Acetonitrile , anodic oxidation

In 1979, Diaz et al. produced the first flexible, stable polypyrrole (PPy) film with high conductivity (1(X) Scm ). The substance was polymerized on a Pt-electrode by anodic oxidation in acetonitrile. The then known chemical methods of synthesis " usually produced low conductivity powders from the monomers. By contrast, electropolymerization in organic solvents formed smooth and manageable films of good conductivity. Thus, this technique soon gained general currency, stimulating further electropolymerization experiments with other monomers. In 1982, Tourillon... 

In solvents that strongly resist anodic oxidation as MeCN, CH2CI2/CF3CO2H, or T SOjH CH-bonds in the alkyl chain can be oxidized. In acetonitrile a preferential acetamidation in the (co-2)- and ((B-l)-position occurs (Eq. 43) [352]. 

The anodic oxidation reaction of sulphoxides was not much studied, and just a few reports are available so far. The conversion into the corresponding sulphones of some phenyl alkyl and diaryl sulphoxides (oxidation potential for 86 + 2.07 V vs. SCE in acetonitrile/NaC104 electrolyte, Pt anode) has been reported. Similarly, diphenyl suiphoxide was long known to be transformed in a quantitative yield into the sulphone (Pt anode, solvent glacial acetic acid). Additional examples of the oxidation of a suiphoxide function attached to aryl groups are available . 

Compound 297 was formed in low yield during anodic oxidation of the corresponding diketopiperazine in acetonitrile (Scheme 72) (70TL3303). 

The oxidation of aromatic aldoximes with ceric ammonium nitrate produces nitrile oxides which undergo subsequent cycloaddition to nitriles to produce 1,2,4-oxadiazoles (Equation 47) <1997PJC1093>. The anodic oxidation of aromatic aldoximes in the presence of acetonitrile has been reported to give low yields of either 3-aryl-5-methyl-1,2,4-oxadiazoles (2-25%) or 3,5-bis-aryl-l,2,4-oxadiazoles (6-28%), although the synthetic utility of this route is limited by competitive deoximation to the carbonyl being the major reaction pathway <1997MI3509>. 

Electrochemical arylation of trialkyl phosphites by anodic oxidation in acetonitrile, a process that is troubled by low yield and formation of a variety of by-products.9... 

On the other hand, Becker et al. also have attempted the anodic oxidation of RfCH2CH2I in acetonitrile and they have achieved the anodic transformation of C8F, 7CH2CH2I to the corresponding acetamide, trifluoroacetate, and benzoate derivatives in good yields [35]. They propose a different reaction mechanism involving a hypervalent iodanyl radical intermediate as shown in Eq. 17. 

Parent (unsubstituted) PF was first synthesized electrochemically by anodic oxidation of fluorene in 1985 [266] and electrochemical polymerization of various 9-substituted fluorenes was studied in detail later [220,267]. Cyclic voltammogram of fluorene ( r1ed= 1.33 V, Eox = 1.75 V vs. Ag/Ag+ in acetonitrile [267]) with repetitive scanning between 0 and 1.35 V showed the growth of electroactive PF film on the electrode with an onset of the p-doping process at 0.5 V (vs. Ag/Ag+). The unsubstituted PF was an insoluble and infusible material and was only studied as a possible material for modification of electrochemical electrodes. For this reason, it is of little interest for electronic or optical applications, limiting the discussion below to the chemically prepared 9-substituted PFs. 

Table 11 Anodic oxidation of ST-Bu4NNu in acetonitrile with tetraethylammonium perchlorate as supporting electrolyte."...

Tab. 6 Anodic oxidation of branched hydrocarbons in acetonitrile/TEABF4 ...

Higher alcohols, however, cannot be used as neat liquids in electrolysis. For anodic oxidation those alcohols must be dissolved in appropriate solvents. Acetonitrile is the most frequently used solvent for that purpose. Electrochemical oxidation of n-butyl alcohol to n-butyraldehyde was achieved in moderately dilute acetonitrile solution in a current yield of 77% [9]. 

The anodic oxidation of alkyl isothiocyanates RNCS in wet acetonitrile (AN) involves the formation of two possible... 

Dienophilic cyclic a-carbonylazo compounds (triazoline diones, indazolone, phthalazine dione) prepared in a flow cell, by anodic oxidation of the corresponding hydrazino compounds in acidic methanol or acetonitrile, react with dienes (Scheme 50) [72, 73]. 

Anodic oxidations of 2,3,4,5-tetra-phenylpyrrole in an organic solvent (nitromethane, acetonitrile) containing trace amounts of water afford 2-hydroxy derivatives (Scheme 108) [197-199]. 

In addition, anodic oxidations, at a platinum or glassy carbon electrode, of heterocycles such as pyrrole or thiophene derivatives in organic solvents (acetonitrile, propylene carbonate, dichloromethane) were widely used to... 

Anodic oxidation of JV,iV-disubstituted trifluoroethanimidamide 45 in dry and in aqueous acetonitrile gave the imidazole 46 and quinoneimine 47 as the reaction products (Scheme 24). The constant current electrolysis on a glassy carbon anode and a platinum cathode was performed in an undivided cell [74]. 

Anodic oxidation of 45 in dry acetonitrile at 60 °C and at low current density provided a quantitative yield of 46, while oxidation of 45 in aqueous acetonitrile at 0 °C provided a high yield of 47. It has been shown that quinoneimine 47 can be transformed to 46 in 93% yield, through BF3Et20 catalyzed cyclization [75]. The reaction pathways leading to the formation of 46 or 47 are summarized in Scheme 25. Two-electron oxidation of 45 leads to the cation 45a through an ECE or e-p-e mechanism. It seems that the cyclization of 45a is the ratedetermining step in the overall intramolecular cyclization of 45 to 46. The high... 

