Palladium-Catalyzed Domino Cycloisomerization/Double Condensation of Acetylenic Acids with Dinucleophiles
Catalysts 12(2) : (2022) // Article ID 127
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Palladium-Catalyzed Domino Cycloisomerization/Double Condensation of Acetylenic Acids with Dinucleophiles
by Nerea Conde
, María Teresa Herrero
, Garazi Urgoitia
and Raul SanMartin
* [ORCID]
Department of Organic and Inorganic Chemistry, Faculty of Science and Technology, University of the Basque Country (UPV/EHU), 48940 Leioa, Spain
*
Author to whom correspondence should be addressed.
Academic Editors: Thomas J. J. Müller and Eelco Ruijter
Catalysts 2022, 12(2), 127; https://doi.org/10.3390/catal12020127
Received: 18 December 2021 / Revised: 13 January 2022 / Accepted: 17 January 2022 / Published: 21 January 2022
(This article belongs to the Special Issue Metal-Catalyzed Processes in One-Pot Syntheses of Heterocycles)
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Abstract
Metal-catalyzed cascade processes based on hydrofunctionalization of alkynes are receiving much more attention because of their potential to provide advantageous approaches to otherwise synthetically challenging compounds. An alternative catalyst system has been found for the domino cycloisomerization/cyclocondensation reaction involving acetylenic acids and heterodinucleophiles. A CNN pincer palladium(II) complex, acting as a homogeneous catalyst, provides the corresponding polyheterocycles with a higher substrate/catalyst ratio. Other palladium sources were also tested and discarded, and a number of mechanistic studies including poisoning assays, kinetic plots, TEM images, XRD spectra and UPLC-MS analysis of reaction intermediates were conducted in order to shed light on the role of this pincer catalyst and the catalytic cycle involved in the cascade reaction. As a result, a more nuanced mechanism is tentatively proposed.
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Bestelakorik adierazi ezean, itemaren baimena horrela deskribatzen da:2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).