Intermediates Stabilized by Tris(triazolylmethyl)amines in the CuAAC Reaction.
Chemistry
; 23(19): 4730-4735, 2017 Apr 03.
Article
em En
| MEDLINE
| ID: mdl-28191741
ABSTRACT
Tris(triazolylmethyl)amine ligands (TL) are widely used to accelerate the CuI -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-CuI3 -acetylide and the dinuclear TL-CuI2 -acetylide complexes in aqueous solution. The apparent second-order rate constants of their reaction with an azide were 27 and 783 m-1 â
s-1 when the alkyne was tethered to TL. In the catalytic system without the tether, the rate constant increased to >146 m-1 â
s-1 for the TL-CuI3 -acetylide, but dropped about 14-fold to approximately 55 m-1 â
s-1 for the TL-CuI2 -acetylide. The results indicated that TL accelerated the reaction by stabilizing the CuI2 - and CuI3 -acetylide and their azide-adduct intermediates, but this role is largely weakened by excess alkyne and other competing ligands under catalytic conditions.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Idioma:
En
Revista:
Chemistry
Ano de publicação:
2017
Tipo de documento:
Article