Phthalic anhydride electrochemical

On the other hand, the reduction of phthalic anhydride to phthalide is simpler. The key step in this synthesis is the electrochemical reduction of ammonium phthalamates... 

As mentioned above, urea and PA are the most cheap phthalocyanine precursors and are produced on an industrial scale, so it is not surprising that numerous articles and patents have been dedicated to the study of their interactions [6,30,41-48], Flowever, only copper and some other strong metals (in relation to the PcM formation and stability) form their phthalocyanines using these precursors. There are almost no reports in the available literature about attempts to electrosynthesize PcF12 or PcM starting from urea and phthalic anhydride, except for a recent work [32] where the interaction between these two precursors, as well as phthalimide, in various nonaqueous solutions by conventional chemical and electrochemical methods is studied in detail (Example 18). 

Most reported phthalocyanine derivatives (sulfo-, nitro-, amino-, triphenylmethyl-, polymeric, etc.) are copper complexes, although at present the synthetic chemistry of other d- and /-metal Pc derivatives is being rapidly developed (Examples 30-36) [5,6,116-118]. Some of them (in particular, copper phthalocyanine sulfonic acids) are of industrial interest because of their usefulness as dyes. Phthalocyanine sulfonic acids themselves are prepared both by urea synthesis from sulfonated phthalic anhydride and by the sulfonation of the phthalocyanine [6], Some substituted metal phthalocyanines can be obtained by chemical or electrochemical reduction [118e]. Among a number of reported peculiarities of substituted phthalocyanines, the existence of three electronic isomers for magnesium derivative PcMn was recently confirmed [118f]. 

Electrochemical reduction of phthaloyl dichloride (73) at a carbon or mercury cathode in acetonitrile containing TEAP led to a complex array of products. Six cathodic waves observed in the CV for the reduction of phthaloyl dichloride arise from the reductions of different electrolysis products, as well as from hydrolytically formed phthalic anhydride (74),. caused by the presence of residual water in the solvent/supporting electrolyte (equation 45). From controlled potential electrolyses of phthaloyl dichloride, a variety of products including 3-chlorophthalide (75), phthalide (76), biphthalyl (77) and dihydrobiph-thalide (78) can be obtained69,70. Reduction of glutaryl dichloride (79) at a mercury cathode in acetonitrile containing 0.1M TEAP results in the formation of 5-chlorovalerolactone (80) and valerolactone (81) as minor products, and a polymeric material (equation 46)68. 

In general, the dissolving metal or electrochemical reductions of acyl halides or acyclic anhydrides are not useful for the preparation of primary alcohols. Such reductions invariably provide acyloin esters, ene-diolate diesters or related species. Cyclic anhydrides may be reduced to give lactones. For example, the reduction of phthalic anhydride at a mercury cathode has been used in the synthesis of phthalide (90%). In general, however, such reduction are not widely employed in synthesis. 

ITie electrochemical properties of silylated tetrathiafulvalenes are assessed and 5,5 -dimethylsilanediyldi(phthalic anhydride) used as a model for aromatic polyimides. ... 

Carboxylic AcidPerivatives. Detailed investigations into the electrolytic reduction of carboxylic acid derivatives (esters, anhydrides, amides) in nonaqueous solutions and the procedures for producing the respective radical anions have been described in the report by iDyasov and his co-workers f39]. They obtained radical anions from esters of aromatic carboxylic acids (benzoates, phtha-lates, isophthalates) and from phthalic anhydride and analyzed their EPR spectra. The production of radical anions of acrylates and methacrylates by electrochemical generation and the effect of proton donors on their stability was also described [11]. 

Other studies concern the electrochemical behavior of derivatives of simple aromatic compounds. Different voltammetric behavior of aniline/ benzoic, and salicylic acids and phthalic anhydride, and of hydroquinone, resorcinol, and catechol was reported at BDD electrode. Nevertheless, bulk electrolysis of these pollutants at BDD electrode leads to their complete mineralization with exception of aniline with about 80 % conversion. Other study was devoted to the determination of residues of selected sulfonamides in egg samples by HPLC with amperometric detection at BDD electrode. ... 

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