4-Methoxyphenol → 3-(4-Methoxy-phenoxy)-but-2-enoic acid ethyl ester

A mixture of 4-methoxy-phenol (1.10 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 1.5 h. At this time, the reaction was cooled to 25° C. and was stirred at 25° C. overnight. At this time, the reaction was concentrated in vacuo. The residue was dissolved in dichloromethane (40 mL) and was washed with a 2N aqueous hydrochloric acid solution (1×100 mL), a 1N 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, rinsed with dichloromethane and concentrated in vacuo. Purification by Analogix flash chromatography (40 g, 10-20% ethyl acetate/hexanes) afforded 3-(4-methoxy-phenoxy)-but-2-enoic acid ethyl ester (0.99 g, 47%) as a clear oil: HR-ES-MS m/z calculated for C13H16O4 [M+H]+ 237.1122, observed 237.1121; 1H NMR (300 MHz, DMSO-d6) δ ppm 1.11 (t, J=7.0 Hz, 3H), 2.41 (s, 3H), 3.76 (s, 3H), 3.98 (q, J=7.0 Hz, 2H), 4.63 (s, 1H), 6.99 (d, J=9.1 Hz, 2H), 7.05 (d, J=9.1 Hz, 2H).