Halogen-Induced Friedel-Crafts Alkenylation Reactions with Haloalkynes: Direct Access to gem-1, 1-Dihaloalkenes

A simple and efficient tactic for the synthesis of gem-hetero- or homo-dihaloalkenes is reported from haloalkynes where Friedel-Crafts alkenylation is a key step. The method provides functionalized tetrasubstituted alkenes which are important precursors in organic synthesis. The strategy is further extended with intramolecular Friedel-Crafts alkenylation on-aryl alkynes to produce annulated arene carbocycles in a simple manner.