257870-28-3Relevant articles and documents
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.
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.
