Solution Self-Assembly of Branched Macromolecules Obtained via Iterative OPE Synthesis and the Passerini Three-Component Reaction

In the last decade, isocyanide-based multicomponent reactions, like the Passerini three-component reaction (P-3CR), have gained significant interest in the synthesis of sequence-defined macromolecules due to their high efficiency and straightforward one-pot procedures. The P-3CR results in unique product structures that are particularly interesting for the synthesis of uniform, branched macromolecules, as they enable the direct introduction of a new branching point into the molecule. In this work, the synthesis of uniform first-generation dendrons is performed via the P-3CR using a divergent approach, utilizing three uniform and poorly soluble oligo(phenylene ethynylene)s (OPEs) of varying lengths as a focal moiety. Self-assembly of the dendrons in cyclohexane solution is confirmed by fluorescence spectroscopy and diffusion-ordered NMR (DOSY NMR) spectroscopy, highlighting the utility of DOSY NMR spectroscopy for the investigation of solution self-assembly. Diffusion coefficients for the dendrons and their aggregates are determined and compared for different lengths of the OPE focal moiety. The successful synthesis of the dendrons in good yields and the selective branching introduced on the OPEs by the P-3CR emphasize the high efficiency and synthetic advantages of multicomponent reactions for the preparation of uniform, branched macromolecules.