Synthesis of coumarins via palladium-catalyzed carbonylative annulation of internal alkynes by o-iodophenols

[GRAPHICS] 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.