The linear arboricity of some regular graphs

We prove that the linear arboricity of every 5-regular graph is 3. That is, the edges of any 5-regular graph are covered by three linear forests. We also determine the linear arboricity of 6-regular graphs and 8-regular graphs. These results improve the known upper bounds for the linear arboricity of graphs with given maximum degree.     

Convection-aided collection of metal ions using chelating porous flat-sheet membranes

Chelating porous membranes were prepared by radiation-induced graft polymerization of an epoxy-group-containing monomer onto a polyethylene flat sheet and subsequent conversion of the epoxy group to an iminodiacetate group as a chelate-forming group. The chelating group density on the resultant porous flat-sheet membrane of 1.0 mol/kg was comparable to that of commercially available chelating beads. The pure water permeability of the membrane was 40% that of the trunk porous membrane, which was used for microfiltration. During the permeation of a copper chloride solution through the membrane, diffusional mass-transfer resistance of copper ion was negligible, since the ion was transported by convective flow through the pore. The tensile strength and elongation at break of the membranes were measured as a function of dose of electron-beam irradiation, the degree of grafting, and the chelating group density to determine an applicable range for practical use.     

Cationic rhodium(I)/PPh3 complex-catalyzed dehydrogenation of alkanethiols to disulfides under inert atmosphere

A cationic rhodium(I)/PPh₃ complex is an effective catalyst for dehydrogenation of primary or secondary alkanethiols to symmetrical disulfides under inert atmosphere. The dependence of reactivity on the structure of thiols is examined in detail.     

Photo‐Cross‐Linked Small‐Molecule Microarrays as Chemical Genomic Tools for Dissecting Protein–Ligand Interactions

We have developed a unique photo‐cross‐linking approach for immobilizing a variety of small molecules in a functional‐group‐independent manner. Our approach depends on the reactivity of the carbene species generated from trifluoromethylaryldiazirine upon UV irradiation. It was demonstrated in model experiments that the photogenerated carbenes were able to react with every small molecule tested, and they produced multiple conjugates in most cases. It was also found in on‐array immobilization experiments that various small molecules were immobilized, and the immobilized small molecules retained their ability to interact with their binding proteins. With this approach, photo‐cross‐linked microarrays of about 2000 natural products and drugs were constructed. This photo‐cross‐linked microarray format was found to be useful not merely for ligand screening but also to study the structure–activity relationship, that is, the relationship between the structural motif (or pharmacophore) found in small molecules and its binding affinity toward a protein, by taking advantage of the nonselective nature of the photo‐cross‐linking process.     

Synthesis of Δ-OPC-8:0 and OPC-6:0

CuCN-catalyzed reaction of the (1R)-isomer of 4-cyclopentene-1,3-diol monoacetate with TBDPSO(CH₂)₆MgCl produced an S_N2-type product regioselectively in high yield. Mitsunobu inversion of the product and subsequent Claisen rearrangement furnished aldehyde with the two side chains, from which the title compounds were synthesized efficiently.     

Synthesis, liquid-crystalline properties, and supramolecular nanostructures of dendronized poly(isocyanide)s and their precursors

A series of novel dendronized pi-conjugated poly(isocyanide)s were synthesized successfully by using a Pd-Pt mu-ethynediyl dinuclear complex ([ClPt{P(C2H5)3}2C[triple bond]CPt{P(C2H5)3}2Cl]) as the initiator. The polymerizations of the dendronized monomers follow first-order kinetics, indicating that living polymerization takes place. The obtained polymers exhibit narrow polydispersities in the range of 1.03-1.20. Thermal properties of the poly(isocyanide)s as well as their isocyanide monomers and precursors with formamido (HCONH-) moieties as apexes were investigated by using differential scanning calorimetry (DSC), polarized optical microscopy (POM) and wide-angle X-ray diffraction (WAXD). Both the peripheries and the apex groups of the dendrons affect the formation of supramolecular column and/or cubic phases of the precursors and monomers. The formamido precursor forms a liquid-crystalline phase due to intermolecular hydrogen bonding. The isocyanide monomer lacks this hydrogen-bonding ability and does not display an organized mesophase. All of the rigid poly(isocyanide)s with the monodendrons exhibit columnar liquid-crystalline phases. Interestingly, cylindrical structures of a poly(isocyanide) were directly visualized by using transmission electron microscopy (TEM).     

Paddlewheel dirhodium complexes bridged by para‐substituted benzoates

The dirhodium complex bis­(benzonitrile)tetra­kis[μ‐4‐(diethyl­amino)benzoato‐κ²O:O′]dirhodium(II)(Rh—Rh) benzonitrile disolvate, [Rh₂(C₁₁H₁₄NO₂)₄(C₇H₅N)₂]·2C₇H₅N, lies about an inversion centre. The dirhodium complex (methanol)tetra­kis(μ‐4‐nitro­benzoato‐κ²O:O′)(pyridine)dirhodium(II)(Rh—Rh) dichloro­methane solvate, [Rh₂(C₇H₄NO₄)₄(C₅H₅N)(CH₄O)]·CH₂Cl₂, lies in a general position in the unit cell, but the complexes dimerize around an inversion centre via O—H⋯O hydrogen bonding of the axial MeOH to a carboxyl­ate O atom. In the latter crystal structure, π–π stacking inter­actions between the bridging 4‐nitro­benzoate ligands and the axial pyridine ligand are observed between adjacent mol­ecules.     

Electrochemical partial fluorination of phenylacetic acids esters and 1-tetralone

Anodic oxidation of some benzyl derivatives (phenylacetic acids esters) 1, and 1-tetralone 4, using ammonium fluorides or ammonium tetrafluoroborate as fluorine sources and supporting electrolytes and CH₂Cl₂ as solvent, allowed the introduction of a fluorine atom in the α position of an electron withdrawing group via carbocation (C), (EC_BEC_N mechanism).