N-{4-fluoro-3-nitro-phenyl}-benzenesulphonamide (3.0 g, 10 mmol), 3,5-bis-trifluoromethylbenzylamine (3.0 g, 12.5 mmol) and N-methylmorpholine (2.2 mL, 20 mmol) in 25 mL dimethylsulphoxide are kept for 6 h at 60-100° C., diluted with 150 mL ethyl acetate, washed with water, dilute hydrochloric acid and water again, dried and concentrated by evaporation until not quite dry. The residue is combined with 80 mL EtOH and evaporated down to a residual volume of about 50 mL. The crystals precipitated after cooling are filtered off and washed with EtOH and petroleum ether.
