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New insights into the reaction capabilities of ionic organic bases in cu-catalysed amination

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Title: New insights into the reaction capabilities of ionic organic bases in cu-catalysed amination
Authors: Lo, Q
Sale, D
Braddock, D
Davies, R
Item Type: Journal Article
Abstract: The application of ionic organic bases in the copper‐catalyzed amination reaction (Ullmann reaction) has been studied at room temperature, with sub‐mol‐% catalyst loadings, and with more challenging amines at elevated temperatures. The cation present in the base has been shown to have little effect on the reaction at standard catalyst and ancillary ligand loadings, whereas the choice of anion is crucial for good reactivity. A substrate scope carried out at room temperature with the best performing bases, TBAM and TBPM, showed both bases to be highly effective under these mild reaction conditions. Moreover, under sub‐mol % catalyst loadings and room temperature conditions, TBPM gave good to excellent yields for a number of different amines and functionalized aryl iodides (14 examples). However, reactions involving more challenging amines gave little or no yield. By using more forceful conditions (120 °C) moderate to excellent yields of cross‐coupled products containing more challenging amines was achievable using TBPM and to a lesser extent with TBAM. As part of this work a study on the stability of the organic bases at 120 °C was undertaken. TBAM is shown to decompose to give nBu3N and mono‐butylmalonate at higher temperatures, and this can be correlated to a decrease in performance in the coupling reaction. The phosphonium cations in TBPM did not undergo analogous reactivity but were shown instead to experience some degree of deprotonation at the α‐CH2 to generate phosphonium ylides. This however did not lead to a significantly degradation in the activity of the TBPM in the cross‐coupling reaction.
Issue Date: 7-Mar-2019
Date of Acceptance: 28-Jan-2019
URI: http://hdl.handle.net/10044/1/67287
DOI: https://dx.doi.org/10.1002/ejoc.201900109
ISSN: 1099-0690
Publisher: Wiley
Start Page: 1944
End Page: 1951
Journal / Book Title: European Journal of Organic Chemistry
Volume: 2019
Issue: 9
Copyright Statement: © 2019 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim. This is the accepted version of the following article, which has been published in final form at https://onlinelibrary.wiley.com/doi/full/10.1002/ejoc.201900109
Keywords: 0305 Organic Chemistry
0304 Medicinal And Biomolecular Chemistry
Organic Chemistry
Publication Status: Published
Embargo Date: 2020-02-13
Online Publication Date: 2019-02-13
Appears in Collections:Chemistry
Faculty of Natural Sciences



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