[C:1]([C:4]1[CH:9]=[CH:8][C:7]([B:10]([OH:12])[OH:11])=[CH:6][C:5]=1[F:13])(=[O:3])[CH3:2].C(O)(=O)C.[Br:18]Br>CO>[Br:18][CH2:2][C:1]([C:4]1[CH:9]=[CH:8][C:7]([B:10]([OH:12])[OH:11])=[CH:6][C:5]=1[F:13])=[O:3]An oven-dried, 500-milliliter, 3-necked, round-bottomed flask was charged with 5 grams (27.4 millimole) of 4-acetyl-3-fluorophenyl boronic acid and 25 milliliters of methanol under a nitrogen atmosphere. The solution was cooled to 0° C. using an ice bath. To this solution was added 0.2 milliliters (0.55 equivalents) of glacial acetic acid. In a 100 milliliters Erlenmeyer flask was taken 1.27 milliliters (3.95 grams, 24 millimole, 0.9 equivalents) of elemental bromine dissolved in 4 milliliters of cold methanol. The bromine solution was added dropwise to the above solution at 0° C. using an addition funnel. With the addition of Br2, the solution slowly turned light orange and finally to dark orange when addition was complete. After about 5-6 hours, the progress of the reaction was monitored by NMR. Depending on the progress of reaction, another 10-20 mole % of bromine was added after cooling the solution to 0° C. Total reaction time was approximately 24 hours.
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