A series of 8-oxabicyclo [3.2. 1] od-6-en-2-ones was prepared by the rhodium (I1)-catalyzed cyclization-cycloaddition reaction of a-diazopentanedione with various alkynes. The photochemical behavior of these oxabicyclic enones was investigated. Both direct and sensitized photolysis cleanly results in a 1, 3-acyl shift. A slower, secondary photoprocess involving intramolecular hydrogen atom transfer and intramolecular cycloaddition of the ...