Synthesis of [6.8]3cyclacene: conjugated belt and model for an unusual type of carbon nanotube.

[6.8]3Cyclacene as the first hydrocarbon being a fully conjugated molecular belt has been synthesized in an eight-step reaction sequence starting from 4,6-dimethylisophthalaldehyde. It is the smallest and most strained member of the [6.8]cyclacene family, and the synthetic path offers a general route to its higher members. The structural pattern of [6.8]3cyclacene represents a model for a novel type of carbon nanotubes.