Photochemistry of estrone derivatives in homogeneous and micro-heterogeneous media

GABRIEL F. GOLA; JAVIER A. RAMÍREZ; MATÍAS I. QUINDT; SERGIO M. BONESI

Denver

Workshop; American Chemical Society Summer School on Green Chemistry and Sustainable Energy; 2019

American Chemical Society

Direct irradiation of some estrone derivatives with 254 nm under N2 atmosphere in homogeneous and micellar media was investigated by means of steady-state condition. Selective irradiation of the aryl chromophore of ester compounds underwent the photo-Fries rearrangement, with concomitant homolytic fragmentation of the C-O or C-S bond and [1;3]-acyl or sulfonyl migration. Thispathway afforded the ortho-sulfonyl and acyl estrone derivatives as the main photoproducts. Photosensitization and chemical quenching demonstrate that the photo-Fries reaction of estrone derivatives occurs from the singlet excited state. Further, estrone and the ortho-regioisomers are found to epimerize upon irradiation with 254 nm light through a Norrish type I photoreaction. This photoreaction involves the triplet excited state of the carbonyl group (C-17)at the D ring of the steroids that are populated from the singlet excited state of the phenolic moiety through an intramolecular energy transfer process.On the other hand, a notable selectivity in favor of the ortho-regioisomers derivatives was observed in micellar media. The photochemical reactions carried out in micro-heterogeneous aqueous media is a promising tool that allows the formation of microreactors inducing a noticeable selectivity on the productdistribution.