Rhodium(III)‐Catalyzed Asymmetric [4+1] and [5+1] Annulation of Arenes and 1,3‐Enynes: A Distinct Mechanism of Allyl Formation and Allyl Functionalization
作者:Jiaqiong Sun、Weiliang Yuan、Rong Tian、Peiyuan Wang、Xue‐Peng Zhang、Xingwei Li
DOI:10.1002/anie.202010832
日期:2020.12.7
cyclopentadienyl‐catalyzed enantioselective synthesis of lactams and isochromenes through oxidative [4+1] and [5+1] annulation, respectively, between arenes and 1,3‐enynes. The reaction proceeds through a C−H activation, alkenyl‐to‐allyl rearrangement, and a nucleophilic cyclization cascade. The mechanisms of the [4+1] annulations were elucidated by a combination of experimental and computational methods.
我们报告了手性Rh III环戊二烯基催化的内酰胺和异色酮的对映体选择性合成,分别通过在芳烃和1,3-炔烃之间进行氧化[4 + 1]和[5 + 1]环氧化。反应通过CH活化,烯基至烯丙基重排和亲核环化级联进行。通过实验和计算方法的结合阐明了[4 + 1]环空的机理。DFT研究表明,在C–H活化和炔烃插入之后,Rh III烯基中间体通过六元环跃迁状态经历了烯丙基C–H的δ-氢消除反应,从而生成Rh III烯丙氢化物中间体。随后的氢化物的插入和重排烯丙基提供了几个铑(III)烯丙基中间体,和稀有的Rh III η 4烯烯丙基物种与π-抓氢键经历SN 2 '由氮亲核型的,而不是C-N还原外部的攻击,消除,作为立体确定步骤。