The mechanistically interesting claim was recently made that the dyesensitized photo-oxygenation of biadmantylidene (1) in pinacolone as solvent gave the corresponding dioxetane (2) and epoxide (2) while solvent was converted to t-butyl acetate.'
This result was interpreted as proof that a perepoxide was initially formed and that, before it expanded to dioxetane, it lost its supernumerary oxygen atom to pinacolone in a Baeyer-Villiger type oxidation.
Subsequently, it was discovered that similar olefins, such as binorbornylidene and norbornene, gave dioxetanes and epoxides not only in pinacolone, but also in inert s01vents.2~3
Clearly a re-examination of 1 is necessary. We now present the corrected results together with the discovery that the dioxetaneepoxide ratio depends on the sensitizer used.
Photo-oxygenations were carried out with different sensitizers in a variety of solvents.4 meso-Tetraphenylporphin uniformly gives dioxetane in most solvents. Contrary to the earlier report,' hardly any epoxide is formed in pinacolone. Moreover a careful search uncovered no trace of t-butyl acetate.