A Way to Avoid Using Precious Metals: The Application of High-Surface Activated Carbon for the Synthesis of Isoindoles via the Diels鈥揂lder Reaction of 2H-Pyran-2-ones

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• 作者：Marko Krivec ; Martin Gazvoda ; Kri拧tof Kranjc ; Slovenko Polanc ; Marijan Ko膷evar
• 刊名：The Journal of Organic Chemistry
• 出版年：2012
• 出版时间：March 16, 2012
• 年：2012
• 卷：77
• 期：6
• 页码：2857-2864
• 全文大小：311K
• 年卷期：v.77,no.6(March 16, 2012)
• ISSN：1520-6904

文摘

The application of activated carbon (Darco KB) for the acceleration and direction of the transformation of various 2H-pyran-2-ones with N-substituted maleimides toward isoindole derivatives through the reaction sequence cycloaddition/elimination/dehydrogenation is described. In this reaction, the catalyst mainly influences the dehydrogenation step, which is essential to avoid the formation of bicyclo[2.2.2]octenes as the other possible products. We found that the combination of Darco KB, as the metal-free catalyst, and decalin, as the solvent in a closed vessel, represents the most successful conditions. A comparison of the effect of various dehydrogenation catalysts and reaction conditions is also presented. In addition, we have proven that the aromatization occurs via a hydrogen transfer from the cyclohexadiene intermediate to the maleimide derivative (therefore producing succinimides). This transfer is facilitated by the active surface of the heterogeneous carbon-based catalyst.