Synthesis of Sumanene

Key words

sumanene - fullerene fragment - bowl-shaped compounds

Significance

As model compounds of fullerenes as well as possible synthetic intermediates for artificially designed fullerene derivatives, bowl-shaped π-conjugated compounds become important. A key partial C _3v -symmetric structure of fullerenes, sumanene, is synthesized in this paper. Sumanene has advantages that allow it to undergo further functionalization to create new bowl-shaped molecules. The authors report a synthetic method that enables access to sumanene under mild conditions in a short series of steps that start from commercially available norbornadiene.

Comment

In this paper, the authors present an efficient strategy to synthesize sumanene. Instead of starting from the planar compounds, the authors constructed the three-dimensional framework by using tetrahedral sp³ carbon units. Two procedures were tried to achieve the trimerization of norbornadiene, and the stepwise transmetalation via an organotin compound increased the overall yield of syn-2 from 2% to 11%. In contrast to the other well-studied bowl-shaped compound corannulene, sumanene is shown to be very rigid and the bowl-to-bowl inversion only occurs at high temperature.