Diels-Alder Synthesis of Trisbicyclo[2.2.1]heptabenzene

Key words

trisbicyclo[2.2.1]-heptabenzene - cyclohexatriene - Diels-Alder cycloaddition

Significance

The authors report the synthesis of a cyclohexatriene containing trisbicyclo[2.2.1]heptabenzene that does not involve highly reactive organometallic intermediates. The critical step involves a triple Diels-Alder cycloaddition between the tri-diene formed from 1,3,4,6,7,9-hexabromotrindane and dimethyl but-2-ynedioate. The desired product 3 was obtained in 32% yield. The structure of trans-3 was confirmed by X-Ray crystal structural analysis.

Comment

The cyclohexatriene motif has a lot of potential for uses in materials and supramolecular chemistry. Compounds containing this subunit have been used in the synthesis of fullerene and trindane analogues. In addition, tris(bicyclo[2.1.1]-hexeno) benzene was the first example of a mononuclear benzenoid compound with observable bond alternation (localization), causing its analogues to be of theoretical interest (J. S. Siegel Angew. Chem. Int. Ed. 1995, 34, 1454). This synthesis provides a less toxic and costly route to such compounds.