New soluble bifunctional polymeric chiral ligands for enantioselectively catalytic reactions

✍ Scribed by Qing-Hua Fan; Guo-Hua Liu; Guo-Jun Deng; Xiao-Min Chen; Albert S.C Chan

• Book ID: 104232048
• Publisher: Elsevier Science
• Year: 2001
• Tongue: French
• Weight: 77 KB
• Volume: 42
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(01)02004-4

✦ Synopsis

Two new soluble bifunctional polymeric ligands (R,R)-4 and (R,R)-5 have been prepared via the direct condensation reaction of (R)-3,3%-diformyl-1,1%-bi-2-naphthol (R)-1 with (R)-5,5%-diamino BINAP (R)-2 and with (R)-5,5%-diamino BINAPO (R)-3, respectively. The different types of catalytic centers, BINOL and BINAP or BINAPO, were alternatively organized in a regular chiral polymer chain. Both polymeric ligands were found to be effective in the addition of diethylzinc to benzaldehyde either in the presence or in the absence of Ti(OPr i ) 4 with different enantioselectivities. (R,R)-4/Ti(IV) catalyst, which showed similar efficiency to the parent catalyst BINOL/Ti(IV), was more enantioselective than (R,R)-5/Ti(IV). (R,R)-4 was also found to be highly effective in the Ru(II)-catalyzed asymmetric hydrogenation of 2-arylacrylic acids. The results demonstrated that the use of the co-polymer catalyst rather than a mixture of monomer catalysts not only simplified the recycling of the catalyst, but also improved the enantioselectivity and/or the activity in some cases.