Under argon protection, 1-(2,2-dibromovinyl)-3,5-dimethoxybenzene (2.99 g, 9.28 mmol, 1 eq.) was dissolved in anhydrous tetrahydrofuran (50 mL) and stirred at -50 °C (dry ice/acetonitrile bath). Slowly n-butyllithium (24.0 mL, 1.6 M hexane solution, 38.4 mmol, 4.1 eq.) was added dropwise and the progress of the reaction was monitored by thin-layer chromatography (TLC) until the reaction was complete. The reaction mixture was quenched with saturated aqueous ammonium chloride solution (40 mL) and subsequently extracted with dichloromethane (3 x 20 mL). The organic phases were combined, dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure to give an orange-brown oil (1.61 g). Purification by fast column chromatography (eluent: pure pentane followed by 19:1 pentane:ether) afforded a colorless crystalline solid 3,5-dimethoxyphenylacetylene (1.22 g, 81% yield) with Rf = 0.24 (pentane) and a melting point of 205 °C. The NMR hydrogen spectrum (400 °F) of 3,5-dimethoxyphenylacetylene was obtained as follows. Its NMR hydrogen spectrum (400.1 MHz, CDCl3) data were as follows: δ 6.72 (d, J = 2.3 Hz, 2H, ArH), 6.50 (t, J = 2.3 Hz, 1H, ArH), 3.76 (s, 6H, OCH3), 3.15 (s, 1H, C≡CH). The NMR carbon spectrum (100.6 MHz, CDCl3) data are as follows: δ 160.6 (C), 123.4 (C), 110.0 (CH), 102.3 (CH), 83.7 (C), 76.9 (CH), 55.4 (CH3).
