Trisubstituted Triptycenes: Toward the Preparation of Three-Dimensional Dendrimers

A synthesis of benzyl trisubstituted triptycenes is described. These triptycenes are precursors for producing a first generation (G1) poly(triptycylether) dendrimer, a derivative of known poly(arylether) dendrimers. The molecule necessary for the further elaboration into the eventual dendrimer is a carboxylic acid ester triptycene terminated with two ether substituents on another ring; the zero generation (G0). The synthesis begins with formation of the Diels-Alder adduct of benzoquinone and methyl 2-anthroate. This adduct is aromatized under basic conditions and the resulting anion trapped with a benzyl halide as an electrophile to form the trisubstituted triptycene. Access to the trisubstituted system is obtained through a highly improved, efficient and chromatography free preparation of anthracene derivatives, mainly methyl 2-anthroate.