Photochemical Rearrangements of β,γ-Cyclopropyl-β',γ'-epoxy Ketones

Article abstract of DOI:10.1021/jo00158a027

Ketones 1-5 have been prepared and photolyzed in benzene and in benzene-methanol (λ > 280 nm).Major volatile products were isolated by gas chromatography and their structures determined by a combination of spectroscopic and chemical methods.The products from 1-4 can be explained by way of a α cleavage and selective fission of the carbon-oxygen bond of the epoxide, according to eq 1 (X = O).No effective competition from cleavage of the cyclopropane ring (eq 1, X = CH2) is observed.Reaction of 2 is slow because of steric crowding, and there is evidence for a small amount of competitive photoisomerisation of 2 to 1.In contrast with 1-4, ketone 5 decarbonylates with formation of 5a.