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Disclosure of some obscure mechanistic aspects of the copper-catalyzed click reactions involving N2 elimination promoted by the use of electron-deficient azides from a DFT perspective

Citation

Roohzadeh, R and Nasiri, B and Chipman, A and Yates, BF and Ariafard, A, Disclosure of some obscure mechanistic aspects of the copper-catalyzed click reactions involving N2 elimination promoted by the use of electron-deficient azides from a DFT perspective, Organometallics, 38, (2) pp. 256-267. ISSN 0276-7333 (2019) [Refereed Article]

Copyright Statement

2018 American Chemical Society

DOI: doi:10.1021/acs.organomet.8b00691

Abstract

We have used density functional theory to explore the copper(I)-catalyzed reaction between a mesyl azide and a terminal alkyne that leads to a ketenimine whose interaction with nucleophilic water produces an amide. It is well reported in the literature that a cuprated triazole intermediate is formed during the course of such a catalytic cycle. In this contribution, we investigated the stability of this key intermediate by varying the R substituent on the azide and found that electron-withdrawing R substituents make this intermediate more reactive toward ring opening/N2 elimination; an electron-withdrawing R substituent facilitates this process by weakening the NN bond being cleaved. We also rationalized why the cycloaddition step in this class of click reactions is required to proceed via a binuclear mechanism. The copper(I) acetylide intermediate formed during the catalysis gains extra stability upon scavenging a second Cu complex, resulting in the cycloaddition step occurring with a lower activation barrier. We also noticed that, similar to the ring closure step, inclusion of a second Cu complex may accelerate the ring opening/N2 elimination process. It was shown that the ketenimine needs to coordinate to a copper center via its nitrogen atom in order to be activated toward hydrolysis.

Item Details

Item Type:Refereed Article
Keywords:density functional theory, activation energy, click reactions, electron-deficient azides
Research Division:Chemical Sciences
Research Group:Organic Chemistry
Research Field:Physical Organic Chemistry
Objective Division:Expanding Knowledge
Objective Group:Expanding Knowledge
Objective Field:Expanding Knowledge in the Chemical Sciences
UTAS Author:Chipman, A (Mr Antony Chipman)
UTAS Author:Yates, BF (Professor Brian Yates)
UTAS Author:Ariafard, A (Associate Professor Alireza Ariafard)
ID Code:134447
Year Published:2019
Funding Support:Australian Research Council (DP180100904)
Web of Science® Times Cited:1
Deposited By:Chemistry
Deposited On:2019-08-13
Last Modified:2019-12-09
Downloads:0

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