Stereoselective synthesis of (E)-chloroenynes or (E,E)-chlorodienes starting from a stereoisomeric mixture of 1,2-dichloroethylenes

Under palladium or nickel catalysis, a stereomeric mixture 1:1 of (Z) and (E)-1,2-dichloroethylene readily reacts with 1-alkynes, vinyl alanes or vinyl boranes to afford selectively the corresponding (E)-coupling product in good to excellent isolated yields. The selectivity of this coupling reaction is discussed.