L-proline adsorbed on gamma-Al2O3 unexpectedly switches the enantioselectivity of the direct asymmetric aldol reaction of acetone with p-nitrobenzaldehyde from 68% ce (R configuration for free L-proline catalyst) with 80% yield to 21% ee (S configuration) with 78% yield. The inversion of enantioselectivity was also observed in the direct asymmetric aldol reactions of acetone with several other aromatic aldehydes catalyzed by the L-proline adsorbed on gamma-Al2O3. This inversion phenomenon is found to be general for different types of amino acids adsorbed on gamma-Al2O3. The hydroxyl groups on gamma-Al2O3 are found to be involved in the inversion induction of enantioselectivity in these direct asymmetric aldol reactions. (c) 2006 Elsevier Inc. All rights reserved.
1.Chinese Acad Sci, Dalian Inst Chem Phys, State Key Lab Catalysis, Dalian 116023, Peoples R China 2.Univ Liverpool, Dept Chem, Liverpool L69 7ZD, Merseyside, England
Recommended Citation:
Zhong, Lin,Xiao, Hanliang,Li, Can. An unexpected inversion of enantioselectivity in direct asymmetric aldol reactions on a unique L-proline/gamma-Al2O3 catalyst[J]. JOURNAL OF CATALYSIS,2006,243(2):442-445.
