1256282-34-4Relevant academic research and scientific papers
Advances towards highly active and stereoselective simple and cheap proline-based organocatalysts
Giacalone, Francesco,Gruttadauria, Michelangelo,Agrigento, Paola,Lo Meo, Paolo,Noto, Renato
experimental part, p. 5696 - 5704 (2010/12/25)
Ten 4-acyloxy-L-prolines were screened as catalysts at loadings of 2-0.1 mol-% for the direct asymmetric aldol reaction in water by using variable amounts of water. Among them, a new catalyst, the L-proline carrying a trans-4-(2,2-diphenylacetoxy) group, and a catalyst previously synthesized by us, the L-proline carrying a trans-4-(4-phenylbutanoyloxy) group, were found to be excellent catalysts for the aldol reaction between cyclohexanone or cyclopentanone and substituted benzaldehydes when employed in only 1 and 0.5 mol-%,respectively, at room temperature without additives. For such catalysts, high turnover numbers were obtained, which are among the highest values obtained for enamine organocatalysis. Finally, these catalysts can be synthesized by direct O-acylation from inexpensive molecules and successfully used in scaled-up reactions. Highest activity and selectivity at minor expense! Simple and cheap 4-acyloxy-L-prolines were easily prepared and successfully employed in the direct asymmetric aldol reaction in water by using a loading of2-0.1 mol-%. Interestingly, high turnover numbers, among the highest values ever reported for enamine organocatalysis, were obtained.
