Sequence-defined oligo( ortho -arylene) foldamers derived from the benzannulation of ortho (arylene ethynylene)s.

A Cu-catalyzed benzannulation reaction transforms ortho (arylene ethynylene) oligomers into ortho -arylenes. This approach circumvents iterative Suzuki cross-coupling reactions previously used to assemble hindered ortho -arylene backbones. These derivatives form helical folded structures in the solid-state and in solution, as demonstrated by X-ray crystallography and solution-state NMR analysis. DFT calculations of misfolded conformations are correlated with variable-temperature ¹ H and EXSY NMR to reveal that folding is cooperative and more favorable in halide-substituted naphthalenes. Helical ortho -arylene foldamers with specific aromatic sequences organize functional π-electron systems into arrangements ideal for ambipolar charge transport and show preliminary promise for the surface-mediated synthesis of structurally defined graphene nanoribbons.