Ethyl 2-butynoate → 3-(2,5-Difluorophenoxy)-but-2-enoic acid ethyl ester

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反応条件

反応手順

A mixture of 2,5-difluoro-phenol (1.15 g, 8.91 mmol) and ethyl-2-butynoate (2.0 g, 17.8 mmol) in tetrahydrofuran (13.7 mL) was treated with 1,8-diazabicyclo[5.4.0]undec-7-ene (1.33 mL, 8.91 mmol). The reaction was then heated at 130° C. for 2 h. At this time, the reaction was cooled to 25° C. and was concentrated in vacuo. The residue was dissolved in dichloromethane (50 mL) and was washed with a 2N aqueous hydrochloric acid solution (1×100 mL), a 0.5N aqueous sodium hydroxide solution (1×100 mL) and a saturated aqueous sodium chloride solution (1×100 mL). The organics were then dried over sodium sulfate, filtered and concentrated in vacuo. Purification by Analogix flash chromatography (40 g, 5% ethyl acetate/hexanes) afforded 3-(2,5-difluoro-phenoxy)-but-2-enoic acid ethyl ester (1.35 g, 63%) as a clear oil: HR-ES-MS m/z calculated for C12H12O3F2 [M+H]+ 243.0828, observed 243.0827; 1H NMR (300 MHz, DMSO-d6) δ ppm 1.13 (t, J=7.0 Hz, 3H), 2.43 (s, 3H), 4.02 (q, J=7.0 Hz, 2H), 4.78 (s, 1H), 7.16-7.30 (m, 1H), 7.37 (ddd, J=8.9, 6.2, 3.0 Hz, 1H), 7.51 (td, J=9.7, 5.1 Hz, 1H).

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