An effective heterogeneous l-proline catalyst for the asymmetric aldol reaction using anionic clays as intercalated support

A heterogeneous catalyst (l-Pro LDHs) was developed using intercalation of l-proline in Mg–Al LDH. An investigation of the thermal stability and optical stability showed that the immobilization of the chiral catalytic centers in restricted galleries enhanced the enantiomeric stability against thermal treatment and light irradiation. Asymmetric aldol reaction of benzaldehyde and acetone was carried out using l-Pro LDHs as catalyst, resulting in a good yield (90%) and a high enantiomeric excess (94%). The enantiomeric selectivity of l-Pro LDHs was found to be more stable to thermal pretreatment compared with the pristine l-proline. The possible reaction mechanism was proposed in light of the homogeneous mechanism. The effects of chemical composition of l-Pro LDHs and reaction conditions on catalytic efficiency were also investigated.