[F:1][C:2]1[CH:7]=[CH:6][C:5]([CH2:8][C:9]([C:11]2[CH:16]=[CH:15][C:14]([S:17]([CH3:20])(=[O:19])=[O:18])=[CH:13][CH:12]=2)=[O:10])=[CH:4][CH:3]=1>C(O)(=O)C>[F:1][C:2]1[CH:3]=[CH:4][C:5]([C:8]2[C:9](=[O:10])[CH:8]=[C:5]([CH3:4])[O:10][C:9]=2[C:11]2[CH:16]=[CH:15][C:14]([S:17]([CH3:20])(=[O:19])=[O:18])=[CH:13][CH:12]=2)=[CH:6][CH:7]=1To a solution of 2-(4-fluorophenyl)-1-(4-methanesulfonylphenyl)ethanone (1 g; 3.4 moles) in glacial acetic acid (15 ml), polyphosphoric acid (10 g) was added and then heated at 140° C. for 16 hours. After cooling, the reaction was poured into ice-water, extracted with ethyl acetate (2×50 ml), the organic solution dried (Na2SO4) and the solvent removed under reduced pressure. The residual oil was purified by column chromatography with silica gel and ethyl acetate as eluent. 3-(4-fluorophenyl)-2-(4-methanesulfonylphenyl)-6-methylpyran-4-one was obtained (0.5 g) m.p. 237° C. (Compound 2 in Table 4).
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