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The ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate [BMIm][BF(4)] has demonstrated high efficiency when applied as a solvent in the oxidative nitro-Mannich carbon--carbon bond formation. The copper-catalyzed cross-dehydrogenative coupling (CDC) between N-phenyltetrahydroisoquinoline and nitromethane in [BMIm][BF(4)] occurred with high yield under the described reaction conditions. Both the ionic liquid and copper catalyst were recycled nine times with almost no lost of activity. The electrochemical behavior of the tertiary amine substrate and beta-nitroamine product was investigated employing [BMIm][BF(4)] as electrolyte solvent. The potentiostatic electrolysis in ionic liquid afforded the desired product with a high yield. This result and the cyclic voltammetric investigation provide a better understanding of the reaction mechanism, which involves radical and iminium cation intermediates.

The electrochemical behavior of the substituted nitrocyclopropanes 3 (n = 1) as well as of the nitrophenylcyclopropanes 7 (n = 1) have been studied at a Pt electrode by cyclic voltammetry, microcoulometry, and preparative electrolysis in DMF-(n-Bu)4PF6. Electroreduction of 8 consumes one electron to give radical anion 8•−, which undergoes a homolytic C-N bond cleavage leading to the formation of the corresponding cyclopropyl radical and the nitrite ion. Electroreduction of 11 consumes 2 electrons. The radical anion 11•− is formed first followed by C-C bond cleavage (homolytic and/or heterolytic) of the cyclopropane ring leading to a distonic radical anion 5•−. The latter is reduced to the corresponding distonic dianion, which is protonated in the aqueous work up.

Redox potential has applications in the food industry, especially to assess the microbiological and organoleptic qualities of milk. Therefore, electroreduction has also been put forward as a means of inhibiting and/or reducing oxidation phenomena in milk by modifying its redox potential. However, these investigations failed to isolate the components contributing to the value of redox potential of milk. In this study, a series of electrolysis treatments were carried out to determine how the different major components of milk as well as thermal treatment influence the redox potential during and after electroreduction. It was found that the fat and protein content of the milk products, together with the heat treatments applied, have a considerable effect on the redox potential of these milk products after electroreduction. Furthermore, this change in redox potential is only temporary, since the redox potential levels of electroreduced milk products return to positive values after only 4 days of storage. Industrial relevance The redox potential of milk, widely studied in the past, gives some indications of the oxidative quality and stability of milk. This paper presents an innovative and clean method to control the redox potential of milk products with the use of electrochemistry. The results presented demonstrated the efficiency of electroreduction to reduce the redox potential and dissolved oxygen concentration of four milk products.

A dairy beverage (pH 6.7) containing 3.5% milk protein was supplemented with linseed oil, β-carotene and iron (as FeSO4) before being pasteurized or sterilized. Electroreduction was applied prior to heat treatment and compared to vacuum degassing for prevention of oxidative degradation. Electroreduction decreased dissolved oxygen concentration (Δ = 5.5 ppm) and redox potential (Δ = 519 mV), resulting in a decreased non-enzymatic browning reactions during storage of the pasteurized beverages and reduced lipid oxidation after sterilization. Heat treatments also reduced the redox potential, sterilization being more effective than pasteurization. However, the redox potential after electroreduction did not remain constant as it increased during storage, likely reflecting the low poising capacity of the beverages. Protection against photo-oxidative degradation of unsaturated fatty acids and β-carotene was more effective in sterilized beverages than in pasteurized beverages. The electroreduced samples showed resistance to photo-oxidative stress similar to that of the degassed or control beverages.

Preparative electrolysis of 1-methyl-5-nitroindole (1b, X = NCH3), 5-nitrobenzofurane (1c, X = O), and 5-nitrobenzothiophene (1d, X = S) at Hg, in acidic hydromethanolic media, leads to the formation of the corresponding 4-substituted amino derivatives 5, which result from the 100% regioselective addition to iminoquinone-type intermediate 4 of methanol or of any other good nucleophile present in the electrolytic solution. In acidic medium, the iminoquinonium intermediates 4b and 4c were trapped in a cycloaddition reaction with cyclopentadiene added to the electrolysis medium. The regiochemistry of the nucleophilic addition is discussed in light of AM1 calculations. Key words: 1-methyl-5-nitroindole, 5-nitrobenzofurane, 5-nitrobenzothiophene, iminoquinone, electrosynthesis.

The electroreductive cleavage of 4-(4′-nitrophenyl)-1,3-dioxolane (1) and of 7-nitro-1,3-benzodioxane (7) was studied at Hg in a basic hydroethanolic medium (EtOH+H2O 60:40 v/v, 0.15 M KOH). The voltammograms show classical behavior: peaks for the reversible substrate/radical anion redox couples (1/1− and 7/7−), a peak corresponding to further reduction of the radical anion to the hydroxylamine and peaks for the hydroxylamine/nitroso reversible redox couple at less negative potentials. Preparative electrolyses performed at the potential of the formation of the radical anion gave, in very good yields, cyclohexanone resulting from cleavage of the radical anion and show that these ketals are good electrolabile protecting groups. The influence of the electrolysis temperature is discussed. The electroreductive cleavage in basic ethanolic medium is more efficient than in aprotic medium.

