A Novel Strained Undecadiyne Cyclophane with Interesting Dienophilic Character

[reaction: see text] Copper-mediated oxidative coupling of 3 afforded the strained product 4 from intramolecular cyclization rather than the triply bridged cyclophane 5 from dimerization. X-ray analysis of the bromo derivative 15 confirmed the distorted nature of the butadiyne bridge (bond angles 164.1 degrees and 153.4 degrees). The distortion in the strained triple bond is reflected in its cycloaddition reactivity. Cyclopentadiene and 1,3-cyclohexandiene afforded the new adduct macrocycles 16 and 17, respectively.