Approach to extended polycyclic aromatic hydrocarbons by benzannulation and intramolecular cyclization; improvement of the reaction conditions by microwave irradiation

The extended π-conjugated compounds 1 – 8 were synthesized by the benzannulation of the corresponding alkyne derivatives followed by Pd-catalyzed intramolecular cyclization . For the Pd-catalyzed intramolecular cyclization, microwave irradiation reduced the amount of the Pd catalyst and the reaction time. Moreover, this protocol can be achieved to prepare the extended and twisted π-conjugated molecule 19 , having anthracene , helicene , and picene skeletons. • Synthesis of extended PHAs in a short step by benzannulation and intramolecular cyclization. • Improvement of reaction conditions of Pd-catalyzed C–H arylation by microwave irradiation . • Reaction mechanism of Pd-catalyzed C–H arylation depending on the substrate. • Applicable to extended and twisted π-conjugated molecule.