Photochemische Reaktionen. 56. Mitteilung [1]. Die Photoisomerisierung des α,β-ungesättigten δ-Diketons 3, 7-Dioxo-4, 4-dimethyl-17 β-acetoxy-δ5-androsten und dessen 3-Ketalderivates

On irradiation with light of wavelengths 2537 or > 3400 Å 4,4-dimethyl-17β-acetoxy-androst-5-ene-3, 7-dione ( 8 ) rearranges to the two diastereoisomeric products 9 and 10 . This isomerization is the only detectable photochemical reaction of 8 in a variety of solvents, including p-dioxane. Complete quenching with 0.5M naphthalene (on irradiation with > 3400 Å) indicates a triplet reaction. The photochemistry of the 3-ethylene ketal derivative 29 differs completely. Irradiation in p-dioxane solution leads exclusively to photoreduction and formation of the four diastereoisomeric dioxanyl allyl tert.-carbinols 30a – d .