SOLVOLYSIS OF CYCLOHEXENYLIODONIUM SALT, A NEW PRECURSOR FOR THE VINYL CATION - REMARKABLE NUCLEOFUGALITY OF THE PHENYLIODONIO GROUP AND EVIDENCE FOR INTERNAL RETURN FROM AN INTIMATE ION-MOLECULE PAIR
SOLVOLYSIS OF CYCLOHEXENYLIODONIUM SALT, A NEW PRECURSOR FOR THE VINYL CATION - REMARKABLE NUCLEOFUGALITY OF THE PHENYLIODONIO GROUP AND EVIDENCE FOR INTERNAL RETURN FROM AN INTIMATE ION-MOLECULE PAIR
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DOI：
10.1021/ja00117a006
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发表时间：
1995-03-29
影响因子：
15
通讯作者：
OCHIAI, M
中科院分区：
文献类型：
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作者：
OKUYAMA, T;TAKINO, T;OCHIAI, M
研究了四氟硼酸（4-叔丁基-1-环己烯基）芳基碘鎓盐在25-70 ℃乙醇和水溶液中的溶剂分解反应。发现苯基碘鎓基团是一种非常好的离核剂，其离核能力比三氟甲磺酸酯大约10（6）倍。除了预期的溶剂分解产物1-烷氧基环己烯和/或环己酮和碘苯之外，还得到内部返回产物（4-叔丁基-1-环己烯基）碘苯，在甲醇和水溶液中的产率为13-15%，在三氟乙醇中的产率为30-40%。邻位衍生物是这些产物的主要同分异构体，这种同分异构体分布被认为表明返回是从亲密的离子-分子对发生的。在1，4-环己二烯或2-丙醇存在下的溶剂分解过程中，检测到自由基产物4-叔丁基环己烯（1%）的形成，而在（2-甲基-1-环己烯基）苯基碘四氟硼酸盐的溶剂分解过程中，得到了相当数量的阳离子重排产物环戊基甲基酮。提出的机制主要涉及异裂解，得到环己烯基阳离子-碘苯对，伴随单电子转移（或竞争性均裂），导致自由基中间体。
Solvolysis of (4-tert-butyl-1-cyclohexenyl)aryliodonium tetrafluoroborates was examined in alcohol and aqueous solutions at 25-70 degrees C. Phenyliodonio group was found to be a remarkably good nucleofuge with a leaving ability about 10(6) times greater than triflate. In addition to the expected solvolysis products, 1-alkoxycyclohexene and/or cyclohexanone and iodobenzene, the internal return products, (4-tert-butyl-1-cyclohexenyl)iodobenzenes, were obtained in yields of 13-15% in methanol and aqueous solutions and of 30-40% in trifluoroethanol. The ortho derivative is the predominant isomer of these products, and this isomeric distribution is taken as indicating that the return is occurring from the intimate ion-molecule pair. The formation of a free-radical product, 4-tert-butylcyclohexene (1%), was detected during the solvolysis in the presence of 1,4-cyclohexadiene or in 2-propanol, while a considerable amount of the cationic rearrangement product, cyclopentyl methyl ketone, was obtained in the solvolysis of (2-methyl-1-cyclohexenyl)phenyliodonium tetrafluoroborate. A proposed mechanism involves mainly heterolysis to give the cyclohexenyl cation-iodobenzene pair with accompanying single electron transfer (or with competing homolysis) to lead to a free radical intermediate.