An improved method for the synthesis of γ-lactones using sodium bromate and sodium hydrogen sulfite

o-Alkylbenzenecarboxylic acids are treated with a sodium bromate and sodium hydrogen sulfite reagent under a two-phase system using ethyl acetate as solvent, under mild conditions to give the corresponding cyclized phthalides in moderate to satisfactory yield. Intermediately the α-brominated alkylbenzenecarboxylic acids are formed by the in situ generated hypobromous acid. These α-brominated acids undergo an intramolecular nucleophilic substitution reaction to afford the corresponding γ-lactones.