Asymmetric Aldol Reaction Catalyzed by a Heterogenized Proline on a Mesoporous Support. The Role of the Nature of Solvents

A heterogenized (S)-proline on mesoporous support MCM-41 catalyzes the asymmetric aldol reaction in a wide range of solvents. The progress of the reaction is dependent on the nature of the solvent. Reactions proceed more efficiently in hydrophilic polar solvents; however, the addition of a small amount of water has a positive effect on the rate and the stereoselectivity of the reaction performed in hydrophobic toluene. The reaction under heterogeneous conditions has also been performed on chiral aldehydes, furnishing useful intermediates for the synthesis of azasugars.