Electrochemical oxidation of catechol

The electrochemical oxidation of catechols in the presence of 6-methyl-1,2,4-triazin-3-thion-5-one and 4-amino-6-methyl-l,2,4-triazin-3-thion-5-one as nucleophiles in aqueous solutions provided an efficient electrosynthesis of thiazolo[3,2-6][l,2,4]triazin-7-one and l,2,4-triazino[3,4-/)J 1,3,4-thiadiazinc derivatives respectively <06TL1713> <06TL8553>. 

D. Nematollahi, and Z. Forooghi, Electrochemical oxidation of catechols in the presence of 4-hydroxy-6-methyl-2-pyrone, Tetrahedron 58(24), 4949 953 (2002). 

As shown below, polyphenol-based benzo[A furans were biosynthetically made from catechols and 1,3-dicarbonyl compounds in the presence of laccase <07T10958 07TL5073>. A similar type of benzo[A]furan was also obtained via electrochemical oxidation of catechols and methyl acetoacetate <07T3894>. 

Electrochemical oxidation of catechol derivatives in the presence of 1 gave 138 via a Michael addition of the formed quinones to 1 (04JOC2637, 06CPB959) (Scheme 23). 

Figure 17.7 (A) Cyclic voltammogram of catechol on a platinum electrode. (B) Effect of poly(aniline-co-o-aminophenol) fiber diameter on the electrochemical oxidation of catechol, at a scan rate of 60 mV Average fiber diameter ( ) 70 nm, (2) 90 nm, (3) 100 nm, (4) 107 nm, in a solution consisting of 5 mM catechol and 0.3 M Na2S04 with pH 5.0. (Reprinted with permission from Electrochimica Acta, Poly(aniline-co-o-aminophenol) nanostructured network Electrochemical controllable synthesis and electrocatalysis byShaolin Mu, 51, 17, 3434-3440. Copyright (2006) Elsevier Ltd)...

Bames EG, Mahony AM, Aldous L, Hardacre C, Compton RG (2010) The electrochemical oxidation of catechol and dopamine on platinum in l-ethyl-3-methylimidazolium bis(trilluor-omethylsulfonyl)imide ([C2mim][NTf2]) and l-butyl-3-methylimidazolium tetralluoroborate [C4mim][BF4] adsorption effects in ionic liquid voltammetry. J Electroanal Chem 646 (1-2) 11-17... 

Electrochemical oxidation of catechol in the presence of carbohydrazide in aqueous solution using carbon electrode resulted in benzimidazole derivatives by cyclic voltammetry and controlled-potential coulometry techniques [20] (Scheme 49). A direct electron transfer mechanism occurred during the process on the surface of carbon. The investigators proposed that the Michael adduct formed between the carbohydrazide and o-quinone (Eqn (2)) leads to the formation of l,3-diamino-5,6-dihydroxy-lH-benzo[d]imidazole-2(3H)-one 52. 

Other Methods. A variety of other methods have been studied, including phenol hydroxylation by N2O with HZSM-5 as catalyst (69), selective access to resorcinol from 5-methyloxohexanoate in the presence of Pd/C (70), cyclotrimerization of carbon monoxide and ethylene to form hydroquinone in the presence of rhodium catalysts (71), the electrochemical oxidation of benzene to hydroquinone and -benzoquinone (72), the air oxidation of phenol to catechol in the presence of a stoichiometric CuCl and Cu(0) catalyst (73), and the isomerization of dihydroxybenzenes on HZSM-5 catalysts (74). 

Anodic oxidation of catechols enables the unstable quinones to be prepared and reacted in situ. Reaction of the 1,2-quinone with a 1,3-dicarbonyi compound gives a high yield of a benzofuran [123, 124]. Both 1,2- and 1,4-quinones, prepared electrochemically in nitromethane, are efficiently topped in Diels-Alder reactions with butadienes [125]. 

Catechols and Hydroquinones. Just as quinones are ideal examples of electrophilic substrates, their fully reduced form (catechols and hydroquinones) illustrates the electrochemical oxidation of aromatic nucleophilic substrates (Lewis bases). Figure 12.3a, b illustrates the oxidation of 3,5-di+m-butyl-catechol (DTBCH2) via an irreversible two-electron process (ECEC) to give the o-quinone (DTBQ) 12... 

Nasr, B., Abdellatif, G., Canizares, P., Saez, C., Lobato, J. and Rodrigo, M. A. (2005), Electrochemical oxidation of hydroquinone, resorcinol, and catechol on boron-doped diamond anodes. Environ. Sci. Technol., 39(18) 7234-7239. 

