New 4-substituted acyloxyproline derivatives with different hydrophobic properties of the acyl group were easily synthesized and used as catalysts in the direct asymmetric aldol reaction between cyclic ketones (cyclohexanone and cyclopentanone) and several substituted benzaldehydes. Reactions were carried out using water, this being the best reaction medium examined. Screening of these catalysts showed that compounds bearing the most hydrophobic acyl chains [4-phenylbutanoate and 4-(pyren-1-yl)butanoate] provided better results. The latter catalysts were successfully used in only 2 mol% at room temperature without additives to give aldol products in excellent stereoselectivities. These results demonstrate that derivatization of the proline moiety with the proper simple hydrophobic substituent in the 4-position can furnish highly active and stereoselective catalysts without the need of additional chiral backbones in the molecule. Finally, an explanation of the observed stereoselectivities in the presence of water is provided.

GIACALONE F, GRUTTADAURIA M, LO MEO P, RIELA S, NOTO R (2008). New simple hydrophobic proline derivatives as highly active and stereoselective catalysts for the direct asymmetric aldol reaction in aqueous medium. ADVANCED SYNTHESIS & CATALYSIS, 350, 2747-2760 [10.1002/adsc.200800555].

New simple hydrophobic proline derivatives as highly active and stereoselective catalysts for the direct asymmetric aldol reaction in aqueous medium

GIACALONE, Francesco;GRUTTADAURIA, Michelangelo;LO MEO, Paolo Maria Giuseppe;RIELA, Serena;NOTO, Renato
2008-01-01

Abstract

New 4-substituted acyloxyproline derivatives with different hydrophobic properties of the acyl group were easily synthesized and used as catalysts in the direct asymmetric aldol reaction between cyclic ketones (cyclohexanone and cyclopentanone) and several substituted benzaldehydes. Reactions were carried out using water, this being the best reaction medium examined. Screening of these catalysts showed that compounds bearing the most hydrophobic acyl chains [4-phenylbutanoate and 4-(pyren-1-yl)butanoate] provided better results. The latter catalysts were successfully used in only 2 mol% at room temperature without additives to give aldol products in excellent stereoselectivities. These results demonstrate that derivatization of the proline moiety with the proper simple hydrophobic substituent in the 4-position can furnish highly active and stereoselective catalysts without the need of additional chiral backbones in the molecule. Finally, an explanation of the observed stereoselectivities in the presence of water is provided.
2008
Settore CHIM/06 - Chimica Organica
GIACALONE F, GRUTTADAURIA M, LO MEO P, RIELA S, NOTO R (2008). New simple hydrophobic proline derivatives as highly active and stereoselective catalysts for the direct asymmetric aldol reaction in aqueous medium. ADVANCED SYNTHESIS & CATALYSIS, 350, 2747-2760 [10.1002/adsc.200800555].
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10447/28780
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