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Inversion of enantioselectivity in the hydrogenation of ketopantolactone on platinum modified by ether derivatives of cinchonidine

✍ Scribed by Simon Diezi; Andras Szabo; Tamas Mallat; Alfons Baiker

Book ID
104360000
Publisher
Elsevier Science
Year
2003
Tongue
English
Weight
178 KB
Volume
14
Category
Article
ISSN
0957-4166

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✦ Synopsis

Asymmetric hydrogenation of ketopantolactone was studied on a 5 wt% Pt/Al 2 O 3 catalyst in the presence of cinchonidine and its O-methyl, -ethyl, -phenyl and -trimethylsilyl derivatives. Inversion of enantioselectivity with the latter two bulky substituents proved that in the enantiodifferentiating step cinchonidine adsorbs via the quinoline ring lying approximately parallel to the Pt surface. The striking nonlinear effect observed with cinchonidine-O-phenyl-cinchonidine mixtures is attributed to differences in the adsorption strength and geometry of the modifiers.

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