Reaction of 2,6-dichloro-4-trifluoromethylaniline with a suspension of nitrosyl sulphuric acid, followed by the reaction with a solution of ethyl 2,3-dicyanopropionate in acetic acid, gave 5-amino-3- cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)pyrazole (1), which was then reacted with acetic anhydride to give 2a, with maleic anhydride to yield 2b, and with benzoyl chloride to afford 2c. All compounds were characterized by elemental analysis, IR, ¹H NMR, ¹³C NMR and MS spectra. The crystal and molecular structures of 2a, 2b and 2c have been determined by single crystal X-ray diffraction analysis. Compound 2a belongs to monoclinic system with space group C2/c and a＝1.88282(6) nm, b＝0.86541(3) nm, c＝1.90766(6) nm, β＝95.5830(10)°, V＝3.09362 nm³, Z＝8, R＝0.0639, wR＝0.170. 2b belongs to monoclinic system with space group P2₁/n and a＝1.28261(10) nm, b＝0.89942(7) nm, c＝1.46896(12) nm, β＝104.217(1)°, V＝1.6427(2) nm³, Z＝4, R＝0.055, wR＝0.165. 2c belongs to triclinic sys-tem with space group P-1 and a＝0.84613(11) nm, b＝0.98923(13) nm, c＝1.14305(15) nm, β＝96.002(2)°, V＝0.9326 nm³, Z＝2, R＝0.0684, wR＝0.1795.

Key words: amide, 2,3-dicyanopropionate, crystal structur, 5-amino-3-cyano-1-arylpyrazole, 2,6-dichloro-4-trifluoromethylaniline