Nitration aldoximes

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>. 

The last authors investigated the reaction with acetaldoxime, propionaldoxime and benzaldoxime. They came to the conclusion that dinitrogen tetroxide both nitrates and oxidizes aldoximes. The nitration is more pronounced with increase of temperature whereas oxidation is most effective at 0°C and below. 

Liu and co-workers developed a AgN02-mediated direct transformation of 2-methyl quinoxalines to related nitriles [124]. The reaction could involve NO radical and aldoxime intermediates. In the presence of K2S2O8, the nitrile would be generated by the Beckmann type rearrangement (cf. Wang s work). Interestingly, nitration of quinoxalines could occur when tertiary benzylic C-H bond presents in it (Scheme 4.27). 

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