Palladium‐Catalyzed Asymmetric Reductive Heck Reaction of Aryl Halides

Asymmetric reductive Heck reaction of aryl halides is realized in high stereoselectivity. Hydrogen‐bond donors, trialkylammonium salts in a glycol solvent, were used to promote halide dissociation from neutral arylpalladium complexes to access cationic, stereoselective pathways.     

Polyaniline‐Induced CH Arylation of Arenes with Arenediazonium Salts

A reduced form of polyaniline has been shown to induce direct arylation of an arenediazonium salt with an arene (Gomberg–Bachmann reaction) to give the cross‐coupling product in moderate to good yields under mild conditions. Various arenediazonium salts and arenes, including heteroarenes such as furans, thiophenes, and pyrroles, are employed for the reaction. The most favorable combination of substrates is an electron‐poor arenediazonium salt with an electron‐rich heteroarene. Investigation of the mechanism by reactions with radical scavengers and experiments on kinetic isotope effects indicated the occurrence of a radical chain reaction initiated by one‐electron reduction of an arenediazonium salt by the polyaniline. Only 1 mol % (based on aniline tetramer) of the polyaniline is required for the cross‐coupling reaction to occur. This reaction proceeds under metal‐free conditions and with no need for photonic activation.     

Communication: a new hybrid exchange correlation functional for band-gap calculations using a short-range Gaussian attenuation (Gaussian-Perdue-Burke-Ernzerhof)

We have developed a new hybrid functional [Gaussian-Perdue-Burke-Ernzerhof (Gau-PBE)] that is suitable for the calculation of solid state bandgaps using a periodic boundary condition. The characteristic of this functional is the use of a Gaussian attenuation scheme (Gau) to include a short-range Hartree-Fock (HF) exchange. This new functional can perform barrier height calculations with an accuracy comparable to the middle-range hybrid functional and bandgap calculations with an accuracy comparable to the Heyd-Scuseria-Ernzerhof (HSE) functional. However, the point is that the performance can be achieved using a Gaussian HF exchange, while the HISS functional calculates twice HF-exchange integrations using an error function to obtain both performances. In addition, Gau-PBE functional can decrease the time cost of bandgap calculations by an average of 40% compared to the HSE functional.     

Comparative reactivity of ferric-superoxo and ferryl-oxo species in heme and non-heme complexes

Ferryl-oxo species have been recognized as a key oxidant in many heme and non-heme enzymes. Recently, less-characterized ferric-superoxo species have been found or suggested to be another electrophilic oxidant. Reactivity of several vital ferryl-oxo and ferric-superoxo model complexes was examined by DFT calculations. Reactivity is found to correlate well with thermodynamic driving force and can increase with higher electrophilicity of the oxidant. Reactivity of the ferric-superoxo oxidants generally is not "superior" to the ferryl-oxo ones. Compared to the high-spin non-heme ferric-superoxo, the lower reactivity of low-spin heme ferric-superoxo, seldom utilized in nature, can be attributed to lower electrophilicity and more pronounced quenching of anti-ferromagnetic coupling between the ferric and superoxo parts. The present comparison should shed some light on mechanistic strategies in heme and non-heme enzymes and provide clues to rational design of ferric-superoxo oxidants.     

Self-assembling properties of (arylimido)vanadium(V) compounds

(Imido)vanadium(V) complexes have attracted much attention because of their potential applications as catalysts. Compared with oxo ligands, imido ligands can possess a substituent on the imido nitrogen so that the steric and electronic characters of the metal center are considered to be controlled by the properties of the nitrogen substituent. In such a sense, the design of the imido ligands is envisioned to be one of the key factors in the development of efficient catalysts. Furthermore, architectural control of transition metal-directed assembly to create organized nanostructures is of importance for advanced materials. This review highlights self-assembling properties of (arylimido)vanadium(V) compounds.     

Synthesis of oxosumanenes through benzylic oxidation

Oxosumanenes were synthesized through benzylic oxidation. The electronic and redox properties were revealed to exhibit the expanded π-conjugation compared to sumanene. Single-crystal X-ray analysis of monooxosumanene showed columnar π-stacking in a concave-convex fashion. Stereoselective trimethylation of the trioxo derivative was performed via 1,2-addition to the carbonyl groups.     

An examination of density functionals on aldol, Mannich and ��-aminoxylation reaction enthalpy calculations

The reaction enthalpies of aldol, Mannich and ??-aminoxylation reactions were calculated by density functional theory (DFT) using long-range-corrected (LC), hybrid B3LYP and other up-to-date functionals to show why conventional DFT including B3LYP has given poor enthalpies for these reactions. As a result, we found that long-range exchange interactions significantly affect the reaction enthalpies. We therefore proposed that the poor enthalpies of B3LYP are due to its insufficient long-range exchange effect. On the other hand, LC functionals accurately reproduce reaction enthalpies for these reactions. However, we noticed that even LC functionals present poor reaction enthalpies for specific reactions, in which many branches are produced or very small molecules such as methane molecule participate.     

Novel enhancement of the reducing ability of ytterbium diiodide by irradiation with near-UV light

Irradiation with near-UV light, dramatically enhances the reducing ability of ytterbium diiodide (YbI₂). Organic bromides, iodides, tosylates, and tellurides are reduced efficiently by a YbI₂-hv system, while these can not be reduced with YbI₂ in the dark.     

Determination of peptide φ angles in solids by relayed anisotropy correlation NMR

A solid state NMR method is presented for determination of a backbone dihedral angle φ in peptides, being based on the previously reported method, relayed anisotropy correlation (RACO) NMR [Y. Ishii et al., Chem. Phys. Lett. 256 (1996) 133]. In the present method, the and the dipolar tensors in the system are two-dimensionally (2D) correlated via polarization transfer from to under magic angle spinning (MAS). This method was applied to N-acetyl , -valine, and the H–C–N–H dihedral angle was determined to be 154.0±1.4° or 206.0±1.4°, the former agreeing with the X-ray value of 154±5°.