Synthesis of Camphor-based Chiral Schiff Base and Its Application in the Asymmetric Reduction of Prochiral Ketones and Formation of Cyanohydrins

• Main Authors: Meng-Jung Tasi, 蔡孟蓉
• Other Authors: Ta-Jung Lu
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/76409990537838018337

碩士 === 中興大學 === 化學系所 === 94 === This thesis reports the development of an effective and enantioselective, camphor-based aminoalcohol chiral ligand modifier for the asymmetric reactions of carbonyl compounds. The chirally modified reducing agent was formed by mixing the Schiff base, derived from (1R,2S,3R)-3-amino-boneol and salicylaldehyde, and LAH at room temperature, which was employed in the asymmetric reduction of ten different prochiral ketones at –40 ºC. Taguchi method was used to find the optimal experimental conditions and the ratio of LAH: Schiff base: prochoral ketones = 1: 1.1: 0.5 was found to achieve the best results. S-Alcohols were obtained as the major products in excellent yields (72 %~>99 %) with moderate enantiomeric excesses (20 %~78 %). However, the addition of ethanol as a secondary modifier did not improve the reaction yields and the facial selectivities. In another application, the Schiff base and Ti(i-OPr)4 were mixed as a chiral catalyst for the asymmetric trimethylsilylcyanation of aldehydes. The reaction afforded the chiral cyanohydrin in excellent yields (91 %~>99 %) and good enantioselectivities (60 %~81 %). Thus, we have developed a camphor-based chiral aminoalcohol whose corresponding Schiff base was used in the asymmetric reduction of prochiral ketones and the formation of cyanohydrins in excellent yields and good enantioselectivites.