1,3,6,9,12,14,17,20-Octaethynyltetrabenz[a,b,f,j,k,o]-4,5,10,11,15,16,21,22- octadehydro[18]annulene:  A Carbon-Rich Hydrocarbon

Dodecaynes 1a−d have been prepared via a convergent strategy that employs Sonogashira couplings as the carbon−carbon bond-forming tool. Due to the steric bulk of the DMTS groups, 1c adopts a nonplanar conformation, the dynamics of which have been probed by VT-NMR. The cobalt-catalyzed isomerization of 1a,b produced the new conjugated phenylenes 2a,b and 3a,b, respectively.