Palladium-Catalyzed Dimerization of Conjugated Diynes: Synthesis of (E)-1,2-Divinyldiethynylethenes Having Donor and Acceptor Chromophores at the Terminus of Alkyne

(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.