Studies of Tetriary Amine Oxides. 9. Thermal Rearrangement of 1-(4-Substituted-phenyl)piperidine N-Oxides to the Corresponding N-Hydroxylamines

Article abstract of DOI:10.1021/jo00385a012

(4-Substituted - phenyl)piperidine N-oxides undergo a thermal rearrangement to O-arylhydroxylamines.Electron withdrawing substituents are essential for the rearrangement and must be ortho or para relative to the <*>N-O function.The reaction has been found to be first order in substrate when rates were measured in dioxane, and the activation parameters were calculated.The order of reactivity in this rearrangement is NO2 >> CN > COPh > COMe > COOEt > CONH2.The rates correlate very well with ?^- constants and the ρ value was positive and large (+3.6) pointing to a highly po lar activated complex with an electron-rich reaction center.All results strongly support an intramolecular cyclic mechanism.