1, 4-Dimethylnaphthalene endoperoxide

The benzo-derivative 16 is accessible through 1,4-dimethylnaphthalene, which on singlet oxygenation leads to the thermally labile naphthalene-1,4-endoperoxide. This endoperoxide expels singlet oxygen at ca. 10 °C, but diimide reduction below 0 °C in MeOH affords the stable dihydro derivative 16 (Eq. 11). 

The DCA-sensitized photooxygenation of 1,4-dimethylnaphthalene, 93, in acetonitrile, afforded a mixture of endoperoxide 94, (65%) and aldehyde 95, (25%), whereas in nonpolar solvents, as well as in the dye-sensitized (MB, RB) photooxygenations of the same substrate, 94 was the only reaction product [211, 212] (Scheme 16). 

Photo-oxidation.—Turro and co-workers report the rate constants for quenching of singlet molecular oxygen ( O2) by several strained molecules. The authors also discuss a non-photochemical method for determination of quenching constants of singlet oxygen involving thermolysis of l,4-dimethylnaphthalene-l,4-endoperoxide. 

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