Synlett 2003(11): 1655-1658
DOI: 10.1055/s-2003-41424
LETTER
© Georg Thieme Verlag Stuttgart · New York

High-Pressure-Promoted Asymmetric Aldol Reactions of Ketones with Aldehydes Catalyzed by l-Proline [1]

Yusuke Sekiguchi, Aika Sasaoka, Ai Shimomoto, Shingo Fujioka, Hiyoshizo Kotsuki*
Laboratory of Natural Products Synthesis, Faculty of Science, Kochi University, Akebono-cho, Kochi 780-8520, Japan
Fax: +81(88)8448359; e-Mail: kotsuki@cc.kochi-u.ac.jp;
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Publikationsverlauf

Received 26 June 2003
Publikationsdatum:
22. September 2003 (online)

Abstract

High-pressure conditions were applied to direct asymmetric aldol reactions between ketones and aldehydes with l-proline as a commercially available chiral amino acid catalyst.

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Typical Experimental Procedure for the Reaction of Acetone with Benzaldehyde (entry 2). A mixture of benzaldehyde (53 mg, 0.5 mmol) and l-proline (17 mg, 0.15 mmol) in acetone (1.5 mL) was placed in a Teflon reaction vessel and allowed to react at 0.2 GPa and r.t. for 24 h. The reaction was quenched by adding H2O, and the mixture was extracted with CH2Cl2. The crude product was purified by preparative TLC (hexane/EtOAc = 2:1) to afford the desired adduct (74 mg, 90%). The ee value was determined by HPLC analysis using a Daicel Chiralpak AD column, with 1% 2-propanol in hexane as the eluent, at 0.5 mL/min.

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According to the literature, [5a] [6a] this type of asymmetric catalysis is best performed in dry DMSO.