PHOTOREARRANGEMENT OF BETA,GAMMA-UNSATURATED KETONES . APPLICATION TO SYNTHESIS OF BRIDGE BICYCLIC KETONES

Ultraviolet irradiation of β,γ-unsaturated ketones such as 3, 5, and 7 in which the double bond occupies an exoeyclic position with respect to the carbonyl group lias been found to give rise exclusively to unsaturated bridged bicyelic ketones. The photorearrangements were shown to be completely reversible, the apparent photostationary states lying substantially in favor of 3, 5, and 7. Although ketones 4, 6, and 8 do not predominate at equilibrium, isolation can be achieved by preparative-scale gas chromatography. These conversions therefore provide synthetic entry to previously unknown and otherwise difficultly accessible carbonyl compounds. The spectra and physical properties of these ketones are presented in some detail. © 1969, American Chemical Society. All rights reserved.