[Synthesis]
1. Under argon protection, methyl 3-bromobenzoate (110 g, 0.51 mol), anhydrous acetonitrile (500 mL), ethynyl (trimethyl) silane (60.0 g, 0.61 mol), diisopropylamine (62.0 g, 0.61 mol), and tetrakis(triphenylphosphine)palladium (23.6 g, 0.02 mol) were added to a 1 L three-necked round-bottomed flask. The mixture was stirred for 30 minutes and then cooled to 10°C. Copper iodide (9.7 g, 0.06 mol) was added and the resulting suspension was stirred at 20 °C for 2.5 h, followed by stirring at 60 °C for 3 h. The mixture was allowed to stand overnight at room temperature. The mixture was allowed to stand at room temperature overnight and then filtered and the hydrobromide precipitate was washed with ether. The filtrates were combined and washed sequentially with saturated aqueous NH4Cl and NaCl, dried over Na2SO4 and the solvent evaporated. The crude product was purified by silica gel column chromatography (hexane) to afford methyl 3-(2-(trimethylmethylsilyl)ethynyl)benzoate in 95% yield (112.8 g).
2. A solution of methyl 3-(2-(trimethylsilyl)ethynyl)benzoate (112.8 g, 0.48 mol), mercury diacetate (16.2 g, 0.005 mol) in THF (350 mL), and concentrated H2SO4 (40 mL) was stirred for 3 h at 60 °C. The solution was then cooled with ether (500 mL), and the solution was purified with hexane. After cooling, the solution was diluted with ether (500 mL), filtered to remove the precipitated mercury salt and washed to neutral. The solution was dried over Na2SO4 and the solvent was evaporated, the residue was purified by silica gel column chromatography (hexane/ethyl acetate 4:1) to afford methyl 3-acetylbenzoate in 75% yield (65.2 g).
3. (Dimethoxymethyl)dimethylamine (90 mL) was added to a solution of methyl 3-acetylbenzoate (65.2 g, 0.27 mol) in toluene (90 mL), and the mixture was refluxed for 9 hours, during which time methanol was distilled. The solution was concentrated in vacuum and the residue was purified by ether crystallization to afford methyl 3-(3-(dimethylamino)acryloyl)benzoate as yellow prismatic crystals in 80% yield (68.1 g).
4. Amide formamide acetate (20.3 g, 0.19 mol) was added to a suspension of methyl 3-(3-(dimethylamino)acryloyl)benzoate (30.3 g, 0.13 mol) in toluene (300 mL) and refluxed for 20 hours, during which time the toluene and the dimethylamido acetate were distilled. Methyleneformamide acetate (6.7 g) and toluene (175 mL) were added and refluxing was continued for 8 hours before vacuum evaporation. The residue was purified by silica gel column chromatography (ethyl acetate/hexane 3:1) to afford methyl 3-(pyrimidin-4-yl)benzoate in 70% yield (19.5 g).
5. A solution of methyl 3-(pyrimidin-4-yl)benzoate (19.5 g, 0.091 mol) and sodium methanolate (7.6 g, 0.14 mol) in ethanol (250 mL) was refluxed for 30 min. After cooling, the precipitate was separated by filtration, dissolved in water and precipitated by acidification with concentrated HCl to pH about 2. After filtration, washing with water and drying, the title compound crystals were obtained in 94% yield (17.2 g). |