Thionyl Chloride → 3-Nitro-5-(trifluoromethyl)benzoyl chloride

A solution of thionyl chloride (30 ml) and 3-nitro-5-(trifluoromethyl)benzoic acid (10 g) was heated to reflux for 2 h. The reaction mixture was concentrated under reduced pressure and azeotroped with toluene (10 ml—removed under reduced pressure) to afford 3-nitro-5-(trifluoromethyl)benzoyl chloride. Step 2: To a solution of 3-nitro-5-(trifluoromethyl)benzoyl chloride (2.35 g, 9.3 mmol) in CH2Cl2 (40 ml) at room temperature was added N-methylpiperazine (1.26 ml, 9.3 mmol) and the mixture was allowed to stir for 30 min. The reaction was concentrated under reduced pressure, taken up in 1 M HCl (50 ml) and the aqueous layer was washed with Et2O (2×20 ml). The aqueous layer was basified to a pH of about 9 with 6N NaOH and extracted with Et2O (3×50 ml). The organic extracts were combined and washed with water (1×20 ml) followed by brine (1×20 ml), dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure to afford (4-methylpiperazin-1-yl)(3-nitro-5-trifluoromethyl)phenyl)-methanone as a tan oil. MS m/z=318 [M+H]+; Calc'd for C13H14F3N3O3: 317.3.