A Supramolecular Hydrogel as a Reusable Catalyst for the Aldol Reaction

Abstract

The aldol reaction using l-proline-based supramolecular hydrogel as an efficient heterogeneous organocatalyst was described. Thus, 4-nitrobenzaldehyde (0.16 mmol) and cyclohexanone (155 µL) in 1mL of toluene was added on the top of the hydrogel at 5 ˚C over 24 hours to give the aldol product (98% yield, anti/syn = 92:8, 88% ee). After decantation of the ­organic layer, the hydrogel did not seem macroscopically affected and was reused for two additional runs without any loss of catalytic activity (2nd: >99% yield, anti/syn = 93:7, 87% ee, 3rd: >99% yield, anti/syn = 92:8, 90% ee, respectively).