<scp>TEMPO‐Regulated</scp>Regio‐ and Stereoselective<scp>Cross‐Dihalogenation</scp>with Dual Electrophilic X<sup>+</sup>Reagents
作者:Yi Kong、Tongxiang Cao、Shifa Zhu
DOI:10.1002/cjoc.202100472
日期:2021.11
method could enable wide applications in organic synthesis, which was exemplified by divergent synthesis of two pharmaceuticals. Detailed mechanistic investigations via radical clock reaction, pinacol ring expansion and Hammett experiments were conducted, which confirmed the intermediacy of halonium ion. In addition, a dynamic catalytic model based on the versatile catalytic role of TEMPO was proposed
TEMPO 催化的交叉二卤化反应是通过氧化还原调节双亲电 X +试剂的复杂系统而建立的。形式上,ICl的,氯化溴,我2和Br 2产生在-原位,这使高区域选择性或立体选择性获得的iodochlorination,bromochlorination和均-二卤化产物无数与功能性的宽光谱。该方法条件温和,操作简单,可广泛应用于有机合成,例如两种药物的发散合成。通过详细的机械调查进行了自由基钟反应、频哪醇扩环和哈米特实验,证实了卤离子的中介作用。此外,提出了一种基于 TEMPO 多功能催化作用的动态催化模型来解释选择性结果。
An efficient bromination of alkenes using cerium(IV) ammonium nitrate (CAN) and potassium bromide
作者:Vijay Nair、Sreeletha B Panicker、Anu Augustine、Tesmol G George、Siji Thomas、M Vairamani
DOI:10.1016/s0040-4020(01)00712-8
日期:2001.8
Bromination of alkenes using a combination of potassium bromide and cerium(iv) ammoniumnitrate (CAN) in a two phase system consisting of water and dichloromethane affords the corresponding dibromides in excellent yield. The reaction most likely involves the addition of the bromine radical generated from bromide ion by CAN and subsequent formation of the dibromide.
A Domino Copper-Catalyzed C-N and C-O Cross-Coupling for the Conversion of Primary Amides into Oxazoles
作者:Frank Glorius、Kerstin Schuh (née Müller)
DOI:10.1055/s-2007-983782
日期:2007.7
A variety of oxazoles can efficiently be prepared, in a single step and in good yield, from primaryamides and 1,2-dihaloalkenes using copper-catalysis. This new method allows the re-gioselective formation of a range of substituted oxazoles. The required 1,2-dihaloalkenes can prepared by simple treatment of alkynes with elemental bromine or iodine.
The oxidativebromination of arenes was induced by a vanadium catalyst in the presence of a bromide salt and a Brønsted acid or a Lewis acid under molecular oxygen, which provides an eco-friendly bromination method as compared with a conventional bromination one with bromine. This catalytic reaction could be applied to the bromination of alkenes and alkynes to give the corresponding vic-bromides. Use
芳烃的氧化溴化反应是在分子氧下,在溴化物盐和布朗斯台德酸或路易斯酸存在下,由钒催化剂诱导的,与传统的溴化溴化方法相比,该方法提供了一种环保的溴化方法。这种催化反应可以适用于烯烃和炔烃的溴化,得到相应的VIC -溴化物。已证明使用卤化铝代替布朗斯台德酸作为路易斯酸可为氧化溴化提供更实用的方法。从酮中获得α-溴化产物。发现AlBr 3既是溴化物源又是路易斯酸,可以顺利地诱导溴化。511 H NMR实验表明,这种催化溴化反应可能取决于分子氧下钒催化剂的氧化还原循环。
Stereoselective Bromination of Acetylenes with Bromine in the Presence of Graphite
Acetylenes were stereoselectively brominated with molecular bromine adsorbed on graphite in dichloromethane to produce (E)-α,β-dibromoalkenes; isomerization of the E-isomer to the Z-isomer, usually catalyzed by bromine, did not occur in the presence of graphite.