Polyfunctional benzylic zinc chlorides by the direct insertion of magnesium into benzylic chlorides in the presence of LiCl and ZnCl2
作者:Albrecht Metzger、Fabian M. Piller、Paul Knochel
DOI:10.1039/b812396a
日期:——
Benzylic zinc chlorides bearing various functional groups are smoothly prepared by the directinsertion of magnesium into benzylic chlorides in the presence of LiCl and ZnCl(2).
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)。
Photofragmentation via single-electron transfer: selective labilization of carbon-carbon bonds in amino alcohols with several bonds between heteroatom substituents
作者:Xiaohong Ci、David G. Whitten
DOI:10.1021/ja00191a069
日期:1989.4
compounds is observed to proceed very cleanly via relatively low energy excitation, an interesting question is whether a correspondingly clean C-C bond fragmentation can occur in molecules in which two heteroatoms are separated by greater distances. Here they report results that indicate selective cleavage can occur for vinylogous aminoalcohols and related compounds via pathways that involve both net reduction
最近的一些研究表明,α},β}-二杂原子取代的有机物的氧化光碎裂可以作为单电子转移的结果发生。光氧化还原过程虽然涉及自由基离子中间体,但与 2 电子 Grob 碎裂非常相似。对各种电子受体和氨基醇的机理研究表明,受体阴离子自由基碱度和阳离子自由基中 CC 键能的显着降低都导致了低 (2.5-5 kcal/mol) 的离子裂解活化能 -激进对。由于α},β}-二杂原子取代的化合物的反应被观察到通过相对低能量的激发非常干净地进行,一个有趣的问题是,在两个杂原子相距较远的分子中是否会发生相应干净的 CC 键断裂。在这里,他们报告的结果表明,乙烯基氨基醇和相关化合物可以通过涉及光激发受体的净还原和催化作用的途径发生选择性裂解。
A Practical Method to Stereospecifically Synthesize trans-Stilbene Derivatives
A practicalmethod to stereospecificallysynthesize trans‐stilbenes was developed via the one‐pot benzylation‐dehydration reaction of aromatic aldehydes with benzyltrimethylsilane (BTMS), which was driven by tetrabutylammonium fluoride (TBAF) in THF. At the same time a plausible description of the whole process was proposed and the effects of substituted groups on the reaction were investigated. Also