Jaegfeldt, H., Kuwana, T., Johansson, G., Electrochemical Stability of Catechols with a Pyrene Side Chain Strongly Adsorbed on Graphite Electrodes for Catalytic Oxidation of Dihydronicotinamide Adenine Dinucleotide , J. Am. Chem. Soc. 105 (1983) 1805-1814. 

On coordination to metals, the quinone-CO stretching frequency shifts at least 200-300cm", which infers a formal reduction to catechol with oxidation of the metal. The possibility of an intermediate radical anion coordination mode for o-benzoquinones has been demonstrated by the reversible chemical and electrochemical oxidation of reduced quinone complexes. ESR spectra of [Ir(Cl)(l,2-02QCl4)(C0)(PR3)2] (PR3 = PPhj, PMePh2) indicate that the unpaired electron is localized in the semiquinone ligand. The quinone coordination mode is stron y affected by the oxidizing ability of the quinone and the nature of the complex itself. 

The analytical application of particle-dispersed-modified electrodes to the selective detection of a single analyte is limited because of broad catalytic activities thus their use as electrochemical detectors following chromatographic separation of carbohydrates is often suggested. Similar nonspecific catalytic PMEs consisting of electrocatalytic RUO2 particles and Ru(OH2)6 in Nafion have been shown to catalyze the oxidation of catechol and of alcohols, respectively these could presumably be used in place of the carbon paste Ru02-modified electrode developed for postseparation detection of carbohydrates and alcohols. Other electrocatalytic particle electrodes were prepared from lead dioxide in polypyrrole and CoPc entrapped behind a permselective cellulose acetate film. ... 

The contrast between the electrochemical method and the method in the literature is very striking in one particular case, namely the formation of the tin(II) compounds by the electrochemical oxidation of the metal in solutions of 1,2-aromatic diols in acetonitrile (R(OH)2 = catechol, 2,3-dihydroxynaphthalene, Br4C5(OH)2, 2,2 -dihydroxybiphenyl). The room temperature, high yield, electrochemical synthesis of Sn(02R) compounds is a great improvement over the high temperature methods used in the earlier syntheses of such compounds [64]. The ready accessibility of the Sn(02R) materials lead to a study of their redox reactions, and their coordination chemistry. Not surprisingly, the direct synthesis of Pb(02R), and its redox chemistry, follow from the tin(II) system [65]. In each case the Ep value of 0.5 mol F can be understood by the sequence... 

Atobe and coworkers also reported the generation of unstable o-benzoquinones using flow electrolysis (Figure 9.10). The anodic oxidation of catechols in an electrochemical flow microreactor gave o-benzoquinones, which were reacted with benzenethiols to obtain the coupled products [29]. 

Chemical and electrochemical oxidations of different catechols were carried out in the presence of Af,Af -dibenzylethylenediamine (DBEDA) in a phosphate buffer/acetonitrile solution for the synthesis of different new dibenzyltetrahydro-quinoxalinedione derivatives (Habibi et al. 2014). The oxidation of catechol 276a,... 

Maldonado, S., Morin, S., and Stevenson, K. J. 2006. Electrochemical oxidation of catecholamines and catechols at carbon nanotube elechodes. Analyst 131 262-267. 

Jaegfeldt H, Kuwana T, Johansson G. Electrochemical stability of catechols with a pyrene side chain strongly adsorbed on graphite electrodes for catalytic oxidation of dihydronicotinamide adenine dinucleotide. J Am Chem Soc 1983 105 1805-1814. 

Krebs and co-workers synthesized a series of dinuclear copper(II) complexes as models for catechol oxidase 91 (365) (distorted SP Cu-Cu 2.902 A), (366) (distorted five-coordinate geometry Cu-Cu 3.002A), (367) (distorted SP Cu-Cu 2.995 A), (368) (distorted five-coordinate geometry Cu-Cu 2.938 A), and (369) (distorted SP Cu-Cu 2.874 A). These complexes were characterized by spectroscopic and electrochemical methods. From kinetic analysis, a catalytic order for catecholase activity (aerial oxidation of 3,5 -di - ter t-buty lcatec h o 1) was obtained.326... 

The condensation of 3-substituted catechols with dimedone under electrochemical oxidation in aqueous medium leads to benzofurans (Equation 120) <2004JOC2637>. 

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