Acetylenic Homocoupling Methodology Towards the Synthesis of 1,3‐Butadiynyl Macrocycles: [142]‐Alleno‐Acetylenic Cyclophanes

[142]-Alleno-acetylenic cyclophanes were synthesized through two different approaches: an intermolecular coupling between two alkynyl fragments, and an intramolecular ring-closure of a linear acyclic bisalkynyl oligomer. The symmetry of the target dictates the choice of the most suitable method. To illustrate these approaches we have used 1,3-diethynyl-substituted allenes as building blocks. Due to the stereogenic character of the allene moiety, the alleno-acetylenic cyclophanes were obtained as a mixture of diastereoisomers, and the major twist isomers were resolved by preparative HPLC. The different symmetry of the isomers allowed the assignment of the relative configuration of the major twist isomers by taking into consideration the number of nonequivalent groups in the respective NMR spectra.