Salicylaldehyde (0.5 mL, 4.69 mmol, Sigma-Aldrich Catalog No. S356) was dissolved in acetonitrile (10 mL), followed by the addition of potassium carbonate (0.97 mL, 7.03 mmol) and 3-bromo-1-propene (0.45 mL, 5.16 mmol, Sigma-Aldrich Catalog No. 337528). The reaction mixture was stirred under reflux conditions for 12 hours. Upon completion of the reaction, the solvent was removed by vacuum evaporation and the residue was dissolved in ethyl acetate (5 mL). Water (10 mL) was added and stirred for 10 min at room temperature. The organic phase was separated and the aqueous layer was extracted with ethyl acetate (2 x 10 mL). The organic phases were combined, dried with anhydrous sodium sulfate, filtered and concentrated under reduced pressure to give o-propenyloxybenzaldehyde in 99% yield. The product was extracted by 1H NMR (400 MHz, CDCl3) δ= 10.25 (1H, s), 7.54-7.52 (1H, m), 7.23-7.19 (1H, m), 6.72-6.66 (2H, m), 5.82-5.75 (1H, m), 5.20-5.15 (1H, d, J = 17.6 Hz), 5.05 -5.03 (1H, d, J = 10.8 Hz), 4.33-4.31 (2H, m) ppm; 13C NMR (CDCl3) δ 188.9,160.6,135.6,132.2,127.8,124.7,120.5,117.5,112.7,68.7 ppm; Liquid Chromatography Mass Spectrometry (LCMS) m/z z (ES+) m/z: 347.0 [2M + Na]+, 185.0 [M + Na]+, 163.0 [M + H]+; Elemental Analysis: C10H10O2: Calculated value C 74.06, H 6.21; Measured value C 74.36, H 6.52.
