Temperature-dependent interconversion of phosphoramidite-Cu complexes detected by combined diffusion studies, 31P NMR, and low-temperature NMR spectroscopy

Journal of the American Chemical Society
Katrin SchoberRuth M Gschwind

Abstract

For copper-catalyzed enantioselective conjugate additions, knowledge about the precatalytic and catalytic complexes has not yet been sufficiently developed to understand the strong influence of different temperatures on these famous reactions. Therefore, NMR experiments with four Cu(I) salts and two phosphoramidite ligands have been performed to elucidate the temperature dependence and the low-temperature structures of these copper complexes. The existence of the precatalytic binuclear complex with a mixed trigonal/tetrahedral coordination on copper is for the first time proven with direct NMR spectroscopic methods. Below 200 K, intermolecular interactions between free ligands and [Cu2X2L3] complexes induce binuclear [Cu2X2L4] complexes similar to the crystal structures. By combining diffusion experiments and (31)P integrals at different temperatures, it is for the first time possible to follow the formation of stoichiometrically different complexes, even under experimental conditions in which the (31)P signals of the complexes are spectroscopically not resolved due to exchange processes. This allows a first correlation between the complex species observed and the synthetic conditions reported. Furthermore, different preference...Continue Reading

Citations

Apr 16, 2015·Dalton Transactions : an International Journal of Inorganic Chemistry·Geetika GuptaSubrato Bhattacharya
Apr 23, 2009·Magnetic Resonance in Chemistry : MRC·Hongxia ZhangRuth M Gschwind
Mar 25, 2010·Angewandte Chemie·Johannes F Teichert, Ben L Feringa
Apr 9, 2010·Chemistry : a European Journal·Akinobu MatsuzawaMasakatsu Shibasaki
Oct 26, 2011·Dalton Transactions : an International Journal of Inorganic Chemistry·Suryabhan SinghSubrato Bhattacharya
Nov 28, 2012·Angewandte Chemie·Naoya Kumagai, Masakatsu Shibasaki
Aug 12, 2015·Angewandte Chemie·J Philipp Wagner, Peter R Schreiner
Nov 18, 2021·Dalton Transactions : an International Journal of Inorganic Chemistry·Daven FosterReto Dorta

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