[CH3:1][C:2]1[CH:6]=[C:5]([CH2:7][C:8]([OH:10])=[O:9])[O:4][N:3]=1.O=S(Cl)Cl.[CH3:15]O>>[CH3:1][C:2]1[CH:6]=[C:5]([CH2:7][C:8]([O:10][CH3:15])=[O:9])[O:4][N:3]=1To a 50 mL RB flask fitted with magnetic stirrer was charged with 10 mL of methanol. To the stirred solvent was added (3-methyl-1,2-oxazol-5-yl)acetic acid (1 g, 7 mmol), was added drop wise SOCl2 (1.25 g, 10.5 mmol) to the reaction mixture at 0° C. and stirred at 50° C. for 4 h. After completion of the reaction, the reaction mixture was concentrated to distill off the solvent; water (25 mL) was added and extracted with ethyl acetate (25 mL). The organic layer was washed with saturated NaHCO3 solution (10 mL) and brine solution (10 mL). The organic layer was dried over anhydrous Na2SO4 and the solvent was removed under reduced pressure. The product was obtained as brown liquid (1 g, yield: 92%). 1H NMR (300 MHz, CDCl3): δ 6.03 (s, 1H), 3.73 (d, 2H), 3.69 (s, 3H), 2.23 (s, 3H).
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