Short Synthesis of [10]Paracyclophanes from Strained [10]Paracyclopha-4,6-diynes Obtained via a Double Negishi...

[10]Paracyclophanes and their nitrogen-containing analogs were synthesized in three steps via the hydrogenation of cyclopha-4,6-diynes prepared from para-dibromoarenes using a double Negishi coupling followed by an intramolecular Glaser cyclization. X-ray crystallographic analyses of the parent cyclophadiynes, pyridinophadiynes, and pyrazinophadiynes revealed that the distance between the aromatic ring and diyne moiety decreased with increasing nitrogen content of the aromatic ring. These observations were corroborated by the results of quantum chemical calculations performed on several hypothetical molecules, demonstrating that electronic effects are more important than steric factors for determining the distance between the aromatic rings and diyne moieties in cyclopha-4,6-diynes.