3-(trifluoromethyl)indenyl cation: Ion pair return in the formation of an antiaromatic and electron-deficient doubly destabilized carbocation
3-(trifluoromethyl)indenyl cation: Ion pair return in the formation of an antiaromatic and electron-deficient doubly destabilized carbocation
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DOI：
10.1021/jo961387k
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发表时间：
1997-01-24
影响因子：
3.6
通讯作者：
Tsuji, Y
中科院分区：
文献类型：
--
作者：
Allen, AD;Fujio, M;Tsuji, Y
3-(三氟甲基)-3-吲哚对甲苯磺酸盐(15)的溶剂分解反应广泛地异构化为1-(三氟甲基)-3-吲哚对甲苯磺酸盐(16)，后者的读取过程较慢，得到了取代产物17。动力学分析表明，与溶剂捕获相比，与溶剂捕获相比，含有中间烯丙基阳离子对的离子对PS在CD3CO2D中的分配比为99.6℃时，7.7中的18个发生了烯丙基重排反应。对15个具有特定O-18标记的研究表明没有争先恐后的进入。反应活性与溶剂电离参数Y-OTS的关系的m值为0.78，明显小于类似的9-(三氟甲基)-9-荧基对甲苯磺酸盐a的m值1.23，在CF3CO2H中以正常盐效应为主，特殊盐效应涉及0.551 M KO2CCF3对溶剂分离离子对的捕获不超过14%。底物15相对于二次吲哚对甲苯磺酸盐22具有超过10(9)的反应性净降低，其中10(6)倍和10(3)倍分别归因于抗芳香性和吸电子CF3基团。15的溶剂分解被认为是通过在相对不受阻碍的烯丙基碳上形成具有显著亲核拯救作用的离子对来进行的，但内部返回优先于溶剂或盐的捕获。重排的甲苯磺酸盐16的溶解发生时，伽马-CF3基团具有很强的速率延迟，很大程度的内部返回，并且具有不正常的盐效应。
The solvolysis of 3-(trifluoromethyl)-3-indenyl tosylate (15) occurs with extensive isomerization to 1-(trifluoromethyl)-3-indenyl tosylate (16), which reads in a slower process to give the substitution product 17. Kinetic analysis of a model involving an intermediate allyl cation/tosylate ion pair PS gave a partitioning ratio in CD3CO2D at 99.6 degrees C for 18 of 7.7 for return with allylic rearrangement compared with solvent capture. Studies of 15 with specific O-18 labeling show no scrambling in. recovered 15 and partial scrambling in rearrangement to 16. The m value measuring the dependence of the reactivity of 15 on the solvent-ionizing parameter Y-OTs is 0.78, which is significantly less than that of 1.23 for the analogous 9-(trifluoromethyl)-9-fluorenyl tosylate a, Normal salt effects in CF3CO2H predominate far 15, and the special salt effect involves no more than 14% capture of solvent-separated ion pairs by 0.551 M KO2CCF3. The substrate 15 has a net diminution in reactivity of more than 10(9) relative to the secondary indanyl tosylate 22, with factors of 10(6) and 10(3) attributable to antiaromaticity and to the electron-withdrawing CF3 group, respectively. The solvolysis of 15 is proposed to occur by formation of an ion pair with significant nucleophilic salvation at the relatively unhindered allylic carbon, but internal return occurs in preference to solvent or salt capture. Solvolysis of the rearranged tosylate 16 occurs with a strong rate retardation by the gamma-CF3 group, a large extent of internal return, and with a nor;mal salt effect.