Abstract The direct electrochemical carboxylation of aryl, benzyl and alkyl halides by CO2 is described using a magnesium anode and a nickel foam cathode in an undivided cell. The process employs a sacrificial anode and does not require the additional use of a transition metal catalyst or demanding conditions, as the reactions are carried out under galvanostatic mode, at −10 °C and with commercial DMF. Under these operationally simple conditions, an important range of carboxylic acids are affordable. Mechanistic investigation account for the in situ generation of a carbanionic species that is not a simple organomagnesium halide.

The electrocarboxylation of α,α-dichloroarylmethane derivatives in the presence of CO2 was achieved, providing several α-chloroarylacetic acid derivatives with modest yields but high selectivity (chlorinated vs. non-chlorinated or dicarboxylic acid products). The obtained products were then involved in several chemical transformations, underlining their potential as versatile intermediates in synthetic chemistry. A mechanism was also proposed based upon a control experiment and cyclic voltammetry (CV) study.

Arylamines represent a class of compounds widely found in natural products and pharmaceuticals. Among methodologies devoted to their synthesis, nickel-catalyzed amination of aryl halides constitutes one of the most employed conventional strategies. However, C-N cross-couplings often involve elaborated nickel complexes, which are expensive and/or air and moisture sensitive. To circumvent this issue, we herein report an electrochemical method based on a sacrificial anode process to in situ generate a catalytic amount of nickel salts allowing amination of aryl halides. The approach, simple to set up, proceeds under mild reaction conditions and enables access to a large panel of arylamines.

Electrochemical C(sp2)−N couplings mediated by nickel salts generated from the sacrificial anode has been described for the first time. In this approach, the sacrificial nickel anode is employed as the sole source of nickel and the process, operationally simple to set up, enables the preparation of functionalized arylamine derivatives with moderate to good yields, under mild reaction conditions and without additional ligand. A cooperative process between the two electrodes is involved in the proposed mechanism.

A mild and useful nickel-catalyzed electrochemical phosphonylation of aryl and vinyl bromides is described. We show that alkyl H-phenylphosphinates can be coupled electrochemically with functionalized aryl and vinyl bromides using very simple conditions (Fe/Ni anode, bench-stable nickel pre-catalyst, undivided cell, galvanostatic electrolysis) to furnish the corresponding aryl and vinyl phosphinates in satisfactory to good yields. Couplings can also be applied to heteroaromatic bromides with some limitations like increased propensity to hydro-dehalogenation.

The electroreduction of SF6 is shown at ambient temperature in acetonitrile using an array of platinum microelectrodes to improve the electrical detection. Its half reduction potential occurs at −2.17 V vs Fc+/Fc. The exact number of electrons for the full consumption of sulfur hexafluoride was determined and this gas further quantitatively transformed into environmentally benign fluoride anion and sulfur by electrochemical reduction.

Mild experimental conditions for a direct phosphonylation of an easily cleavable N-carbamate-tetrahydroisoquinoline have been described under constant current electrolysis. The developed electrochemical process allowed to prepare α-aminophosphonates in moderate to good yields. On the basis of the experimental results, a mechanism proceeding through a convergent paired electrochemical process was enabled to be postulated.

The reductive Barbier coupling of aromatic halides and electrophiles has been achieved using a CoBr2 /1,10-phenanthroline catalytic system and over stoichiometric amounts of zinc. The reaction displayed a broad scope of substrates, including (hetero)aryl chlorides as pro-nucleophiles and aldehydes or imines as electrophiles, leading to diarylmethanols and diarylmethylamines in moderate to excellent yields, respectively.

Phenylzinc bromide enables a pseudo three-component reaction of methyl glutaconate and aromatic aldehydes. Unsaturated trisubstituted 8-valerolactones (dihydropyranones) are obtained in fair to good yields by an aldol/aldol/elimination/lactonization domino process that allows the formation of four new bonds in a single step. A putative reaction mechanism is proposed. (C) 2018 Academie des sciences. Published by Elsevier Masson SAS. This is an open access article under the CC BY-NC-ND license.

The use of a CoBr2/1,10-phenanthroline catalytic system together with Zn as the reductant was developed to prepare diversely substituted indanamines by a Co(I)-catalyzed [3 + 2] annulation of o-haloaryl imines with electron-deficient alkenes in good yields. The use of Mn as the reductant allowed the elaboration of a three-component version of this reaction. These conditions were also found to be suitable for the activation of various halides and were extended to the preparation of the indenamine and strigolactam scaffolds.

Various 3-amino-, 3-aryloxy- and alkoxy-6-arylpyridazines have been synthesized by an electrochemical reductive cross-coupling between 3-amino-, 3-aryloxy- or 3-alkoxy-6-chloropyridazines and aryl or heteroaryl halides. In vitro antiproliferative activity of these products was evaluated against a representative panel of cancer cell lines (HuH7, CaCo-2, MDA-MB-231, HCT116, PC3, NCI-H727, HaCaT) and oncogenicity prevention of the more efficient derivatives was highlighted on human breast cancer cell line MDA-MB 468-Luc prior establishing their interaction with p44/42 and Akt-dependent signaling pathways.

