Enantioselective organocatalytic formal [3 + 3]-cycloaddition of alpha,beta-unsaturated aldehydes and application to the asymmetric synthesis of (-)-isopulegol hydrate and (-)-cubebaol

[reaction: see text] The first highly enantioselective organocatalyzed carbo [3 + 3] cascade cycloaddition of alpha,beta-unsaturated aldehydes is reported. Using this methodology, crotonaldehyde is converted to 6-hydroxy-4-methylcyclohex-1-enecarbaldehyde, which is used in the synthesis of (-)-isopulegol hydrate, (-)-cubebaol, and p-tolualdehyde as well as (-)-6-hydroxy-4-methyl-1-cyclohexene-1-methanol acetate, an intermediate in the total synthesis of lycopodium alkaloid magellanine. Other alpha,beta-unsaturated aldehydes give rise to chiral cyclohexadienes via formal [4 + 2] reactions.     

Nickel-catalyzed, cascade cycloadditions of 1-ethynyl-8-halonaphthalenes with nitriles: synthesis, structure, and physical properties of new pyrroloarenes

The reaction of 1-ethynyl-8-halonaphthalenes 1 with nitriles in the presence of the catalytic system [NiBr(2)(dppe)]/Zn (dppe=1,2-bis(diphenylphosphino)ethane) is found to produce unusual pyrroloarenes 2. The carbon-nitrogen triple bond in nitrile is activated twice, and five new bonds are formed in a one-pot transformation, which causes a pyrrole and two six-membered rings to be generated simultaneously. The scope and limitations of this reaction are examined. Similarly, alkyl-bridged diynes also furnish the corresponding polycycles. Diaryl-substituted cycloadducts 2 (R(1)=Ar) are fluxional, because of the restriction in rotation of the aryl groups. The rotational barrier is studied by performing (1)H NMR experiments at various temperatures. The structures of several compounds are determined by X-ray crystallographic analysis. The photophysical and electrochemical properties of the pyrroloarenes are also investigated.     

Atomic Xα calculations based on EHFS(α) = Eexp

The total energies and one-electron energies for first- and second-row atoms were calculated by using the Hartree–Fock and the Hartree–Fock-Slater Hamiltonian with X_α orbitals, u_i(α_exp); α was parametrized from E^HFS (α_exp) = E^exp. The E^HF (α_exp) total energies are always higher than the Hartree–Fock energies for the atoms. The relation of the calculated ionization potential to the experimental ionization potential depends on the α used to define u_i(α), α_exp, or α_HF.     

Comparisons of <Emphasis Type=Italic>n</Emphasis>th-order kinetic algorithms and kinetic model simulation on HMX by DSC tests

Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) is a typical highly energetic material that has been widely used in national defense industries since the 1940s. The aim of this study was to establish a reaction kinetic model on thermal decomposition properties via differential scanning calorimetry (DSC) by well-known kinetic equations and kinetic model simulation. Furthermore, the aim also was to compare kinetic algorithms for thermal decomposition energy parameters under various conditions. Experimental results highly depended on the reliability of the kinetic concept applied, which is essentially defined by the proper choice of a mathematical model of a reaction. In addition, the correctness of the methods is used for kinetics evaluation.     

Benzyl alcohol oxidation and hydrogen generation over MoS2/ZnIn2S4 composite photocatalyst

Research on Chemical Intermediates - Owing to the simultaneous utilization of photogenerated electrons and holes, coupling light-driven hydrogen (H2) evolution reaction (HER) and biomass-derived...     

Diffusiophoresis in suspensions of highly charged soft particles

Diffusiophoresis phenomenon of aoft particles suspended in binary electrolyte solutions is explored theoretically in this study based on the spherical cell model, focusing on the chemiphoresis component in absence of diffusion potential. Both the electrostatic and hydrodynamic aspects of the boundary confinement, or steric effect, due to the presence of neighboring particles are examined extensively under various electrokinetic conditions. Significant local extrema are found in mobility profiles expressed as functions of the Debye length in general, synchronized with the strength of the motion-inducing double layer polarization. Moreover, a seemingly peculiar phenomenon is observed that the soft particles may move faster in more concentrated suspensions. The competition between the simultaneous enhancement of the motion-inducing electric driving force and the motion-retarding hydrodynamic drag force from the boundary confinement effect of the neighboring particles is found to be responsible for it. The above findings are also demonstrated experimentally in a very recent study on the diffusiophoretic motion of soft particles through porous collagen hydrogels. The results presented here are useful in various practical applications of soft particles like drug delivery.     

Module-Designed Carbon-Coated Separators for High-Loading,High-Sulfur-Utilization Cathodes in Lithium–Sulfur Batteries

Lithium–sulfur batteries have great potential as next-generation energy-storage devices because of their high theoretical charge-storage capacity and the low cost of the sulfur cathode. To accelerate the development of lithium–sulfur technology, it is necessary to address the intrinsic material and extrinsic technological challenges brought about by the insulating active solid-state materials and the soluble active liquid-state materials. Herein, we report a systematic investigation of module-designed carbon-coated separators, where the carbon coating layer on the polypropylene membrane decreases the irreversible loss of dissolved polysulfides and increases the reaction kinetics of the high-loading sulfur cathode. Eight different conductive carbon coatings were considered to investigate how the materials’ characteristics contribute to the lithium–sulfur cell’s cathode performance. The cell with a nonporous-carbon-coated separator delivered an optimized peak capacity of 1112 mA∙h g⁻¹ at a cycling rate of C/10 and retained a high reversible capacity of 710 mA∙h g⁻¹ after 200 cycles under lean-electrolyte conditions. Moreover, we demonstrate the practical high specific capacity of the cathode and its commercial potential, achieving high sulfur loading and content of 4.0 mg cm⁻² and 70 wt%, respectively, and attaining high areal and gravimetric capacities of 4.45 mA∙h cm⁻² and 778 mA∙h g⁻¹, respectively.     

The Synthesis of Alanine Oligopeptides

The oligopeptides of alanine (penta-, deca-, and pentadeca-) were synthesized by solid phase method and new peptide-resin cleaving reagent TFA-BBr₃ was used to cleave the peptides from resin-support. Penta-alanine was also synthesized by liquid phase for the comparision and FAB-Mass method was used to determine the molecular weight of penta-alanine. HPLC separation of these new oligopeptides were described.     

Photoswitchable Composite Polymer Electrolytes Using Spiropyran-Immobilized Nanoporous Templates

Composite polymer electrolytes (CPEs) with smart, stimuli-responsive characteristics have gained considerable attention owing to their noninvasive manipulation and applications in future technologies. To address this potential, in this work, we demonstrate photoresponsive composite polymer electrolytes, consisting of gel polymer electrolyte (GPE) and spiropyran-immobilized nanoporous anodic aluminum oxide (SP-AAO) templates. Under UV irradiation, the close SP form isomerizes to the open merocyanine (MC) form, creating extremely polarized AAO surfaces; whereas, under visible light irradiation, the MC form reverts to the SP form, creating neutral surface conditions. The electrostatic interactions between ions and AAO surfaces are investigated by attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy. Moreover, the behavior of ionic conductivity of the GPE@SP-AAO is found to be consistent with the kinetics of isomerization tracked by UV-Vis spectroscopy. This work provides a promising platform for developing next-generation photoelectronic smart devices.