Asymmetric dearomatization enabled by chiral Brφnsted acid activation of ynamides

• 作 者: Xingguang Li Jianwei Sun
• 机 构: Department of Chemistry,the Hong Kong University of Science and Technology,Clear Water Bay,Kowloon,H
• 出 处: 中国科学：化学（英文版）
• 发表日期: 2022年1期

Chiral Brφnsted acid catalysis has evolved into a powerful synthetic tool in asymmetric synthesis in the past two dec-ades or so.However,despite the broad scope of reactions achieved by chiral Brφnsted acid catalysis,they only involve the activation of a small number of functional groups.Among them,imines and carbonyls are most studied owing to the defined orientation of their lone pairs for hydrogen bonding with acids (Figure 1 a).In contrast,the activation of unsaturated C-C bonds by chiral Brφnsted acids toward asymmetric bond formation is much more challenging.In particular,the activation of C=C bonds has met with limited success.While asymmetric Michael-type addition has been known by indirect activation of C=C bonds (e.g.,ynones,ynoates,Figure 1b),asymmetric control initiated by direct protonation of C=C bonds is rare.This would generate an ion pair between a carbocation and a chiral counteranion(Figure 1a).Different from the strong directionality of hy-drogen bonding,asymmetric induction by counteranion ty-pically relies on much weaker and less directional electrostatic interaction [1].