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Abstract
The Cu-catalyzed azide-alkyne cycloaddition (CuAAC) reaction is used as a ligation tool throughout chemical and biological sciences. Despite the pervasiveness of CuAAC, there is a need to develop more efficient methods to form 1,4-triazole ligated products with low loadings of Cu. In this paper, we disclose a mechanistic model for the ynamine-azide (3 + 2) cycloadditions catalyzed by copper(II) acetate. Using multinuclear nuclear magnetic resonance spectroscopy, electron paramagnetic resonance spectroscopy, and high-performance liquid chromatography analyses, a dual catalytic cycle is identified. First, the formation of a diyne species via Glaser-Hay coupling of a terminal ynamine forms a Cu(I) species competent to catalyze an ynamine-azide (3 + 2) cycloaddition. Second, the benzimidazole unit of the ynamine structure has multiple roles: assisting C-H activation, Cu coordination, and the formation of a postreaction resting state Cu complex after completion of the (3 + 2) cycloaddition. Finally, reactivation of the Cu resting state complex is shown by the addition of isotopically labeled ynamine and azide substrates to form a labeled 1,4-triazole product. This work provides a mechanistic basis for the use of mixed valency binuclear catalytic Cu species in conjunction with Cu-coordinating alkynes to afford superior reactivity in CuAAC reactions. Additionally, these data show how the CuAAC reaction kinetics can be modulated by changes to the alkyne substrate, which then has a predictable effect on the reaction mechanism.
Original language | English |
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Pages (from-to) | 13558-13570 |
Number of pages | 13 |
Journal | Journal of the American Chemical Society |
Volume | 146 |
Issue number | 19 |
Early online date | 7 May 2024 |
DOIs | |
Publication status | Published - 15 May 2024 |
Keywords
- multinuclear NMR spectroscopy
- benzimidazole
- copper (Cu)
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Dive into the research topics of 'Mechanistic basis of the Cu(OAc)2 catalyzed azide-ynamine (3+2)cycloaddition reaction'. Together they form a unique fingerprint.Activities
- 2 Invited talk
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Mechanism inspired ynamine modification of biomolecules
Glenn Burley (Speaker)
9 Jun 2024 → 14 Jun 2024Activity: Talk or presentation types › Invited talk
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Invited speaker - School of Chemistry
Glenn Burley (Speaker)
8 May 2024Activity: Talk or presentation types › Invited talk