反应详情

29.4 g. 1-(2-Mercapto-4-methoxyphenyl)-5-carboxypyrimidine-2,6-dione are boiled for 6 hours in 300 ml. of a semi-concentrated dioxane solution of hydrochloric acid. The 7-methoxy-1-oxo-1H-pyrimido[6,1-b]benzthiazole-4-carboxylic acid which is thereby formed can be obtained in practically quantitative yield by suction filtration of the hot solution. The physical data of the product agree with those of the compound prepared according to Variant I.