Oxidative cyclization of aryl-substituted (Z)-N-acetyl-α-dehydroalanines having a dialkylamino group, in the presence of dioxygen

It was found that the reactions of the title compounds (1) with dioxygen in methanol proceed according to the first-order kinetics to give (Z)-2-imidazolin-5-one derivatives and hydrogen peroxide in quantitative yields. Substituent and solvent effects on the rate constant for this oxidative cyclization reaction are consistent with the rate-determining electron transfer from the dialkylamino nitrogen in the starting 1 to dioxygen.