NITRO DERIVATIVES OF THE THIOPHENE SERIES. 4. NITRATION OF THIOPHENE DERIVATIVES WITH METAL NITRATES IN ACETIC ANHYDRIDE

Article abstract of DOI:10.1007/BF00506032

The nitration of 2-formylthiophene, 2-acetothienone, and unsaturated ketones of the thiophene series with copper and aluminum nitrates in acetic anhydride at various temperatures was studied.At low temperatures 2-acetothienone gives a mixture of 4- and 5-nitro isomers, while 2-formylthiphene gives only a 5-nitro-substituted compound in the diacetate form; α,β-unsaturated ketones are not nitrated under these conditions.When the reaction is carried out at 70-90 degC, one can obtain mixtures of nitro ketones in the case of unsaturated ketones; 2-formylthiophene is oxidized to thiophene-2-carboxylic acid, while 2-acetothienone gives a substance, the structure of which could not be established.The reaction of copper and aluminum nitrates with acetic anhydride was investigated by means of thermal and X-ray diffraction analysis.It is shown that the reaction is accompanied by the formation of free nitric acid, and the nitrating agent in these mixtures is consequently the nitronium cation.