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Monitoring Surface Processes During Heterogeneous Asymmetric Hydrogenation of Ketones on a Chirally Modified Platinum Catalyst by Operando Spectroscopy
Author(s) -
Meemken Fabian,
Hungerbühler Konrad,
Baiker Alfons
Publication year - 2014
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201402981
Subject(s) - ketone , catalysis , chemistry , diastereomer , platinum , noyori asymmetric hydrogenation , enantiomer , enantiomeric excess , photochemistry , hydrogen bond , hydrogen , organic chemistry , enantioselective synthesis , molecule
Surface processes occurring at the catalytic chiral surface of a cinchona‐modified Pt catalyst during the asymmetric hydrogenation of activated ketones have been monitored for the first time using operando ATR‐IR spectroscopy. Fundamental information about this catalytic system could be gained, including the chiral modification process of the catalyst, the surface interaction of reactant ketone with preadsorbed chiral modifier, the role of hydrogen as well as the influence of the product enantiomers in the catalytic cycle. The formation of a diastereomeric transient surface complex between ketone and chiral modifier was found to be related to the ketone consumption. Among the studied activated ketones, a correlation between stereoselection and the strength of the intermolecular hydrogen bond was identified. Dissociated hydrogen from the catalytic surface is found to play a crucial role in the formation of the diastereomeric surface complex.