Anomalous Ligand Acceleration on Cinchona-modified Pd/C during Asymmetric Hydrogenation of Properly Substituted Phenylcinnamic Acid

作者：Ogawa Hiroyuki; Mameda Takuya; Misaki Tomonori; Okamoto Yasuaki; Sugimura Takashi^*

来源：Chemistry Letters, 2013, 42(8): 813-815.

DOI：10.1246/cl.130245

The hydrogenation of 4,4%26apos;-dimethoxy-alpha-phenylcinnamic acid over Pd/C showed a large ligand acceleration effect when a cinchonidine modifier was used; the hydrogen rate increased to 370% relative to the reaction rate on unmodified Pd/C and resulted in a 91% enantiomeric excess (ee). Another good substrate, 4-fluoro-2%26apos;-methoxyphenylcinnamic acid, also resulted in a high ee value of 92%; however, the rate increased only to 230% when this modifier was used. On the basis of the difference in the degree to which the reaction rate was accelerated, the ee(max) for each substrate was analyzed.

• 出版日期2013-8-5