It was established that 5-bromo-2-cyclopropylthiophene and 5-methyl-2-cyclo-propylthiophene undergo transformations during nitration with nitric acid in acetic anhydride that are a consequence of ipso attack of the nitryl cation in the 2 or 5 positions of the thiophene rings of the starting compounds.
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 189–194, February, 1981.