[F:1][C:2]1[C:3]([OH:11])=[C:4]([C:8](=[O:10])[CH3:9])[CH:5]=[CH:6][CH:7]=1.[C:12](OCC)(=[O:18])[C:13]([O:15][CH2:16]C)=[O:14].[O-]CC.[Na+]>C(O)C>[F:1][C:2]1[C:3]([OH:11])=[C:4]([C:8]([C:9]2[CH2:16][O:15][C:13](=[O:14])[C:12]=2[OH:18])=[O:10])[CH:5]=[CH:6][CH:7]=1A solution of 1-(3-fluoro-2-hydroxyphenyl)ethanone (30 g) and diethyl oxalate (31 g) in ethanol (600 mls) was added dropwise to sodium ethoxide (from 9.85 g of sodium) in ethanol (600 mls) and the mixture was stirred and heated at reflux for 2 days. After the mixture had cooled, it was diluted with 60-80 petrol and the solid was collected and dried. A suspension of the product in water (1.2 l) was stirred with formaldehyde (24 mls of 37%) for 1.5 hours. The solid was filtered out, the filtrate was washed with ether, and traces of ether were removed by evaporation under vacuum. The aqueous solution was acidified to pH 3, the precipitate was collected, washed with water and recrystallised from acetone/water to give the title compound as yellow needles (18.7 g). M.p. 194°-208°.
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