Cations or Radicals? Inherent Reactivity of Biosynthetic Intermediates in the B-Ring Formation of Rotenoid Natural Products

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• 作者：Adam K. Kirkpatrick ; Matthew R. Siebert
• 刊名：Journal of Physical Chemistry A
• 出版年：2016
• 出版时间：April 21, 2016
• 年：2016
• 卷：120
• 期：15
• 页码：2372-2379
• 全文大小：482K
• 年卷期：0
• ISSN：1520-5215

文摘

Compounds of the rotenoid class are naturally occurring in the Leguminosae and Nyctaginacae families. Rotenoids have found a myriad of uses, for example, in the agricultural industry as an insecticide and piscicide, and as an anticancer therapeutic. The scientific literature questions whether cyclization of the rotenoid B-ring occurs via a pathway containing either cationic or free-radical intermediates. In this work, both propositions are analyzed using DFT (B3LYP and M06-2X) and the G3 composite method in gas- and (implicit) solution-phase. The accuracy of these methods is compared to several experimental C–H bond dissociation energies (BDEs). We find that of the methods surveyed M06-2X provides the most accurate BDEs. Further, there is a clear thermodynamic preference for the free-radical pathway.