Synthesis of 4-Substituted Chromenes

A solution of 1 (1 mmol), ethyl bromoacetate (1 mmol) in dry acetone (10 mL) containing anhydrous potassium carbonate (1 mmol) was refluxed for 12 h (TLC, n-hexane/ethylacetate 3:1). The organic layer was extracted using ethyl acetate, dried over anhydrous sodium sulphate. The solvent was evaporated under vacuum and a white solid was obtained in an extremely pure state and used without further purification.
Off white ppt, m.p.85–92 °C; yield: 90%; 1H NMR (500 MHz, DMSO-d6) δ 10.28 (s, 1H, CHO), 7.00 (s, 1H, CH pyranone ring), 6.07 (s, 1H, CH benzene ring ), 5.01 (s, 2H, OCH₂), 4.15 (dd, J = 12.2, 7.2 Hz, 2H, COOCH₂), 3.80 (s, 3H, OCH₃), 2.27 (s, 3H, CH₃), 1.20 (t, 3H, CH₃).