Mechanism of scandium ion catalyzed Diels-Alder reaction of anthracenes with methyl vinyl ketone
Mechanism of scandium ion catalyzed Diels-Alder reaction of anthracenes with methyl vinyl ketone
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DOI：
10.1021/jp050347u
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发表时间：
2005-04-14
影响因子：
2.9
通讯作者：
Suenobu, T
中科院分区：
文献类型：
--
作者：
Fukuzumi, S;Yuasa, J;Suenobu, T
三氟甲磺酸钪[Sc（OTf）（3）]的存在显著加快了蒽与甲基乙烯基酮（MVK）的Diels-Alder环加成反应，Sc（OTf）（3）也显著促进了不同电子供体到MVK的光诱导电子转移反应.比较了Sc（OTf）（3）在MVK光诱导电子转移反应中的促进作用和Sc（OTf）（3）在9，10-二甲基蒽与MVK的Diels-Alder反应中的催化作用，发现MVK-Sc（OTf）（3）配合物是Diels-Alder反应和光诱导电子转移反应的活性中间体。所观察到的Sc（OTf）（3）-催化的蒽与MVK的Diels-Alder反应的二级速率常数远大于从所观察到的具有比MVK更强的电子受体的蒽的Diels-Alder反应的线性吉布斯能关系所预期的那些，已知其通过电子转移进行。这表明Sc（OTf）（3）催化的蒽与MVK的Diels-Alder反应不是通过从蒽到MVK-Sc（OTf）（3）络合物的电子转移过程进行的。
Rates of Diels-Alder cycloadditions of anthracenes with methyl vinyl ketone (MVK) are accelerated significantly by the presence of scandium triflate [Sc(OTf)(3)], Sc(OTf)(3) also promotes photoinduced electron-transfer reactions from various electron donors to MVK significantly. Comparison of the promoting effect of Sc(OTf)(3) in photoinduced electron-transfer reactions of MVK with the catalytic effect of Sc(OTf)(3) in the Diels-Alder reaction of 9,10-dimethylanthracene with MVK has revealed that the MVK-Sc(OTf)(3) complex is a reactive intermediate in both the Diels-Alder and photoinduced electron-transfer reactions. The observed second-order rate constants of the Sc(OTf)(3)-Catalyzed Diels-Alder reactions of anthracenes with MVK are by far larger than those expected from the observed linear Gibbs energy relation for the Diels-Alder reactions of anthracenes with stronger electron acceptors than MVK, which are known to proceed via electron transfer. This indicates that the Sc(OTf)(3)-catalyzed Diels-Alder reactions of anthracenes with MVK does not proceed via an electron-transfer process from anthracences to the MVK-Sc(OTf)(3) complex.