A Phenyl-Ethynyl-Macrocycle: A Model Compound for "Geländer" Oligomers Comprising Reactive Conjugated Banisters

Macrocycle 1 is assembled as smallest member of a series of “Geländer” oligomers with a conjugated banister comprising exclusively sp2‐ and sp‐hybridized carbon atoms. The synthesis of 1 is based on an acetylene scaffolding approach, comprising Sonogashira cross‐coupling reactions in combination with protection group strategies and a final cyclization based on an oxidative acetylene coupling using Eglinton‐Breslow reaction conditions. Macrocycle 1 serves as model compound for the investigation of the structural integrity of the strained 1,3‐diyne subunit. An enhanced reactivity of the strained 1,3‐diyne subunit is documented by its engagement in Huisgen's (2+3) cycloaddition when exposed to an azide at elevated temperature. Both structures, macrocycle 1 and cycloaddition‐product 2, are fully characterized including their solid‐state structure obtained by X‐ray diffraction analysis.