A general and efficient copper(I)-catalyzed cross-coupling and heterocyclization reaction of terminal alkynes and b-iodo-a,b-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 regioand stereoselectivity. This procedure does not require the use of any expensive supplementary additives, and is palladium-free.

Ring-expansion of strained small-size rings to forge larger all-carbon ones, allows a rapid build-up of molecular complexity.