Intermediates Stabilized by Tris(triazolylmethyl)amines in the CuAAC Reaction.

Autor: Chen H; Department of Chemistry, University of Houston, 3585 Cullen Blvd., Houston, Texas, 77204-5003, USA., Cai C; Department of Chemistry, University of Houston, 3585 Cullen Blvd., Houston, Texas, 77204-5003, USA., Li S; Department of Chemistry, University of Houston, 3585 Cullen Blvd., Houston, Texas, 77204-5003, USA., Ma Y; Department of Pharmacological and Pharmaceutical Sciences, University of Houston, 1441 Moursund St., Houston, Texas, 77030, USA., Luozhong S; Department of Chemical Engineering, Tsinghua University, Beijing, 100084, P. R. China., Zhu Z; Department of Chemistry, University of Houston, 3585 Cullen Blvd., Houston, Texas, 77204-5003, USA.
Jazyk: angličtina
Zdroj: Chemistry (Weinheim an der Bergstrasse, Germany) [Chemistry] 2017 Apr 03; Vol. 23 (19), pp. 4730-4735. Date of Electronic Publication: 2017 Mar 15.
DOI: 10.1002/chem.201700555
Abstrakt: Tris(triazolylmethyl)amine ligands (TL) are widely used to accelerate the Cu I -catalyzed azide-alkyne cycloaddition (CuAAC) reaction, but its mechanistic role remains unclear. Using electrospray ionization mass spectrometry, we detected for the first time the trinuclear TL-Cu I 3 -acetylide and the dinuclear TL-Cu I 2 -acetylide complexes in aqueous solution. The apparent second-order rate constants of their reaction with an azide were 27 and 783 m -1 ⋅s -1 when the alkyne was tethered to TL. In the catalytic system without the tether, the rate constant increased to >146 m -1 ⋅s -1 for the TL-Cu I 3 -acetylide, but dropped about 14-fold to approximately 55 m -1 ⋅s -1 for the TL-Cu I 2 -acetylide. The results indicated that TL accelerated the reaction by stabilizing the Cu I 2 - and Cu I 3 -acetylide and their azide-adduct intermediates, but this role is largely weakened by excess alkyne and other competing ligands under catalytic conditions.
(© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)
Databáze: MEDLINE
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