Hydrochloric Acid → Ethyl 5-hydroxy-8-isopropyl-2-(methylthio)-7-oxo-7,8-dihydropyrido[2,3-d]pyrimidine-6-carboxylate

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Reaction Steps

To a solution of sodium ethoxide (0.9 g. 0.039 g. atom of sodium in 75 ml. of ethanol) was added 6.24 g. (0.03 mole) of diethyl malonate. The ethanol was removed in a rotary evaporator. To the residue was added 100 ml. of dimethyl formamide followed by 3.3 g. (0.013 mole) of 7-methylthio-1-isopropyl-2H-pyrimido[4,5-d][1,3]oxazine-2,4(1H)-dione. The reaction mixture was heated under reflux for 1 hour, cooled in ice and poured into 400 ml. of water. The solution was acidified with conc. hydrochloric acid and the resulting product was collected by suction filtration. Recrystallization from ethanol gave 2 g. of product--m.p. 138°-140° C.

Provenance & Evidence