Remote Enantioselective Friedel-Crafts Alkylations of Furans through HOMO Activation
作者:Jun-Long Li、Cai-Zhen Yue、Peng-Qiao Chen、You-Cai Xiao、Ying-Chun Chen
DOI:10.1002/anie.201403082
日期:2014.5.19
Catalytic asymmetric Friedel–Crafts alkylation is a powerful protocol for constructing a chiral C(sp2)C(sp3) bond. Most previous examples rely on LUMO activation of the electrophiles using chiral catalysts with subsequent attack by electron‐rich arenes. Presented herein is an alternative strategy in which the HOMO of the aromatic π system of 2‐furfuryl ketones is raised through the formation of a formal
催化不对称Friedel-Crafts烷基化反应是构建手性C(sp 2)C(sp 3)键的强大方法。以前的大多数示例都依赖于使用手性催化剂的亲电子的LUMO活化,随后又被富电子芳烃攻击。本文提出了一种替代策略,其中通过使用手性伯胺形成正式的三烯胺物种,提高了2-糠基酮的芳族π系统的HOMO。亚烷基丙二腈在5位发生独家区域选择性烷基化,并且通过这种远程活化获得了高反应活性和出色的对映选择性(高达95%ee)。