Development of a highly efficient catalytic method for synthesis of vinyl ethers

A new method for the preparation of alkyl vinyl ethers has been developed. Thus, various types of alkyl vinyl ethers were synthesized by the reaction of alcohols with vinyl acetate under the influence of a catalytic amount of [Ir(cod)Cl]2 combined with Na2CO3 in good to excellent yields.     

Catalytic reductive alkylation of secondary amine with aldehyde and silane by an iridium compound

[reaction: see text] An efficient methodology for the reductive alkylation of secondary amine with aldehyde and Et(3)SiH using an iridium complex as a catalyst has been developed. For example, treatment of dibutylamine with butyraldehyde and Et(3)SiH (a 1:1:1 molar amount of amine, aldehyde, and silane) in 1,4-dioxane at 75 degrees C under the influence of a catalytic amount of [IrCl(cod)](2) gave tributylamine in quantitative yield. In this reaction, no reduction of aldehyde took place. It was found that IrCl(3), which is a starting material for preparation of iridium complexes such as [IrCl(cod)](2), acts as an efficient catalyst for the present reductive alkylation of amine. In addition, a cheaper, easy-to-handle, and environmentally friendly reducing reagent such as polymethylhydrosiloxane (PMHS) in place of Et(3)SiH was also useful. Thus, a variety of secondary amines could be alkylated by allowing them to react with aldehydes and PMHS in the presence of an iridium catalyst to afford the corresponding tertiary amines in good to excellent yields. From the deuterium label experiments, it was revealed that silane and water, generated during the formation of enamine by the reaction of amine and aldehyde, seem to behave as a hydrogen source. The catalytic cycle was discussed.     

Hydrogel microrobots actuated by optically generated vapour bubbles

A novel hydrogel microrobot made of poly(ethylene glycol) diacrylate (PEGDA) is reported. This disk-shaped microrobot is optothermally actuated by laser-induced bubbles. A pulsed laser is used to smoothly actuate an 80-μm-diameter bubble microrobot at up to 320 μm s(-1). A single microrobot or a pair of microrobots working in cooperation were used to assemble 20-μm-diameter polystyrene beads into different patterns. The microrobots were also used to assemble patterns made of single yeast cells and cell-laden agarose microgels. The patterned yeast cells and cell-laden microgels were cultured, and the cells successfully multiplied.     

Inside Cover: Charge‐Conversional Polyionic Complex Micelles—Efficient Nanocarriers for Protein Delivery into Cytoplasm (Angew. Chem. Int. Ed. 29/2009)

A highly efficient protein delivery into cytoplasm is described by K. Kataoka, and co‐workers on page 5309 ff. The charge‐density increase of a protein cargo by reversible modification, which was based on the charge‐conversional moieties citaconic amide and cis‐aconitic amide, helped the stability of protein/block copolymer polyionic complex (PIC) micelles. The rapid protein charge conversion in endosomes induced the dissociation of the PIC micelles and efficient endosomal escape.

     

Photo‐ and Redox‐Active Dendritic Molecules with Soft,Layered Nanostructures

Molecules with one photoactive group (porphyrin) and multiple redox‐active groups (ferrocenes) are described. The molecules are based on dendritic frameworks, with the ferrocenyl groups attached at the “internal” positions and the porphyrin attached at the focal point, leading to a characteristic layer architecture. Molecules of up to the third generation were synthesized and examined. The results of ¹H NMR spectroscopy and fluorescence quenching indicated that the ferrocenyl groups at the second layer approach the core porphyrin most closely, which is consistent with the results of molecular‐dynamics simulations. The electrochemistry of the molecules was also examined in detail, and a new formula is proposed for the analysis of multiple‐electron transfer in these “redox‐pool” molecules.     

One‐Pot Synthesis of Lactams from Cycloalkanes and tert‐Butyl Nitrite by Using N‐Hydroxyphthalimide as Key Catalyst

Lactams were successfully synthesized in the one‐pot reaction of cycloalkanes and tBuONO in the presence of N‐hydroxyphthalimide as a key catalyst. Cyclododecane and cyclohexane were treated with tBuONO followed by triethylamine and then cyanuric chloride in a one‐pot manner to give laurolactam and ε‐caprolactam, respectively, in good yields. The Beckmann rearrangement of oximes by cyanuric chloride was found to be accelerated by the use of 1,1,1,3,3,3‐hexafluoro‐2‐propanol as solvent. The method provides the first successful environmentally benign direct synthetic route to lactams from cycloalkanes without the formation of any salt.     

Electrical properties of boron-doped MWNTs synthesized by hot-filament chemical vapor deposition

We have synthesized a large amount of boron-doped multiwalled carbon nanotubes (MWNTs) by hot-filament chemical vapor deposition. The synthesis was carried out in a flask using a methanol solution of boric acid as a source material. The scanning electron microscopy, transmission electron microscopy, and micro-Raman spectroscopy were performed to evaluate the structural properties of the obtained MWNTs. In order to evaluate the electrical properties, temperature dependence of resistivity was measured in an individual MWNTs with four metal electrodes. The Raman shifts suggest carrier injection into the boron-doped MWNTs, but the resistivity of the MWNTs was high and increased strongly with decreasing temperature. Defects induced by the plasma may cause this enhanced resistivity.     

Asymptotic analysis for the eikonal equation with the dynamical boundary conditions

We study the dynamical boundary value problem for Hamilton‐Jacobi equations of the eikonal type with a small parameter. We establish two results concerning the asymptotic behavior of solutions of the Hamilton‐Jacobi equations: one concerns with the convergence of solutions as the parameter goes to zero and the other with the large‐time asymptotics of solutions of the limit equation.     

Hypothesis tests for high-dimensional covariance structures

We consider hypothesis testing for high-dimensional covariance structures in which the covariance matrix is a (i) scaled identity matrix, (ii) diagonal matrix, or (iii) intraclass covariance matrix. Our purpose is to systematically establish a nonparametric approach for testing the high-dimensional covariance structures (i)–(iii). We produce a new common test statistic for each covariance structure and show that the test statistic is an unbiased estimator of its corresponding test parameter. We prove that the test statistic establishes the asymptotic normality. We propose a new test procedure for (i)–(iii) and evaluate its asymptotic size and power theoretically when both the dimension and sample size increase. We investigate the performance of the proposed test procedure in simulations. As an application of testing the covariance structures, we give a test procedure to identify an eigenvector. Finally, we demonstrate the proposed test procedure by using a microarray data set.