Cycloaddition Reaction of Vinylphenylfurans and Dimethyl Acetylenedicarboxylate to [8+2] Isomers via Tandem [4+2]/Diradical Alkene-Alkene Coupling/[1,3]-H Shift Reactions: Experimental Exploration and DFT Understanding of Reaction Mechanisms
Cycloaddition Reaction of Vinylphenylfurans and Dimethyl Acetylenedicarboxylate to [8+2] Isomers via Tandem [4+2]/Diradical Alkene-Alkene Coupling/[1,3]-H Shift Reactions: Experimental Exploration and DFT Understanding of Reaction Mechanisms
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乙烯基苯基呋喃和乙炔二甲酸二甲酯通过串联 [4 2]/双自由基烯烃-烯烃偶联/[1,3]-H 变换反应生成 [8 2] 异构体：实验探索和 DFT 了解反应机制
DOI：
10.1021/acs.joc.6b00792
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发表时间：
2016
影响因子：
3.6
通讯作者：
Zhu Shifa
中科院分区：
文献类型：
--
作者：
Chen Kai;Wu Feng;Ye Lijuan;Tian Zi-You;Yu Zhi-Xiang;Zhu Shifa
对设计的乙烯基苯基呋喃与二甲基乙酰二羧酸酯（DMAD）[8 + 2]反应进行了实验测试，结果表明该反应在不同条件下产生了意想不到的加成产物。在甲苯中进行热反应时，生成了[8 + 2]同分异构体——环氧菲。本研究探讨了该反应的范围。此外，还通过实验和DFT计算研究了乙烯基苯基呋喃与DMAD之间的反应过程。令人惊讶的是，该反应没有涉及预期的[8 + 2]中间体邻喹诺二甲烷。相反，反应从DMAD和乙烯基苯基呋喃的呋喃部分之间的分子间diols - alder反应开始，然后是意想不到的分子内烯-烯偶联。这一步骤产生一种双自由基，然后发生[1,3]-H移位，得到实验观察到的环氧菲。DFT计算表明，与[1,3]-H向[8 + 2]异构体的转移相比，[1,5]-乙烯基转移中间体的[1,5]-H转移过程在动力学上更不利，因此不能得到[8 + 2]环加合物。
An experimental test of designed [8 + 2] reaction of vinylphenylfuran and dimethyl acetylenedicarboxylate (DMAD) has been carried out, showing that the reaction gave unexpected addition products under different conditions. When the reaction was conducted under thermal conditions in toluene, expoxyphenanthrene, which was named as a [8 + 2] isomer, was generated. The scope of this reaction has been investigated in the present study. In addition, experiments and DFT calculations have been conducted to investigate how the reaction between vinylphenylfuran and DMAD took place. Surprisingly, the reaction did not involve the expected [8 + 2] intermediate,o-quinodimethane. Instead, the reaction starts from intermolecular Diels–Alder reactions between DMAD and the furan moiety of vinylphenylfuran, followed by unexpected intramolecular alkene–alkene coupling. This step generates a diradical species, which then undergoes [1,3]-H shift to give the experimentally observed expoxyphenanthrene. DFT calculations revealed that, the [8 + 2] cycloadduct cannot be obtained because the [1,5]-H shift process from the [1,5]-vinyl shift intermediate is disfavored kinetically compared to the [1,3]-H shift to the [8 + 2] isomer.