Synthesis of 1,4-Dichloro-1,3-butadienes by Rhodium Complex Catalyzed Reaction of Terminal Alkynes with Trichloroacetyl Chloride

Chlorinative dimerization of terminal alkynes with trichloroacetyl chloride as chlorine donor proceeds in the presence of rhodium catalysts to give (Z,Z)-1,4-dichloro-1,3-butadienes stereoselectively. Ligand screening has revealed that reactions using sterically bulky and electron-donating ligands like trimesitylphosphine are high yielding. The reaction is compatible with a range of functional groups to give the title compounds nearly quantitatively in most cases. A mechanistic possibility involving coupling of β-chloroalken-1-yl intermediate has been discussed.