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

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]-).