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The general procedure for the synthesis of 5-chloro-6-methylpyrimidin-4(1H)-one from formamidine acetate and ethyl 2-chloroacetoacetate was as follows: a methanolic solution of 4-hydroxy-5-chloro-6-methylpyrimidine (8.80 g, 0.16 mol) was slowly added to a 50 mL methanolic solution containing 11.30 g (0.11 mol) of formamidine acetate, and the reaction was carried out with stirring at room temperature. After the addition was completed, the mixture continued to be stirred at room temperature for 2 hours. Subsequently, 11.17 g (0.068 mol) of ethyl 2-chloro-3-oxobutanoate was added and the reaction continued to be stirred for 5-7 hours at room temperature. The reaction process was monitored by thin layer chromatography (TLC). After completion of the reaction, the reaction mixture was concentrated under reduced pressure, the pH was adjusted to 5-6 with hydrochloric acid (HCl) and filtered to give an orange-yellow solid. The aqueous phase was extracted with ethyl acetate (3 x 50 mL), the organic phases were combined, dried with anhydrous magnesium sulfate, filtered and concentrated under reduced pressure. The residue was dissolved in 50 mL of ethyl acetate and allowed to stand overnight to give 6.48 g of orange-yellow solid product in 66% yield with a melting point of 181-184°C.

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