Triacetonamine in the Chemistry of Nitroxyl Radicals

The discovery in 1961 of a novel class of organic paramagnetics,** capable of entering into diverse chemical reactions with involving no free valence, served as the basis for a rapid development of the chemistry of nitroxyl radicals.*** In recent years a tremendous number of nitroxyl radicals have been synthesized. They are representatives of different classes of organic compounds: piperidine, pyrroline, pyrrolidine, piperazine, isoindoline, carboline, azetidine, imidazoline, tetrahydropyrimidine, oxazolidine, tetrahydrooxazine, azaphosphorinane, and others. However, nitroxyl radicals of the 2,2,6,6-tetramethylpiperidine are most popular and extensively employed. This may be explained not only by historical reasons but, mainly, by the availability of the radicals of this type, many of which have become industrially produced reagents.