The general procedure for the synthesis of 2-chloro-3-(trifluoromethyl)benzaldehyde from N,N-dimethylformamide was as follows: n-butyllithium (1.6 M hexane solution, 173 mL, 277 mmol) was added dropwise to the reaction system at -70 °C. Subsequently, a tetrahydrofuran (500 mL) solution of 2-trifluoromethylchlorobenzene (50.0 g, 277 mmol) was slowly added. The reaction temperature was maintained at -70°C and the reaction mixture was stirred for 2 hours. Then, a tetrahydrofuran (100 mL) solution of N,N-dimethylformamide (21.3 mL, 277 mmol) was added. The reaction mixture was gradually warmed to room temperature and stirred overnight. Upon completion of the reaction, the reaction was quenched by the addition of water (200 mL) and the mixture was extracted with ether (2 x 200 mL). The organic phases were combined, dried with anhydrous magnesium sulfate, filtered and concentrated under reduced pressure to remove the solvent. The residue was purified by fast column chromatography (eluent: heptane/ethyl acetate=20:1) to afford the target product 2-chloro-3-(trifluoromethyl)benzaldehyde (37.4 g, 65% yield). Analyzed by liquid chromatography-mass spectrometry: retention time t R = 0.96 min.
