Jean Yves Nédélec

Electrosynthesis of functionalized 2-arylpyridines from functionalized aryl and pyridine halides catalyzed by nickel bromide 2,2′-bipyridine complex

Abstract 2-Arylpyridines substituted on aryl and/or on pyridine nuclei can be obtained in good to high yields in one step by electroreduction of mixtures of the corresponding aryl and pyridyl halides using the sacrificial iron anode process and a nickel 2,2′-bipyridine complex catalyst in DMF as solvent.

Electrochemical cross-coupling between functionalized aryl halides and 2-chloropyrimidine or 2-chloropyrazine catalyzed by nickel 2,2′-bipyridine complex

Abstract 2-Arylpyrimidines and 2-arylpyrazines have been obtained in good to high yields from 2-chloropyrimidine and 2-chloropyrazine and various functionalized aryl halides by electroreduction using an iron rod as the anode and a catalytic amount of nickel–bipyridine complex in a mixture of DMF and pyridine as solvent.

Electrosynthesis of 3-thienylzinc bromide from 3-bromothiophene via a nickel catalysis

Abstract 3-Thienylzinc bromide is prepared under mild conditions by electroreduction of a DMF solution of 3-bromothiophene, zinc bromide, and a catalytic amount of nickel-bipyridine complex, using a magnesium rod as sacrificial anode. The resulting organometallic is then coupled with aryl halides using a palladium catalysis.

Nickel-catalyzed electrochemical homocoupling of alkenyl halides: rates and mechanisms

Abstract We describe the electroanalytical determination of the successive electron transfer/chemical steps involved in the nickel-catalyzed electrosynthesis of conjugated dienes from alkenyl halides in DMF. Two catalytic sequences are proposed, depending on the potential applied. The first mechanism is shown to proceed through oxidative addition of the vinyl halide to electrogenerated Ni 0 and vinyl-Ni 1 species. The diene is obtained by reductive elimination from a Ni 111 species. An alternative coupling mechanism is proposed which involves both oxidative addition of RX on Ni 0 and electron transfer from Ni 0 to RNiX. The influence of various parameters on the rates are discussed, such as the nature of both the halide and the stereoisomer used, as well as the coordination environment of the nickel complex.

Electrochemical synthesis of ketones from acid chlorides and alkyl and aryl halides catalysed by nickel complexes

Abstract The nickel-catalysed electrochemical cross-coupling of acid chlorides and alkyl or aryl halides in acetonitrile affords unsymmetric ketones in good to high yields. The reaction can be performed under very simple and mild conditions in a diaphragmless cell. A zinc rod as the sacrificial anode has been found to be the most efficient.

Electrochemical synthesis of trifluoromethylcadmium and trifluoromethylzinc species using bromotrifluoromethane and sacrificial anodes

Abstract Trifluoromethylcadmium and trifluoromethylzinc species are easily prepared by electrolysis of bromotrifluoromethane in dimethylformamide using a one-compartment cell fitted with a cadmium or zinc anode. Both CF 3 CdBr and (CF 3 ) 2 Cd result from the chemical reaction of CF 3 Br with cadmium electrodeposited on the cathode. The formation of trifluoromethylzinc species involves a much more complex mechanism. Chemical corrosion of the electroscored zinc anode occurs; if the zinc anode is afterwards used as the cathode, the formation of CF 3 ZnBr and (CF 3 ) 2 Zn increases significantly.

New and efficient access to 3-substituted 2,5-dibromothiophenes. Consecutive nickel-catalyzed electrochemical conversion to thienylzinc species

We have achieved the stepwise synthesis of 3-substituted thienylzinc reagents using both electrochemical methods and an original bromination procedure. For several compounds 3-bromothiophene was the starting substrate, which was functionalized according to recently developed electrochemical procedures. The nickel-catalyzed electrochemical reduction of the resulting 3-substituted 2,5-dibromothiophenes in the presence of zinc salts allowed the formation of monothienylzinc species in good yields. The selectivity of this reaction is discussed within the context of the electrochemical synthesis of regioregular polythiophenes.

Electrochemical synthesis of tertiary phosphine from organic halides and chlorophosphines

Abstract The electrochemical synthesis of a wide range of tertiary mono- and diphosphines has been achieved in very simple and mild conditions, in an undivided electrolytic cell with a sacrificial anode of magnesium.

Analysis of the surface layer on a petroleum coke electrode in tetraglyme solutions of lithium salts

Abstract The surface layer on a petroleum coke in tetraglyme solutions of LiAsF 6 or LiCF 3 SO 3 was analysed with X-ray Photoelectron Spectroscopy, Scanning Electron Microscopy, Gas Chromatography and fluoride selective electrode. Results indicate that solvent reduction is a minor process and salt reduction a major one. Results are consistent with the reduction mechanism of LiAsF 6 proposed in the literature. But with LiCF 3 SO 3 , we suggest that reduction proceeds via the cleavage of a CF bond instead of a CS bond.

Effect of magnesium and lithium salts on the electroreduction of benzophenone in N, N-dimethylformamide as solvent

Abstract We have studied the effect of magnesium and lithium salts on the electroreduction of benzophenone in DMF as solvent. Cyclic voltammetric studies and analysis of the products allow us to propose a mechanism. It appears that the dianion of benzophenone, obtained transiently by disproportionation of the ion pairs of the radical anion and the metallic cations, reacts with DMF to lead to a stable intermediate in the presence of a magnesium salt; work up of the solution gives the α-hydroxyaldehyde Ph2COHCHO. In the presence of lithium salts, the same but less stable intermediate leads to stilbene diolate by a rapid phenyl migration. Oxygen, which is very reactive towards all the species, should be avoided for these reactions to occur.