It has been reported that a hindered amine, 2, 2, 6, 6-tetramethyl-4—oxopiperidine (I), was easily oxidized with 30% aqueous hydrogen peroxide in the presence of EDTA and sodium tungstate to give a free radical, 2, 2, 6, 6—tetramethyl-4-oxopiperidine-l-0xyl (II), which was extremely stable in air at room temperature?) However, cyclohexane—l-spiro-2'-(4'- oxoimidazolidine)-5'-spiro-1"-cyclohexane (III) 3) did not give the corresponding N—oxyl ...
