Photo-Fries Rearrangement of Some 3?Acylestrones in Homogeneous Media: Preparative and Mechanistic Studies

Article

Authorship:

Quindt, Matías Iván ; GOLA, GABRIEL FRANCISCO ; RAMIREZ, JAVIER ALBERTO ; BONESI, SERGIO MAURICIO

Date:

2019

Publishing House and Editing Place:

AMER CHEMICAL SOC

Magazine:

JOURNAL OF ORGANIC CHEMISTRY, vol. 84 (pp. 7051-7065) AMER CHEMICAL SOC

Summary

Irradiation of a series of 3-acylestrones under a nitrogen atmosphere in cyclohexane, acetonitrile (MeCN), and methanol (MeOH) was investigated under steady-state conditions. The molecules underwent the photo-Fries rearrangement, with concomitant homolytic fragmentation of the ester group and [1;3]- acyl migration. This pathway afforded the ortho-acyl estrone derivatives, the main photoproducts, together with estrone. During the irradiation of 3-benzoyl estrone, epimerization of estrone through the Norrish type I reaction occurred, providing lumiestrone as the photoproduct. This photoreaction involves the fragmentation of the C-? at the carbonyl group (C-17) of the steroid. On the other hand, epimerization of ortho-regioisomer 2-acetyl estrone occurred during the irradiation of 3-acetyl estrone. Photosensitization with acetone and chemical quenching with N,N,N,N-tetramethyldiazetinedioxide of the photo-Fries reaction confirmed that the photoreaction took place from the singlet excited state while the Norrish type I reaction proceeds efficiently from the triplet excited state. Solvent effects, as well as the nature of the acyl group on the photoreactions, were also studied.

Key Words

NorrishPhoto-FriesPhotorearrangementEstrone

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http://hdl.handle.net/11336/142989