Ammonium Hydroxide → 2,4-Diamino-5-(3,4-dihydro-7,8-dimethoxy-2-methyl-4-oxo-2H-1-benzopyran-5-ylmethyl)pyrimidine

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A mixture of 2,4-diamino-5-(3-hydroxy-4,5-dimethoxybenzyl)pyrimidine (2.76 g, 0.01 mole) and crotonic acid (0.87 g, 0.01 mole) in polyphosphoric acid (27 g) was stirred and heated on a steam bath for 4 hr. The reaction mixture was cooled to 50° and poured onto ice (100 g) with stirring. The resulting solution was basified to pH 8.0 with concentrated ammonium hydroxide, giving a suspension which was then extracted with methylene chloride (3×100 mL). The combined extracts were washed with 0.1N sodium hydroxide (2×100 mL), water (100 mL) and then dried over anhydrous magnesium sulfate. Evaporation of solent in vacuo gave the title compound (1.0 g, 29%). This was recrystallised from 95% ethanol to give 2,4-diamino-5-(3,4-dihydro-7,8-dimethoxy-2-methyl-4-oxo-2H-1-benzopyran-5-ylmethyl)pyrimidine as the hemihydrate, mp 128°-132°. Anal. Calcd for C17H20N4O4.1/2H2O: C, 57.78; H, 5.99; N, 15.85. Found: C, 57.79; H, 6.02; N, 15.86.

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