Extending the chemistry of [5,5,5,5]fenestranes - Eightfold peripheral functionalization of fenestrindanes

Directed multiple functionalization of tetrabenzo[5.5.5.5]-fenestranes (fenestrindanes) at the molecular arene periphery has been achieved for the first time, starting from the fourfold bridgehead-methylated congener 2. In particular, 2,3,6,7,10,11,14,15-octabromofenestrindane (3) and 2,3,6,7,10,11,14,15-octaiodofenestrindane (7) have been synthesized as key intermediates in excellent yields. Further eight-fold functionalized analogs, such as the corresponding octa(n-butyl) thioether 5 and the octacyanofenestrindane 8, are now accessible as well as other fenestrane hydrocarbons with an extended carbon framework, including the octakis-(phenylethynyl) and the octaphenyl derivatives 6 and 9, respectively. The S-4-symmetrical conformation of these fenestranes is evident from their H-1 and C-13 NMR spectra. It is suggested that, owing to their uniquely curved convex/concave molecular shape, fenestrindanes with eightfold peripheral functionalization could serve as unusual motifs for liquid crystal engineering and dendrimer chemistry, and for the construction of graphite cuttings bearing a saddle-like, three-dimensionally distorted core.