A cobalt-zinc-diimine multicatalytic system for the syn-diastereoselective multicomponent assembly of aromatic bromides, acrylates and aromatic aldehydes under reductive conditions is described. In the presence of catalytic CoBr(2)phen and the ZnBr2N,N '-diphenyl cyclohexyldiimine complex, beta-hydroxyesters are obtained with a significant up to 8:1 syn diastereoselectivity whereas reactions conducted without L2-1 show negligible stereoselectivity. This preliminary study should open the way to further improvements including enantioselective catalysis of the reaction.

The electrochemically-assisted synthesis of (hetero)arylphosphonates from (hetero)aryl halides and dimethyl phosphite is described. Very mild and simple conditions are employed as the cross-coupling is carried out in galvanostatic mode, in an undivided cell at room temperature, using NiBr2bpy as the easily available pre-catalyst and acetonitrile as the solvent. In addition, both aryl bromides and iodides can be used as well, providing the corresponding (hetero)arylphosphonates in generally good yields. A mechanism involving the in situ generation of a Ni ate complex is proposed.

1,2-Disubstituted indolines have been prepared in fair to good yields by a Zn-mediated organometallic Mannich reaction, followed by an intramolecular Pd-catalyzed aromatic amination. The reactions are easy to set up and compatible with a large variety of simple or commercially available reagents. The method was further extended to the preparation of a 1,2,3-trisubstituted indoline.

The first examples of cobalt-catalyzed multicomponent couplings of mixed aromatic arylzinc reagents with Michael acceptors and carbonyl compounds or imines is described. The reaction system employs a cobalt(II)-2,2′-bipyridine or a cobalt(II)-1,10-phenanthroline complex as a catalyst for both organozinc generation and subsequent multicomponent assembly by formal Michael addition/aldol coupling or Mannich reaction. This study brings new insights into the synthetic scope and mechanism of the reaction.

Due to their widespread presence in functional materials and pharmaceuticals, biaryls are of fundamental importance in organic chemistry. Methods for the synthesis of symmetrical biaryls generally involve both metallic reduction and transition-metal catalysis. In this work, we show that electroreduction can also constitute a very relevant way to achieve the nickel-catalyzed reductive synthesis of symmetrical biaryl compounds. Therefore, it is demonstrated that both aryl and heteroaryl halides undergo reductive coupling to furnish the corresponding symmetrical biaryls in fair to excellent yields. Reactions are performed under very mild conditions thus ensuring important functional group tolerance.

The rarely described 4‐(hetero)aryl‐6‐pyrrolylpyrimidines are prepared by electroreductive nickel‐catalysed cross‐coupling reactions between aryl halides and chloropyrimidines. Inherent predictable issues of such metal‐catalysed reactions that involve or produce highly nitrogenated compounds – like catalyst poisoning – are tackled by the process described in this paper. The relevance of the strategy is validated by a thorough comparison of the results obtained under electrochemical conditions with those obtained under classical Suzuki–Miyaura conditions.

The cobalt-catalyzed multicomponent reaction between sp2 -hybridized organic halides, Michael acceptors, and unsaturated electrophiles has been developed. The reaction proceeds through a formal conjugate addition/aldol or aza-aldol (Mannich) tandem reaction initiated by the in situ metalation of the organic halide by cobalt catalysis. The essentially new reaction conditions that have been developed are very mild and atom-economic. Under these conditions, a broad range of β-hydroxy- and β-aminocarbonyl compounds are obtained in good to high yields.

A new electrochemical synthetic method for the transition metal-catalyzed homocoupling of 2-halopyridinic compounds into symmetrical 2,2'-bipyridines is described. Experiments were carried out in a cavity cell under various reaction conditions, using a nickel complex as catalyst, and controlled-potential or constant-current electrolyses. A graphite powder/carbon nanotube 9:1 ratio mixture proved to constitute the optimal cathode material. Excellent homocoupling product yields were observed using aqueous KCl solution as anolyte. The cathode material proved to be recyclable with possible reuse three times without notable loss of activity. (C) 2015 Elsevier Ltd. All rights reserved.

Benzyl chloride reduction was studied in a powder macroelectrode (PME) made of silver, graphite or silver/graphite mixtures (1: 3, 1: 1 and 3: 1) in absence of solvent, or using a very low amount of DMF as solvent (PhCH2Cl/DMF 3: 1). A 0.1 mol L-1 KCl aqueous solution was used as anolyte. A competitive hydrogenation and dimerization process was observed, affording the respective toluene and bibenzyl products. The well-known electrocatalytic effect of silver on reduction of the C-Cl bond was confirmed by a significant positive shift of the benzyl chloride reduction potential in comparison with pure graphite powder. The products distribution was analysed after linear sweep voltammetries at low scan rate (0.1 mV s(-1)), indicating high yields of bibenzyl produced on Ag/graphite-PME. Pure graphite-PME was not selective towards dimer formation. The best results for bibenzyl production occurred at more positive potentials, in the presence of silver. A small amount of solvent (DMF) play an important role on the electrode surface desorption and diffusion of intermediary species. (c) 2015 Elsevier Ltd. All rights reserved.