Cations or Radicals? Inherent Reactivity of Biosynthetic Intermediates in the B-Ring Formation of Rotenoid Natural Products
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.
cyclization, bond cleavage, oxygen, solvents, crystal cleavage
Kirkpatrick, Adam K., and Matthew R. Siebert. "Cations or Radicals? Inherent Reactivity of Biosynthetic Intermediates in the B-Ring Formation of Rotenoid Natural Products." The Journal of Physical Chemistry A 120, no. 15 (2016): 2372-2379.
The Journal of Physical Chemistry A