257870-28-3Relevant academic research and scientific papers
Metal-Free Phosphorus-Directed Borylation of C(sp2)?H Bonds
Bouhadir, Ghenwa,Bourissou, Didier,Hidalgo, Nereida,Le Gac, Arnaud,Mallet-Ladeira, Sonia,Miqueu, Karinne,Sadek, Omar
supporting information, (2021/11/27)
Spectacular progress has recently been achieved in transition metal-catalyzed C?H borylation of phosphines as well as directed electrophilic C?H borylation. As shown here, P-directed electrophilic borylation provides a new, straightforward, and efficient access to phosphine–boranes. It operates under metal-free conditions and leverages simple, readily available substrates. It is applicable to a broad range of backbones (naphthyl, biphenyl, N-phenylpyrrole, binaphthyl, benzyl, naphthylmethyl) and gives facile access to various substitution patterns at boron (by varying the boron electrophile or post-derivatizing the borane moiety). NMR monitoring supports the involvement of P-stabilized borenium cations as key intermediates. DFT calculations reveal the existence and stabilizing effect of π-arene/boron interactions in the (biphenyl)(i-Pr)2P→BBr2+ species.
One-Pot Synthesis of 1,3-Bis(phosphinomethyl)arene PCP/PNP Pincer Ligands and Their Nickel Complexes
Shih, Wei-Chun,Ozerov, Oleg V.
, p. 4591 - 4597 (2015/10/06)
A one-pot synthesis of arene-based PCP/PNP ligands has been developed. The reaction of 1,3-bis(bromomethyl)benzene or 2,6-bis(bromomethyl)pyridine with various chlorophosphines in acetonitrile afforded bis-phosphonium salts. These salts can then be reduced by magnesium powder to yield PCP or PNP ligands. In comparison to traditional synthetic methods for making PCP/PNP ligands involving the use of secondary phosphines, this new alternative method allows for the use of chlorophosphines, which are cheaper, safer to handle, and have a broader range of commercially available derivatives. This is especially true for the chlorophosphines with less bulky alkyl groups. Moreover, the one-pot procedure can be extended to allow for the direct synthesis of PCP/PNP nickel complexes. By using nickel powder as the reductant, the resulting nickel halide was found to directly undergo metalation with the PCP or PNP ligand to generate nickel complexes in high yields.
Orthopalladated phosphinite complexes as high-activity catalysts for the suzuki reaction
Bedford, Robin B.,Hazelwood, Samantha L. Welch,Horton, Peter N.,Hursthouse, Michael B.
, p. 4164 - 4174 (2007/10/03)
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.
