2.3. Synthesis of 3,5-bis(propargyloxy)benzyl Alcohol

3,5-Dihydroxybenzyl alcohol (1.4 g, 10 mmol), 3-(trimethylsilyl)propargyl bromide (4.2 g, 22 mmol), 18-crown-6 (264 mg, 1 mmol), K₂CO₃ (3.45 g, 25 mmol) and acetone (80 mL) were added into a round-bottom flask in nitrogen atmosphere. This mixture solution was placed in oil-bath at 80 °C for 48 h. The mixed solution was filtered to remove indissoluble solid, and the filtrate was then concentrated. The solution was extracted with CH₂Cl₂ for three times and washed by 1 mol/L HCl and brine. The collected organic phase was dried using MgSO₄. After evaporating the solution, the crude product was purified by silica gel chromatography (eluent: petroleum ether/ethyl acetate = 4/1) to get a white solid (1.2 g, yield: 57.3%). ¹H NMR (CDCl₃, 300 MHz, ppm, Figure S1): 6.63 (a, 2H), 6.54 (b, 1H), 4.67 (c, 6H), 2.53 (d, 2H), 1.70 (e, 1H). ¹³C NMR: (CDCl₃, 75 MHz, ppm): 158.92, 143.70, 106.31, 101.58, 78.49, 75.81, 65.14, 56.01.