A Fluorous Proline Organocatalyst with Acetone-Dependent Aldolase Behavior

A polyfluoroalkyl derivative of 4-hydroxyproline, assembled through a 1,2,3-triazole linker (i.e., 7), displays high catalytic activity and enantioselectivity in aldol reactions of acetone with aromatic aldehydes featuring electron-withdrawing groups. The scope of the reaction with respect to the aldehyde acceptor can be expanded with the use of a bifunctional urea cocatalyst. The presence of the fluorous tag allows the aldol reactions to be performed in a perfluorohexane/acetone biphasic system. In this way, both the catalyst and the perfluorinated solvent can be easily recycled and reused (>6 times). In addition, the combination of the fluorous tag, triazole linker, and catalytic proline unit confers unprecedented substrate specificity for acetone upon 7.