Triethylamine → (E)-3-(3-methyl-4-oxo-1-n-propyl-1,5-dihydro-4H-pyrazolo[3,4-d]pyrimidin-6-yl)-4-n-propoxycinnamic acid t-butyl ester

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To a solution of 6-(5-bromo-2-n-propoxyphenyl)-3-methyl-1-n-propyl-1,5-dihydro-4H-pyrazolo[3,4-d]pyrimidin-4-one (Example 11; 2.14 g, 0.0053 mol) and triethylamine (0.81 g, 0.008 mol) in acetonitrile (4 ml), was added palladium(II) acetate (0.06 g, 0.00027 mol), tri-o-tolylphosphine (0.16 g, 0.00053 mol) and t-butyl acrylate (1.03 g, 0.008 mol). The mixture was heated under reflux for 4 hours, cooled to room temperature and then partitioned between water (30 ml) and dichloromethane (30 ml). The organic phase was removed and the aqueous phase extracted with dichloromethane (2×30 ml). The combined organic solutions were dried (Na2SO4) and the solvent removed by evaporation under vacuum to give a greenish brown solid. Purification by column chromatography (SiO2, CH2Cl2 then 2% MeOH in CH2Cl2) and crystallisation from ethyl acetate-hexane afforded the title compound as white crystals (1.48 g, 58%), m.p. 181-182° C. Found: C, 66.50; H, 6.75; N, 12.27. C25H32N4O4 requires C, 66.35; H, 7.12; N, 12.38%.

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