Aldoximes anodic oxidation

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>. 

Compounds containing the C=N functional group derivatives undergo anodic oxidation when the nitrogen atom bears an electron-rich heteroatom. Perhaps the simplest such species are aldoximes, which are anodically oxidized to nitrile oxides (34)38. The reaction was carried out in an undivided cell3 , hence the species 34 underwent immediate reduction to a nitrile (equation 19). However, since nitrile oxides are 1,3-dipolar species, one could in principle carry out the oxidation in a divided cell in the presence of a good 1,3-dipolarophile40 to effect the synthesis of substituted heterocycles. 

Aldoximes may be transformed into nitriles via nitrile oxides, obtained by indirect anodic oxidation of the aldoxime in methanol, followed by cathodic reduction of the nitrile oxide [92]. 

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). 

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See also in sourсe #XX -- [ ]

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