On the photochemistry of alpha, beta-unsaturated gamma-aldehydoketones. I. The UVirradiation of 3, 19-dioxo-17-beta-acetoxy-delta-4-androstene

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.