Oximes anodic oxidation

Quinone dyes, 9 503 Quinone ketals, anodic oxidation of hydroquinone ethers to, 21 264 Quinone methides, 2 209-211 Quinone Michael addition chemistry, 21 248-249, 250, 252 Quinone monoacetals, 21 251 Quinone monoimine (QMI), 19 246 Quinone oximes, formation of,... 

The anodic oxidation of methyl-3,5-dibromo-4-hydroxyphenylpyruvate oxime affords a spiroisooxazole in almost quantitative yield (Scheme 27) [38]. 

A great variety of substituted radicals for dimerization can be generated by anodic oxidation of anionic species r5"Me5+, e.g., sodium salts of 1,3-dicarbonyl compounds, aliphatic nitro compounds, phenols, oximes, alkynes, thio-lates or organometallics (Eq. (157) ). 

Cleavage of oximes to the parent carbonyl compound may be performed under mild conditions by anodic oxidation in CH3CN/H2O [123]. Thus, anodic oxidation of 4-sub-stituted acetophenone oximes in wet acetonitrile furnishes the corresponding acetophenones in high yields, while the oxidation of benzaldoximes is unselective [124] [Eq. (18)]. By indirect electrochemical oxidation using the Mn(II)/Mn(III) mediator system in the... 

Anodic oxidation of azomethine, hydrazone, oxime, formazane, and semicarbazone structures has been used to initiate the intramolecular cyclization [119] under formation of heterocycles like triazoles [126,127], oxadiazoles [128,129], triazolinones [129], benzoxa-zoles [130,131], benzimidazoles [130,131], pyrazoles [132], indazoles [133], furoxanes [134], and tetrazolium salts [135] (see Chapter 18). Some of these reactions can be performed advantageously by indirect electrolysis using tris(4-bromophenyl)amin or 2,3-dihydro-2,2-dimethylphenothiazine-6(l/7)-one as mediators [119,136]. Two examples are given in Eqs. (19) and (20). 

Oxiranes may be ring opened in acidic methanol to or-methoxy alcohols, which can be cleaved anodically. This has been used to transform a propylene side chain to an aldehyde [31]. /3-Hydroxyhydroxylamines may be cleaved to aldehydes and oximes on anodic oxidation at pH 8. [32] ... 

Intramolecular nucleophilic substitution of electrogenerated phenoxonium ions has been investigated . In connection with naturally occurring bromo compounds, methyl 3,5-dibromo-4-hydroxyphenyl pyruvate oxime (98) was subjected to anodic oxidation (-1-1.3 V Vi. SCE 2.1 Fmol ) in MeOH to afford spiro-isoxazole 99 in almost quantitative yield . Methyl 3-bromo-4-hydroxyphenyl pyruvate oxime (100) was also electrolyzed under similar conditions to give three compounds 101, 102 and 103 in 34, 14 and 17% yields, respectively. The latter two products are formed by C—O and C—C radical couplings, respectively, as shown in Scheme 19 °. 

The action of hydroxylamine on the dibromo-ketone (327) unexpectedly resulted in the isoxazoline (328)." The spiro-isoxazoline (330) is formed by anodic oxidation of the phenolic oxime (329)." Three novel reactiom leading to isoxazolines have been reported the nitrone PhCH=CHCPh=N-(CH2SMe)-0 undergoes 1,5-dipolar cyclization and elimination on heating, to yield compound (331)," silylation of secondary nitro-alkanes gives silyl-nitronates, which, in the presence of triethylamine, undergo 1,3-cyclo-addition to olefins thus sequential treatment of MejCHNOa with trimethyl-... 

Triazoles and Benzotriazoles. - The alkenediazonium salt (431 Ar = P-NO2C6H4) is converted into the triazoles (432 R = H or alkyl) by the action of amines. Anodic oxidation of the oxime phenylhydrazone of benzil, HON=CPhCPh=NNHPh, gives the AA-oxide (433). The alkenyl-triazolines (434 R = H or alkyl) afford the aziridines (435) on flash vacuum py roly sis.Photolysis of the 4-alkylaminotriazoles (436 R = alkyl) yields 2-alkylpyrroles rather than the expected 3-alkyIpyrroles. The... 

Interest is mounting in this state, promoted once again by its possible implication in biological systems. Galactose oxidase, for example, is a copper enzyme which catalyses the oxidation of galactose to the corresponding aldehyde. The tervalent oxidation state may be prepared from Cu(II) by chemical, anodic and radical oxidation. Cu(III) complexes of peptides and macrocycles have been most studied, particularly from a mechanistic viewpoint. The oxidation of I" by Cu(III)-deprotonated peptide complexes and by imine-oxime complexes have a similar rate law... 

Electrochemical oxidation of aldoximes using halide ions as mediators afforded the corresponding nitrile oxides in the anode compartment, which were simultaneously reduced to nitriles by cathodic reduction (equation 15). Sodium chloride affords the best result among the supporting electrolytes (Cl > Br > 1 > C104 > TsO ). Accordingly, the electrochemical reaction of oximes carried out in the presence of dipolephiles yielded isooxazolines (equation 16). 

Oxidation of silyl tosylhydrazones (35) in an aprotic medium (dichloromethane) also results in the formation of nitriles, but in this case the conversion is apparently a true anodic process41 in which the key difference from the anodic behavior of oximes is the presence of the p-toluensulfonyl group, which facilitates cleavage of the N—N single bond (equation 20). 

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