[OH:1][C:2]1[CH:9]=[CH:8][C:5]([CH:6]=[O:7])=[CH:4][C:3]=1[O:10][CH3:11].C([O-])([O-])=O.[K+].[K+].[C:18]([O:21][CH2:22][CH2:23]Br)(=[O:20])[CH3:19]>CC(C)=O.C(OCC)C>[C:18]([O:21][CH2:22][CH2:23][O:1][C:2]1[CH:9]=[CH:8][C:5]([CH:6]=[O:7])=[CH:4][C:3]=1[O:10][CH3:11])(=[O:20])[CH3:19]A mixture of 4-hydroxy-3-methoxy-benzaldehyde (2.5 g, 16.4 mmol), K2CO3 (6.81 g, 49.3 mmol) and 2-bromoethyl acetate (5.49 g, 32.9 mmol) in acetone (50 mL) is refluxed for 48 h before it is diluted with diethyl ether (250 mL) and washed with water (2×200 mL). The washings are extracted with diethyl ether (200 mL). The combined organic extracts are dried over MgSO4 and concentrated. The remaining residue is purified by column chromatography on silica gel eluting with heptane/EA 1:1 to afford the title compound (2.94 g) as colourless solid. 1H NMR (CDCl3): δ 9.85 (s, 1H), 7.45-7.41 (m, 2H), 6.99 (d, J=7.6 Hz, 1H), 4.51-4.47 (m, 2H), 4.34-4.30 (m, 2H), 3.94 (s, 3H), 2.11 (s, 3H).
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