Photoenolization of o‐Methylvalerophenone Ester Derivative |
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| Authors: | Anushree Das Emily A. Lao Anna D. Gudmundsdottir |
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| Affiliation: | Department of Chemistry, University of Cincinnati, Cincinnati, OH |
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| Abstract: | Photolysis of ester 1 in argon‐saturated methanol and acetonitrile does not produce any product, whereas irradiation of 1 in oxygen‐saturated methanol yields peroxide 2 . Laser flash photolysis studies demonstrate that 1 undergoes intramolecular H atom abstraction to form biradical 3 (λ max ~ 340 nm), which intersystem crosses to form photoenols Z ‐ 4 and E ‐ 4 (λ max ~ 380 nm). Photoenols 4 decay by regenerating ester 1 . With the aid of density functional theory calculations, it was concluded the photoenol E ‐ 4 does not undergo spontaneous lactonization or electrocyclic ring closure because the transition state barriers for these reactions are too large to compete with reketonization of E ‐ 4 to form 1 . |
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