Oxidative and dehydrative cyclizations of nitroacetate esters with Mn(OAc)3

Reaction of α-unsubstituted nitroacetates with Mn(OAc)3 gives mixtures of isoxazolines, formed by dehydration to a nitrile oxide that undergoes cycloaddition, and isoxazoline oxides or cyclopropane, formed by oxidative cyclization. Oxidative cyclization is favored with electron-rich alkenes and cycloaddition with the nitrile oxide to give isoxazolines is favored with electron-poor alkenes. On the other hand, α-substituted nitroacetates cannot dehydrate and undergo only radical reactions.