Substrate adsorption on the cinchonidine-modified Pd/C during the enantio-differentiating hydrogenation as a vital stereocontrol factor
✍ Scribed by Tomonori Misaki; Hisafumi Otsuka; Takayuki Uchida; Takeshi Kubota; Yasuaki Okamoto; Takashi Sugimura
- Book ID
- 103835125
- Publisher
- Elsevier Science
- Year
- 2009
- Tongue
- English
- Weight
- 426 KB
- Volume
- 312
- Category
- Article
- ISSN
- 1381-1169
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✦ Synopsis
Two regioisomeric ␣-phenyl--pyridylacrylic acids were hydrogenated with cinchonidine (CD)-modified Pd/C. The low ee obtained was attributed to the strong adsorption of the substrate, which caused desorption of CD from the catalyst surface. The ee was improved at the low substrate/CD ratio up to 82% for the 4-pyridyl isomer. The unmodified site in the CD-modified Pd catalyst was experimentally proved to be variable depending on the relative adsorption strength between the substrate and CD. At the low substrate/CD ratio, the ee with the 3-pyridyl isomer was also improved, but the highest ee was only 45%. The difference between the isomers suggests that the strong adsorption of the substrate on the metal surface may interrupt the interaction between CD and the substrate.