Sulfuric Acid → 4-Iodo-2-(trifluoromethyl)benzoic acid

To a suspension of 4-amino-2-(trifluoromethyl)benzoic acid (10 g, 48.7 mmol, Apollo) in water (43 ml) in an ice-water bath (internal temperature at 5° C.) was added concentrated sulphuric acid specific gravity 1.84 (7 mL, 131 mmol). To the slight suspension was added a solution of sodium nitrite, super free flowing (3.76 g, 54.5 mmol, Aldrich) in ice cold water (20 ml) dropwise. The suspension was stirred in an ice-water bath for 20 min. To the mixture was added a solution of potassium iodide, extra pure briquettes (12.14 g, 73.1 mmol, Acros) in ice cold 1 M sulphuric acid (30 ml). The mixture was allowed to warm to ambient temperature and then heated to 80° C. for 45 min under nitrogen. The mixture was allowed to cool to ambient temperature. The mixture was partitioned between ethyl acetate (300 ml) and water (300 ml). The phases were separated and the organic phase washed with brine (50 ml×2), dried (MgSO4), filtered and the solvent removed in vacuo to give the title compound as a dark brown solid (16.7 g); LCMS: (System 4) (M-H)−=315, tRET=2.64 min.