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Updated: Aug 22, 2026

Free Radicals in Chemical Biology: from Chemical Behavior to Biomarker Development
Published on: April 15, 2013
Cope reaction families: to be or not to be a biradical
Armando Navarro-Vázquez1, Matthias Prall, Peter R Schreiner
1Institute of Organic Chemistry, Justus-Liebig-University, Heinrich-Buff-Ring 58, D-35392 Giessen, Germany.
Abstract:
The cyclization reactions of polyunsaturated systems such as enediynes, enyne-allenes, as well as many others, can be structurally related to the Cope reaction and grouped into two branches: 6pi (e.g., Cope, allenyl-Cope) and [2sigma + 4pi] systems (e.g., Bergman, Myers-Saito). After extensive computional (BCCD(T)/cc-pVDZ//UBLYP/6-31G) examination of a large set of Cope-related reactions, we derive the following simple rule: biradical intermediates are involved along the reaction path if they are stabilized by allylic resonance or aromaticity.
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