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 benzenesulfonyl chloride to yield 2a, with 4-methylbenzenesulfonyl chloride to 2b, and with methansulfonyl chloride to 2c. All compounds were characterized by elemental analysis, IR, ¹H NMR, ¹³C NMR and MS spectra. The crystal and molecular structures of 1, 2a and 2c have been determined by single crystal X-ray diffraction analysis. Compound 1 belongs to orthorhombic system with space group Pbca and a＝1.61739(7) nm, b＝1.62480(7), c＝3.10857(13) nm, α＝β＝γ＝90, V＝8.1691 nm³, Z＝24, R＝0.1089, wR＝0.2545, 2a to monoclinic system with space group C2/c and a＝3.35144(18) nm, b＝0.97948(5) nm, c＝2.44717(12) nm, β＝102.460(1), V＝7.8440(7) nm³, Z＝8, R＝0.1831, wR＝0.2600, and 2c to triclinic sys-tem with space group P-1 and a＝0.84681(7) nm, b＝0.89652(83) nm, c＝1.43497(12) nm, α＝75.198(2), β＝87.918(1), γ＝65.395(1), V＝0.9546 nm³, Z＝2, R＝0.049, wR＝0.135.

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