Homolytic substitution in indolinone nitroxides. IV. Reactions with aminyl radicals. A spectroscopic and crystallographic study.

The reactions between 2,2-diphenyl-indolinone-N-oxyl (3) and a series of aminyl radicals generated in situ by oxidation of secondary aromatic amines with PbO2 led to aminated hydroxylamines (4), which in the presence of PbO2 are converted to the aminated nitroxides (5). When starting from primary amines, these are further oxidated to quinonimine-N-oxides (6) which then undergo nucleophilic substitution by another amine molecule to give the diaminated hydroxylamines (7). These are further oxidated to nitroxides (8), the final products of the reaction being the aminated quinone-imine-N-oxides (9). The paramagnetic species (5) and (8) have been characterized using ESR spectroscopy; in addition, the molecular geometry of one of the N-oxides (9) was elucidated by means of X-ray structure analysis.