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Shedding light on the use of Cu(ii)-salen complexes in the A3 coupling reaction

Shedding light on the use of Cu(ii)-salen complexes in the A3 coupling reaction

Sampani, Stavroula I., Zdorichenko, Victor, Danopoulou, Marianna, Leech, Matthew C., Lam, Kevin ORCID: 0000-0003-1481-9212, Abdul-Sada, Alaa, Cox, Brian, Tizzard, Graham J., Coles, Simon J., Tsipis, Athanassios and Kostakis, George E. (2019) Shedding light on the use of Cu(ii)-salen complexes in the A3 coupling reaction. Dalton Transactions, 2020:49. pp. 289-299. ISSN 1477-9226 (Print), 1477-9234 (Online) (doi:https://doi.org/10.1039/C9DT04146J)

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Abstract

One Cu(II) complex, {Cu(II)L} (1S), has been synthesised, in two high yielding steps under ambient conditions, and characterised by single-crystal X-Ray diffraction (SXRD), IR, UV-Vis, circular dichroism (CD), elemental analysis, thermogravimetric analysis (TGA) and electron spray ionization mass spectroscopy (ESI-MS). This air-stable compound enables the generation, at room temperature and in open-air, of twenty propargylamines, nine new, from secondary amines, aliphatic aldehydes and alkynes with a broad scope with yields up to 99%. Catalyst loadings can be as low as 1 mol%, while the recovered material retains its structural integrity and can be used up to 5 times without loss of its activity. Control experiments, SXRD, cyclic voltammetry and theoretical studies shed light on the mechanism revealing that the key to success is the use of phenoxido salen based ligands. These ligands orchestrate topological control permitting alkyne binding with concomitant activation of the C–H bond and simultaneously acting as a template temporarily accommodating the abstracted acetylenic proton, and continuously generating, via in situ formed radicals and a Single Electron Transfer (SET) mechanism, a transient Cu(I) active site to facilitate this transformation. The scope and limitations of this protocol are discussed and presented.

Item Type: Article
Uncontrolled Keywords: Electrochemistry, catalysis, copper
Subjects: Q Science > Q Science (General)
Q Science > QC Physics
Q Science > QD Chemistry
Faculty / Department / Research Group: Faculty of Engineering & Science
Faculty of Engineering & Science > School of Science (SCI)
Last Modified: 09 Jan 2020 10:18
Selected for GREAT 2016: None
Selected for GREAT 2017: None
Selected for GREAT 2018: None
Selected for GREAT 2019: None
URI: http://gala.gre.ac.uk/id/eprint/26459

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