Several compounds containing multiple phenylethynyl substituents were prepared and polymerized to thermosets through the acetylenic units. Pyrolysis of the polymers afforded high carbon yields. The acetylenic-based compounds were synthesized from the palladium-catalysed coupling reaction of phenylacetylene with multiple-brominated benzenes. Inconsistencies were observed in the reaction yields with time, which were attributed to poisoning of the palladium. A procedure was developed for the activation of palladium using magnesium. The activated palladium gave consistent high yield of cross-coupled products.