Electrophilic Cleavage of Cyclopropylmethystannanes: An Experimental Comparison of σ−σ and σ−π Conjugation
作者:Andrew J. Lucke、David J. Young
DOI:10.1021/jo047822p
日期:2005.4.1
Cyclopropylmethyltrimethylstannanes undergo electrophiliccyclopropanecleavage in chloroform with simple inorganic electrophiles (H+, SO2, I2) in a homologous reaction to the SE‘ cleavage of allylic stannanes. The σ−σ conjugation between the carbon−tin bond and cyclopropane orbitals observed spectroscopically in the parent cyclopropylmethyltrimethylstannane is responsible for a rate enhancement of
环丙基甲基三甲基锡烷酮与简单的无机亲电试剂(H +,SO 2,I 2)在氯仿中进行亲电环丙烷裂解,与烯丙基锡烷的S E '裂解发生同源反应。在母体环丙基甲基三甲基锡烷中通过光谱观察到的碳-锡键与环丙烷轨道之间的σ-σ共轭可提高ca的速率。相对于可比较的烷基锡烷,10 2趋向碘解。但是,该加速度远小于约1。10 9烯丙基锡烷中相应的σ-π共轭提供的倍数速率增强。甲醇-锡配位似乎减少了金属的活化作用,从而促进了在环丙烷裂变中用酸和碘进行甲基裂解。降低的σ-σ共轭也可以解释与三甲基锡对应物相比环丙基三苯基锡烷的反应性降低。在促进烯丙基锡烷的相应反应的条件下,环丙基甲基锡烷不经过合成有用的醛加成。
Ring-opening of some radicals containing the cyclopropylmethyl system
作者:Athelstan L. J. Beckwith、Graeme Moad
DOI:10.1039/p29800001473
日期:——
Mono- and bi-cyclic radicals containing the cyclopropylmethyl system are readily generated by interaction of the appropriate halides with triphenyl- or tributyl-stannane. Each radical studied underwent ring-opening by fission of the more substituted βγ-bond. In the case of the secondary radical (12b) the new double bond was formed preferentially in the trans-configuration. Rate constants, which cannot
通过适当的卤化物与三苯基或三丁基锡烷的相互作用,容易产生含有环丙基甲基系统的单环和双环基团。每个被研究的基团都通过更取代的βγ键的裂变而开环。在第二自由基(12b)的情况下,优先以反式构型形成新的双键。无法通过此方法高精度确定的速率常数在1×10 7 –3×10 8 s –1的范围内在25°C下。当通过流动方法在esr腔中产生时,α-羟基环丙基甲基自由基经历β裂变,随后进行1,5-氢原子转移以提供烯氧基。与非极性溶剂相比,后者在水中的反应更慢。刚性羟基降三环基自由基(43)可能会由于过渡态的偶极性质而优先发生取代度较低的βγ键的裂变。
Iron-Catalyzed Regioselective Reductive Fluoroalkylalkenylation of Unactivated Alkenes
The example of iron-catalyzed reductive fluoroalkylalkenylation of unactivated alkenes has been disclosed, affording the stereodefined homoallylic fluoroalkanes with high efficiency and regioselectivity. This three-component cross-electrophile coupling features directing groups free, good functional group tolerance, broad substrate scope, and late-stage difunctionalization of biorelevant molecules
Ligand-free Ag(I)-catalyzed carboxylative coupling of terminal alkynes, chloride compounds, and CO2
作者:Xiao Zhang、Wen-Zhen Zhang、Ling-Long Shi、Chuang Zhu、Jiao-Lai Jiang、Xiao-Bing Lu
DOI:10.1016/j.tet.2012.08.053
日期:2012.11
Simple silver(I) slats were found to be highly efficient and selective catalyst for carboxylative coupling of aryl- or alkyl-substituted terminal alkynes, CO2, and various allylic, propargylic or benzylic chlorides to exclusively yield functionalized 2-alkynoates. The activity is about 300 times that of the previously reported N-heterocyclic carbene copper(I) catalytic system. The ligand-free silver(I) catalytic system showed the wide generality of substrates involving both functionalized terminal alkynes and chloride compounds. (C) 2012 Elsevier Ltd. All rights reserved.