Kinetics of the Reactions of Carboxonium Ions and Aldehyde Boron Trihalide Complexes with Alkenes and Allylsilanes
Kinetics of the Reactions of Carboxonium Ions and Aldehyde Boron Trihalide Complexes with Alkenes and Allylsilanes
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碳鎓离子和醛三卤化硼配合物与烯烃和烯丙基硅烷的反应动力学
DOI：
10.1021/ja00135a002
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发表时间：
1995
影响因子：
15
通讯作者：
Gorden Gorath
中科院分区：
文献类型：
--
作者：
H. Mayr;Gorden Gorath
在CH_2Cl_2溶液中，测定了碳鎓离子Ar（MeO）CH ~+和三卤化硼络合物ArCH= 0-3与烯丙基硅烷和烯丙基烯烃反应的二级速率常数。这些亲电试剂的相对反应性几乎与亲核试剂的性质无关，并且可以给出平均反应性顺序。对于亲电体PhCH= O-BF 3、PhCH= O-BC 13、Phtp-MeOC 3DCH 4-和Ph（MeO）CH+，即对于PhCHX+，其中X= F3 BO ™、CI 3BO ™、p-MeOC 3 Ht、MeO，相对平均反应性为1：5 × 10* 12：1 × 104：4 × 105（CH_2Cl_2，~ 70 ℃），表明BHaly-C_2H_2O络合物的亲电性仅比相应的羧鎓离子小3-6个数量级。甲氧基取代的苄基阳离子Ar（MeO）CH+的反应性（CH 2Cl 2，20 ℃）比它们的苯基二苯甲基类似物ArCp-MeOCeH/OCH 4-高3-16倍。
Second order rate constants for the reactions of carboxonium ions Ar (MeO) CH+ and aldehyde—boron trihalide complexes ArCH= 0—3 with allylsilanes and alkenes have been determined in CH2CI2 solution. The relative reactivities of these electrophiles are almost independent of the nature of the-nucleophiles, and it is possible to give an averaged reactivity order. For the electrophiles PhCH= 0—BF3, PhCH= 0—BCI3, Phtp-MeOCstDCH4", and Ph (MeO) CH+, ie, for PhCHX+ with X= F3BO™, CI3BO™, p-MeOCsHt, MeO relative averaged reactivities of1: 5 x 10* 12: 1 x 104: 4 x 105 (CH2CI2,-70 C) are determined indicating that the electrophilicities of aldehyde-BHaly complexes are only 3-6 orders of magnitude smaller than those of the corresponding carboxonium ions. The-methoxy substituted benzyl cations Ar (MeO) CH+ are 3—16 times more reactive (CH2CI2, 20 C) than their phenylogous benzhydryl analogues ArCp-MeOCeH/OCH4".