Trimethyl-4-phenyl-3-azahexane-3-nitroxide TIPNO

NMP [191-193] can be applied to a wide range of monomers such as styrenes, acrylates, acrylamides, acrylonitrile, and 1,3-dienes. Acyclic nitroxides such as 2,2,5-trimethyl-4-phenyl-3-azahexane-3-nitroxide (TIPNO) or Af-tert-butyl-iV-(l-diethyl phosphono-2,2-dimethylpropyl) nitroxide (DEPN) enables the reversible termination of the growing polymer chains. 

The hydroxylamine or N-hydroxy compounds can be easily oxidized to nitroxides by a large number of oxidizing agents. The most suitable for this purpose are lead, mercury, or silver oxides. Air, in combination with a catalyst or used alone, may also turn hydroxylamines into nitroxides. For example, the 2,2,5-trimethyl-4-phenyl-3-azahexane-3-oxyl (TIPNO) nitroxide (Table 2, 29) is obtained upon treatment of the corresponding hydroxylamine by a copper(II)-catalyzed oxidation at ambient temperature. When multiple-step synthesis must be carried out prior to oxidation, the hydroxylamine can be protected either by O-acetylation or O-silylation with tert-butylchlorodimethylsilane... 

Fig. 1 Structure of nitroxides frequently used for SI-NMP. TEMPO 2,2,6,6-tetramethylpi-peridinyl-l-oxy TIPNO 2,2,5-trimethyl-4-phenyl-3-azahexane-3-oxyl and SGI IV-tert-butyl-JV-[ 1 -diethylphosph(Hio-(2,2-dimetliylpropyl)] nitroxide...

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