Premium
Enantioselective Hydrogenation of N ‐Acetyldehydroamino Acids over Supported Palladium Catalysts
Author(s) -
Szöllősi György,
Szabó Emese,
Bartók Mihály
Publication year - 2007
Publication title -
advanced synthesis and catalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.541
H-Index - 155
eISSN - 1615-4169
pISSN - 1615-4150
DOI - 10.1002/adsc.200600304
Subject(s) - cinchonidine , chemistry , cinchonine , enantioselective synthesis , benzylamine , enantiomeric excess , catalysis , cinchona , asymmetric hydrogenation , enantiomer , palladium , organic chemistry , cinchona alkaloids , medicinal chemistry
The enantioselective hydrogenation of two N ‐acetyldehydroamino acids over Cinchona alkaloid‐modified, supported palladium catalysts has been studied. Moderate enantioselectivities, up to 36 %, were obtained in the hydrogenation of 2‐acetamidocinnamic acid over cinchonidine‐modified Pd/TiO 2 under low hydrogen pressure. Increase in the pressure or use of benzylamine as additive led to a gradual decrease in the enantiomeric excess and eventually inversion of the sense of the enantioselectivity. On the contrary, the optical purity of the product resulting from the hydrogenation of 2‐acetamidoacrylic acid was significantly increased by addition of benzylamine to the reaction mixture. Enantiomeric excess values up to 58 % and 60 % were obtained over Pd/Al 2 O 3 modified by cinchonidine and cinchonine, respectively. These optical purities are the best obtained in the hydrogenation of dehydroamino acid derivatives over chirally modified heterogeneous metal catalysts.