ipso-Attack in the nitration of aromatic amines. Part 2. Isolation of salts and other products resulting from ipso-attack

In 70% nitric acid at 0 °C, NN,2,4,6-pentamethylaniline undergoes ipso-attack at the 4-position to form the relatively stable ipso-intermediate (2); this ion can be precipitated as the hexafluorophosphate. In more aqueous media, the dimethylamino group is displaced by water to form the hexadienone (4). In aqueous nitric acid at 0 °C, NN,2,4-tetramethyl-6-nitroaniline undergoes both ipso-attack and addition of water to the ring to form the adduct (8); this ion can also be precipitated as the hexafluorophosphate. The reaction of NN,2,6-tetramethyl-4-methoxyaniline with 52% nitric acid at 0 °C also involves displacement of the dimethylamino group and gives finally 2,6-dimethylbenzoquinone. The initial stages of the reactions of the above amines require the presence of nitrous acid and the reactions are inhibited by hydrazine.