Concerning the mechanism of α-elimination : hypervalent ion pairing in an iodocarbenium iodide
Concerning the mechanism of α-elimination : hypervalent ion pairing in an iodocarbenium iodide
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关于α-消除机制：碘化碳鎓中的高价离子配对
DOI：
10.1002/anie.199408931
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发表时间：
1994
影响因子：
--
通讯作者：
F. Hampel
中科院分区：
文献类型：
--
作者：
R. Weiss;Michael Rechinger;F. Hampel
契尼森工业公司。第3部分：[SC].[**I Iodocarbenium Ions，Part 4.这项工作得到了基金会的支持“]从力学的观点来看，可以为这些过程建立一个由两个电子互补的极限情况表征的一般反应坐标。R.霍夫曼等人。通过使用氯与二氟卡宾的加成的例子(方案1，左分支)，(定性理论)考虑了这些极限情况之一。根据这些研究，卤素分子X，2的极性a加成反应是由卤素分子(HOMO)的Then*轨道和(S)-卡宾1(LUMO)的2p轨道之间的价态(即2c/2e)LaB(Lewis酸碱)相互作用引发的，由此应该主要产生卤素叶立德3。正如在Stevens重排中一样，后一过程也可能涉及自由基对(在我们的情况下是3a)，这是H~ffmann没有讨论的一个机械性选择。[~]在这种情况下，1和2之间的反应将由卡宾的SP、孤立对和卤素的CT*LUMO之间的超价实验室相互作用启动(方案1.右分支)。这种相互作用最初应该导致在卤素X上的S，2反应的框架内的高价3c/4e情况4。取决于取代基R‘/R2以及
Cheinischen Industrie. Part 3:[Sc].[** I Iodocarbenium Ions, Part 4. This work was supported by the Fonds der tions."] From a mechanistic point of view a general reaction coordinate, which is characterized by two electronically complementary limiting cases, can be formulated for these processes. R. Hoffmann et al. have considered (qualitative theory) one of these limiting cases by using the example of chlorine addition to difluorocarbene (Scheme 1, left branch). 121 According to these studies the polar a-addition of the halogen molecule X, 2 is initiated by a valent (ie 2c/2e) LAB (Lewis Acid Base) interaction between then* orbital of the halogen (HOMO) and the 2p, orbital of the (S)-carbene 1 (LUMO), from which primarily the halonium ylide 3 should result.[21 Its conversion to the methane derivative 6 can now proceed by the familiar route of sigmatropic 1, 2-shifts in ylides. As in the Stevens rearrangement the latter process could also involve radical pairs (in our case 3a) a mechanistic option not discussed by H~ ffmann.[~] In this case the reaction between 1 and 2 would be initiated by a hypervalent LAB-interaction between the sp, lone pair of the carbene and the CT* LUMO of the halogen (Scheme 1. right branch). This interaction should initially lead to the hypervalent 3c/4e situation 4 within the framework of an S, 2 reaction at the halogen X. Depending on the substituents R'/R2 as well as the