A Combinatorial Approach to Heterogeneous Asymmetric Aquacatalysis

Significance

A library of chiral phosphine ligands was prepared on polystyrene-poly(ethylene glycol) (PS-PEG) resin, and the enantiocontrolling ability as well as catalytic potency of the ligands were examined in water for the palladium-catalyzed π-allylic substitution. A library of PS-PEG resin-supported amino acid linked phosphine ligands 1 (84 members) was prepared from the amino acids (A-K, 12 members including dummy) and the phosphine carboxylic acids (a-g, 7 members) by the split method (eq. 1). The palladium complex of (R)-2-(diphenylphosphino)binaphthyl ligand anchored onto the PS-PEG resin by an (S)-alanine 1Cg-Pd was found to provide the highest enantio­selectivity (90% ee) for the reaction of 1,3-diphenylpropenyl acetate with 3-methyl-2,4-pentanedione (eq. 2).