Electrosynthesis of 3-chloro-1,4-disubstituted-2(1H)- quinolinones and 3,3-dichloro-4-hydroxy-1,4-disubstituted- 3,4-dihydro-2(1H)-quinolinones,as well as a new convenient process to dioxindoles

Cathodic reduction of N-(2-acyl(or aroyl)phenyl)-2,2,2,-trichloro-N-alkylacetamide at -1.2 V (vs SCE) under aprotic conditions yields 3-chloro-1,4-disubstituted-2(1H)-quinolinones (1) as the major product. When the reaction is carried out at -0.8 V (vs SCE), 3,3-dichloro-4-hydroxy-1,4-disubstituted-3,4-dihydro-2(1H)-quinolinones (2) and 1,4-disubstituted-1,4-dihydro-quinoline-2,3-dione (3) are formed. Ring contraction of 2 and 3 in aqueous sodium hydroxide resulted in the formation of 3-hydroxy-1,3-dihydroindol-2-ones (5). The most plausible reaction mechanisms are proposed.     

Paired electrosynthesis of cyanoacetic acid

Cyanoacetic acid is formed by cathodic reduction of CO(2) and anodic oxidation of the tetraalkylammonium salt anion; the process is conduced in acetonitrile using a divided cell with a medium porosity glass-frit diaphragm. A mechanism for this paired electrochemical reaction is proposed.     

Electrochemical study of antioxidants at a polypyrrole electrode modified by a nickel phthalocyanine complex. Application to their HPLC separation and to their FIA system detections

A polypyrrole electrode modified with a tetrasulfonated nickel(II) phthalocyanine complex (GCE/PPy/NiPcTs) was used as amperometric electrochemical detector in a flow injection system, in order to determine some antioxidants in foods. The lather were separated by HPLC and detected at the modified electrode. Previous investigations carried out in our laboratory employed this electrode and cyclic voltammetry (CV), obtaining excellent results, due to an electrocatalytic effect on the oxidation of certain alimentary antioxidants, such tert-butylhydroquinone (TBHQ), 3-tert-butyl-4-hydroxyanisole (BHA) and propylgallate (PG). In order to obtain good separation, the chromatographic conditions were optimised. The geometry of the flow injection analysis (FIA) circuit and the reproducibility of the results were also optimised and, finally, the linear relationship between the signal and the concentration was verified. The proposed procedure is more precise and accurate than the conventional voltammetry methods. These results offer new analytical possibilities to this type of modified electrodes. The developed methods were applied to the determination of these antioxidants in commercial food.     

Electrochemical dimerization of phenacyl bromides N-acylhydrazones—a new way to 1-N-acylamino-2,5-diaryl-pyrroles

Cathodic reduction of phenacyl bromides N-acyl hydrazones lead to dimeric 1,4-diaryl-1,4-butanedione di-N-acylhydrazones, which give the corresponding 1-N-acylamino-2,5-diarylpyrroles in good yields.     

Facile preparation of 3-substituted 2-quinazolinones via electrogenerated base

A new series of 3,4-disubstituted quinazolin-2-ones, with potential T-type calcium channel antagonist activity, and new 4-methylene-quinazolin-2-ones, promising catalysts as N-heterocyclic olefins, have been prepared in good yield by a simple reaction between 2-aminobenzophenone, or 2-aminoacetophenone, and cyanomethyl anion electrogenerated by acetonitrile reduction at a graphite electrode, followed by the addition of different organic isocyanates and subsequent heterocyclization.     

EGB-promoted electrochemical synthesis of 6-thioxo-[1,3,5]-triazinane-2,4 dione derivatives

A simple method for the synthesis of 6-thioxo-[1,3,5]-triazinane-2,4-dione derivatives was reported. The electrogenerated cyanomethyl base obtained from electroreduction of neat acetonitrile assisted the reaction between thiourea derivatives and alkyl or aryl isocyanate. This protocol had the advantage of giving good yields using mild conditions. The obtained products have been identified by spectroscopic data, mass spectrometry, and high-resolution mass spectra or elemental analysis.     

Electrosynthesis of tryptanthrin

Tryptanthrin is obtained in a high yield by cathodic reduction of isatin via a low-energy consumption process where an electron transfer to the oxygen in air is involved.     

Preparation of a polypyrrole electrode modified with a nickel phthalocyanine complex. Application to the determination of an antioxidant (propylgallate) in foods

In this paper a study of the electrocatalytic oxidation of propylgallate (PG) by using a polypyrrole electrode modified with tetrasulfonate nickel (II) phthalocyanine complex (Pt/PPy/NiPcTs) was carried out. Several parameters of this polymeric electrode, such as: (a) its stability in hydroorganic solution, by using an indium tin oxide (ITO) electrode and spectrophotometry; and (b) its thickness using electrochemical techniques, have been studied. In addition, several parameters affecting the PG voltammetric peak, such as pH, methanol water ratio, potential scan rate and analyte concentration, were considered. Finally, the developed method was applied to the determination of PG in spiked potato flakes and cornflakes, showing its validity.