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Photochemische Reaktionen. 47. Mitteilung [1]. Zur photochemischen Umwandlung eines α,β‐ungesättigten γ,δ‐Epoxyketons: 3‐Oxo‐6α, 7α‐oxido‐17β‐acetoxy‐Δ 4 ‐androsten
Author(s) -
Saboz J. A.,
Iizuka T.,
Wehrli H.,
Schaffner K.,
Jeger O.
Publication year - 1968
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19680510619
Subject(s) - chemistry , acetophenone , photochemistry , anhydrous , double bond , yield (engineering) , benzene , enone , absorption band , medicinal chemistry , stereochemistry , organic chemistry , materials science , physics , optics , metallurgy , catalysis
The α,β‐unsaturated γ,δ‐epoxyketone 7 is isomerized almost exclusively to the δ‐diketone 9 both upon irradiation in the n → π* absorption band with light of wavelengths above 310 nm (in anhydrous dioxane or benzene solutions) and upon triplet sensitization using acetophenone in benzene. The reaction may be formulated by the cleavage of the C γ O oxide bond and the shift of the δ‐hydrogen to the γ‐position, and thus bears a formal “double bond homology” to the photochemical α,β‐epoxyketone rearrangement. Excitation in the π → π* absorption band of 7 with light of wavelength 253,7 nm (in anhydrous dioxane solution) leads to the formation of product 10 as well as to the triplet rearrangement to 9 . With this result a novel partial synthesis of O‐acetyl‐B‐nortestosterone has been accomplished, which has the advantages of fewer steps and higher product yield ( 7 → 10 : ∼30% yield) than previously published syntheses. On the basis of the presently available experiments, the mechanism of the transformation 7 → 10 , which constitutes one of the still few examples of enone photoreactions induced selectively from the π,π* excited singlet, remains unknown.