Naphthalene anodic oxidation

Anthraquinone is being made at pilot plant scale from anthracene. The Ce3+/4+ couple is used with methane sulfonic acids. The steps involve anodic oxidation of Ce3+ and the use of Ce4+ outside the cell to convert naphthalene to napthaquinone, which is then converted to anthraquinone via a step involving butadiene. 

Crown ether-functionalized polyphenylenes are a class of electroactive polymers obtained by electropolymerization (anodic coupling) of (di)benzo- or (bi)naphthalene-crown ethers <1998CCR1211, 1998PAC1253>. Tricyclic triphenyl-ene derivatives, such as 78, can be electrogenerated from benzo-15-crown-5 <1989NJC131> and benzo-18-crown-6 <1992JEC399>. Similarly, the anodic oxidation of dibenzo-crown ethers has produced poly(dibenzo-crown ethers), best represented by 79, where triphenylene moieties are presumably two-dimensionally linked via polyether bridges. 

The 1,2- and 1,4-addition reactions have been observed also for alkyl-substituted aromatics, but the yields are often low, in particular for benzene derivatives, owing to competing side-chain substitution reactions. Examples include the addition of MeOH to methyl-substituted benzenes [38-42], naphthalenes [43], and anthracenes [43,44]. In a similar fashion, the anodic oxidation of 1,3-dienes in MeOH [45,46] results in mixtures of 1,2- and 1,4-addition products accompanied by substitution products and methoxy-containing dimers and trimers [46]. Styrenes are oxidized in MeOH to the 1,2-addition product together with products formed by dimerization-addition [47,48]. Oxidation of allenes results in most cases in complicated product mixtures resulting from single and double addition reactions [49-52]. 

Related to these reactions is the formation of mixed biaryls, for example, during the anodic oxidation of naphthalene in the presence of alkylbenzenes [106]. 

The anodic oxidation of benzene produces a mixture of polyphenylene compounds. This oligomerization can be performed in acetonitrile [21] or in liquid sulfur dioxide [22]. Mixed coupling between naphthalene and alkyl benzenes has also been demonstrated (Table 1, numbers 12-16). The relative yield of mixed coupling products increases with the basicity of the alkyl benzene with mesitylene 19%, with tetramethylbenzene 42%, and with pentamethylbenzene 64% of mixed coupling products are obtained. This suggests an electrophilic reaction between naphthalene cation radicals and alkylbenzenes. The mixed coupling reaction of phenanthrene with anisole has been studied kinetically. The results indicate that initially a complex PA is formed between the phenanthrene radical cation and anisole, followed by an electron transfer from the complex. The resulting PA" -anisole complex then decomposes to the product [23]. 

In 1970, Rozhkov and coworkers reported the first example of anodic partial fluorination of aromatic compound [Eq. (3)] [14,15]. They found that anodic oxidation of naphthalene in Et4NF-3HF/MeCN provided 1-fluoronaphthalene mainly, while the use of Et4NF instead of Et4NF-3HF led to the efficient formation of 1,4-difluoronaphthalene solely. 

The change in the CV behavior of the aniline upon addition of pyridine clearly shows the intermediacy of the cation radical in the reaction sequence. A similar ECE sequence, via the cation radical, followed by intramolecular coupling occurs during the anodic oxidation of crowded 8-t-butyl-l-(2-pyridyl) naphthalenes (Popp,... 

Anodic oxidation of various aromatic compounds Uke anisole, mesitylene, and fused aromatic compounds like naphthalene and anthracene was carried out in various ionic liquids such as [BMIM][PF6] and [BMIM][NTf2] to provide the corresponding dimmers in moderate to good yields [25]. Under similar conditions, anodic oxidation of 1,2-dimethoxybenzene leads to the corresponding trimer as shown in Scheme 7 [25]. 

Aromatic compounds such as benzene, substituted benzenes, and naphthalene are selectively fluorinated by constant potential anodic oxidation in Et4N-3HF/MeCN [5, 6] (Scheme 2). 

Yoshida s cation pool method is also applicable to the coupling of aromatics (Scheme 8.56). The radical cation pool (112), which is generated by the anodic oxidation of naphthalene and pyrene, has been added to a variety of aromatics such as substituted benzenes and indoles to provide the CDC products (113) in good yields. 

Anodic substitution reactions of aromatic hydrocarbons have been known since around 1900 [29, 30]. The course of these processes was established primarily by a study of the reaction between naphthalene and acetate ions. Oxidation of naphthalene in the presence of acetate gives 1-acetoxynaphthalene and this was at first taken to indicate trapping of the acetyl radical formed during Kolbe electrolysis of... 

