联苯二酚的手性拆分及相转移催化不对称烷基化研究

Chiral Resolution of Biphenol and Asymmetric Alkylation under Phase Transfer Catalysis

手性相转移催化剂在手性药物、天然产物核心结构、手性功能分子构建中起着极其重要的作用,因此近年来备受关注.以廉价易得的(R)-α-甲氧基苯乙酸为拆分剂与联苯衍生物进行酯化反应,成功地对联苯衍生物骨架进行了手性拆分,并基于拆分的光学纯C2轴手性联苯刚性骨架,构建了系列新型联苯类相转移催化剂.对该系列相转移催化剂进行不对称催化烷基化反应,产率高达97%,对映体选择性高达96%.对催化剂进行构效关系研究发现,对2位和2'位的羟基进行甲基化有利于催化反应的选择性,3位和3'位引入叔丁基不利于反应的选择性.催化剂经过结构优化后,在5位和5'位引入3,4,5-三氟苯基和3,5-双(三氟甲基)苯基都显示出较好的反应活性和选择性.

Chiral phase transfer catalysts play extrememly important role in the construction of natural products,the core structures of chiral drugs,and functional chiral chemicals,therefore have attracted more and more attention in recent years.In this paper,the chiral resolution of biphenyl skeletons was achieved by utilizing the readily available(R)-α-methoxy benzene acetic acid as resolution agent.A series of new biphenyl type of phase transfer catalysts were designed and synthesized based on the optically pure C2-symmetric chiral biphenyl framework.These catalysts are readily applicable to asymmetric alkylation of N-(diphenylmethylene)glycine tert-butyl ester with excellent enantioselectivity(up to 96%)and yield(up to 97%).The structure-activity relationship study on these catalysts showed that the methylation of hydroxyl group at C2 and C2'position is favorable for the selectivity,introduction of tert-butyl group at C3 and C3'position is unfavorable to both selectivity and reactivity.The catalysts bearing 3,4,5-trifluorophenyl group or 3,5-bis(trifluoromethyl)phenyl group at C5 and C5'position showed good reactivity and selectivity.