MECHANISM OF THE REACTION OF MONO-OLEFINS WITH DIENOPHILES .2. A POSSIBLE FREE-RADICAL MECHANISM
MECHANISM OF THE REACTION OF MONO-OLEFINS WITH DIENOPHILES .2. A POSSIBLE FREE-RADICAL MECHANISM
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DOI：
10.1021/jo01121a015
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发表时间：
1955-01-01
影响因子：
3.6
通讯作者：
WARK, BH
中科院分区：
文献类型：
--
作者：
RONDESTVEDT, CS;WARK, BH
烯烃与亲双烯体的热缩合可以通过离子机理（1）来解释，其要求亲双烯体连接到烯烃双键的碳之一（2）。一个例外是与离子机理不一致，除非在反应前假设不可能的双键位移; Bickford及其同事（3）注意到油酸甲酯与马来酸酐在220 ℃反应，不仅形成离子机理预测的产物II和III，而且还形成I和IV。尽管他们没有给出I和IV的完整结构证明，但他们的氧化实验构成了指定结构的强有力证据。他们提出了一种自由基机制，类似于油酸甲酯自氧化的机制，其中a-碳8或11失去一个氢原子，然后将两种极端形式的内消旋自由基加成到马来酸酐中。然后通过常规的链增长步骤继续反应。它们的机理解释了I和IV的形成，其中马来酸酐与原始分子的碳原子连接。1
The thermal condensation of olefins with dienophiles can be explained by an ionic mechanism (1), which requires that the dienophile become attached to one of the carbons of the olefinic double bond (2). One exception is inconsistent with the ionicmechanism unless one assumes improbable double-boned shifts before reaction; Bickford and co-workers (3) noted that methyl oleate reacted with maleic anhydride at 220 to form not only the products II and III predicted by the ionic mechanism, but also I and IV. Although they did not present a complete structure proof for I and IV, their oxidationexperiments constitute strong evi-dence for the assigned structures. They suggested a free-radical mechanism, by analogy to that accepted for autoxidation of methyl oleate, in which a hydrogen atom is lost from either a-carbon 8 or 11, followed by addition of the mesomeric radical in either extreme form to maleic anhydride. The reaction then continues by conventional chain propagation steps. Their mechanism accounts for the formation of I and IV, in which the maleic anhydride becomes attached to an-carbon of the original molecule. 1