Copper-catalyzed preparation of g-alkylidenebutenolides and isocoumarins under mild palladium-free conditions

A general and efficient copper(I)-catalyzed cross-coupling and heterocyclization reaction of terminal alkynes and ?-iodo-a,?- unsaturated acid derivatives has been developed under very mild conditions. This method provides easy access from good to excellent yields of a variety of 5-ylidenebutenolides and 3-substituted isocoumarins with excellent regio- and stereoselectivity. This procedure does not require the use of any expensive supplementary additives, and is palladium-free.