Publication details

p-Hydroxyphenacyl photoremovable protecting groups - Robust photochemistry despite substituent diversity



Year of publication 2011
Type Article in Periodical
Magazine / Source Canadian journal of chemistry
MU Faculty or unit

Faculty of Science

Field Organic chemistry
Keywords Photoremovable Protecting Group; p-Hydroxyphenacyl Protecting Group; Fluorinated Photoremovable Protecting Groups; Laser Flash Photolysis
Description A broadly based investigation of the effects of a diverse array of substituents on the photochemical rearrangement of p-hydroxyphenacyl esters has demonstrated that common substituents such as F, MeO, CN, CO2R, CONH2, and CH3 have little effect on the rate and quantum efficiencies for the photo-Favorskii rearrangement and the release of the acid leaving group or on the lifetimes of the reactive triplet state. A decrease in the quantum yields across all substituents was observed for the release and rearrangement when the photolyses were carried out in buffered aqueous media at pHs that exceeded the ground-state pKa of the chromophore where the conjugate base is the predominant form. Otherwise, substituents have only a very modest effect on the photoreaction of these robust chromophores. Une etude detaillee des effets de divers arrangements de substituants sur le rearrangement photochimique des esters de p-hydroxyphenacyle a demontre que les substituants communs, tel F, MeO, CN, CO2R ou CH3, n'ont que peu d'effet sur la vitesse et les efficacites quantiques du rearrangement de photo-Favorskii et sur la liberation du groupe acide partant ou sur les temps de vies de l'etat triplet reactif. On a observe que tous ces substituants provoquent des diminutions des rendements quantiques pour la liberation et le rearrangement quand les reactions de photolyse sont effectuees dans un milieu aqueux tamponne a un pH superieur a celui du pK(a) de l'etat fondamental du chromophore pour lequel la base conjuguee est la forme predominante. Autrement, les substituants n'ont qu'un effet modeste sur la photoreaction de ces robustes chromophores.
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