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 a-brominated alkylbenzenecarboxylic acids are formed by the in situ generated hypobromous acid. These alpha -brominated acids undergo an intramolecular nucleophilic substitution reaction to afford the corresponding gamma -lactones. (C) 2001 Published by Elsevier Science Ltd.