Issue 14, 2018

Understanding the mechanism and regioselectivity of the copper(i) catalyzed [3 + 2] cycloaddition reaction between azide and alkyne: a systematic DFT study

Abstract

The copper(I) catalyzed azide–alkyne [3 + 2] cycloaddition (32CA) reaction and its uncatalyzed version have been studied for systematic understanding of this relevant organic transformation, using DFT calculations at the B3LYP/6-31G(d) (LANL2DZ for Cu) computational levels. In the absence of a copper(I) catalyst, two regioisomeric reaction paths were studied, indicating that the 32CA reaction takes place through an asynchronous one-step mechanism with a very low polar character. The two reactive channels leading to 1,4- and 1,5-regisomer present similar high activation energies of 18.84 and 18.51 kcal mol−1, respectively. The coordination of copper(I) to alkyne produces relevant changes in this 32CA reaction. Analysis of the global and local electrophilicity/nucleophilicity allows explaining correctly the behaviors of the copper(I) catalyzed cycloaddition. Coordination of the copper to alkyne changes the mechanism from a non-polar one-step mechanism to a polar stepwise one, as a consequence of the high nucleophilic character of the dinuclear Cu(I)-acetylide complex. Parr and Fukui functions and Dual Descriptor correctly explain the observed regioselectivity by means of the most favorable two-center interaction that takes place along the 1,4 reaction path.

Graphical abstract: Understanding the mechanism and regioselectivity of the copper(i) catalyzed [3 + 2] cycloaddition reaction between azide and alkyne: a systematic DFT study

Supplementary files

Article information

Article type
Paper
Submitted
26 Sept. 2017
Accepted
31 Janv. 2018
First published
16 Febr. 2018
This article is Open Access
Creative Commons BY license

RSC Adv., 2018,8, 7670-7678

Understanding the mechanism and regioselectivity of the copper(I) catalyzed [3 + 2] cycloaddition reaction between azide and alkyne: a systematic DFT study

H. Ben El Ayouchia, L. Bahsis, H. Anane, L. R. Domingo and S. Stiriba, RSC Adv., 2018, 8, 7670 DOI: 10.1039/C7RA10653J

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