Synthesis of chiral sequence-defined oligomers via sulfur–fluoride and sulfur–phenolate exchange reactions

Abstract

Sequence-defined oligomers have been synthesized with increasing complexity, but the participation of chiral centres in the oligomerization process remains challenging. Here we report the synthesis of sequence-defined oligosulfonimidates (up to thirteen-mers) obtained via a series of sulfur–fluoride exchange and sulfur–phenolate exchange reactions. Next, we demonstrate that the use of chiral sulfonimidoyl fluorides allows the construction of chiral oligomers, in which the chirality of each linking S-centred site can be tuned independently of the rest of the molecule, thereby opening a way to a potentially vast increase in the information density of such oligomers. Finally, by activating a dormant fluorous tag used for the separation of oligomers, a tail-to-head-type sulfur–phenolate exchange polymerization strategy was developed using these oligomers, resulting in sequence-controlled polymers. The high variability of sulfonimidates and the chiral control provided to macromolecules through this technique results in another step towards full control over nature-mimicking polymers. Precise control over both sequence and chirality remains a challenge in polymer chemistry. Here sulfur–fluoride exchange and sulfur–phenolate exchange reactions are used to create chiral oligosulfonimidates with tunable sulfur-centred chirality. This strategy enables precise three-dimensional structural control over oligomers and polymers, marking a step towards fully nature-mimicking macromolecules.

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