Zirconium phosphonate immobilized chiral amino alcohol for heterogeneous enantioselective addition of diethylzinc to benzaldehyde

Abstract

Abstract The chiral (1 R ,2 S )-(−)-2-amino-1,2-diphenylethanol and (1 S ,2 R )-(+)-2-amino-1,2-diphenylethanol had been immobilized on the layered frame of zirconium phosphate to obtain zirconium phosphonates (1 R ,2 S )-(−)- 4a and (1 S ,2 R )-(+)- 4b . The enantioselective addition of Et 2 Zn to benzaldehyde using zirconium phosphonates (1 R ,2 S )-(−)- 4a and (1 S ,2 R )-(+)- 4b as heterogeneous catalysts yielded secondary alcohol in 80.1% yield and e.e. values of up to 54.3%, which was only 7.6% e.e. lower than that using the corresponding ligands (1 R ,2 S )-(−)- 2a and (1 S ,2 R )-(+)- 2b as homogeneous catalysts. The zirconium phosphonates (1 R ,2 S )-(−)- 4a and (1 S ,2 R )-(+)- 4b were characterized by IR, SEM, XRD and TG analysis. SEM and XRD data showed that the catalysts (1 S ,2 R )-(+)- 4b and (1 R ,2 S )-(−)- 4a were in aggregate and mesopore structure with the same interlayer spacing 2.48 nm and pore diameter 5.6 nm.