Photochemical Reactions. IV. [1] Irradiation of 17 β‐acetoxy‐4‐aza‐androst‐5‐en‐3‐one with UV.‐light

Summary. The photo-oxidation of the title compound (1) is described. The isolated productsIn recent times, the photo-oxidation of the enamine function has received considerable attention [Zj. These compounds suffer [Z + 21 siglet oxygen addition, with formation of unstable l,Z-dioxetanes, that ultimately yield carbonylic fragments. The decomposition of these dioxetanes are usually accompanied by luminiscence phenomena. On the other hand, oxidation products of enamides seem to play an important role in bioluminiscence phenomena [3]. For all this and considering the photoreactivity of the 4 5 double bond in compound 1 [l], it was thought of interest to study its bchaviour in photo-oxidation conditions. When 1, easily obtained from testosterone acetate [4], was irradiated during 12 h in benzene (Merck, analytical purity), with the light of a low-pressure Hg lamp, under a current of oxygen, a mixture of compounds was obtained, containing starting material (1, !I%), the hydroxy derivative 2 (5%), the diol 3 (16%), the dioxetane 4 (5%) and the keto-alcohol 5 (30%) (Scheme 7). All the structures were assigned on basis of the corresponding spectroscopic and analytical dataz). Scheme 1are the result of a [2+ 21 oxygen addition to the olefinic double bond of the cnamide.

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Photochemical reactions. VI. Photo‐Beckmann rearrangement with vinyl migration. Preliminary communication

Armengol

Coll

Reixach

et al. 1976

Helvetica Chimica Acta

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Sumnzary. The carefully controlled UV. irradiation of 3-hydroxyimino-d4-and 3-hydroxyimino-A4,A6-steroids yield as a result of vinyl and alkyl migration, lactams besides products expected.Rearrangement of conjugated steroidal ketonic nitrones yields N-substituted lactams as a result of vinyl migration (1 -+ 2) [Z]. Synthesis of the analogous N-nonsubstituted compounds 3 seems not to be feasible: The Beckmann rearrangement of the appropiate oximes gives only the alkyl migration isomers (e.g. 5 and 6 + 7) [3], and by irradiation 5 and 6 or similar unsaturated oximes show either a remarkable lack of reactivity [4], or syn-anti isomerization and fragmentation to ketone, followed by a slow and extensive decomposition [4] [5]. In no case have the least mentioned authors reported the formation of lactams as a result of a photo-Beckmann rearrangement. Nevertheless, from our previous work, a) the isolation of a lactam after UV. irradiation of 3-hydroxyimino-17~-acetoxy-androsta-l, 5-diene [6], and b) the photolability of conjugated lactams to give mainly dimers [7], suggest that the photoBeckmann rearrangement of 5 or 6 and of analogous oximes may take place, the primarily formed lactamic products not being detected owing to their further photochemical reaction.A systematic study was therefore undertaken and the following were found to be the most suitable conditions for photo-rearrangement : 1) Use of a medium pressure Hg lamp without filter, short irradiation time (-30 min), and low concentration (-O.lyo) ensure that the photo-Beckmann rearrangement takes place quickly, and secondary reactions (dimerization) are minimized; 2) use of a hydroxylic solvent, l)For part V, see [l].

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Photochemical Reactions. IV. [1] Irradiation of 17 β‐acetoxy‐4‐aza‐androst‐5‐en‐3‐one with UV.‐light

Cited by 5 publications

References 7 publications

ChemInform Abstract: PHOTOCHEMICAL REACTIONS. IV. IRRADIATION OF 17β‐ACETOXY‐4‐AZAANDROST‐5‐EN‐3‐ONE WITH UV LIGHT

ChemInform Abstract: PHOTOCHEMICAL REACTIONS. IV. IRRADIATION OF 17β‐ACETOXY‐4‐AZAANDROST‐5‐EN‐3‐ONE WITH UV LIGHT

Photochemical Reactions. V. [1] Photo‐oxidation of 17 β‐acetoxy‐4‐aza‐androst‐5‐en‐3‐one

Photochemical reactions. VI. Photo‐Beckmann rearrangement with vinyl migration. Preliminary communication

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