Preparation of Polyfunctional Arylmagnesium, Arylzinc, and Benzylic Zinc Reagents by Using Magnesium in the Presence of LiCl
作者:Fabian M. Piller、Albrecht Metzger、Matthias A. Schade、Benjamin A. Haag、Andrei Gavryushin、Paul Knochel
DOI:10.1002/chem.200900575
日期:2009.7.20
magnesium reagent with ZnCl2. This method can also be applied to the preparation of functionalized benzylic zinc reagents from benzylic chlorides. In the case of di‐ or tribromoaryl derivatives, directing groups such as ‐OPiv, ‐OTs, ‐N2NR2, or ‐OAc orient the zinc insertion (Zn/LiCl) to the ortho‐position, while the reaction with Mg/LiCl or Mg/LiCl/ZnCl2 leads to regioselective insertion into the para‐carbon–bromine
LiCl的存在极大地促进了镁向各种芳族和杂环溴化物中的插入。几个功能组,如-OBoc,-OTs,-Cl,-F,-CF 3,-OMe,-NMe 2和-N 2 NR 2,具有很好的耐受性。氰基的存在在某些情况下导致有机卤化物竞争性还原为相应的ArH化合物。通过ZnCl 2原位捕获中间镁试剂可以耐受甲基或乙基酯等敏感基团的存在。该方法也可用于由苄基氯化物制备官能化的苄基锌试剂。如果是二溴或三溴芳基衍生物,则应使用诸如-OPiv,-OTs,-N之类的指导基团2 NR 2或-OAc将锌插入(Zn / LiCl)定向到邻位,而与Mg / LiCl或Mg / LiCl / ZnCl 2的反应导致区域选择性插入对碳-溴键中。描述了所有金属化步骤的大规模实验(20–100 mmol)。