Photochemical Behavior of Some Estrone Aryl and Methyl Sulfonates in Solution: Preparative and Mechanistic Studies

• Published in: Photochemistry and photobiology 2021-01, Vol.97 (1), p.8-21
• Main Authors: Quindt, Matías I., Gola, Gabriel F., Ramirez, Javier A., Bonesi, Sergio M.
• Format: Article
• Language: English
• Subjects: Aromatic compounds; Derivatives; Estrone; Irradiation; Organic solvents; Photochemicals; Photochemistry; Photosensitization; Radiation; Solvent effect; Solvents; Sulfonates
• ISSN: 0031-8655; 1751-1097
• DOI: 10.1111/php.13272

Direct irradiation of estrone aryl and methyl sulfonates in different organic solvents under nitrogen atmosphere was investigated under steady‐state conditions. The estrone derivatives reacted efficiently through the photo‐Fries rearrangement reaction involving [1;3]‐sulfonyl migration providing the ortho‐sulfonyl estrone derivatives and estrone as the photoproducts. In addition, estrone and 2‐arylsulfonyl estrone derivatives were epimerized involving a Norrish Type‐I reaction. Chemical quenching and photosensitization experiments on the photoreaction have been also carried out to establish the photoreactive excited state. Likewise, the solvent effect and the nature of the sulfonyl group on the photoreactions have been also studied. Direct irradiation of estrone aryl and methyl sulfonates in organic solvents underwent the photo‐Fries rearrangement reaction, with consecutive homolytic fragmentation of the sulfonic ester group and [1;3]‐aryl or methylsulfonyl migration. Simultaneously, the photoepimerization reaction of estrone and 2‐arylsulfonyl estrone occurred through the Norrish Type‐I reaction mechanism involving the fragmentation of the C‐α at the carbonyl group (C‐17) of the steroid. Photosensitization and chemical quenching experiments showed that singlet and triplet excited states are involved in the photo‐Fries and Norrish Type‐I reactions, respectively.