Abstract The photo-oxidation product of 1-(9-phenanthryl)-4-phenylbut-1-en-3-yne has been elucidated by chemical and spectroscopic methods (IR, UV, 1 H-NMR, 13 C-NMR) and independently by X-ray analysis. The structure 6-phenyl-8, 9-10, 11-dibenzotricyclo [5.4. 0.0 1, 6]-4-oxaundeca-2, 8, 10-trien-5-one has a cyclopropapyrone unit which decomposes on thermolysis or by catalytic hydrogenation.
