title: Transition-metal-free oxidative coupling reactions for the formation of C-C and C-N bonds mediated by TEMPO and its derivatives.
abstract: The application of nitroxides for the development of new synthetic methods and their implementation in polymer chemistry, material science and beyond is one of the major research topics in our laboratory in the institute of organic chemistry at the WWU Münster. This short review  focuses on our recent progress towards nitroxide-based transition-metal-free oxidative coupling reactions. The demand for organic surrogates for transition metals in such transformations is in our eyes unquestionable, since environmental and economic issues have become progressively more important  in recent years. For this purpose, the 2,2,6,6-tetramethylpiperidine-N-oxyl radical (TEMPO) is shown to be a highly efficient oxidant for the homo- and cross-coupling of Grignard reagents. This powerful C-C bond forming strategy allows the generation of conjugated polymers  from bifunctional Grignard reagents. Moreover, cross-coupling of alkynyl Grignard compounds and nitrones can be accomplished under aerobic atmosphere with catalytic amounts of TEMPO. It is also shown that TEMPO-derived N-oxoammonium salts can act as suitable oxidants for  formation of C-N bonds between non-preactivated benzoxazoles and secondary amines under metal-free conditions.
authors.affiliation: Organisch-Chemisches Institut, Westfälische Wilhelms-Universität Münster, Corrensstraße 40, D-48149 Münster, Germany.
authors.forename: Sandip
authors.initials: S
authors.lastname: Murarka
authors.forename: Sebastian
authors.initials: S
authors.lastname: Wertz
authors.forename: Armido
authors.initials: A
authors.lastname: Studer
mesh_terms: D003497:Cyclic N-Oxides / Q000737:chemistry*; D005609:Free Radicals / Q000737:chemistry; D006841:Hydrocarbons, Aromatic / Q000138:chemical synthesis* / Q000737:chemistry; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry; D010084:Oxidation-Reduction
chemical_list: D003497:Cyclic N-Oxides; D005609:Free Radicals; D006841:Hydrocarbons, Aromatic; D009942:Organometallic Compounds; C003959:TEMPO