TEMPO in Chemical Transformations: From Homogeneous to Heterogeneous

The organic nitroxyl radical, TEMPO (2,2,6,6-tetramethylpiperidine-N-oxyl), finds a variety of industrial applications for chemical transformations. Because of economic and environmental concerns, the recovery and reuse of TEMPO with maintained high activity are of the utmost importance. In this Review, we summarize the most important advances made by the scientific community in TEMPO immobilization on various organic and inorganic support materials for recovery and reuse, and we discuss the activity and stability, as well as the procedures. Also summarized is the wide range of applications of TEMPO in both homogeneous and heterogeneous forms in chemical transformations, beginning from methodology tuning in synthetic chemistry to the use in polymer chemistry.