Phenol → 1,6-Dihydro-5-(2-hydroxyphenyl)-1-methyl-3-propyl-7H-pyrazolo[4,3-d]pyrimidin-7-one

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A mixture of 5-(2-allyloxyphenyl)-1-methyl-3-n-propyl-1,6-dihydro-7H-pyrazolo[4,3-d]pyrimidin-7-one (0.25 g, 0.0008 mol), phenol (0.145 g, 0.0015 mol), piperidine (0.131 g, 0.0015 mol) and tetrakis(triphenylphosphine)palladium(O) (0.046 g, 0.00004 mol) in absolute ethanol (5 ml) was refluxed overnight under nitrogen. The mixture was allowed to cool, the solvent evaporated under vacuum and the residue dissolved in ethyl acetate (40 ml). This solution was washed with water (3×10 ml), 1M HCl (3×10 ml) and brine (1×10 ml). After drying (Na2SO4) and filtration, the filtrate was evaporated under vacuum to give the crude product. The title phenol (0.021 g, 10%) was obtained after trituration with diethyl ether and crystallisation from ethyl acetate/pentane, m.p. 233°-238° C. Found: C,63.17; H,5.65; N, 19.52. C15 H16N4O2 requires C,63.36; H, 5.67; N, 19.71%.

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