Reactivity of Arynes for Arene Dearomatization.

An unprecedented aryne-mediated dearomatization reaction is described. An aryne intermediate generated from arenesulfonyl ynamide-tethered triynes and tetraynes reacts with both the π-systems of a tethered alkene and the arenesulfonyl group to generate cyclohexa-1,3-diene-containing pentacyclic and hexacyclic frameworks. Density functional theory (DFT) calculations show a nucleophilic dearomatization mechanism involving a zwitterionic intermediate derived from an aryne. A novel halogen effect on the efficiency of the dearomatization and deterrence of aromatization of the cyclohexa-1,3-diene moiety was also observed.