Toward Nanoamphiphiles: Efficient Synthesis of Desymmetrized Polyphenylene Dendrimers

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Abstract
A new synthetic approach for the desymmetrization of polyphenylene dendrimers (PPDs) is described. Tetrakis(4-ethynylphenyl)methane undergoes facile Diels−Alder cycloaddition with substoichiometric quantities of tetraphenylcyclopentadienones bearing one polar functional group. A single ethynyl group is thereby converted to a rigid, selectively functionalized polyphenylene moiety, which serves as a focal point for further transformations or interfacial anchoring. This is the key feature for the design of desymmetrized monodisperse macromolecules with a spherical shape. The remaining unreacted ethynyl groups provide a trifold core for the stepwise elaboration of first- and second-generation polyphenylene dendrons, which may, in turn, bear specific numbers of different peripheral functional groups at their terminae. Moreover, the resulting macromolecules exhibit the characteristic shape-persistence and monodispersity of PPDs. This approach is an important achievement in nanosciences, especially for tailoring new nanoamphiphiles. It is also of synthetic importance, as it enables the separation of two regioisomeric polyphenylene dendrimers for the first time.