Yolande Rollin

The coupling of organic groups by the electrochemical reduction of organic halides: Catalysis by 2,2′-bipyridinenickel complexes

Abstract The electrochemical reduction of a dilute solution of NiX 2 bipy (bipy = 2,2′-bipyridine) in N -methylpyrrolidone gives the corresponding Ni 0 complex, which undergoes oxidative addition with an excess of an organic halide RX to form RNiX. Decomposition of RNiX gives the dimer R 2 in good yield and nickel(II). The nickel(0) species is regenerated to give an electrocatalytic process. The possible mechanism of these reactions is discussed briefly.

Catalyse par des complexs σ-aryl-nickel de l'electroreduction en biaryles des halogenures aromatiques

Abstract In mixed THF/HPMA, electrochemical reduction of NiX 2 L 2 (L = PPh 3 , X = Cl or Br) yields a zerovalent nickel complex which reacts very rapidly with ArX (X = I, Br, Cl) by oxidative addition to give ArNiXL 2 , which also is electroreducible. Thus it is possible to obtain a catalytic electroreduction of ArX which affords mainly biaryls when X = Cl. A mechanism is suggested according the various results especially with a view to explain the loss of catalytic activity. A clear indication of increasing activity is given when aliphatic bromides are added to the solutions.

DBU/DMSO promoted dehydrobromination of 1,1-dibromoolefins. A general synthesis of 1-bromoaromatic alkynes under mild conditions

Abstract A new procedure for the synthesis of 1-Bromoalkynes by DMSO/DBU induced dehydrobromination of 1,1-dibromoethylenes under mild conditions is described.

Electrosynthesis of symmetrical ketones from organic halides and carbon dioxide catalysed by 2,2'-bipyridine-nickel complexes

Abstract The electrochemical reduction of a 2,2′-bipyridine-nickel complex, in the presence of carbon dioxide in N -methylpyrrolidone or dimethylformamide as solvent gives the corresponding nickel(0) complex associated with two molecules of CO. Oxidative addition of an alkyl halide to this complex, followed by an internal CO shift and reductive elimination, leads to the formation of a symmetrical ketone in high yield along with nickel(II), whereas aryl or vinyl halides mainly give acyl derivatives. The nickel(0) species is electrochemically regenerated, thus giving rise to an efficient catalytic process. The possible mechanism of these reactions is discussed.

A zerovalent nickel-2,2′-bipyridine complex: an efficient catalyst for electrochemical homocoupling of ortho-substituted halides and their heterocoupling with meta- and para-substituted halides

Abstract Electroreduction of ortho-substituted halides ArX in a nickel-2,2′-bipyridyl system and N-methylpyrrolidone as solvent gave the homocoupling product ArAr. The nickel-2,2′-bipyridyl system is also a catalyst for the electrochemical heterocoupling of ArX with meta- or para-substituted halides Ar′X′.

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.

Catalyse chimique par le systeme nickel-2,2′-bipyridine de la reduction electrochimique d'halogenures aliphatiques

Abstract In dimethylformamide or N -methylpyrrolidone the Ni-bipyridyl system catalyses the electrochemical reduction of functionalised or non-functionalised aliphatic halides. High yields of dimeric products are obtained besides primary mono- or di-bromides. Analysis of the reaction products shows the formation of dialkylnickel which can be isolated by coulometry. This species acts as a reducing agent for aliphatic halides.

Electrocatalyse par des complexes du nickel de la synthese d'iodures aromatiques ou vinyliques a partir de derives bromes correspondants

Resume In the solvent N-methyl-2-pyrrolidone the electrochemical reduction of nickel bromide in the presence of potassium iodide, leads to Ni(O) species which are very efficient in the catalytic halogen exchange. Conversion of non-activated aromatic bromides into the corresponding iodides is achieved in good yields, specially when anisole is added to the medium.

Electrochemical activation of zinc in the coupling reaction of α-bromoesters with carbonyl compounds

Abstract The Reformatsky reaction has been examined using a mild and effective method of electrochemical zinc activation, based on the cathodic reduction of a catalytic amount of zinc bromide in acetonitrile.

Catalyse par des complexes du nickel l'electrosynthese de 1,1-diarylethane a partir d'halogenures aromatiques et d'ethylene.

Abstract In mixed THF-HMPA, the electrochemical reduction of nickel bromide leads to catalytic nickel very efficient towards the electro-reductive coupling of ethylene with arylhalides yielding 1,1 diarylethane as the main product.