Abstract
The application of camphor derived chiral ligands in catalytic asymmetric catalysis are described in this thesis which consists of three parts. The first part describes camphor-based hydroxamic acid catalyzed asymmetric epoxidation of allylic alcohols. The second and third dealt with the asymmetric addition of alkyl and alkenyl-zincs to aldehydes. 1. Asymmetric epoxidation of allylic alcohols：Epoxidation was carried out in the presence of 7.5 mol % of 9e and the corresponding epoxy alcohol was obtained in 44 % e.e. with a (2S, 3S) configuration. The chiral epoxy alcohols were produced in 46-89% e.e. with a (2R, 3R) configuration when 11f was used. Contrary to both Yamamoto’s and Bolm’s results, we found that decreasing the bulk of the N-substituent led to better selectivity. The steric influence of the bornane C2-substituent on the enantioselectivities of epoxidation was evidenced from the enhancement of the e.e. as the size of the substituent increased. 2. A new class of camphor-derived □-amino alcohols was prepared from ketopinic acid in two steps. When the addition of Et2Zn to benzaldehyde was conducted in the presence of 10 mol % of 17b, 1-phenylpropanol was obtained in 80 % e.e. New □-amino thiols were prepared from (S)-(+)-Camphorsulfonic acid in few steps. Asymmetric addition of Et2Zn to aldehydes was achieved in excellent selectivity using catalytic amount of 37. Nonlinear effect studies showed that the presence of 15 mol % of 37 (30 % e.e.) was able to give1-phenylpropanol in 97 % e.e. and high yield. 3. The application of catalytic amount of □-amino thiol 37 in asymmetric addition of alkenylzincs to aldehydes gave the corresponding allylic alcohols in up to > 99 % e.e. which provided a pratical method for the synthesis of chiral (E)-allylic alcohols. Highlights of this reaction are the excellent enantioselectivies observed with the new ligand 37 and aromatic aldehydes as well as the efficiency of the reaction with internal alkyne (3-hexyne) and highly substituted terminal alkyne.