Amisulpride impurity and preparation method thereof

[0034] Example 1

[0035] Add 4-amino-5-(ethylsulfonyl)-2-methoxybenzoic acid (Compound I) (8.0g, 30.84mmol) and N,N-dimethylformamide (30ml) to a 50mL three-necked flask , Stir to dissolve, add 4-dimethylaminopyridine (1.88g, 15.4mmol), 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (2.96g, 15.4mmol) in sequence , The temperature was raised to 25-40°C, the reaction was stirred for 12h, water (300ml) was added, and the mixture was stirred for 1h. A solid precipitated out and filtered to obtain a light yellow solid. The pale yellow solid was stirred and dissolved with ethyl acetate (300ml), washed with water (100ml×2), washed with 1mol/L hydrochloric acid (100ml), washed with saturated sodium bicarbonate aqueous solution (100ml), washed with saturated brine (100ml) Wash, dry with anhydrous sodium sulfate, filter, and concentrate under reduced pressure at 40°C to obtain 10g of crude product. Add ethyl acetate (100ml) to the crude product. Heat to 60~70℃ and stir for 2~3h. Cool to 5~10℃ and stir for 2~3h. , A large amount of solids precipitated, filtered and dried to obtain 5.60 g with a yield of 72.52%. 1 H NMR (500MHz, DMSO-d6) δ: 8.11 (s, 2H), 6.93 (s, 4H), 6.53 (s, 2H), 3.81 (s, 6H), 3.22 (q, J = 7.25 Hz, 4H) , 1.15(t, J=7.3Hz, 6H); TOF MS ES(-)(m/z): 499.10[MH] - ); TOF MS ES(+)(m/z): 523.10[M+Na] + ).