Synthesis of Coumarins via Palladium-Catalyzed Carbonylative Annulation of Internal Alkynes by o-Iodophenols

A variety of substituted coumarins have been prepared in good yields by the palladium-catalyzed coupling of o-iodophenols with internal alkynes and 1 atm of carbon monoxide. Unlike most of the previous work on the palladium-catalyzed carbonylation of alkynes, the insertion of the internal alkyne occurs in preference to the insertion of CO.