Hydrochloric Acid → 8-Ethyl-7,8-dihydro-5-hydroxy-7-oxo-2-phenylpyrido[2,3-d]pyrimidine-6-carboxylic acid ethyl ester

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Reaction Steps

To a 40 ml. solution of NaOEt (1.0 g. Na-0.042 mole) was added 6.8 g. (0.042 mole) of diethyl malonate and this is stirred 10 minutes, then stripped to dryness. Dimethylformamide was added until a solution formed and to this was added 5.7 g. (0.021 mole) of 1-ethyl-7-phenyl-2H-pyrimido[4,5-d][1,3]oxazine-2,4(1H)-dione and the mixture heated at reflux for 2 hours. The reaction was then cooled and poured into dilute HCl and the resulting precipitate filtered off and rinsed well with water. Recrystallization with hexane-ethyl acetate gave 5.1 g. of the title product--m.p. 177°-180° C.

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