Reactions of Diones with Oxygen

This explanation was shown to be incorrect by investigation 95) of reactions of a number of a-diketones (benzil, biacetyl, 1-phenyl-1,2-propanedione) in the presence of olefins in oxygen saturated solutions. Slow consumption of diketone was observed with relatively rapid consumption of olefin and concomitant formation of epoxides, often in high yield. Many of the olefins which underwent this reaction do not form epoxides at all with singlet oxygen. For example, tetraphenylporphin-sensitized photooxygenation of tetramethylethylene afforded hydroperoxide 111 quantitatively while a biacetyl-sensitized reaction yielded the epoxide 112. Further, it was shown that the 

The present state of mechanistic understanding of these reactions is ideal for the speculator since the encumbrance of facts is still quite limited. Any mechanistic proposal must, however, account for the lack of stereospecificity, for the survival of 

Further investigations of these intriguing reactions will undoubtedly be forthcoming. We note that those reactions of diones originating from singlet states proceed (cf. Sections IV, V, VI) equally well in the presence or absence of oxygen. 

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