Whereas Cgg and C g are easy to reduce, their oxidation occius at comparatively high anodic potentials [1, 2]. Theoretical investigations predict the first oxidation potential ofCgg to be comparable to that of naphthalene [3]. Anodic electrochemistry with fuUerenes has been carried out with Cgg films [4] as well as in solution [5-7]. Cyclic voltammetry of Cgg in a 0.1 M solution of Bu4NPFg in trichloroethylene (TCE) at room temperatare exhibits a chemically reversible, one-electron oxidation wave at -tl.26 V vs Fc/Fc (Figiue 8.1) [7]. Under identical conditions, a one-electron, chemically reversible oxidation is also observed for Cyg. The oxidation of Cyg occurs 60 mV more negative than that of Cgg at -tl.20 V vs Fc/Fc. The energy difference between the first oxidation and the first reduction potential is a measiue of the... 

Addition of cerium salts accelerates the electrolytic oxidation of anthracene, naphthalene, and phenanthrene, which yield the corresponding quinones. The hydrocarbons may be in solution or in the form of a finely divided suspension. Anthracene, for example, is oxidised to Anthraqtjinone in 20 per cent, sulphuric acid anode current density is about 5 amps, per dm.2, and by the addition of 2 per cent, of cerium sulphate the current efficiency 8 is stated to reach nearly 100 per cent. 

The electrochemical oxidation at BDD as final treatment in a combined two-step biological/electrochemical process was investigated by Panizza et al. (2006) for the removal of naphthalene sulfonates contained in infiltration water of an industrial site. Mono and disulfonate naphthalenes were easily removed in the biological step, whereas bio-refractory compounds with complex molecules were oxidised by electrolysis at BDD anodes. With this combination the energy demand was significantly lowered with respect to mat required in a single electrochemical step. 

When Nu is electron donating the product is as a rule more easily oxidized than the starting material, resulting in further oxidation under the reaction conditions and, frequently, complex reaction mixtures. The anodic methoxylation of naphthalene, which results in 1-methoxy-, 1,2-dimethoxy-, and 1,4-dimethoxynaphthalene, approximately in a 1 2 1 ratio, serves as an illustration of this problem [67]. However, in other cases, a single major product is obtained after a sequence of reactions, such as the oxidation of mesitylene in MeCN-diluted H2SO4 to 2,4,6-trimethyl-4-hydroxycyclohexa-2,5-dien-l-one in a substitution-elimination reaction [68] or the oxidation of anthracene in MeOH to 9,9,10,l0-tetramethoxy-9,10-dihydroanthracene in a substitution-addition reaction [Eq. (28)] [69]. 

A valuable goal appears to be the anodic conversion of substituted toluenes into the corresponding aldehydes. The reaction can be achieved either in methanol [194] (intermediate formation of a ketal) or in aqueous solution in an indirect manner (presence of Mm11 or/and Cem ions as mediators [195]). The indirect oxidation of polyaromatic hydrocarbons (naphthalene, anthracene) into the corresponding quinones could be achieved in the presence of electrogenerated ceric ions. 

Fluoride ion reactions are somewhat puzzling. Oxidation of fluoride ion by a cation radical is out of the question and nucleophilic attack would appear to be certain. However, this reaction has failed completely with several cation radical perchlorates, such as those from perylene (Ristagno and Shine, 1971b), and phenothiazine (Shine et al., 1972). It appears that fluoride ion is too weak a nucleophile to participate in such substitution reactions. On the other hand, several cases of anodic fluorination are known oxidation of some aromatics, in solutions containing fluoride ion and at potentials lower than the oxidation potential of fluoride ion, has led to fluorination. This has occurred with naphthalene, which gave... 

An example is the oxidation of naphthalene with cerium, which has been demonstrated on a pilot scale [47]. Ce(III) in and aqueous solution of methane-sulfonic add is oxidized to Ce(IV) at the anode. The Ge(IV) reacts with naphthalene in a separate vessel to form naphthoquinone and Ge(III). The aqueous phase containing the methanesuUbnic add and Ge(III) is separated and returned to the electrolytic cell. The naphthoquinone is an intermediate for dyes, agricultural chemicals, and anthraquinone, which is made by a Diels-Alder reaction with butadiene. 

The simplest organic metals can in fact be produced starting from naphthalene and similar arenes such as pyrene, perylene, fluoranthene or triphenylene. 4-16 if these compounds are electro-chemically oxidized in an otherwise inert solvent containing a supporting electrolyte with anions of low nucleophili city, coloured crystals of high conductivity will grow at the anode. These crystals... 

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