Cobalt-catalyzed annulation of styrenes with α-bromoacetic acids

We report a method for addition of α-bromophenylacetic acids to vinyl C&z.dbd;C bonds in styrenes to afford γ-lactones. Reactions employed a simple cobalt catalyst Co(NO 3 ) 2 ·6H 2 O in the presence of dipivaloylmethane (dpm) ligand. Many functionalities including halogen, ester, and nitro groups were compatible with reaction conditions. If α-bromoesters were used, vinylacetates were the major products. Cobalt-catalyzed addition of α-bromoacetic acids/acetates to C&z.dbd;C bonds in styrenes is reported for the first time. Good tolerance of functional groups was observed.