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Investigation of Base-free Copper-Catalysed Azide–Alkyne Click Cycloadditions (CuAAc) in Natural Deep Eutectic Solvents as Green and Catalytic Reaction Media

preprint
revised on 01.04.2021, 17:08 and posted on 02.04.2021, 07:44 by Salvatore V. Giofrè, Matteo Tiecco, Angelo Ferlazzo, Roberto Romeo, Gianluca Ciancaleoni, Raimondo Germani, Daniela Iannazzo

The click cycloaddition reaction of azides and alkynes affording 1,2,3-triazoles is a widely used and effective chemical transformation, applied to obtain relevant products in medicine, biology and materials science. In this work, a set of Natural Deep Eutectic Solvents (NADESs) as green and “active” reaction media, has been investigated in the copper-catalysed azide–alkyne cycloaddition reactions (CuAAc). The use of these innovative solvents has shown to improve the reaction effectiveness, giving excellent yields. NADESs proved to be “active” in these transformations for the absence of added bases in all the performed reactions and in several cases, for their reducing capabilities. The reactions outcomes were rationalized by DFT calculations which demonstrated the involvement of H-bonds between DESs and alkynes as well as a stabilization of copper catalytic intermediates. The green experimental conditions, namely the absence of a base, the low temperatures, the lowering of reagents and the possibility of recycling of the green solvents, outline the great potential of NADESs for CuAAc and in general, for green organic synthesis.

History

Email Address of Submitting Author

matteotiecco@gmail.com

Institution

Università di Perugia

Country

Italy

ORCID For Submitting Author

0000-0002-1867-421X

Declaration of Conflict of Interest

There are no conflicts to declare.

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