4-Hydroxy-5-methoxy-2H-1-benzopyran-2-one

Synthesis

4-Hydroxy-5-methoxy-2H-1-benzopyran-2-one is obtaned by 2-Hydroxy-5-methoxy-acetophenone with sodium hydride in diethyl carbonate.2-Hydroxy-5-methoxy-acetophenone (1.50 g, 9.03 mmol) in diethyl carbonate (8.3 ml) was added dropwise into a suspension of sodium hydride (60% dispersion in mineral oil, 1.81 g, 45.2 mmol) in diethyl carbonate (8.3 ml) and heated under reflux at 100 ?C for 3 hours. The resultant mixture was left to cool to 0 ?C in an ice bath and quenched by dropwise addition of water until effervescence ceased. The aqueous layer was washed with diethyl ether (3 × 16 ml) then acidified using concentrated hydrochloric acid to pH 1. The precipitate was filtered and washed with water, followed by petroleum ether and left to dry overnight at 90 ?C to give the title compound as a colourless solid (902 mg, 52%): mp: 150 – 153 ?C (Lit.: 155 ?C); vmax/cm-1 3207bw (O-H), 1727s (C=O), 1655m (C=C), 1606s (aro. ring C=C); δH (300 MHz; DMSO-d6) 11.34 (1H, br. s., OH), 7.57 (1H, t, J 8.4, C(7)H), 6.95 (2H, d, J 8.4, C(6)H and C(8)H), 5.51 (1H, s, C(3)H), 3.90 (1H, s, OCH3); δC (75 MHz; DMSO-d6) 167.2 (Ar-C), 161.4 (Ar-C), 157.3 (Ar-C), 155.2 (Ar-C), 133.0 (Ar-CH), 109.2 (Ar-CH), 106.8 (Ar-CH), 105.0 (Ar-C), 90.8 (C(3)H), 56.5 (OCH3); m/z (-ES) 191 (100%, [M-H]-).