Kentaro Okano

Alloying with other metals is an effective strategy for enhancing the catalytic performance of intrinsically low-activity, non-precious metals. Liquid-phase reduction is a powerful method for synthesizing well-defined metal alloy nanoparticles with narrow size distributions and controlled structures; however, combining non-precious metals with early-transition metals remains largely unexplored due to their significantly different chemical properties. Herein, we report the development of a well-defined Ni–W nanoalloy (nano-NiW) by using a liquid-phase reduction method and its application as a heterogeneous catalyst for the hydrogenation of nitriles to secondary amines. The nano-NiW catalyst exhibited higher activity compared with monometallic Ni and conventionally impregnated Ni–W catalysts, enabling the selective nitrile hydrogenation to secondary amines even at 0.1 MPa H2. The catalyst also showed a broad substrate scope and could be recycled without loss of activity. Comprehensive structural and kinetic analyses revealed that incorporation of W into nano-NiW facilitates Schiff base reduction, a key step in the catalytic cycle. Overall, this study substantially advances the performance of Ni-based catalysts and offers a promising strategy for more efficient and economical organic synthesis.

A series of quantum mechanical calculations and kinetic analysis was conducted on enantioinversion processes involving multiple chiral elements, with a particular focus on winding vine-shaped biaryls (bithiophene with/without methyl substituent and biphenyl types) exhibiting molecular asymmetry in both axial and planar chiralities. The inversions of the chiral elements were shown to take place in a stepwise manner, whereas the experimental racemization behavior appeared kinetically synchronized. Conformational analysis of the vine-shaped bithiophene revealed eight possible conformers for the pair of enantiomers using the CONFLEX method. Quantum mechanics calculations were carried out at the B3LYP/6-31G(d)//B3LYP/6-31G(d), B3LYP/6-311G++(d,p)+GD3//B3LYP/6-31G(d), MP2/cc-pVDZ//MP2/cc-pVDZ, and MP2/cc-pVTZ//MP2/cc-pVDZ levels of theory. Calculations at the B3LYP/6-31G(d) level were primarily used to search for each pathway, revealing that enantioinversion proceeded via three distinct steps. The first conformational transition leading to the second intermediate was calculated to occur with an activation energy of Δ E = 49.2 kJ/mol, without the inversion of chirality. Subsequently, an inversion of axial chirality was observed with a value of ΔE = 106.5 kJ/mol. This was followed by the final inversion of planar chirality, which also exhibited a value of Δ E = 70.3 kJ/mol. It was also established that the enantioinversion of the related biphenyl occurred in a manner analogous to that previously observed, whereas the inversion barrier of the axial chirality was found to be considerably higher (Δ E = 217.9 kJ/mol). The analytical solutions of the rate of racemization and pathway contributions under the quasi-equilibrium approximation were derived, which assumes rapid equilibration of low-barrier conformational changes while treating the kinetics of axial chirality inversion explicitly. DFT studies were conducted also on the enantioinversion of the vine-shaped bithiophene bearing a methyl substituent at the alkenyl moiety. This was because experimental evidence had shown that this process had hardly occurred. The DFT studies revealed that a much higher barrier existed at the initial inversion (Δ E = 205.9 kJ/mol). Conversely, a high barrier has not been identified in the calculation of the second transition state, where the dihedral angle of the axial chirality is estimated to be 0°.

