Asymmetric Catalytic Formal 1,4‐Allylation of β,γ‐Unsaturated α‐Ketoesters: Allylboration/Oxy‐Cope Rearrangement
作者:Qiong Tang、Kai Fu、Peiran Ruan、Shunxi Dong、Zhishan Su、Xiaohua Liu、Xiaoming Feng
DOI:10.1002/anie.201905533
日期:2019.8.19
allylboronic acids to β,γ‐unsaturated α‐ketoesters has been realized by employing a chiral NiII/N,N′‐dioxide complex as the catalyst. This transformation proceeds by an allylboration/oxy‐Cope rearrangement sequence, providing a facile and rapid route to γ‐allyl‐α‐ketoesters with moderate to good yields (65–92 %) and excellent ee values (90–99 % ee). The isolation of 1,2‐allylboration products provided insight
通过使用手性Ni II / N,N'-二氧化物络合物作为催化剂,已实现了对β,γ-不饱和α-酮酸酯的烯丙基硼酸的高度对映体选择性形式共轭烯丙基加成。该转化过程通过烯丙基硼化/ oxy-Cope重排序列进行,提供了简便且快速的途径,以中等至良好的收率(65-92%)和出色的ee值(90-99%ee)转化为γ-烯丙基-α-酮酸酯)。1,2-烯丙基化产物的分离提供了对随后oxy-Cope重排反应机理的认识:底物诱导的手性转移和手性Lewis酸加速过程。在实验研究和DFT计算的基础上,提出了一种罕见的船状过渡态模型,作为氧-科普重排过程中高手性转移的起源。