Carbonyl-to-Alkyne Electron Donation Effects in up to 10-nm-Long, Unimolecular Oligo(p-phenylene ethynylenes)

We synthesized some of the longest unimolecular oligo(p-phenylene ethynylenes) (OPEs), which are fully substituted with electron-withdrawing ester groups. An iterative convergent/divergent (a.k.a. iterative exponential growth – IEG) strategy based on Sonogashira couplings was utilized to access these sequence-defined macromolecules with up to 16 repeating units and 32 ester substituents. The carbonyl groups of the ester substituents interact with the triple bonds of the OPEs, leading to (i) unusual, angled triple bonds with increased rotational barrier, (ii) enhanced conformational disorder, and (iii) associated broadening of the UV/Vis absorption spectrum. Our results demonstrate that fully air-stable, unimolecular OPEs with ester groups can readily be accessed with IEG chemistry, providing new macromolecular backbones with unique geometrical, conformational, and photophysical properties.

Extended Enantiopure ortho-Phenylene Ethylene (o-OPE)-based Helical Systems as Scaffolds for Supramolecular Architectures. A Study of Chiroptical Response and its Connection to the CISS effect

A novel synthetic strategy based on a bifunctional stapled chiral nucleus from which segments of different lengths can be added to both ends of o-phenylene ethynylenes (o-OPEs) has been developed...

One-Pot Transformation of Me3Si-/Ph2P(O)-Protected Ethynes to Unsymmetrical Arylethynes

Me3Si-/Ph2P(O)-protected ethynes were successfully transformed to unsymmetrical arylethynes via a one-pot Ph2P(O)-deprotection/ [Pd(dppf)Cl2]-catalysed coupling and one-pot Me3Si-deprotection/Sonogashira coupling under mild conditions and in high yield. Unsymmetrical phenylethynes, unsymmetrical extended phenylene ethynylenes and unsymmetrical anthrylethynes were successfully synthesised in good to excellent yields.