Hydrochloric Acid → 7-Methoxy-1-oxo-1H-pyrimido[6,1-b]benzthiazole-4-carboxylic acid

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Reaction Steps

4.5 g. Ethyl 8-methoxy-4-oxo-4H-pyrimido[2,1-b]-benzthiazole-3-carboxylate (prepared by the method described by Alaimo, J. Het. Chem., 10, 769/1973) are mixed with a mixture of 75 ml. 10% aqueous sodium hydroxide solution and 25 ml. ethanol and heated under reflux for 30 minutes. After neutralizing the reaction mixture with 2 N hydrochloric acid, 1-(2-mercapto-4-methoxyphenyl)-5-carboxypyrimidine-2,6-dione precipitates out. The yield is 3.5 g. (80% of theory); m.p. 266°-267° C. (decomp.).

Provenance & Evidence