A new polymer supported BINOL ligand(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 dihydr...A new polymer supported BINOL ligand(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 BINOL by 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 DCC and 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 IR spectrum of (4) at 1 644 cm -1 in comparing with what of the polystyrene. By mixing (4) with Ti(OiPr) 4 in dry CH 2Cl 2, 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 BINOL in ligand (4) reduced the ee of addition product; and R form of products was resulted. [WT5HZ]展开更多
文摘A new polymer supported BINOL ligand(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 BINOL by 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 DCC and 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 IR spectrum of (4) at 1 644 cm -1 in comparing with what of the polystyrene. By mixing (4) with Ti(OiPr) 4 in dry CH 2Cl 2, 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 BINOL in ligand (4) reduced the ee of addition product; and R form of products was resulted. [WT5HZ]
