Document Type


Publication Date

Fall 11-5-2023




Six-electron electrocyclic reactions usually require relatively high temperatures; however recent research has shown that such reactions can occur at significantly lower temperatures in biosynthetic and biomimetic pathways. Pathways resulting in bicyclo[4.2.0]octa-2,4-diene moieties arise from thermally allowed 8π-6π electrocyclization cascade reactions of 1,3,5,7-octatetraenes, as in the biosynthesis of endiandric acids, elysiapyrones, and numerous other natural products. We report multidimensional tunneling calculations to explore the possible contribution of heavy-atom tunneling (e.g. by carbon) to biosynthetic pathways and biomimetic syntheses, and thus to provide a more complete picture of biochemical kinetics. M06-2X/cc-pVDZ calculations on the 8π-6π cascade cyclizations of methylated octatetraene model systems suggest that at 240 to 340K, tunneling contributions were low at 20% to 10% during the 8π electrocyclization, and moderate at around 32% to 17% during the 6π electrocyclization. These values suggested tunneling contributes significantly to––but does not dominate––the thermally allowed 8π-6π cascade.


This poster was produced for the Bay Area Chemistry Symposium held at UCSF Mission Bay (Fall 2023) and funded by the Whitehead Summer 2023 Fellowship. This work is part of the Castro/Karney Research Group at USF.