Synthesis of Shape-Persistent Meta-Arylene-butadiynylene Macrocycles with a Different Ring Size

A series of meta-phenylene-butadiynylene macrocycles was obtained by homocoupling of terminal bis(ethynyl) precursors using Eglinton conditions. Cyclotetramers and cyclopentamers were isolated from the mixture. However, a hexameric analogue was synthesized using a step-by-step approach. Molecular structures of the resulting macrocycles obtained by X-ray single-crystal analysis manifest conformational diversity, indicating significant flexibility of the meta-arylene-butadiynylene macrocycle conjugated skeleton.