This Concept article discusses the potential of oxidative carbene catalysis in synthesis and comprehensively covers pioneering studies as well as recent developments. Oxidative carbene catalysis can be conducted by using inorganic and organic oxidants. Applications in cascade processes, in enantioselective catalysis, and also in natural product synthesis are discussed.

The first catalytic asymmetric bromonium ion-induced polyene cyclization has been achieved by using a chiral BINOL-derived thiophosphoramide catalyst and 1,3-dibromo-5,5-dimethylhydantoin as an electrophilic bromine source. Bromocyclization products are obtained in high yields, with good enantiomeric ratios and high diastereoselectivity, and are abundantly found as scaffolds in natural products.

This edge article reports the synthesis and full characterization including X-ray analysis of three different acylazolium ions. The reactivity of these acylazolium ions as acylating reagents of amines and alcohols is discussed. Whereas benzylamine slowly reacts with the acylazolium ions, benzyl alcohol acylation does not occur. However, upon activation of the alcohol with an N-heterocyclic carbene (NHC) as catalyst, efficient esterification is achieved. Importantly, benzylester formation is obtained in the presence of benzylamine upon selective alcohol activation by the NHC. High level DFT calculations reveal that alcohol activation occurs by strong H-bond formation between the NHC and the alcohol thereby increasing the nucleophilicity of the alcohol. For oxidatively generated acylazolium ions under NHC catalysis, the carbene has a dual role (cooperative catalysis): (a) the NHC is used for generation of the acylazolium ion and (b) the NHC is used for activation of the alcohol in the subsequent acylation step. NHC-catalyzed selective acylation of benzyl alcohol in the presence of benzylamine can also be achieved with trifluoroethyl and hexafluoroisopropylesters as acylation reagents. Moreover, an enol acetate also shows high O-selectivity as a chemoselective acetylation reagent. Kinetic and mechanistic studies are provided and some examples of the chemoselective acylation of amino alcohols are presented.reaction kinetics, theoretical methods and NMR spectra. CCDC 919089 and 919090. For ESI and crystallographic data in CIF or other electronic format see

Nickel‐catalyzed electrochemical C−H aminations were accomplished by chemo‐ and position‐selective C−H activation with ample scope. Detailed mechanistic studies highlighted a facile C−H cleavage with unique chemo‐selectivity, while cyclovoltammetric analysis provided support for a nickel(II/III/IV) manifold.

Electrophilic halogenation is used to produce a wide variety of halogenated compounds. Previously reported methods have been developed mainly using a reagent-based approach. Unfortunately, a suitable "catalytic" process for halogen transfer reactions has yet to be achieved. In this study, arylamines have been found to generate an N-halo arylamine intermediate, which acts as a highly reactive but selective catalytic electrophilic halogen source. A wide variety of heteroaromatic and aromatic compounds are halogenated using commercially available N-halosuccinimides, for example, NCS, NBS, and NIS, with good to excellent yields and with very high selectivity. In the case of unactivated double bonds, allylic chlorides are obtained under chlorination conditions, whereas bromocyclization occurs for polyolefin. The reactivity of the catalyst can be tuned by varying the electronic properties of the arene moiety of catalyst.