Issue 5, 2011

Simple and practical direct asymmetric aldol reaction of hydroxyacetone catalyzed by 9-aminoCinchona alkaloidtartrates

Abstract

A novel organocatalytic procedure for the direct aldol reaction of unprotected acetol and activated aromatic aldehydes catalyzed by 9-amino-9-epi-Cinchona ditartrates is presented. The protocol presented avoids the use of problematic solvents and toxic reagents as well as chromatographic purification of the products – instead a simple extraction has been applied for the isolation of pure aldols from the reaction mixture. This catalytic system provides exclusively linear aldols with quantitative yields and good syn-diastereoselectivity and enantioselectvitiy up to 90% ee. Further upgrading of the enantiomeric excess of syn-aldols up to 99% ee is easily accomplished by a single and reliable crystallization. The use of cinchonine or quinine-derived catalysts gives access to both enantiomers of syn-aldols for which the absolute configuration has been determined by X-ray diffraction. The operationally convenient and scalable organocatalytic procedure using cheap and renewable chemicals – both acetol and the catalysts, offers a sustainable and green way for the synthesis of a number of α-keto-syn-diols.

Graphical abstract: Simple and practical direct asymmetric aldol reaction of hydroxyacetone catalyzed by 9-amino Cinchona alkaloid tartrates

Supplementary files

Article information

Article type
Paper
Submitted
17 Jan 2011
Accepted
25 Feb 2011
First published
25 Mar 2011

Green Chem., 2011,13, 1280-1287

Simple and practical direct asymmetric aldol reaction of hydroxyacetone catalyzed by 9-amino Cinchona alkaloid tartrates

P. Czarnecki, A. Plutecka, J. Gawroński and K. Kacprzak, Green Chem., 2011, 13, 1280 DOI: 10.1039/C1GC15064B

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