TEMPO (2,2,6,6-Tetramethylpiperidinyloxy or 2,2,6,6-Tetramethylpiperidine 1-oxyl) and its derivatives are stable nitroxy radicals used as catalysts in organic oxidation reactions. TEMPO was discovered by Lebedev and Kazarnovskii in 1960. The stable free radical nature of TEMPO is due to the presence of bulky substituent groups, which hinder the reaction of the free radical with other molecules.1
TEMPO and its derivatives are used mainly for the oxidation of primary and secondary alcohols. TEMPO has excellent solubility properties in both organic solvents and aqueous media,1 and is used with various reoxidants, such as hypochlorite (for oxidations in aqueous media) and Cu/O2 (for oxidations in organic media).2 In aqueous media, TEMPO is oxidized by the stoichiometric oxidant (sodium hypochlorite) to generate a nitrosonium cation, which is the actual oxidant of the alcohol. During the oxidation of the alcohol, the cation is reduced to a hydroxylamine. The hydroxylamine is then reoxidized back to a nitrosonium ion by a suitable oxidant, completing the catalytic cycle. Hypochlorite is employed as primary oxidant along with bromide as co-catalyst.2
Figure 2.Mechanism of the TEMPO mediated oxidation of alcohols2
TEMPO (2,2,6,6-tetramethylpiperidine 1-oxyl radical) and its derivatives are also catalysts for other oxidation reactions. They are economical substitutes for heavy metal reagents as highly selective oxidation catalysts. They catalyze synthetic reactions involved in the formation of C-C, C-O, C=O, C-N, and C=N bonds.3
TEMPO-mediated oxidation reaction has found applications in the following areas:
Figure 3.Carbonyl Compounds
Figure 4.Nitroxide derivatives-and macroradical
Research. Development. Production.
We are a leading supplier to the global Life Science industry with solutions and services for research, biotechnology development and production, and pharmaceutical drug therapy development and production.