Photochemische Reaktionen: 46. Mitteilung [1]: Zur Photochemie von α,β‐ungesättigten γ‐Aldehydoketonen I. Die UV.‐Bestrahlung von 3,19‐Dioxo‐17β‐acetoxy‐Δ 4 ‐androsten

Irradiation of 3,19‐dioxo‐17β‐acetoxy‐Δ 4 ‐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.