A novel montmorillonite-enwrapped scandium as a heterogeneous catalyst for Michael reaction

Treatment of a Na+-exchanged montmorillonite with an aqueous Sc(OTf)3 solution afforded a robust Sc3+ aqua complex enwrapped by the silicate layers of the montmorillonites (Sc3+-mont). The resulting Sc3+-mont showed outstanding catalytic activities for the Michael reaction of 1,3-dicarbonyls under aqueous and solvent-free conditions. Moreover, this heterogeneous catalyst had an advantage of a strikingly simple workup procedure over the Lewis acids reported to date and was reusable without any appreciable losses in its activity and selectivity.     

Structural and thermodynamic behavior of eukaryotic initiation factor 4E in supramolecular formation with 4E-binding protein 1 and mRNA cap analogue, studied by spectroscopic methods

The structural and thermodynamic behavior of the complex formation of eIF4E with either or both mRNA cap analogue (m7GTP, m7GpppA, or m7GpppG) and 4EBP1 has been investigated by spectroscopic measurements. Although the circular dichroism (CD) spectrum of eIF4E was little affected by the association with any cap analogue, the association constant of eIF4E with m7GpppA/G, estimated from the fluorescence quenching, was about 10 times larger than that with m7GTP. The van't Hoff analyses showed that the m7GpppA/G binding is enthalpy-driven with a large negative deltaH(o), and this is in contrast with the entropy-driven binding of m7GTP, where the positive deltaS(o) is large enough to overcome an increase of deltaH(o). This different behavior obviously originates in the interaction of the second nucleotide in m7GpppA with eIF4E, suggesting the importance of the nucleotide sequence linked to the m7Gppp terminal moiety, in addition to the specific interaction with the m7G base, for the recognition of mRNA cap structure by eIF4E. On the other hand, the CD spectra indicated that the binding of 4EBP1, an endogenous eIF4E-regulatory protein without having any defined secondary structure, shifted the m7GTP- or m7GpppA/G-bound eIF4E to an irregular structure, although such a structural change was not observed for eIF4E alone. The association constant of 4EBP1 with m7GTP- or m7GpppA/G-bound eIF4E was by two orders of magnitude larger than that with eIF4E alone. These results suggest the close interrelation in the supramolecular formation of 4EBP-eIF4E-mRNA cap structure.     

Design of hydroxyapatite-bound transition metal catalysts for environmentally-benign organic syntheses

Novel heterogeneous catalysts, which were designed with atomic precision, easy to prepare, and recyclable, have been developed using a unique inorganic support hydroxyapatite, Ca₁₀(PO₄)₆(OH)₂. The introduction of a Ru cation into the apatite framework can generate a stable monomeric phosphate complex, which exhibits prominent catalytic performances for various oxidation reactions using molecular oxygen as a primary oxidant. Treatment of the RuHAP with an aqueous solution of AgX affords cationic Ru phosphate complexes as Lewis acid catalysts, promoting Diels–Alder and aldol reactions under mild and neutral conditions. Furthermore, two classes of heterogeneous Pd catalysts were synthesized with both stoichiometric and Ca-deficient hydroxyapatites, which show specific functions for aerobic oxidation of alcohols and carbon–carbon bond-forming reactions with extremely high turnover numbers. The catalytic systems described here are simple, efficient, and general for practical organic syntheses; thus meeting the increasing demands for environmentally-benign chemical processes.     

Highly efficient heterogeneous acylations of aromatic compounds with acid anhydrides and carboxylic acids by montmorillonite-enwrapped titanium as a solid acid catalyst

Montmorillonite-enwrapped titanium hydroxide species (Ti⁴⁺-mont) acted as a highly efficient heterogeneous acid catalyst for the acylation of aromatic compounds with acid anhydrides or carboxylic acids. The catalytic activity of the Ti⁴⁺-mont was higher than those of other acid catalysts such as zeolites, SO ₄ ²⁻ /ZrO₂ and p-toluenesulfonic acid. For example, the reaction of anisole with dodecanoic acid in the presence of the Ti⁴⁺-mont catalyst gave 1-(4-methoxyphenyl)-1-dodecanone in 97% yield. Furthermore, the Ti⁴⁺-mont catalyst was easily separated from the reaction mixture and was recyclable.     

Synthesis,structure, and swelling behavior of two-component copolymer networks

A two-component copolymer network comprising polystyrene (PS) and poly(dimethylsiloxane) (PDMS) as copolymer components was prepared by cross-linking PS with telechelic PDMS with a new method. The microphase structure of the dry PS/PDMS network was found to be irregular from DSC and small angle X-ray scattering measurements. The swelling behavior was observed in three kinds of mixed solvents which were chosen so as to contrast with one another in respect of solubility of the component polymers. The observed swelling degree depended on the solvent composition in a manner peculiar to the respective mixed solvent systems. The Flory swelling equation extended to the two-component polymer network qualitatively reproduced the experimental swelling behavior.     

NMR measurements of the anisotropy effect of the phenylimino group

Two peaks due to -methylene protons adjacent to the phenylimino group are observed in NMR spectra of phenyliminocyclohexane, phenyliminocyclopentane and 2-phenyliminotetrahydrofuran. In order to assign these two peaks, conformation of the phenylimino group is discussed in relation to the IR, UV and NMR spectra. It is concluded that the plane is nearly perpendicular to the phenyl plane and that hybridization of the nitrogen atom is of sp² type. Thus the higher field signal is assigned to the syn proton and the lower field signal to the anti proton.