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Updated: May 7, 2026

Preparation of Stable Bicyclic Aziridinium Ions and Their Ring-Opening for the Synthesis of Azaheterocycles
Published on: August 22, 2018
Potential nonadiabatic reactions: ring-opening 4,6-dimethylidenebicyclo[3.1.0]hex-2-ene derivatives to aromatic
Kyle S Stumetz1, Jason T Nadeau, Matthew E Cremeens
1Department of Chemistry and Biochemistry, Gonzaga University , 502 East Boone Avenue, Spokane, Washington 99258, United States.
Abstract:
Potential singlet-triplet surface crossings for the ring opening of 4,6-dimethylidenebicyclo[3.1.0]hex-2-ene derivatives were explored using density functional theory (DFT) and complete active space self-consistent field (CASSCF) methods. Since these ring openings involve relatively high energy species that lead to relatively stable aromatic species, a good scenario for potential nonadiabatic events, we posited that the reaction paths of these ring openings might come close to or cross excited state surfaces. At the DFT level of theory, all reaction paths exhibited characteristics suggestive of singlet-triplet intersections along their paths. 6-Methylidenebicyclo[3.1.0]hex-3-en-2-one and a closely related derivative (4-methylidenebicyclo[3.1.0]hex-2-en-6-one) were explored at the CASSCF level of theory; CASSCF results were qualitatively similar to DFT results and yielded spin-orbit couplings of 1.1-1.4 cm(-1) at the singlet-triplet crossing points.
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