Iodocarbocyclization reaction of beta-ketoesters and alkynes.

Iodocyclopentenes are formed at room temperature upon straight reaction of delta-alkynyl-beta-ketoesters with I2 for several hours. Cyclizations involving terminal and substituted (alkyl, aryl, Br, I) alkynes were accessed. Twelve examples with yields ranging from 20% up to 80% are reported (out of them eight cases are above 60%). These results present the first examples of the iodonium-promoted 5-endo-dig carbocyclization of active methyne substrates onto alkynes.