Criegee mechanism for ozonolysis

The Criegee mechanism for ozonolysis a dramatic sequence with successively a 1,3-dipolar cycloaddition, a 1,3-dipolar cycloreversion and another 1,3-dipolar cycloaddition, all taking place below room temperature. 

The formation of metallocyclic complexes by addition of ketones to dioxygen complexes resembles a three-step Criegee mechanism for ozonolysis. " " In each case one envisages the formation of a dipolar 0-0 bond that leads to electrocyclic ring closure with the ketone. No proven oxidation of aldehydes or ketones has yet been achieved with these metal-locycles. Nevertheless, in the catalytic conversion of cyclic ketones to lactones using hydrogen peroxide and a molybdenum complex as catalyst, it is believed that such an intermediate metallocycle is first formed and that it subsequently converts to lactone and molybdenyl products (16). " ... 

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