[Br:1][C:2]1[CH:14]=[CH:13][C:12]2[C:11]3[C:6](=[CH:7][CH:8]=[CH:9][CH:10]=3)[CH2:5][C:4]=2[CH:3]=1.S(=O)(=O)(O)O.O.O.[I:22](O)(=O)(=O)=O.S([O-])(O)=O.[Na+]>O.C(O)(=O)C>[Br:1][C:2]1[CH:14]=[CH:13][C:12]2[C:11]3[C:6](=[CH:7][C:8]([I:22])=[CH:9][CH:10]=3)[CH2:5][C:4]=2[CH:3]=1
A mixture of 2-bromofluorene (compound 19) (25.0 g, 0.1020 mol), glacial acetic acid (250 cm3), concentrated sulphuric acid (3 cm3) and water (20 cm3) became homogeneous on heating to 75° C. Periodic acid dihydrate (H5IO6, 4.56 g, 0.0200 mol) and pulverised 12 (10.2 g, 0.0402 mol) were added. The initial deep-purple colour changed to a brown during 2 h of heating and stirring at 75° C. Upon dilution with sodium hydrogensulphite (2.50 g) in water (25 cm3), the colour changed to yellow. The solution was subsequently diluted with water (500 cm3) and cooled to 0° C. to give a yellow precipitate. The excess liquid was decanted and the solid filtered off, washed repeatedly with cold ethanol (4×50 cm3), aqueous NaOH (5% solution, 4×50 cm3) and with water (4×50 cm3) to leave a yellow powder. The product was recrystallised from a solvent mixture of DCM and ethanol to yield a yellow powder (28.4 g, 74.9%). Melting point/° C.: 185.
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