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Selectivity in the Photo-Fries Rearrangement of Some Aryl Benzoates in Green and Sustainable Media. Preparative and Mechanistic Studies
journal contribution
posted on 2019-03-15, 00:00 authored by Gastón Siano, Stefano Crespi, Mariella Mella, Sergio M. BonesiIrradiation
of a series of p-substituted aryl
benzoates under N2 atmosphere in homogeneous and micellar
media was investigated by means of steady-state condition and of time-resolved
spectroscopy. A notable selectivity in favor of the 2-hydroxybenzophenone
derivatives was observed in micellar media. The benzophenone derivatives
were the main photoproduct. On the other hand, in homogeneous media
(cyclohexane, acetonitrile, and methanol) the observed product distribution
was entirely different, viz. substituted 2-hydroxybenzophenones, p-substituted phenols, benzyl and benzoic acid were found.
The binding constants in the surfactant were also measured and NOESY
experiments showed that the aryl benzoates were located in the hydrophobic
core of the micelle. Laser flash photolysis experiments led to the
characterization of both p-substituted phenoxy radical
and substituted 2-benzoylcyclohexadienone transients in homogeneous
and micellar environment.