Michael addition-elimination mechanism for nucleophilic substitution reaction of cycloalkenyl iodonium salts and selectivity of 1,2-hydrogen shift in cycloalkylidene intermediate.
Michael addition-elimination mechanism for nucleophilic substitution reaction of cycloalkenyl iodonium salts and selectivity of 1,2-hydrogen shift in cycloalkylidene intermediate.
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DOI：
10.1021/jo049218k
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发表时间：
2005-01
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影响因子：
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通讯作者：
Morifumi Fujita;W. Kim;K. Fujiwara;T. Okuyama
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文献类型：
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作者：
Morifumi Fujita;W. Kim;K. Fujiwara;T. Okuyama
环己烯基和环戊烯基碘鎓盐在氯仿中与氰离子反应，得到烯丙基和乙烯基形式的氰取代产物。氘标记实验表明，烯丙基产物是通过氰化物与乙烯基碘鎓盐的Michael加成反应形成的，然后在2-氰基环亚烷基中间体中消除碘鎓基团和1，2-氢转移。的氢移位优先发生从亚甲基，而不是次甲基的β-位置的卡宾，和选择性是合理的DFT计算。环戊烯碘鎓盐与乙酸根离子在氯仿中的反应也观察到Michael反应。乙烯基取代产物归因于配体偶联（通过三碘烷）和消除加成（通过环己炔）途径。
Reactions of cyclohexenyl and cyclopentenyl iodonium salts with cyanide ion in chloroform give cyanide substitution products of allylic and vinylic forms. Deuterium-labeling experiments show that the allylic product is formed via the Michael addition of cyanide to the vinylic iodonium salt, followed by elimination of the iodonio group and 1,2-hydrogen shift in the 2-cyanocycloalkylidene intermediate. The hydrogen shift preferentially occurs from the methylene rather than the methine beta-position of the carbene, and the selectivity is rationalized by the DFT calculations. The Michael reaction was also observed in the reaction of cyclopentenyliodonium salt with acetate ion in chloroform. The vinylic substitution products are ascribed to the ligand-coupling (via lambda3-iodane) and elimination-addition (via cyclohexyne) pathways.