A differentially protected diboron bearing the naphthalene-1,8-diaminato group on one of the two boron atoms undergoes highly regioselective diboration with terminal alkynes in the presence of Pt or ...Ir catalysts, giving 1-alkene-1,2-diboronic acid derivatives in which the less reactive B(dan) group is located at the terminal position. The products undergo selective Suzuki−Miyaura coupling with aryl bromides at the internal boronyl group, leading to the formation of 2,2-disubstituted alkenylboronic acid derivatives.
Helical chirality of poly(quinoxaline-2,3-diyl)s bearing a boronyl pendant at the 5-position of the quinoxaline ring was induced by condensation with chiral guests such as a diol, diamine, and ...amino alcohol. Reversible induction of a single-handed helical structure was achieved by using less than an equimolar amount of chiral amino alcohols to the boronyl pendants. Majority-rule-effect-based chiral amplification on the polyquinoxaline main chain was demonstrated with chiral amino alcohols with low enantiomeric excess (ee). The helical macromolecular scaffold whose helicity was thus induced was utilized in palladium-catalyzed asymmetric silaboration of meso-methylenecyclopropane (up to 92% ee) by introducing (diarylphosphino)phenyl pendants at their side chains.
Taking a new turn: An asymmetric Suzuki–Miyaura coupling of 1‐bromo‐2‐naphthalenephosphonic esters with o‐methyl‐substituted phenylboronic acids proceeds with high enantioselectivity in the presence ...of high‐molecular‐weight helically chiral polyquinoxaline‐based phosphines (PQXphos) bearing pendant diarylphosphino groups.
o-C−H silylation of arylboronic acids has been achieved using 2-pyrazol-5-ylaniline as an ortho-directing agent, which was temporarily attached to the boronyl group via Ru-catalyzed silylation with ...hydrosilanes. Condensation products of arylboronic acids with 2-pyrazol-5-ylaniline were prepared in situ and subjected to reaction with triorganosilanes in the presence of RuH2(CO)(PPh3)3 at 135 °C. Regioselective silylation at their ortho-positions proceeded in good yields for phenylboronic acids bearing para-substituents such as chloro, fluoro, methyl, methoxy, and trifluoromethyl groups. p-Methoxycarbonyl-substituted phenylboronic acid provided the corresponding silylated product in moderate yield. m-Tolyl- and 2-naphthylboronic acids underwent silylation selectively at the less sterically hindered ortho-positions. The silylated products were utilized in Suzuki−Miyaura coupling, followed either by iodination with ICl or by Tamao oxidation to furnish iodine- or hydroxy-substituted biaryls.
A polyquinoxaline-based helical polymer ligand bearing both helical-sense-determining chiral side chains and coordinating diarylphosphino side chains exhibits solvent-dependent formation of P- or ...M-helical structures, with which either the S- or R-hydrosilylation product was obtained with high (>93% enantiomeric excess) enantioselectivities.
Pyrazolylaniline serves as a temporary directing group attached to the boron atom of alkylboronic acids in Ir-catalyzed C(sp3)–H borylation. The reaction takes place at α-, β-, and γ-C–H bonds, ...giving polyborylated products including di-, tri-, tetra-, and even pentaborylalkanes. α-C–H borylation was generally found to be the preferred reaction of primary alkylboronic acid derivatives, whereas β- or γ-borylation also occurred if β- or γ-C–H bonds were located on the methyl group.
Pyridine undergoes addition of pinacolborane at 50 °C in the presence of a rhodium catalyst, giving N-boryl-1,2-dihydropyridine in a high yield. The selective 1,2-hydroboration also takes place in ...the reactions of substituted pyridines. In the reaction of 3-substituted pyridines, 3-substituted N-boryl-1,2-dihydropyridines are formed regioselectively.
Post‐polymerization CH activation of poly(quinoxaline‐2,3‐diyl)‐based helically chiral phosphine ligands (PQXphos) with palladium(II) acetate afforded chiral phosphapalladacycles quantitatively. In ...situ generated palladacycles exhibited enantioselectivities up to 94 % ee in the palladium‐catalyzed asymmetric ring‐opening arylation of 1,4‐epoxy‐1,4‐dihydronaphthalenes with arylboronic acids.
Polymers with a twist: Poly(quinoxaline‐2,3‐diyl)‐based helically chiral phosphine ligands (PQXphos) have been used to generate chiral phosphapalladacycles. The palladacycles resulted in enantioselectivities of up to 94 % ee in the palladium‐catalyzed asymmetric ring‐opening arylation of 1,4‐epoxy‐1,4‐dihydronaphthalenes with arylboronic acids.
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