Chem. J. Chinese Universities ›› 2000, Vol. 21 ›› Issue (10): 1524.

• Articles • Previous Articles     Next Articles

Preparation of a Polymer Supported BINOL-Ti Catalyst and Its Application in Asymmetric Addition of Diethylzinc to Aldehydes

WANG Heng-Shan, SU Wu, LIU Da-Xue, YANG Xiao-Wu, DA Chao-Shan, WANG Rui    

  1. School of Life Sciences, State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou 730000, China
  • Received:1999-11-18 Online:2000-10-24 Published:2000-10-24

Abstract: Anew polymer supported BINOLligand(4) was prepared by means of anchoring binaphthyl molecule(3) to aminoethylated polystyrene through a procedure of solid phase peptide synthesis. The key compound (R)-2,2'-dihydroxy 1,1'-binaphthyl-3-carboxylic acid(3) was prepared from R BINOLby protection of hydroxyl groups and then reaction with n-butyllithium followed by carboxylation. By controlling the amount of BuLi, (3) was obtained in 55% overall yield. Ligand (4) was prepared through condensation of (3) with aminoethylated polystyrene in the presence of DCCand HOBt and found to have a loading of 0.40 mmol/g (by mass increase). The linkage between binaphthyl and aminoethylated polystyrene was indicated by a new absorption in IRspectrum of (4) at 1644 cm-1 in comparing with what of the polystyrene. By mixing (4) with Ti(OiPr)4 in dry CH2Cl2, a complex was easily prepared and this complex was found to be an efficient heterogeneous catalyst in asymmetric addition of diethylzinc to aldehydes. Optical active alcohols with up to 82% ee were obtained from the asymmtric addition with high chemical yields when 20% of (4) was used. And when benzaldehyde was used as substrate, we found that enantioselectivity increased obviously when the amount of (4) used in reaction increased from 5% to 20%;decreased the load of BINOLin ligand (4) reduced the ee of addition product; and Rform of products was resulted.

Key words: 1,1'-Bi-2-naphthol, Heterogeneous catalyst, Enantioselective addition

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