Nitrogen inversion and N–O bond rotation in some hydroxylamine and isoxazolidine derivatives

Abstract

A series of trisubstituted hydroxylamine derivatives, both cyclic and acyclic, has been prepared. The energy barriers in these hydroxylamines are found to be dominated either by nitrogen inversion or N–O bond rotation depending on the nature of the substituents attached to the nitrogen. In several series of compounds, having XC₆H₄CH₂ substituents attached to nitrogen, Hammett free energy correlations are obtained with positive ρ values, indicating increased electron density at the transition state for the inversion process. Isoxazolidines with C(5) ethoxy substituents demonstrate a strong anomeric effect.