[7]Helicene to a Planar Hetero[8]Circulene Bodil Lousen,[A] Stephan K
Communication Chemistry—A European Journal doi.org/10.1002/chem.201905339 & Non-Planar Aromatics Compressing aNon-Planar Aromatic Heterocyclic [7]Helicene to a Planar Hetero[8]Circulene Bodil Lousen,[a] Stephan K. Pedersen,[a] Pernille Bols,[a] Kasper H. Hansen,[a] MichelleR.Pedersen,[a] Ole Hammerich,[a] Sergey Bondarchuk,[b] Boris Minaev,[b] Glib V. Baryshnikov,[c] Hans gren,[c, d] and MichaelPittelkow*[a] cally chiral moleculeshave found vast applications in such di- Abstract: This work describes asyntheticapproachwhere verse fields as molecular recognition,catalysis anddetection or anon-planar aromatic heterocyclic [7]helicene is com- emissionofcircularlypolarized light.[2–5] Structurally related pressedtoyield ahetero[8]circulene containing an inner motifstothe [n]helicenes are the [n]circulenes. These struc- antiaromatic cyclooctatetraene (COT) core. This [8]circu- tures also consist of ortho-annulatedaromatic rings, but in- lene consists of four benzene rings and four heterocyclic stead forms acyclic structure, having acentral ring with n rings, and it is the first heterocyclic[8]circulenecontaining sides.Itisillustrative to view the all-benzene series of [n]circu- three differentheteroatoms. The synthetic pathway pro- lenes,which consistsofthe bowl-shaped carba[5]circulene ceeds via athe flattened dehydro-hetero[7]helicene, (corannulene), the planar carba[6]circulene(coronene) andthe which is partially ahelicene and partially acirculene:itis saddle-shaped[7]- and [8]circulenes. Hetero[8]circulenes incor- non-planar and helically chiral as helicenes, and contains a poratingfour five-membered heterocycles(furans,pyrroles, COT motif like [8]circulenes. The antiaromaticity of the thiophenes)are planar,[6,7] and these structures can be viewed COT core is confirmed by nucleusindependent chemical as containingantiaromaticcyclooctatetraene(COT) cores.
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