A series of quantum mechanical calculations and kinetic analysis was conducted on enantioinversion processes involving multiple chiral elements, with a particular focus on winding vine-shaped biaryls (bithiophene with/without methyl substituent and biphenyl types) exhibiting molecular asymmetry in both axial and planar chiralities. The inversions of the chiral elements were shown to take place in a stepwise manner, whereas the experimental racemization behavior appeared kinetically synchronized. Conformational analysis of the vine-shaped bithiophene revealed eight possible conformers for the pair of enantiomers using the CONFLEX method. Quantum mechanics calculations were carried out at the B3LYP/6-31G(d)//B3LYP/6-31G(d), B3LYP/6-311G++(d,p)+GD3//B3LYP/6-31G(d), MP2/cc-pVDZ//MP2/cc-pVDZ, and MP2/cc-pVTZ//MP2/cc-pVDZ levels of theory. Calculations at the B3LYP/6-31G(d) level were primarily used to search for each pathway, revealing that enantioinversion proceeded via three distinct steps. The first conformational transition leading to the second intermediate was calculated to occur with an activation energy of Δ E = 49.2 kJ/mol, without the inversion of chirality. Subsequently, an inversion of axial chirality was observed with a value of ΔE = 106.5 kJ/mol. This was followed by the final inversion of planar chirality, which also exhibited a value of Δ E = 70.3 kJ/mol. It was also established that the enantioinversion of the related biphenyl occurred in a manner analogous to that previously observed, whereas the inversion barrier of the axial chirality was found to be considerably higher (Δ E = 217.9 kJ/mol). The analytical solutions of the rate of racemization and pathway contributions under the quasi-equilibrium approximation were derived, which assumes rapid equilibration of low-barrier conformational changes while treating the kinetics of axial chirality inversion explicitly. DFT studies were conducted also on the enantioinversion of the vine-shaped bithiophene bearing a methyl substituent at the alkenyl moiety. This was because experimental evidence had shown that this process had hardly occurred. The DFT studies revealed that a much higher barrier existed at the initial inversion (Δ E = 205.9 kJ/mol). Conversely, a high barrier has not been identified in the calculation of the second transition state, where the dihedral angle of the axial chirality is estimated to be 0°.

Borylative functionalization of the C–F bond of aryl fluorides occurs under mild conditions with ⁱ PrOBpin and sodium dispersion (SD).

Winding vine-shaped biphenyl derivatives with molecular asymmetry were employed for the linker moiety of the macrocyclic triangular gold complex. The vine-shaped biphenyl bearing boronic acid at the 4,4'-position of biphenyl was prepared and subjected to the reaction of dinuclear gold complex [Au2Cl2(dcpm)] (dcpm: dicyclohexylphosphinomethane) affording the macrocyclic triangular complex composed of six gold atoms and three vine-shaped biphenyl linkers. A larger macrocycle was also synthesized using the vine-shaped biphenyl composed of four benzene rings (quaterphenyl) through the reaction of [Au2Cl2(dcpm)] in a similar manner.

A method for the C-2-selective deprotonative functionalization of halopyridines and other heteroarenes is described. The heteroaryllithium species generated by kinetic deprotonation is trapped by a zinc chloride diamine complex to form the heteroarylzinc species at room temperature. In this transformation, thermodynamically favorable competing reactions, including intermolecular proton transfer, halogen dance, and aryne formation, are suppressed. The resulting organozinc species were treated with electrophiles to afford the corresponding products in 44%-96% yields.

Borylative functionlization of aryl fluoride was perfomed by a transition metal-free process with sodium dispersion (SD). The reaction of 4-fluorobiphenyl with SD in the prsence of boron alkoxide (iPrOBpin) afforded the borylated product in up to 62% yield. The borylation reaction also proceeded with several aryl fluorides in good to excellent yields.

Poly(ethylenedioxythiophene) (PEDOT) bearing oligosiloxane moiety at the side chain was synthesized by oxidative polymerization. The formation of the thin film was also carried out with FeIII oxidant on the substrate. Alternatively, the thin-film formation was performed by electrolytic polymerization on the electrode. The obtained thin films exhibited electric conductivities up to 101 Scm–1 and thermal stabilities up to 300 °C. Introduction.

Side chains, which was soluble in organic solvent, was carroed out via nickel-catalyzed cross-coupling polymerization. The synthesis of monomer EDOT (ethylenedioxythiophene) derivative was performed by the condensation of ene-diol derived from 3-allyoxy-1,2-propanediol with 3,4-dimethoxypropane followed by dibromination of the thiophene ring and hydrosilylation of the ene moiety. Treatment of the dibromo-EDOT monomer thus obtained with a Grignard reagent and following addition of nickel catalyst composed of N-heteroaromatic carbene as a ligand underwent the polymerization to afford the corresponding polymer PEDOT. The introduction of siloxane moieties at the side chain significantly improved solubility in organic solvents and thus allowed to show a high electric conductivity (up to 10³ Scm–1) upon doping, particularly with NOPF₆.