esters can be carried out with high levels of enantioselectivities utilizing commercially available isothiourea catalysts under base-free conditions. The reaction, which proceeds via the in situ formation of chiral C1 ammonium enolates, is best carried out under cryogenic conditions combined with a direct trapping of the activated α-chlorinated ester derivative to prevent epimerization, thus allowing
活化芳基
乙酸酯的不对称 α-
氯化可以在无碱条件下使用市售的异
硫脲催化剂以高
水平的对映选择性进行。该反应通过原位形成手性 C1 烯醇化
铵进行,最好在低温条件下进行,同时直接捕获活化的 α-
氯化酯衍
生物以防止差向异构化,从而实现高达 er 99 的对映选择性: 1.