Beyond Triphenylene

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Science  16 Jul 2004:
Vol. 305, Issue 5682, pp. 311
DOI: 10.1126/science.305.5682.311c

The aromatic molecule triphenylene, (C6H4)3, in which three six-carbon-atom rings fuse to form a common fourth ring, has been known for more than a century. Triphenylene can be described as a member of the triannulenylenes, which result from the fusion of three conjugated rings, each containing a triple bond that forms part of the central fusion ring (triphenylene itself forms from benzyne). However, until recently, triphenylene would have been the only member of this family reported. Kiesewetter et al. have now synthesized the next larger symmetric member of the family, tri-[8]annulenylene. The reaction under high vacuum of C8H7Br with potassium-tert-butoxide and subsequent reduction with potassium metal appears to occur in a stepwise fashion, and thus the [8]annulyne generated attacks the C8H7Br.− radical anion to form a dimer and then finally the trimer. Electron paramagnetic resonance (EPR) analysis shows that the reaction actually goes beyond completion to the radical anion [(C8H6)3.−]. Quenching with I2 in pentane and subsequent distillation allows enough of the fragile, antiaromatic neutral (C8H6)3 species to be isolated so that its nuclear magnetic resonance spectrum can be taken. — PDS

J. Am. Chem. Soc. 10.1021/ja049020h (2004).

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