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Photoenolization of o ‐Methylvalerophenone Ester Derivative
Author(s) -
Das Anushree,
Lao Emily A.,
Gudmundsdottir Anna D.
Publication year - 2016
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/php.12590
Subject(s) - chemistry , intramolecular force , methanol , photochemistry , photodissociation , acetonitrile , flash photolysis , derivative (finance) , ring (chemistry) , intersystem crossing , density functional theory , dehydrogenation , peroxide , medicinal chemistry , computational chemistry , catalysis , stereochemistry , organic chemistry , excited state , reaction rate constant , singlet state , kinetics , physics , quantum mechanics , economics , financial economics , nuclear physics
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 .