Molecular rearrangements through thermal [1,3] carbon shifts
Molecular rearrangements through thermal [1,3] carbon shifts
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DOI：
10.1039/b711494j
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发表时间：
2008-01-01
影响因子：
3.2
通讯作者：
Leber, Phyllis A.
中科院分区：
文献类型：
--
作者：
Baldwin, John E.;Leber, Phyllis A.
通过热[1，3]碳位移的分子重排，如乙烯基环丙烷到环戊烯和乙烯基环丁烷到环己烯的异构化，在1960-1964年被反复确认和举例说明。在过去的40年里，对这些和相关重排的认真的机理研究为将它们解释为通过构象灵活但统计上不平衡的双自由基中间体发生的过程提供了充分的理由。轨道对称理论不能解释[1，3]碳位移的立体化学特征。对于这类σ迁移反应，该理论不能再作为机械论解释的有效基础，甚至不能作为考虑机械论可能性的有力竞争者。
Molecular rearrangements through thermal [1,3] carbon shifts, such as vinylcyclopropane-to-cyclopentene and vinylcyclobutane-to-cyclohexene isomerizations, were recognized and exemplified repeatedly from 1960-1964. Serious mechanistic studies of these and related rearrangements over the past 40 years have provided ample grounds for interpreting them as processes taking place by way of conformationally flexible but not statistically equilibrated diradical intermediates. Orbital symmetry theory fails to account for the stereochemical characteristics of [1,3] carbon shifts. For sigmatropic reactions of this class the theory can no longer be retained as a valid basis for mechanistic interpretations, or even as a serious contender for consideration as a mechanistic possibility.