A solution of 4-[5-(3,5-dichlorophenyl)-5-(trifluoromethyl)-4H-isothiazol-3-yl]-2-methyl-benzoic acid (1.65 g) was suspended in dichloromethane (16 mL). A catalytic amount of N,N-dimethylformamide (“DMF”) and oxalyl chloride (1.2 eq.) were added to the suspension. The reaction mixture was stirred at ambient temperature for 1.5 hour. The reaction mixture was concentrated and the residue dissolved in dry tetrahydrofuran (16 mL). To the solution was added a solution of ammonium hydroxide (8 mL, 25%). The reaction mixture was stirred at ambient temperature for two hours. It was then quenched by addition of water and extracted with ethyl acetate. The organic extract was washed with a saturated solution of sodium hydrogenocarbonate, dried over magnesium sulfate and concentrated in vacuo. The crude residue was triturated with tert-butylmethylether then the precipitate was filtered and dried under vacuo to give the title compound (841 mg) as a solid. 1H-NMR (CDCl3, 400 MHz): δ=7.50-7.61 (m, 2 H), 7.39-7.50 (m, 1 H), 7.29-7.39 (m, 1 H), 7.14-7.27 (m, 2 H), 6.40 (br. s., 1 H), 6.05 (br. s., 1 H), 4.16 (m, J=17.4, 1 H), 3.74-3.91 (m, 1 H), 2.44-2.49 (m, 3 H).
