A mixture of n-butyllithium (8 mL, 20 mmol, 1 equiv, 2.5 M hexane) in Et2O (12 mL) was cooled to -78 0 C. The mixture was then cooled to -78 0 C. The mixture was then cooled to -78 0 C. The mixture was then cooled to -78 0 C. The mixture was then cooled to -78 0 C. A solution of 1-bromo-2-methoxy-4-trifluoromethoxybenzene (20 mmol) in Et2O (20 mL) was added to it dropwise via cannula. after 15 min, DMF (1.7 mL, 22 mmol, 1.1 eq) was added in batches via syringe, and the reaction mixture was stirred for an additional 15 min, and then heated to 0C. The reaction was then quenched with 1 M H2SO4 (20 mL) and partitioned. The aqueous phase was extracted with Et2O (3x) and the combined organic phases were washed and dried (brine, Na2SO4), filtered and concentrated. The resulting solid was recrystallized from hexane to give the desired product 4-methoxy-2-trifluoromethoxybenzaldehyde.
