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The organic photocatalyst (9-mesityl-10-methylacridinum tetrafluoroborate) in the presence of visible light is used to initiate thiol–ene and thiol–yne reactions. Thiyl radicals are generated upon quenching the photoexcited catalyst with a range of thiols. The highlighted mild nature of the reaction conditions allows a broad substrate scope of the reactants. Relying on this efficient metal-free condition, both thiol–ene and thiol–yne reactions between carbohydrates and peptides could be realized in excellent yields.
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Effects of Thiol Substitution on the Kinetics and Efficiency of Thiol-Michael Reactions and Polymerizations
- Award ID(s):
- 1808484
- PAR ID:
- 10300055
- Date Published:
- Journal Name:
- Macromolecules
- Volume:
- 54
- Issue:
- 7
- ISSN:
- 0024-9297
- Page Range / eLocation ID:
- 3093 to 3100
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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null (Ed.)The acid-catalyzed thiol–ene reaction (ACT) is a unique thiol–X conjugation strategy that produces S,X-acetal conjugates. Unlike the well-known radical-mediated thiol–ene and anion-mediated thiol-Michael reactions that produce static thioether bonds, acetals provide unique function for various fields such as drug delivery and protecting group chemistries; however, this reaction is relatively underutilized for creating new and unique materials owing to the unexplored reactivity over a broad set of substrates and potential side reactions. Solution-phase studies using a range of thiol and alkene substrates were conducted to evaluate the ACT reaction as a conjugation strategy. Substrates that efficiently undergo cationic polymerizations, such as those containing vinyl functional groups, were found to be highly reactive to thiols in the presence of catalytic amounts of acid. Additionally, sequential initiation of three separate thiol–X reactions (thiol-Michael, ACT, and thiol–ene) was achieved in a one-pot scheme simply by the addition of the appropriate catalyst demonstrating substrate selectivity. Furthermore, photoinitiation of the ACT reaction was achieved for the first time under 470 nm blue light using a novel photochromic photoacid. Finally, using multifunctional monomers, solid-state polymer networks were formed using the ACT reaction producing acetal crosslinks. The presence of S,X-acetal bonds results in an increased glass transition temperature of 20 °C as compared with the same polymeric film polymerized through the radical thiol–ene mechanism. This investigation demonstrates the broad impact of the ACT reaction and expands upon the diverse thiol–X library of conjugation strategies towards the development of novel materials systems.more » « less
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Abstract Arylthioamides have been frequently employed to assess the chemical biology and pharmacology of hydrogen sulfide (H2S). From this class of donors, however, extremely low H2S releasing efficiencies have been reported and proper mechanistic studies have been omitted. Consequently, millimolar concentrations of arylthioamides are required to liberate just trace amounts of H2S, and via an unidentified mechanistic pathway, which obfuscates the interpretation of any biological activity that stems from their use. Herein, we report that H2S release from this valuable class of donors can be markedly enhanced through intramolecular nucleophilic assistance. Specifically, we demonstrate that both disulfide‐ and diselenide‐linked thioamides are responsive to biologically relevant concentrations of glutathione and release two molar equivalents of H2S via an intramolecular cyclization that significantly augments their rate and efficiency of sulfide delivery in both buffer and live human cells.more » « less
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1021/acs.macromol.0c02677
