Bulky-yet-flexible carbene ligands and their use in palladium cross-coupling

In recent years, several classes of new N-heterocyclic carbene (NHC) ligands were developed around the concept of flexible steric bulk. The steric hindrance of these ligands brings stability to the active species, while ligand flexibility still allows for the approach of the substrate. In this review, the synthesis of several types of new classes, such as IBiox, cyclic alkyl amino carbenes (CAAC), ITent, and IPr* are discussed, as well as how they move the state-of-the-art in palladium catalyzed cross-coupling forward

Gold-NHC complexes in catalysis

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Conducting olefin metathesis reactions in air : breaking the paradigm

The authors gratefully acknowledge the Royal Society (University Research Fellowship to CSJC) and the EC (CP-FP 211468-2 EUMET) for funding.The first study of low catalyst loading olefin metathesis reactions in air is reported. TON values of up to 7000 were obtained using non-degassed solvents with commercially available pre-catalysts Caz-1, Hov-II and Ind-II. The simple experimental conditions allow olefin metathesis reactions to be carried out on the benchtop using technical grade solvents in air.PostprintPeer reviewe

Chalcogenourea derivatives of N-heterocyclic carbenes

Over the last few years, selenourea derivatives have attracted significant attention from the organic and inorganic scientific communities (1), (2), (3). This is mainly due to their ease of access and their coordination bond stability with transition metals such as copper, gold and silver, making them highly useful in many different applications (4), (5). A series of seleno-, thio- and tello-ureas derived from a wide range of N-heterocyclic carbenes (NHCs) were synthesized, their coordination to various metals and the possible oxidation addition to halogens were investigated. All the complexes were characterized by 1H, 13C and 77Se NMR spectroscopy and several examples were characterized and studied by X-ray crystallography showing that the geometry of a complex is highly affected by the electronic properties and the π-accepting ability of the ligands

Palladate precatalysts for the formation of C-N and C-C bonds

A series of imidazolium-based palladate precatalysts has been synthesized and the catalytic activity of these air- and moisture-stable complexes evaluated as a function of the nature of the imidazolium counterion. These precatalysts can be converted under catalytic conditions to Pd-NHC species capable of enabling the Buchwald-Hartwig aryl amination and the alpha-arylation of ketones. Both reactions can be carried out efficiently under very mild operating conditions. The effectiveness of the protocol was tested on functionality-laden substrates

Cu–NHC azide complex : synthesis and reactivity

The first example of a NHC-based copper azide complex is reported. Its reactivity was investigated with various reagents affording 8 new complexes