Heterogeneous organo/metal cooperative catalysis: One-pot immobilization of Pd(PPh3)4 and chiral phosphoric acid to hollow mesoporous polystyrene nanospheres for efficient asymmetric α-allylation of aldehydes

The widely used combinations of palladium catalysts and chiral phosphoric acids face with the problems of cooperative catalysis and low-cost immobilization of binary catalysts in heterogeneous catalysis, due to the significant decline in the freedom of anchored catalysts. In this paper, the one-pot immobilization of both chiral phosphoric acid (TRIP) and Pd(PPh3)4 to hollow mesoporous polystyrene nanospheres (HMPNs) via FriedelCrafts alkylation is developed to fabricate HMPNs-supported dual organo/metal catalysts (Pd (PPh3)4#TRIP@HMPNs) at a low cost. The efficient cooperative catalysis of anchored TRIP and Pd(PPh3)4 with good to excellent yields (89-93 %) and enantioselectivities (80-87 % ee) is achieved in the direct asymmetric alpha-allylation of aldehydes with allylic alcohols. The higher molar ratio of TRIP to Pd(PPh3)4 and a lower crosslinking degree of HMPNs are beneficial to the cooperative catalysis of the anchored catalysts. Overall, this paper showcases a success in solving the key problems in heterogeneous asymmetric metal/oragano catalysis.