Medium-sized carbocycles by samarium diiodide-induced carbonyl-alkene cyclizations.

Intramolecular samarium diiodide-induced carbonyl-alkene or carbonyl-alkyne coupling reactions afforded without high dilution conditions 9- and 10-membered benzannulated carbocycles of type II and III in surprisingly good yields and stereoselectivities. A novel samarium diiodide-mediated cascade process leading to tricyclic compounds of type IV was also observed. Bisbenzannulated 10- and 11-membered carbocycles were prepared in very good yields.