A very active and highly enantioselective catalytic resin, designed for minimal perturbation of the catalytic center by the polymer matrix, has been assembled in two steps from (S)-triphenylethylene oxide, piperazine, and Merrifield resin and tested in the enantioselective ethylation of aldehydes. 1-Arylpropanols of 94-95% ee are obtained in high yield by the use of only 2 mol % of catalytic resin at 0 °C for 4 h.
Polystyrene-Supported (R)-2-Piperazino-1,1,2-triphenylethanol: A Readily Available Supported Ligand with Unparalleled Catalytic Activity and Enantioselectivity
J. Org. Chem. 2005, 70, 433-438.