[F:1][C:2]([F:15])([F:14])[C:3]1[C:8]([C:9]([F:12])([F:11])[F:10])=[CH:7]O[C:5](=O)[CH:4]=1.[C:16]1(=[O:23])C=[CH:20][C:19](=[O:22])[CH:18]=[CH:17]1>ClC1C=CC=CC=1Cl.C(Cl)(Cl)Cl.O=[Mn]=O>[F:1][C:2]([F:15])([F:14])[C:3]1[CH:4]=[C:5]2[C:20](=[CH:7][C:8]=1[C:9]([F:12])([F:11])[F:10])[C:19](=[O:22])[CH:18]=[CH:17][C:16]2=[O:23]23.47 g (0.1011 mol) of 4,5-bis-trifluoromethyl-2-oxo-2H-pyran, 54.62 g (0.5053 mol) of 1,4-benzoquinone and 26.30 g (0.3026 mol) of MnO2 in 225 ml of 1,2-dichlorobenzene are heated at 180° C. for 12 hours. The reaction mixture is then diluted with 200 ml of CHCl3 and filtered through Hyflo®. After the chloroform has been removed by distillation, the distillation residue is chromatographed over a column packed with 1300 g of SiO2 (mobile phase: first cyclohexane and then CHCl3 ; 0.3 bar excess pressure). Yield 17.94 g (60.3%), melting point: 91°-94° C.
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