Electrochemical Studies on New Chelating Compounds of the Mono‐ and Bis(imidazolyl)pyridine Type

Abstract

Recently designed and synthetized mono-imidazolinone (I and III) and bisimidazolinone (II and IV) chelating ligands were electrochemically characterized at mercury and carbon paste electrodes. Based on polarographic, voltammetric and coulometric investigations in buffered aqueous media, the general reduction pathway has been suggested. Reduction of the mono-imidazolinone derivatives proceeds in acidic and neutral media in two two-electron steps. In the first step, the 2,3-C¼N double bond of the imidazolone ring is reduced yielding a mixture of two diastereoisomers (V and VI). In the second step, the 2,3-CÀN single bond (in protonated form) is further reductively split and as the only final product the compound VII was formed. Both intermediates (V and VI) as well as the final product (VII) were prepared using controlled potential electrolysis on the first and second wave, respectively, isolated and identified by means of NMR. The reduction of bis-derivatives proceeds most probably in an analogical way: in the first step, both imidazoles are reduced simultaneously at the same potential, whereas the following reduction (ring-opening) proceeds stepwise. In the case of compound III, the covalent hydration of the parent compound takes place in acidic media, partially preventing its reduction. Finally, voltammetric behaviour of mono-and bisimidazolinones at carbon paste electrode is also discussed and, in prospect, possible electroanalytical applications outlined.

2-Amino-2-alkyl(aryl)propanenitriles as key building blocks for the synthesis of five-membered heterocycles

“…The prepared aminonitriles were partially hydrolyzed to give the respective aminoamides, which were acylated with aromatic acid chlorides; the acylation products were cyclized to prepare several series of substituted 4,5-dihydro-1H-imidazol-5-ones. [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37] The substituted 4,5-dihydro-1H-imidazol-5-ones prepared in this way were used in studies of their physico-chemical properties [20][21][22][23][24][25][26][27][28] also including studies of kinetics and mechanism of their formation and decomposition. [23][24][25] The substituted 4,5-dihydro-1H-imidazol-5-ones attached to a benzene ring or to a pyridine ring at 2-or 2,6-position(s) were used for preparation and characterization of the corresponding coordination [29][30][31][32][33][34][35][36] or organometallic 37 compounds with the following transition metals: Fe(III), 29,[30][31][32][33]…”

Highly Sensitive Determination of Cadmium and Lead Using a Low-cost Electrochemical Flow-through Cell Based on a Carbon Paste Electrode

“…The amount of mineral oil was carefully controlled because excessive oil decreases the conductivity, as reported by Tomáš et al, 15 while with insufficient oil it is not possible to obtain a uniform carbon paste. The resulting paste was packed into the end of each electrode holder.…”

“…20 In the first method, Bi 3+ ions were directly added into the analyte ion solution and the Bi-film was electrodeposited on the electrode simultaneously with the analytes. In the second method, Bi2O3 nanopowder was homogeneously mixed with the carbon paste prior to the preparation of the CPE.…”

Stereoselective Electrochemical Reduction of Imazapyr in Aqueous Media Without Chiral Auxiliaries

“…Synthesis and characterization of related compounds with similar structures 8 and their respective chelate complexes with some metal ions using structural analysis by 1 H-NMR, 13 C-NMR, optical rotation, absorption, electron paramagnetic resonance spectroscopy, X-ray diffraction, elemental analysis, and others have been reported.…”

“…Only two research groups have published something about the reduction mechanism. 8,17 On the electrochemical reduction of mono͑imidazolyl͒pyridines, Mikysek et al 8 referred to the appearance of a pair of diastereoisomers but made no statement on the stereoselectivity of the reduction process.…”