The heteronuclear multiple bond correlation NMR spectrum (400 MHz, CDCl3) of dimer 4 with the corresponding 1D ¹H NMR and ¹³C NMR traces exhibited ten acetylene carbon resonances, a duplication of the propargyl methylene proton resonances that coupled with four and six acetylene carbons, respectively, as well as two new olefin carbon resonances that coupled only with the propargyl methylene protons on the ‘shorter’ side of the molecule. The inset is a magnified view of the region of the acetylene cross-peaks. For a more detailed discussion, see the Supplementary Information.