Cyclophanes. Part LII: Ethynyl[2.2]paracyclophanes - New building blocks for molecular scaffolding

The synthesis of seven ethynyl[2.2]paracyclophanes is described. The five diethynyl derivatives 4,5-diethynyl[2.2]paracyclophane (12), pseudo-gem- (13), pseudo-ortho- (14), pseudo-meta- (15), and pseudo-para-diethynyl[2.2]paracyclophane (16), the tetraethynyl compound 4,7,13,16-tetraethynyl[2.2]paracyclophane (17). and for comparison the mono-ethynylated hydrocarbon 4-ethynyl[2.2]paracyclophane (11) have been prepared. The structures of these new building blocks for carbon rich systems were determined by the usual analytical and spectroscopic methods.