Electrochemistry-enabled Rh-catalyzed regioselective [4 + 1] and [4 + 2] cycloaddition of benzoic acid with alkynyl esters/amides

A Rh(iii)-catalyzed additive-controlled regioselective [4 + 1] and [4 + 2] cyclization of benzoic acids with alkynyl esters/amides under electrochemical conditions has been developed for the synthesis of phthalides and isocoumarins. The selectivity for the product formation was attained by merely changing the additive. Employment of NaOAc in the reaction produces isocoumarins whereas AcOH favors phthalides. Cyclic voltammetry and control experiments reveal the mechanistic pathway of the reaction.