Photochemische Reaktionen: 46. Mitteilung [1]: Zur Photochemie von α,β-ungesättigten γ-Aldehydoketonen I. Die UV.-Bestrahlung von 3,19-Dioxo-17β-acetoxy-Δ4-androsten



Irradiation of 3,19-dioxo-17β-acetoxy-Δ4-androstene (2) at room temperature in either of its two absorption bands centered at about 245 and 315 nm, respectively, led to products 21, 22, and 23 (Chart 3). Compounds 21 and 22 result from rearrangements involving intramolecular formal 1,2- (→21) and 1,3-shifts (→22) of the angular formyl group, and the formation of compound 23 proceeds through the elimination of the formyl radical and the incorporation of a hydrogen from the medium. Evidence favors the latter process to be a secondary radical reaction rather than a primary photochemical step.