(A) study on asymmetric alkylation of aldehydes with chiral catalysts

Abstract

The chiral β-amino alcohols containing indoline moiety was synthesized from (S)-Indoline-2-carboxylic acid and chiral disulfonamide ligands were synthesized from chiral β-amino aicds and. These chiral ligands have new examined in the catalytic asymmetric addition reaction of diethylzinc to aldehydes to give the corresponding chiral sec-alcohols. Treatment of benzaldehydes with $Et_2Zn$ in the presence of catalytic amount of chiral ligands of β-amino alcohols gave sec-alcohols with high enantiomeric excess (up to > 93%) with an (R) or (S)-configuration depending of the configuration of chiral catalysts. When the same reaction was carried out in the presence of $Ti(O-i-Pr)_4$, the lower enantiomeric excess was obtained. The addition of diethylzinc to p-substituted aromatic aldehydes in the presence of catalytic amount of 13 led to the corresponding sec-acohols in higher enantiomeric excess ( up to ＞6%) in 91 % chemical yield. The catalytic asymmetric ethylation of benzaldehyde using 4c or 4e gave the corresponding (S)-1-phenylpropanol with high enantioselectivity 81%ee or 88%ee respectively.