Nitric Acid → Nitrodenafil

Participants

Reaction Steps

Concentrated nitric acid (0.5 ml) was added dropwise to a stirred solution of 5-(2-ethoxyphenyl)-1-methyl-3-n-propyl-1,6-dihydro-7H-pyrazolo[4,3-d]pyrimidin-7-one (2.0 g, 0.0064 mol) in concentrated sulphuric acid (10 ml) at 0° C., and the resulting orange solution was stirred at room temperature for 18 hours. The reaction solution was then added dropwise to stirred ice and water (200 g) and the solid precipitate collected by filtration. This solid was then dissolved in dichloromethane (50 ml) and the solution washed succesively with brine (2×30 ml) and water (30 ml), dried (Na2SO4) and evaporated under vacuum to give a yellow solid. Crystallisation from acetonitrile gave the title compound as yellow needles (1.40 g, 61%), m.p. 214°-216° C. Found: C,57.36; H,5.21; H,19.49. C17H19N5O4 requires C,57.13; H,5.36; N,19.60%.

Provenance & Evidence