Phosphorylformonitrile oxides as spin traps for carbon-centered free radicals: co-formation with radicals in the generation of nitrile oxides from C-phosphorylformohydroximoyl halides in the presence of alcohols or ethers

One-electron oxidation of the oximes R₂P(=O)C(=NOH)X (X = Cl or Br) generates the nitrile oxides R₂P(=O)C⁺=NO⁻, which serve as spin traps for unstable carbon-centered radicals.The latter are generated upon addition of PbO₂ to a mixture of formohydroximoyl halide with an alcohol or an ether of the general formula R¹OCHR²R³ under the action of atomic chlorine (bromine) released during the generation of nitrile oxide. This gives rise to new, more persistent C phosphoryliminoxyls R₂P(=O)C(=NO^·)C(OR¹)R²R³ (R¹, R², R³ = H, Alk). When primary alcohols (R¹ = R² = H) are used, acyl radicals generated at the initial step of the reaction are also trapped by nitrile oxides to give C-acyl-C phosphoryl iminoxyl radicals R₂P(O)C(=NO^·)C(=O)R³. Hyperfine coupling constants for more than 20 C-phosphoryl-iminoxyls existing in solutions as mixtures of Z- and E-isomers were determined.The effect of the structure of the primary radical (length of the carbon chain, degree of branching, the presence of a ring, and its size) on the radiospectroscopic characteristics of new C-phosphoryliminoxyl radicals was studied.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 336–341, February, 2005.