Base‐free Enantioselective C(1)‐Ammonium Enolate Catalysis Exploiting Aryloxides: A Synthetic and Mechanistic Study
作者:Calum McLaughlin、Alexandra M. Z. Slawin、Andrew D. Smith
DOI:10.1002/anie.201908627
日期:2019.10.14
An isothiourea-catalyzed enantioselective Michael addition of aryl ester pronucleophiles to vinyl bis-sulfones via C(1)-ammonium enolate intermediates has been developed. This operationally simple method allows the base-free functionalization of aryl esters to form α-functionalized products containing two contiguous tertiary stereogenic centres in excellent yield and stereoselectivity (all ≥99:1 er)
已经开发了一种异硫脲催化的对映体,通过C(1)-烯醇铵中间体将芳基酯原核糖对映体选择性迈克尔加成。这种操作简单的方法可以使芳基酯进行无碱官能化,从而以优异的收率和立体选择性(均≥99:1 er)形成包含两个连续的三级立体异构中心的α-官能化产物。该方法成功的关键是芳基氧化物的多功能作用,该芳基氧化物在催化周期内作为离去基团,布朗斯台德碱,布朗斯台德酸和路易斯碱起作用。已经进行了全面的力学研究,包括可变时间归一化分析(VTNA)和同位素同位素竞争实验。这些研究已经确定(i)所有反应物的顺序;(ii)限制营业额的迈克尔加法步骤,