Friedel-crafts alkylation of aromatic compounds with optically active 2-(mesyloxy)propionates. Synthesis of the optically active anti-inflammatory agent (S)-2-(4-iosbutylphenyl)propionic acid

Alkylation of benzene, toluene and isobutylbenzene with (S)-2-mesyloxypropanoate substrates 2a-g in the presence of aluminium chloride, affords the corresponding (S)-methyl-2-phenylpropionates in good chemical yields under ultrasound mediated conditions. This method leads to the synthesis of (S)-brufen in 50% yield within 2 hours at 40 degrees C compared with only 17% under conventional conditions when isobutylbenzene was treated with 2b, thus leading to a significant improvement in selectivity for (S)-ibuprofen (40% to 59%).