- Orthopalladated phosphinite complexes as high-activity catalysts for the suzuki reaction
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The synthesis of a range of phosphinite ligands PR2(OAr) (R = Ph, iPr), their simple complexes with palladium(II) and their palladacyclic complexes has been investigated. The crystal structure of one of the palladacyclic complexes, [{Pd(μ2-Cl)} {κ2-P, C-PiPr2(OC6H2-2,4-t Bu2)} 2], has been determined. The palladacyclic complexes show extremely high activity in the Suzuki coupling of aryl bromide substrates with phenylboronic acid and can also be used with alkylboronic acid substrates. A comparison of the phosphinite-based catalysts with equivalent phosphite- and phosphine-based systems highlights their superior activity. The orthometallation of the phosphinite ligand in the pre-catalyst appears to be crucial for optimal activity. While the phosphinite palladacycles are only moderately active in the coupling of activated and non-activated aryl chloride substrates, their tricyclohexylphosphine adducts prove to be highly active in the coupling of the deactivated substrate, 4-chloroanisole. This high activity compared with other palladacyclic systems is explained in terms of catalyst longevity. The orthometallated precatalysts appear to undergo a reductive activation process to generate zerovalent active catalysts via reductive elimination of the orthometallated ring with a phenyl introduced by the boronic acid. This implies that the true active catalysts contain 2-arylated ligands. Catalysts formed with such 2-arylated ligands tend to show markedly higher activity than their parent ligands.
- Bedford, Robin B.,Hazelwood, Samantha L. Welch,Horton, Peter N.,Hursthouse, Michael B.
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p. 4164 - 4174
(2007/10/03)
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- Palladacyclic phosphinite complexes as extremely high activity catalysts in the Suzuki reaction
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Phosphinite based palladacycles show extremely high activity in the Suzuki coupling of both sterically hindered and electronically deactivated aryl bromides, especially in the presence of one equivalent of free ligand.
- Bedford,Welch
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p. 129 - 130
(2007/10/03)
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- P/O ligand systems: Synthesis, reactivity, structure of tertiary o-phosphanylphenol derivatives
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Reactions of C,O-dilithium reagents 1 (M = M′ = Li) or C,O-lithium-sodium reagents 1 (M = Li, M′ = Na) with chlorophosphanes afford C,O-disubstitution products 2 or phosphanylphenolates 3 which are treated subsequently with ClSiMe3 to give 4-me
- Heinicke, Joachim,Kadyrov, Renat,Kindermann, Markus K.,Koesling, Manuela,Jones, Peter G.
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p. 1547 - 1560
(2007/10/03)
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