2,2,6,6‐Tetramethylpiperidinyloxyl (TEMPO) Radical Mediated Electro‐Oxidation Reactions: A Review

Abstract

Over the last few decades, the interest in green and sustainable chemistry has led to the development of different synthetic methodologies which utilize clean reagents. In that direction, the electro-oxidation reactions are considered as one of the most interesting and promising methods. This is predominantly due to their environmentally benign nature, as oxidation can be achieved without the need for commonly used oxidizing agents. 2,2,6,6-Tetramethylpiperidinyloxyl radical commonly known as TEMPO is a stable aminoxyl radical utilized for the oxidation of various classes of alcohols to carbonyl compounds by using cyclic voltammetry. The present review focuses on the various electrochemical reactions utilizing TEMPO as a mediator such as the oxidative conversion of alcohols, carbohydrates, amines, sulphur-containing compounds, and alkenes in both laboratory as well as industrial scales and covers literature from 1950 till present date. The properties, reactivity, and yield percentages of these reactions would provide a basis for better electrocatalyst design in future studies involving TEMPO and its derivatives as mediators.

Composites Containing Nanohydroxyapatites and a Stable TEMPO Radical: Preparation and Characterization Using Spectrophotometry, EPR and 1H MAS NMR

“…Since both TEMPO and hydroxyapatites can be used as catalysts, it is possible that the combined material will also have this application. Nitroxide radicals and compounds modified by them are mainly used in oxidation reactions [ 68 , 69 ], while hydroxyapatites can be employed in numerous processes, e.g., racemization, biogasoline synthesis and reactions requiring transition metal catalysts [ 70 ]. The issue of whether the HA/TEMPO composites will have additional benefits as catalysts requires further investigation.…”

t‐BuONa‐Mediated Redox Condensation between o‐Nitroanilines and Benzyl Alcohols towards 2‐Phenyl Benzimidazoles under Transition‐Metal‐Free Conditions

“…Meanwhile, performing the reaction added a stable radical (2,2,6,6‐tetramethylpiperidin‐1‐yl)oxyl (TEMPO) led to a quantitative yield of 3 aa (Scheme 6a). TEMPO and its derivatives were used as catalysts for oxidation processes [34–37] . It was therefore proposed that TEMPO could somehow facilitate the redox condensation towards 2‐phenyl benzimidazole.…”

“…TEMPO and its derivatives were used as catalysts for oxidation processes. [34][35][36][37] It was therefore proposed that TEMPO could somehow facilitate the redox condensation towards 2-phenyl benzimidazole. The standard experiment after 2 h showed traces of 4-methyl-o-phenylenediamine and benzaldehyde, implying the successful hydrogen transfer process between the starting materials under basic conditions (Scheme 6b).…”

Recent Advances in Electrochemical Synthesis of Nitriles: A Sustainable Approach

“…In recent years N-Oxoammonium salts have found wide applications in organic synthesis as a catalyst. [96][97][98][99] Aerobic oxidation of aldehydes to nitriles with transition metal/TEMPO catalyst, [26] transition metal-free aerobic oxidation by TEMPO and its derivatives [70,100] electrochemical synthesis of nitriles from aldehydes by TEMPO with HMDS, [101] synthesis of nitriles by using 4-AcNH-TEMPO and ammonium acetate as nitrogen source [102] are a few of the reported routes.…”