Palladium-catalyzed dimerization of conjugated diynes:: Synthesis of (E)-1,2-divinyldiethynylethenes having donor and acceptor chromophores at the terminus of alkyne

[graphics] (E)-1,2-Divinyldiethynylethenes (DVDEEs) having donor and acceptor chromophores at the terminals of alkyne unit 7' were synthesized by the palladium/HOAc-catalyzed dimerization of the conjugated diynes 8 bearing an Si group at the terminus of alkyne (R-1 position), followed by desilylation and subsequent Sonogashira reaction of the resulting terminal alkyne 10 with aryl iodides.