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The Quest for the Ideal Base: Rational Design of a Nickel Precatalyst Enables Mild, Homogeneous C–N Cross-Coupling
Name
Manuscript_Final.pdf
Description
Submitted version
Size
4.26 MB
Format
Adobe PDF
Checksum (MD5)
4e1fc8688583a53e1b6ae30d6c1db12f
Author(s)
Liu, Richard Y
Dennis, Joseph M
Buchwald, Stephen L
Journal
Journal of the American Chemical Society
Publisher
American Chemical Society (ACS)
Version
Original manuscript
Abstract
© 2020 American Chemical Society. Palladium-catalyzed amination reactions using soluble organic bases have provided a solution to the many issues associated with heterogeneous reaction conditions. Still, homogeneous C-N cross-coupling approaches cannot yet employ bases as weak and economical as trialkylamines. Furthermore, organic base-mediated methods have not been developed for Ni(0/II) catalysis, despite some advantages of such systems over those employing Pd-based catalysts. We designed a new air-stable and easily prepared Ni(II) precatalyst bearing an electron-deficient bidentate phosphine ligand that enables the cross-coupling of aryl triflates with aryl amines using triethylamine (TEA) as base. The method is tolerant of sterically congested coupling partners, as well as those bearing base- and nucleophile-sensitive functional groups. With the aid of density functional theory (DFT) calculations, we determined that the electron-deficient auxiliary ligands decrease both the pKa of the Ni-bound amine and the barrier to reductive elimination from the resultant Ni(II)-amido complex. Moreover, we determined that the preclusion of Lewis acid-base complexation between the Ni catalyst and the base, due to steric factors, is important for avoiding catalyst inhibition.
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Creative Commons Attribution-Noncommercial-Share Alike
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DOI of Published Version
10.1021/JACS.0C00286
