Butanoic acid, 2-ethyl-3-oxo-, ethyl ester → 6-ethyl-3,7-dimethyl-5-oxo-5H-thiazolo[3,2-a]pyrimidine-2-carboxylic acid, ethyl ester

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반응 단계

2-amino-4-methyl-thiazole-5-carboxylic acid, ethyl ester (10 g) was reacted with ethyl 2-ethyl-acetoacetate (17 g) in polyphosphoric acid (50 g) under stirring at 100° C. for 4 hours. After cooling, dilution with ice water and neutralization with 35% NaOH, the precipitate was filtered, washed with water until neutral and crystallized from hexane to give 6-ethyl-3,7-dimethyl-5-oxo-5H-thiazolo[3,2-a]pyrimidine-2-carboxylic acid, ethyl ester, m.p. 122°-124° C. (9.9 g) which was reacted with N-bromo succinimide (13.75 g) in benzene (260 ml) at the reflux temperature for 11 hours.

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