REMOVAL OF THE ORTHO ISOMER OF 4,4-BIS(4-FLUORO PHENYL) BUTANOIC ACID BY SULFONATION

4,4-Bis(4-fluorophenyl) butanoic acid is an important pharmaceutical intermediate. It is usually prepared by Friedel-Crafts reaction of 4-(4-fluorophenyl) butyrolactone with fluorobenzene. But the ratio of products is often affected by reaction conditions. By applying sulfonation, the undesired isomer can be successfully removed.