Dual Catalysis with Copper and Rhenium for Trifluoromethylation of Propargylic Alcohols: Efficient Synthesis of α‐Trifluoromethylated Enones

Trifluoromethylation of propargylic alcohols to provide (Z)‐α‐trifluoromethylated enones and β‐unsubstituted α‐trifluoromethylated enones proceeded with high yield and selectivity in the presence of CuI/Re₂O₇. The Z isomer was formed under kinetic control, though it is less stable than the E isomer in terms of steric repulsion.     

Symmetry-itemized enumeration of RS-stereoisomers of allenes. I. The fixed-point matrix method of the USCI approach combined with the stereoisogram approach

After the RS-stereoisomeric group \(\mathbf{D}_{2d\widetilde{\sigma }\widehat{I}}\) of order 16 has been defined by starting point group \(\mathbf{D}_{2d}\) of order 8, the isomorphism between \(\mathbf{D}_{2d\widetilde{\sigma }\widehat{I}}\) and the point group \(\mathbf{D}_{4h}\) of order 16 is thoroughly discussed. The non-redundant set of subgroups (SSG) of \(\mathbf{D}_{2d\widetilde{\sigma }\widehat{I}}\) is obtained by referring to the non-redundant set of subgroups of \(\mathbf{D}_{4h}\) . The coset representation for characterizing the orbit of the four positions of an allene skeleton is clarified to be \(\mathbf{D}_{2d\widetilde{\sigma }\widehat{I}}(/\mathbf{C}_{s\widetilde{\sigma }\widehat{I}})\) , which is closely related to the \(\mathbf{D}_{4h}(/\mathbf{C}_{2v}^{\prime \prime \prime })\) . According to the unit-subduced-cycle-index (USCI) approach (Fujita, Symmetry and combinatorial enumeration of chemistry. Springer, Berlin 1991), the subduction of \(\mathbf{D}_{2d\widetilde{\sigma }\widehat{I}}(/\mathbf{C}_{s\widetilde{\sigma }\widehat{I}})\) is examined so as to generate unit subduced cycle indices with chirality fittingness (USCI-CFs). Then, the fixed-point matrix method of the USCI approach is applied to the USCI-CFs. Thereby, the numbers of quadruplets are calculated in an itemized fashion with respect to the subgroups of \(\mathbf{D}_{2d\widetilde{\sigma }\widehat{I}}\) . After the subgroups of \(\mathbf{D}_{2d\widetilde{\sigma }\widehat{I}}\) are categorized into types I–V, type-itemized enumeration of quadruplets is conducted to illustrate the versatility of the stereoisogram approach.     

A Tray‐Shaped,PdII‐Clipped Au3 Complex as a Scaffold for the Modular Assembly of [3×n] Au Ion Clusters

A tray‐shaped Pd^II₃Au^I₃ complex ( 1 ) is prepared from 3,5‐bis(3‐pyridyl)pyrazole by means of tricyclization with Au^I followed by Pd^II clipping. Tray 1 is an efficient scaffold for the modular assembly of [3×n] Au^I clusters. Treatment of 1 with the Au^I₃ tricyclic guest 2 in H₂O/CH₃CN (7:3) or H₂O results in the selective formation of a [3×2] cluster ( 1 ⋅ 2 ) or a [3×3] cluster ( 1 ⋅ 2 ⋅ 1 ), respectively. Upon subsequent addition of Ag^I ions, these complexes are converted to an unprecedented Au₃–Au₃–Ag–Au₃–Au₃ metal ion cluster.     

Pressure-Induced Solidification of 1-Butyl-3-methylimidazolium Tetrafluoroborate

We have used Raman spectroscopy to investigate the high-pressure phase behavior of 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF₄]), a representative ionic liquid, at pressures up to ~7.5 GPa. We have also studied how increasing pressure leads to conformational changes in the [bmim]⁺ cation. We have found that liquid [bmim][BF₄] undergoes pressure-induced solidification (freezing) into a superpressed (metastable) state at 2.5 GPa; another structural change probably occurs at ~6 GPa. Remarkably, conformational changes in the [bmim]⁺ cation between trans and gauche conformers are concordant with the metastable structural changes of [bmim][BF₄]. As the pressure is increased from ambient, the fraction of gauche conformers increases, but the gauche fraction decreases above the solidification pressure (2.5 GPa), and slope of the gauche/trans ratio changes again above 6 GPa. We interpret these results in terms of the fragility of the ionic liquid.     

Connectivity keeping edges in graphs with large minimum degree

The old well-known result of Chartrand, Kaugars and Lick says that every k-connected graph G with minimum degree at least 3k/2 has a vertex v such that G−v is still k-connected. In this paper, we consider a generalization of the above result [G. Chartrand, A. Kaigars, D.R. Lick, Critically n-connected graphs, Proc. Amer. Math. Soc. 32 (1972) 63–68]. We prove the following result:Suppose G is a k-connected graph with minimum degree at least 3k/2+2. Then G has an edge e such that G−V(e) is still k-connected.The bound on the minimum degree is essentially best possible.     

High-performance olefin polymerization catalysts discovered on the basis of a new catalyst design concept

This critical review highlights the "ligand oriented catalyst design concept", a new catalyst design concept for olefin polymerization that has led to the development of high-activity catalysts. The concept has created a series of highly active ethylene polymerization catalysts, many of which show high activities comparable to those of group 4 metallocene catalysts. Moreover, these catalysts display unique polymerization catalysis to produce a wide variety of polymers that possess unprecedented molecular architectures that are either difficult or impossible to achieve using conventional catalysts (98 references).     

Cerium complexes of cyclodextrin dimers as efficient catalysts for luminol chemiluminescence reactions

The chemiluminescence of a luminol-H(2)O(2) system is found to be remarkably enhanced by the Ce(IV) complexes of EDTA-bridged cyclodextrin dimers. The dimers were proved to work much more efficiently than the corresponding monomer. The cavity shape of cyclodextrin moieties and their cooperation displayed an important role in amplifying the chemiluminescence. Further modification of either the cyclodextrin rims or the EDTA linker altered significantly the catalytic abilities of the cyclodextrin dimers, and the examination of the effect of substituents on the chemiluminescence outputs suggested that the proximity between the cyclodextrin cavity and the metallic center might account for the amelioration of the chemiluminescence output.