Synthesis of Tribenzo[a,c,e]cyclooctene Oligomers: Toward Negatively Curved Nanocarbons.

Tribenzo[a,c,e]cyclooctene oligomers, which are potential precursors for synthesis of negatively curved nanographenes and nanobelts, have been designed and synthesized. The key to this synthesis is connecting 1,3-di(4-t-butylphenyl)-dibenzo[e,i]-2H-cyclopentacycloocten-2-one, dibenzo[3,4 : 7,8]cycloocta[1,2-c : 5,6-c']difuran and the Sondheimer-Wong diyne through Diels-Alder reactions. As revealed by X-ray crystallography, the trimer with a C8 -C6 -C8 -C6 -C8 backbone is shaped like a letter C in the crystalline state.