Effective Synthesis of Ethynylanthracene Derivatives and Their Applications to Oligomer Synthesis

Abstract

Effective synthesis of ethynylanthracene derivatives as novel π-conjugated compounds and their applications to the synthesis of anthracene-acetylene oligomers are described. Ethynyl groups were introduced into anthracene moieties by cross-coupling reactions (Kumada-Tamao and Sonogashira couplings), addition-aromatization reactions, or double-elimination reactions from suitable starting materials. In some cases, the reaction integration techniques such as one-pot or one-shot processes were useful to simplify the experimental procedures. Diacetylene derivatives were synthesized by oxidative coupling of terminal alkynes or Sonogashira coupling. The desilylation and silylation of ethynylanthracene derivatives under appropriate conditions are important processes on preparation of unsymmetrical building units. Thus prepared building units were accumulated by Sonogashira coupling or oxidative coupling to synthesize cyclic oligomers ranging from trimers to dodecamers as well as 9,10-bis(phenylethynyl)anthracene oligomers. Each oligomer shows characteristic structural, stereochemical, and electronic properties depending on the number of anthracene units, the mode of connections, and the shape of anthracene units. Enantiomers of some chiral cyclic oligomers were successfully resolved by chiral HPLC.