A new synthesis of nitronic esters has been developed by mixing 2,6-di-t-butyl-4-nitrophenol with an acrylate ester and an alkyl phosphite. The rates of thermal decomposition of methyl, ethyl, and isopropyl 3,5-di-t-butyl-4- oxo-2,5-cyclohexadienenitronate to give 3,5-di-t-butylbenzoquinone monoxime have been measured in dimethylformamide and methylcyclohexane and activation parameters have been calculated. The rates were comparable in both solvents and consistent with a cyclic intramolecular decomposition. Saponification of the esters was found but a base-catalyzed decomposition to the oxime could not be detected even in 0.1 N sodium butoxide. Acid-catalyzed hydrolysis cleaved the methyl and isopropyl esters readily to give 2,6-di-t-butyl-4-nitrophenol.