A solution of tBuONO (35.2 g) and CuCl (38.6 g) in CH3CN (375 mL) was warmed to 45-50° C. The compound (50.0 g) obtained in step 2 was added slowly while cooling the reaction mixture to maintain 45-50° C. After stirring at 50° C. for 30 min, the mixture was cooled to 10° C. 6N Hydrochloric acid (250 mL) was added and the mixture was stirred for 10 min. The resultant product was extracted twice with ethyl acetate. The organic layer was-washed with 10% aqueous citric acid solution and water and dried, and the solvent was evaporated under reduced pressure. The obtained residue was purified by silica gel column chromatography (solvent gradient; 10→25% ethyl acetate/hexane) to give 3-chloro-5-(trifluoromethyl)benzoic acid (33.1 g, 60%) as a white powder.
