Expedient Synthesis of Dihaloalkenynes via Pd-Catalyzed Haloalkynylation Reaction.

Herein, the Pd II -catalyzed construction of functionalized dihaloalkenynes from haloalkynes via a self-haloalkynylation reaction, without specialized ligands or oxidizing additives, is reported. The method tolerates a diverse range of haloalkynes, including electron-donating and electron-withdrawing functional groups, such as macrocyclic alkynols, spiro-oxy ring alkynols, and even carbazole-containing, pyrrolidine-2,5-dione-containing and silyl-protected bromoalkynes. Using an opposite lithium halide (LiX) to the haloalkyne starting material, remarkably high regio- and stereoselectivity of the haloalkynylation reaction is possible, yielding 1-bromo-2-chloroalkenyne or 2-bromo-1-chloroalkenyne products as desired.