Modifier-substrate interactions of various types in the Orito reaction: Reversal of the enantioselection in the hydrogenation of ketopantolactone on Pt modified by ¦Â-isocinchonine and O-phenylcinchonidine

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• 作者：Gyö ; rgy Sző ; llő ; si^a ; ^{szollosi@chem.u-szeged.hu} ; Katalin Balá ; zsik^a ; Imre Bucsi^b ; Tibor Bartó ; k^c ; Mihá ; ly Bartó ; k^a ; ^b ; ^{bartok@chem.u-szeged.hu}
• 关键词：Enantioselective hydrogenation ; Platinum ; Cinchona alkaloid ; Ketopantolactone ; Reversal of enantioselectivity ; Intermediate complexes
• 刊名：Catalysis Communications
• 出版年：2013
• 出版时间：5 February, 2013
• 年：2013
• 卷：32
• 期：Complete
• 页码：81-85
• 全文大小：474 K

文摘

The enantioselective hydrogenation of ketopantolactone (KPL) on Pt-alumina catalyst modified by ¦Â-isocinchonine (¦Â-ICN) and O-phenylcinchonidine (PhOCD) in toluene, acetic acid and their mixtures under otherwise identical experimental conditions was studied. Reversal of the enantioselection was obtained dependent on the concentration of acetic acid (ee_max = 17 % (S) on Pt-PhOCD and 50 % (R) on Pt-¦Â-ICN, respectively). The possible role in enantioselection of adducts forming in the reaction mixture and the stability of PhOCD under the conditions of the hydrogenation was investigated by ESI-MS. The results of the nonlinear phenomenon measurements on ¦Â-ICN + PhOCD mixtures suggest that the intermediate surface complexes ¦Â-ICN-KPL and PhOCD-KPL responsible for the opposite enantioselection include different types of interactions and the enantioselection is directed by the competition between these interactions.