Steroid photochemistry : The photocycloaddition of an enone and dienone to norbornene and norbornadiene |
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Authors: | George R. Lenz |
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Affiliation: | Division of Chemical Research, G.D. Searle & Co. P.O. Box 5110, Chicago, Illinois 60680 U.S.A. |
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Abstract: | The photocycloaddition of a steroidal 4-en-3-one and a 4,6-dien-3-one to bicyclo[2.2.1]heptene and bicyclo[2.2.1]heptadiene has been studied. The photocycloaddition to norbornene furnished only the trans-4α,5β-cyclobutane, while the enone gave a mixture of cis and trans-[2+2] adducts as well as the first example of hydrogen transfer in this series to form a 4-(2-norbornanyl 1)-conjugated enone. The photocycloaddition of the dienone to norbornadiene formed the 4-(7-norbornenyl)-dienone by a 1,4-hydrogen shift as the major product, together with lesser amounts of the unrearranged trans-4α,5β-[2+2]-cyclobutane. On the other hand, the cycloaddition of the enone to norbornadiene yielded the 4α-(7-norbornene)-β,γ-enone as the major product; accompanied again by the unrearranged trans-[2+2]-adduct. In addition, the 4α,5α-cis-[3+2] adduct was obtained and was formed by rearrangement of the norbornenyl radical portion of the intermediate diradical. |
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