Nitroxide chemistry. Part XII. Free radical formation in the reactions between trifluoronitrosomethane and some 1,3-diketones

Abstract

The 1,3-diketones RCO·CH₂·COR′(R = R′= CH₃ or CF₃, and R = CH₃, R′= CF₃) react with trifluoronitrosomethane to generate the nitroxide radicals CF₃·N(Ȯ)·CH(COR′)·COR and their tautomers CF₃N(Ȯ)·C(COR′):C(OH)R together with the iminoxy-radicals (RCO)(R′CO)C:N·O, all detected by e.s.r. spectroscopy. Diethyl 2-methyl-3-oxosuccinate affords only the radical CF₃·N(Ȯ)·CMe(CO₂Et)CO·CO₂Et under similar conditions. Intermediate hydroxylamine anions CF₃·N(Ō)·CH(COR)·COR′, are proposed as intermediates which can undergo further reaction by two different pathways to give the observed radicals. The e.s.r. parameters of the various nitroxide radicals are given, and these are interpreted in terms of a deviation from planarity at the nitrogen atom.