Three triphenylamines mono-, di-, and trisubstituted by boronic ester(s) have been synthesized and their electrochemical behavior has been investigated in the absence and in the presence of F − as a guest anion. New redox systems assigned to each complexed form were observed at less positive potentials as a result of the stabilization of the radical cation species.

The electroreductive cleavage of 4-(4′-nitrophenyl)-1,3-dioxolanes 1, 7-nitro-1,3-benzodioxane 2 and 5-nitro-1,3-benzodioxanes 3 was studied in aprotic medium (DMF/Et4NClO4 (0.1 M)). The voltammetric behavior of these compounds showed the formation of a radical anion which is relatively stable on the time scale of cyclic voltammetry. When the electroreduction of these compounds was carried out at ca. −1.5 V vs Ag/Ag+ (0.01 M), at the potential of the formation of the radical anion, its cleavage did occur with the formation of the corresponding ketone. We also investigated the electroreduction of the 4-halomethyl- and 4,5-dihalomethyl-1,3-dioxolanes (4 and 5).

The methanolysis of allylic alcohols, benzylic tertiary alcohols and epoxides in the presence of a catalytic amount of ceric ammonium nitrate (CAN) is shown to be catalysed by protons generated from the oxidation of methanol. This reaction is also catalysed by Lewis acids.

L'hydrogenation electrocatalytique (HEC) du phenanthrene (1), sur des electrodes a base de nickel de Raney, a ete conduite en mode intensiostatique, dans un melange glycol d'ethylene-eau legerement acide a 80 °C. Les electrodes fabriquees a partir de nickel de Raney dope avec d'autres metaux de transition ( electrodes RNiXY avec XY = CrMo, CrTi, CoCr, CuCr et CuTi) sont moins efficaces que les electrodes preparees a partir de nickel de Raney non dope.

The electrohydrogenation of 2-iodonitrobenzene at mercury and Raney metal electrodes (R-Ni, R-Co and D-Cu) was studied in aqueous methanolic solutions. Four different media were used: a basic KOH medium (pH > 13), a neutral acetate buffered medium (pH 7) and two media containing a pyridine buffer (pH 3 and pH 10). Cyclic voltammetric reductions were carried out at mercury, bright nickel and bright copper cathodes. The product distribution of preparative-scale electrolyses at a mercury pool cathode was compared with that of electrohydrogenation at Raney metal electrodes and of catalytic hydrogenation (open-circuit experiments) at Raney metals. Electrohydrogenation at R-Co and D-Cu electrodes gave 2-iodoaniline with high selectivity ( ⩾ 94%). The results are discussed in the light of the various mechanistic pathways.

The electrocatalytic hydrogenation (ECH) of phenanthrene has been investigated under galvanostatic control at Raney nickel electrodes in ethylene glycol—water at 80°C. The influence of square wave current control on the efficiency of the process determined by the current efficiency was studied. Higher current efficiencies were obtained using periodic current control compared to steady current control. An optimum periodic current was determined.

While the anodic trimerization of veratrole (leading to hexamethoxytriphenylene) is now a very well known reaction, developments concerning either mixed electrolysis (mixture of two orthodiethers) and/or oxidation of dissymmetrical substrates have not been conducted go far. The presented method, often specific, allows the synthesis of a new palette of liquid crystal precursors.

mixed anodic trimerization of aromatic orthodiethers and benzocrown ethers may lead to the formation of new triphenylenes possessing one (or two) complexing site(s).

mixed anodic trimerization of aromatic orthodiethers and benzocrown ethers may lead to the formation of new triphenylenes possessing one (or two) complexing site(s).

While the anodic trimerization of veratrole (leading to hexamethoxytriphenylene) is now a very well known reaction, developments concerning either mixed electrolysis (mixture of two orthodiethers) and/or oxidation of dissymmetrical substrates have not been conducted go far. The presented method, often specific, allows the synthesis of a new palette of liquid crystal precursors.

The electrochemical reduction of 4-, 5-, 6- and 7-nitroindoles, at Hg, in basic (KOH 0.15 M, pH > 13) and acidic (HX 0.15 M, pH = 0.3) aqueous methanol (MeOH-H2O 95:5, v/v) gave substituted aminoindoles (mono and disubstituted) and/or the corresponding aminoindole in a ratio depending on the nitroindole, the pH and the nucleophile present in the medium. A mechanistic hypothesis supported by theoretical calculations is proposed.

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