Concentric-ringed structures in polymer thin films

Novel polymer crystalline structures containing micrometer-sized concentric rings (or bands) were observed in thin poly(bisphenol A hexane ether) (BA-C6) films. The origin of the banded structures was found to be different from that of traditional banded spherulites in polymer systems. Analyses based on optical microscopy (OM) and atomic force microscopy (AFM) revealed that the banded structures contained alternating ridge and valley bands of polymer crystals in the flat-on orientation. No lamellar twisting was observed within the concentric-ringed structures, which were developed as a result of the formation of a depletion zone during crystallization. The formation of a depletion zone was determined to be caused by the specific volume decrement between the crystal and the melt and by the diffusion of polymer chains to the fold surfaces of the flat-on lamellae. The height of the ridges and the interband widths could be adjusted by controlling the diffusion rate. Time-of-flight secondary ion mass spectrometry ion images showed higher concentrations of low-molecular-weight polymer chains on the surfaces of the ridges than in the valleys.     

Intermolecular amidation of unactivated sp2 and sp2 C-H bonds via palladium-catalyzed cascade C-H activation/nitrene insertion

This communication describes the Pd(OAc)2-catalyzed intermolecular amidation reactions of unactivated sp2 and sp3 C-H bonds using primary amides and potassium persulfate. The substrates containing a pendent oxime or pyridine group were amidated with excellent chemo- and regioselectivities. It is noteworthy that reactive C-X bonds were well-tolerated and a variety of primary amides can be effective nucleophiles for the Pd-catalyzed C-H amidation reactions. For the reaction of unactivated sp3 C-H bonds, beta-amidation of 1 degrees sp3 C-H bonds versus 2 degrees C-H bonds is preferred. The catalytic reaction is initiated by chelation-assisted cyclopalladation involving C-H bond activation. Preliminary mechanistic study suggested that the persulfate oxidation of primary amides should generate reactive nitrene species, which then reacted with the cyclopalladated complex.     

Oxidative amide synthesis and N-terminal alpha-amino group ligation of peptides in aqueous medium

A new method for oxidative synthesis of amides from alkynes and amines in high yields (up to 96%) using [Mn(2,6-Cl2TPP)Cl] 1 as a catalyst and Oxone/H2O2 as an oxidant in aqueous medium has been developed. This method could be used for N-terminal alpha-amino group ligation of unprotected peptides with aryl, aliphatic, and internal alkynes under mild conditions.     

Gold(III) porphyrin-catalyzed cycloisomerization of allenones

[reaction: see text] Gold(III) porphyrin-catalyzed cycloisomerization of allenones gave the corresponding furans in good to excellent yields (up to 98%) and with quantitative substrate conversions. By recovering the Au(III) catalyst, a recyclable catalytic system is developed with over 8300 product turnovers attained for the cycloisomerization of 1-phenyl-buta-2,3-dien-1-one. The versatility of the gold(III) porphyrin catalyst was exemplified by its application to the hydroamination and hydration of phenylacetylene in 73% and 87% yield, respectively.     

On some methods for performance ranking and correspondence analysis in the DEA context

Two novel methods named performance baseline and performance correspondence matrices are proposed to evaluate the performance of decision making units (DMUs) based on the techniques of singular value decomposition (SVD). The performance baseline matrix can be used to rank all the DMUs because it provides a common basis for performance comparison. The performance correspondence matrix can be used to conduct performance cluster analysis, with which to explore the structure of input/output variables that are associated with DMUs. The analysis can reveal the performance difference of the DMUs and the key input/output variables determining the efficiency of a certain DMU, and provides valuable quantitative information for adjusting variables to improve efficiency of the DMU. Three case studies are presented to demonstrate that the proposed methods in this work are effective and easy to use and can provide insights into proper selection of input/output variables for performance comparison to avoid over manipulating DEA models in practice.     

Generalized 2-KKM theorems and their applications in hyperconvex metric spaces

In this work, we first define the 2-KKM mapping and the generalized 2-KKM mapping on a metric space, and then we apply the property of the hyperconvex metric space to get a KKM theorem and a fixed point theorem without a compactness assumption. Next, by using this KKM theorem, we get some variational inequality theorems and minimax inequality theorems.     

Alkene cyclopropanation catalyzed by Halterman iron porphyrin: participation of organic bases as axial ligands

With the iron(III) complex of the Halterman iron porphyrin [P*Fe(Cl)] and ethyl diazoacetate (EDA) as catalyst and carbene source, respectively, styrene-type substrates were converted to cyclopropyl esters with high trans/cis ratio (not less than 12) and high enantioselectivity for the trans-isomers (74-86% ee). The isomeric distribution of the cyclopropyl esters so obtained is akin to that obtained from the previously reported Ru(II) counterpart [P*Ru(CO)]. A linear Hammett correlation log(k(X)/k(H)) = sigma(+)rho was observed with rho = -0.57 suggesting the involvement of an electrophilic cyclopropanating species derived from the iron(II) center as the reactive intermediate in the catalytic cycle. This is further supported by a dramatic decrease in the enantioselectivity and trans/cis ratio observed in an experiment of styrene cyclopropanation when the reaction mixture was deliberately exposed to air. Axial ligand effects on the selectivities was also investigated. Substantial improvement in trans/cis ratios could be achieved by addition of organic bases such as pyridine (py) and 1-methylimidazole (MeIm) to the catalytic reaction. The existence of axially ligated iron carbene moieties, [P*Fe(CHCO(2)Et)(py)] and [P*Fe(CHCO(2)Et)(MeIm)], was established by electrospray mass spectrometry. Study of secondary kinetic isotope effect indicated that a more product-like transition state was generated by addition of MeIm.     

Complexation of Nucleotides in Water with Cyclotetrachromotropylene

The stability constants K of the 1 : 1host to guest complexes formed betweencyclotetrachromotropylene and the two nucleotides,uridine 2',3'-cyclicmonophosphate, sodium salt andadenosine 2',3'-cyclicmonophosphate, sodium salt, inwater were determined by proton NMR spectroscopy. Theyare 35 and 195 M^-1, respectively, at 25 °C.The base component of each nucleotide is included inthe hydrophobic cavity of the host in the twocomplexes.