Different reaction modes for the oxidative dimerization of epoxyquinols and epoxyquinones. Importance of intermolecular hydrogen-bonding.
Different reaction modes for the oxidative dimerization of epoxyquinols and epoxyquinones. Importance of intermolecular hydrogen-bonding.
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DOI：
10.1021/jo0355303
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发表时间：
2004-01
期刊：
影响因子：
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通讯作者：
M. Shoji;H. Imai;Isamu Shiina;H. Kakeya;H. Osada;Y. Hayashi
中科院分区：
文献类型：
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作者：
M. Shoji;H. Imai;Isamu Shiina;H. Kakeya;H. Osada;Y. Hayashi
对2-烯基-3-羟甲基-2-环己烯-1- 1衍生物环氧喹啉3、环氧醌6和环己烯酮10的氧化二聚化反应进行了实验和理论研究。在环氧醌6和环己酮10的氧化/6 -电环化/Diels-Alder反应级联的16种可能模式中，分别只观察到内抗（环氧化物）-抗(Me)-杂和内抗(Me)-杂的反应模式，而在环氧醌3中存在内抗（环氧化物）-抗(Me)-杂和外抗（环氧化物）-抗(Me)-同源反应模式。虽然环氧醌6和环己酮10都选择性地只生成了环氧醌A型产物，但分子间的氢键是与3形成环氧醌A型和B型的关键原因。在环氧喹啉3二聚化过程中，两个单体2h -吡喃5相互作用，形成被氢键稳定的中间配合物28或29，并由此发生Diels-Alder反应。理论计算也揭示了环氧醌6和环己酮10在反应谱上的差异。即前者的速率决定步骤是Diels-Alder反应，后者的速率决定步骤是6 -电环化。
An oxidative dimerization reaction, involving the three successive steps of oxidation, 6 pi-electrocyclization, and Diels-Alder reaction, has been experimentally and theoretically investigated for the three 2-alkenyl-3-hydroxymethyl-2-cyclohexen-1-one derivatives epoxyquinol 3, epoxyquinone 6, and cyclohexenone 10. Of the sixteen possible modes of the oxidation/6 pi-electrocylization/Diels-Alder reaction cascade for the epoxyquinone 6, and eight for the cyclohexenone 10, only the endo-anti(epoxide)-anti(Me)-hetero and endo-anti(Me)-hetero modes are, respectively, observed, while both endo-anti(epoxide)-anti(Me)-hetero and exo-anti(epoxide)-anti(Me)-homo reaction modes occur with the epoxyquinol 3. Intermolecular hydrogen-bonding is found to be the key cause of formation of both epoxyquinols A and B with 3, although epoxyquinone 6 and cyclohexenone 10 both gave selectively only the epoxyquinol A-type product. In the dimerization of epoxyquinol 3, two monomer 2H-pyrans 5 interact with each other to afford intermediate complex 28 or 29 stabilized by hydrogen-bonding, from which Diels-Alder reaction proceeds. Theoretical calculations have also revealed the differences in the reaction profiles of epoxyquinone 6 and cyclohexenone 10. Namely, the rate-determining step of the former is the Diels-Alder reaction, while that of the latter is the 6 pi-electrocyclization.