Preparation Of Aluminum Phosphonate-supported Multifunctional Organocatalyst And Application In Asymmetric Aldol Reactions

Cinchona alkaloid-derived primary amine and Br?nsted acid could catalyze synergistically lots of asymmetric reactions such as Aldol. The immobilization of alkaloid-derived primary amine organocatalyst was a important strategy to achieve the green catalytic reaction. However, the simultaneous immobilization of primary amine and Br?nsted acid was seldom reported.In this paper, novel aluminium phosphonate-supported multifunctional organocatalyst performing the cooperative catalysis of enamine and Br?nsted acid was prepared by means of the facile precipitation of phosphonate with sodium aluminate. These heterogeneous solid catalysts with multiple catalytic sites efficiently promoted the aqueous asymmetric aldol addition of cyclohexanone to benzaldehyde derivatives(o, m, p-NO2,Cl and CN) in good yields(65–98%) and high steroselectivities(anti/ syn = 4.5–20.3 and 92–98 %ee) without additional co-catalyst. The catalyst could be quantitatively recoveredfrom the reaction mixture by centrifugation and reused ten consecutive runs without significant loss in catalytic performances(95%, anti/syn = 10.1 and 92 %ee anti). Furthermore, the arm length(n) of organocatalyst and H+ exchange capacity resulted from the P-OH defects had significant effects on the cooperative catalysis of enamine and Br?nsted acid.