Synthesis, Structure, and Isomerization of Decapentynylcorannulene: Enediyne Cyclization/Interconversion of C₄₀R₁₀ Isomers

Decapentynylcorannulene (5) is prepared via aryl−alkyne coupling chemistry of decachlorocorannulene and trimethylstannylpentyne. The crystal structure of 5 is compared with the ab initio computed structure of decaethynylcorannulene (3). The relative structure and energetics of 3 and its carbon nanotube isomer C40H10 (2) are discussed. Per-alkynyl-polynuclear aromatic hydrocarbons, such as 3, constitute a high energy form of carbon-rich compounds. During the synthesis of 3, enediyne cyclization forms the diradical, which ring-opens to the biscumulenyl [10]annulene (6). Discovery of this process supports the idea that derivatives of 2 could result from corresponding derivatives of 3 through electrocyclic mechanisms and demonstrates a new carbon skeletal rearrangement for strained polynuclear aromatic networks. Derivatives of 3, like 5, warrant further investigation to find viable precursors for monodispersed single-walled carbon-based nanotubes.