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Biomimetic Chemoselectivity Control of Aldol Reactions
Y. Chi, S. T. Scroggins, E. Boz, J. M. J. Fréchet*
University of California, Berkeley, USA
22 January 2009 (online)
The synthesis and utilization of polymeric catalyst 1 bearing proline moieties as active sites is reported. This catalyst aggregate was applied successfully in aldol reactions of aldehydes and ketones in aqueous media. In a self-aldol process of butanal, mainly reversibly formed β-hydroxyaldehyde 2 was obtained, whereas the formation of aldol condensation product 3 could be suppressed. These results were transferred to more complex dynamic catalytic cross-aldol reactions, giving rise to α,β-unsaturated ketones 4, favored over formation of self-condensation product 5. The likewise expected ketones 6 were not observed.