The anodic oxidation of substituted allenes [76-79] and hetero-allenes [80-85] has been extensively studied by Becker and coworkers. Oxidation of secondary and tertiary alkyl isothiocyanates resulted in an ot-cleavage processes [77]. Primary alkyl isocyanates yielded amides and carbonyl compounds due to the nucleophilic involvement of either acetonitrile or water [80]. Primary alkyl isothiocyanates 48 afforded five-membered thiadiazolidine 49 and 50 and... 

It has been found that the electrochemically generated NO radical addes to the substituted olefins 81, and the radical species 81a formed is further oxidized to the cationic intermediate 81b which reacts with acetonitrile and yields 82 (Scheme 41). The anodic oxidation was carried out in a mixed solvent CH3CN-Et20 with NaNOa as a supporting electrolyte. The oxazoline derivatives 82 were isolated in 69-77% yield [103],... 

The chemical oxidation of 1,3,5-triarylformazans to tetrazolium salts was first accomplished in 1894 [127], Almost no attention was given to these compounds for about 50 years after their discovery. This situation began to alter markedly because of the application of tetrazolium salts in histochemical, pharmacological, and other biomedical research areas [128]. Specifically, the tetrazolium salt is reduced to a colored formazan derivative by reducing enzymes found only in metabolically active cells. Anodic transformation of for-mazans to tetrazolium salts was performed in acetonitrile solution using cotrolled potential electrolysis [17,129], In our view this reaction could be considered as a method of choice for the preparation of tetrazolium salts. The products were obtained in high yield and the electrolysis can be performed in a divided cell under constant current and decoloration of the solution indicates the end point of the reaction. Recently the anodic oxidation of formazans to tetrazolium salts was performed successfully in aqueous ethanol solution [130]. 

Electrochemical reactions require a solvent and electrolyte system giving as small a resistance as possible between the anode and cathode. Erotic solvents used include alcohol-water and dioxan-water mixtures and the electrolyte may be any soluble salt, an acid or a base. Duiing reaction, protons are consumed at the cathode and generated at die anode so that a buffer will be required to maintain a constant pH. Aprotic solvents are employed for many reactions [18], the most commonly used being acetonitrile for oxidations and dimethylforraamide or acetonitrile for reductions. In aprotic solvents, the supporting electrolyte is generally a tetra-alkylammonium fluoroborate or perchlorate [19], Tlie use of perchlorate salts is discouraged because of the possibility that traces of perchlorate in the final product may cause an explosion. 

Alkanes are functionalised by anodic oxidation in acetonitrile, methanol, acetic acid and more acidic solvents such as trifluoracetic acid and fluorosulphuric acid. Reaction requires very positive electrode potentials (see Table 2.1) and platinum has generally been used as anode materials in laboratory scale experiments. On a larger scale carbon is used as anode material. The first stage in these reactions in-... 

Reactions between aromatic hydrocarbon radicabcations and cyanide ions, with few exceptions, give low yields of nuclear substitution products [76], In some cases, better results have been obtained by anodic oxidation of the aromatic compound in an emulsion of aqueous sodium cyanide and dichloromethane with tetra-butylammonium hydrogen sulphate as a phase transfer agent [77, 78]. Methoxy-benzenes give exceptionally good yields from reactions in acetonitrile containing tetraethylammonium cyanide, sometimes with displacement of methoxide [79, 80]... 

Anodic oxidation of triphenylamine gives the radical-cation which is rapidly converted to the dehydrodimer, tetraphenylbenzidine. A para-substituent prevents this dimerization and gives radical-cations very stable in acetonitrile solution against nucleophiles [155], This class of compound was first prepared as the per-... 

Anodic oxidation of fiirans in acetic acid leads to the 2,5-diacetoxy-2,5-dihydro-furan 58 [185, 186]which is readily converted to 2-acetoxyfiiran, This has proved a valuable intermediate for the synthesis of butenolides [187]. Reactions in moist acetonitrile yield the 2,5-dihydro-2,5-dihydroxyfurans which can be oxidised to the maleic anhydride 59 [188], Oxidation of furan-2-carboxylic acid in methanol and sulphuric acid is a route to the ester of a-ketoglutaric acid [189]. 

Oxidation of acridine in anhydrous acetonitrile leads to a dimer 65 formed by reaction of the nitrogen in one molecule of the substrate with the point of highest positive charge density in a radical-cation [208]. Anodic oxidation of neat pyridine... 

The ruthenium tetroxide dioxide catalytic system is effective for the oxidation of alkanols, although it will also react with any alkene groups or amine substituents that are present. The catalyst can be used in aqueous acetonitrile containing tetra-butylammonium hydroxide with platinum electrodes in an undivided cell Primary alcohols are oxidised to the aldehyde and secondary alcohols to the ketone [30]. Anodic oxidation of ruthenium dioxide generates the tetroxide, which is the effective oxidising agent. 

N,N-Dialkylamides undergo a related series of reaction steps on anodic oxidation. The immonium ion from dimethylformamide can be generated in solution by oxidation in acetonitrile with no added nucleophile [100]. Solutions of the ion are used in further reactions such as with 1,1-diphenylethene forming 22. When acetic... 

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