2,3-Dichloro-5,6-dicyano-1,4-benzoquinone → 2,4-Dichloro-5-methoxy-6-vinylpyrimidine

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Reaction Steps

2,6-Dichloro-5-methoxy-6-vinyl pyrimidine may be prepared using 2,6-dichloro-5-methoxy pyrimidine, which is commercially available. To a solution of 2,6-dicholoro-5-methoxy pyrimidine (100 g, 0.55 mol) in dry tetrahydrofuran (THF) solvent was added, dropwise, 1M vinyl magnesium bromide in THF solvent (124 g, 0.94 mol) for one hour at room temperature. The mixture was then stirred for 4 h at room temperature. Excess Grignard reagent was quenched by addition of acetone (200 mL) while the temperature of the mixture was maintained at a temperature below 20° C. Thereafter, 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) (151 g, 0.67 mol) was added at once and stirred overnight. A yellow solid precipitated out. The solid was filtered and washed with ethyl acetate (500 mL). The filtrate was concentrated under reduced pressure and the resulting crude compound was diluted with ethyl acetate (2 L). The resulting undissolved, dark, semi-solid was separated by filtration using ethyl acetate. It was further concentrated under reduced pressure to provide a crude compound, which was purified by column chromatography. The compound was eluted with 5% to 10% ethyl acetate in hexane mixture to provide the title compound (70 g, 60% yield): mp 60-61° C.; 1H NMR (CDCl3) δ 3.99 (s, 3H), 5.85 (d, 1H). 6.75 (d, 1H), 6.95 (dd, 1H).

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