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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 N–N 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 Type:	Article
Authors/Creators:	Roohzadeh, R and Nasiri, B and Chipman, A and Yates, BF and Ariafard, A
Keywords:	density functional theory, activation energy, click reactions, electron-deficient azides
Journal or Publication Title:	Organometallics
Publisher:	Amer Chemical Soc
ISSN:	0276-7333
DOI / ID Number:	10.1021/acs.organomet.8b00691
Copyright Information:	© 2018 American Chemical Society
Related URLs:	Google Scholar: Yates, BF UTAS Profile: Yates, BF Google Scholar: Ariafard, A UTAS Profile: Ariafard, A
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