Towards more chemically robust polymer-supported chiral catalysts for the reactions of aldehydes with dialkylzincs

N-Methyl-α,α-diphenyl- -prolinol derivatives with para-bromo substituents in one or both of the phenyl rings are easily bound to crosslinked polystyrene beads containing phenylboronic acid residues using Suzuki reactions. When the products were used as catalysts for the reactions of aldehydes with diethylzinc in toluene at 20 °C, the alcohols were produced in chemical yields >90% and with ees of upto 94%. The better of the two supported catalysts gave ees only 0–9% lower than those obtained with the corresponding soluble catalyst. One of the supported catalysts was recycled successfully nine times.