Photochemische Reaktionen. 34. Mitteilung. Die Photoisomerisierung von 3‐Oxo‐Δ1;4‐Steroiden in Dioxanlösung. 3,11‐Dioxo‐17β‐acetoxy‐Δ1;4‐androstadien und 3‐Oxo‐17β‐acetoxy‐Δ1;4;9,11‐androstatrien

Ultraviolet irradiation of the steroidal cross‐conjugated dienones 3 and 7, and of the bicyclohexenone derivative 16 in dioxane solution produced the virtually quantitative isomerizations 3 → 11 (Chart 3) and 7 → 16 → 17 (Chart 6). These conversions are consistent with the previously established general scheme a → b → c → d → e (Chart 1). By analogy with these results, it is suggested that the photo‐isomers 9 and 10 of O‐acetylprednisone (8) represent products resulting from multiple photorearrangements rather than from direct transformations, as had been proposed in the literature.