Diversification of a β-Lactam Pharmacophore via Allylic C-H Amination: Accelerating Effect of Lewis Acid Co-Catalyst

This report describes the use of Pd(II)/bis-sulfoxide 1 catalyzed intra- and intermolecular allylic C-H amination reactions to rapidly diversify structures containing a sensitive β-lactam core similar to that found in the monobactam antibiotic Aztreonam. Pharmacologically interesting oxazolidinone, oxazinanone, and linear amine motifs are rapidly installed with predictable and high selectivities under conditions that use limiting amounts of substrate. Additionally, we demonstrate for the first time that intramolecular C-H amination processes may be accelerated using catalytic amounts of a Lewis acid co-catalyst [Cr(III)(salen)Cl 2].     

Efficient synthesis of (Z)- and (E)-methyl 2-(methoxyimino)-2-phenylacetate

Direct oximation of 2-oxo-2-phenylacetate (3) gave the (Z)-methyl 2-(methoxyimino)-2-phenylacetate (1) in 71% yield, while the E oxime 2 was prepared from 3 in 65% yield via oxime isomerization of 2-(methoxyimino)-2-phenylacetic acid (5). Computational studies suggest that the isomerization of 5 is thermodynamically driven, while the direct oximation of ketoester 3 is kinetically controlled.     

Melting in two-dimensional Yukawa systems: a Brownian dynamics simulation

We studied the melting behavior of two-dimensional colloidal crystals with a Yukawa pair potential by Brownian dynamics simulations. The melting follows the Kosterlitz-Thouless-Halperin-Nelson-Young (KTHNY) scenario with two continuous phase transitions and a middle hexatic phase. The two phase-transition points were accurately identified from the divergence of the translational and orientational susceptibilities. Configurational temperatures were employed to monitor the equilibrium of the overdamped system and the strongest temperature fluctuation was observed in the hexatic phase. The inherent structure obtained by rapid quenching exhibits three different behaviors in the solid, hexatic, and liquid phases. The measured core energy of the free dislocations, E(c) = 7.81 ± 0.91 k(B)T, is larger than the critical value of 2.84 k(B)T, which consistently supports the KTHNY melting scenario.     

Assembly of a Novel Dumbbell‐type Dinuclear Copper(II) Complex: Synthesis,Structure and Properties

A new dumbbell‐type 4,4′‐bipy‐bridged dinuclear copper(II) complex, [Cu₂(4,4′‐bipy)L₂(H₂O)₂](ClO₄)₄ · 8CH₃OH · 10H₂O, where L = 1‐[bis(3‐aminopropyl)amino]‐2‐ propanol and bipy = bipyridine, has been synthesized and characterized, X‐ray crystallographic analysis shows that the [Cu₂(4,4′‐bipy)L₂(H₂O)₂]⁴⁺ cations and water molecules generate layer structures extending parallel to bc planes through hydrogen bonding interactions of O–H ··· O and C–H ··· O. The layers are also connected by hydrogen bonding interactions involving methanol, water, and perchlorate anions. These interactions lead to the formation of rectangular channels of 12.3 Å × 6.0 Å along the crystallographic c axis. Perchlorate anions fill in each channel in a sandwich‐like packing mode, they are joined with the adjacent layers by water heptamers. Magnetic susceptibility measurements show that the magnetic exchange interaction is weak although it has a regular π‐type electron transfer pathway. Furthermore, the electrochemical and thermogravimetric properties of the complex were also investigated.     

Novel efficient procedure for the conjugate addition of amines to electron deficient alkenes

The novel efficient procedure has been developed for the conjugate addition of amines to electron deficient alkenes using the novel SO₃H functionalized ionic liquid as catalyst. The results showed that the novel catalyst owned high activities for the reactions with excellent yields within several minutes. Various amines and electron deficient alkenes were successfully transformed to the corresponding products in the catalytic system. Operational simplicity, without need of any solvent, low cost of the catalyst used, room temperature, high yields, reusability, excellent chemoselectivity and wide applicability are the key features of this methodology.     

Electrodeposition of silver nanoparticles on a zinc oxide film: improvement of amperometric sensing sensitivity and stability for hydrogen peroxide determination

A strategy to fabricate a hydrogen peroxide (HP) sensor is developed by electrodepositing silver nanoparticles (Ag NPs) on a modified glassy carbon electrode (GCE) with a zinc oxide (ZnO) film. The Ag NPs/ZnO/GCE has been characterized by scanning electron microscopy, cyclic voltammetry, and chronoamperometry. It has been found that the Ag NPs synthesized in the presence of ZnO film provide an electrode with enhanced sensitivity and excellent stability. The sensitivity to HP is enhanced 3-fold by using Ag NPs/ZnO/GCE compared to Ag NPs/GCE. The HP sensor exhibits good linear behavior in the concentration range 2 µM to 5.5 mM for the quantitative analysis of HP with a detection limit of 0.42 µM (S/N?=?3).     

Experimental Study of Capacitive RF <Emphasis Type="Italic">c</Emphasis>-C<Subscript>4</Subscript>F<Subscript>8</Subscript> Discharge with Synchrotron Vacuum Ultraviolet Photoionization Mass Spectrometry

Capacitive radio frequency (RF) discharge of c-C₄F₈ (octafluorocyclobutane) has been studied with synchrotron vacuum ultraviolet (SVUV) photoionization mass spectrometry (PIMS) at 4 Torr and 33.33 kHz. Various free radicals and reactive intermediates have been identified through measurement of photoionization mass spectra and photoionization efficiency (PIE) spectra. CF₂=CF₂ is main product in the plasma, indicating that the dissociation of c-C₄F₈ into CF₂=CF₂ is one of prominent reactions in the present experimental conditions. The observation of large species including C₅F₈, C₅F₁₀ and C₆F₁₀ is presented in our work. Besides, the dependences of the signals of neutral species in the discharge of c-C₄F₈ on RF power are presented in this paper.     

Simulated Microgravity Affects Growth of <Emphasis Type="Italic">Escherichia coli</Emphasis> and Recombinant β-<Emphasis Type="SmallCaps">d</Emphasis>-Glucuronidase Production

Effects of simulated microgravity (SMG) on bacteria have been studied in various aspects. However, few reports are available about production of recombinant protein expressed by bacteria in SMG. In this study growth of E. coli BL21 (DE3) cells transformed with pET-28a (+)-pgus in double-axis clinostat that could model low shear SMG environment and the recombinant β-d-glucuronidase (PGUS) expression have been investigated. Results showed that the cell dry weights in SMG were 16.47%, 38.06%, and 28.79% more than normal gravity (NG) control, and the efficiency of the recombinant PGUS expression in SMG were 18.33%, 19.36%, and 33.42% higher than that in NG at 19 °C, 28 °C, and 37 °C, respectively (P < 0.05).     

A general synthetic procedure for 2-chloromethyl-4(3H)-quinazolinone derivatives and their utilization in the preparation of novel anticancer agents with 4-anilinoquinazoline scaffolds

In our ongoing research on novel anticancer agents with 4-anilinoquinazoline scaffolds, a series of novel 2-chloromethyl-4(3H)-quinazolinones were needed as key intermediates. An improved one-step synthesis of 2-chloromethyl-4(3H)-quinazolinones utilizing o-anthranilic acids as starting materials was described. Based on it, 2-hydroxy-methyl-4(3H)-quinazolinones were conveniently prepared in one pot. Moreover, two novel 4-anilinoquinazoline derivatives substituted with chloromethyl groups at the 2-position were synthesized and showed promising anticancer activity in vitro.     

Synthesis and application in polypropylene of a novel of phosphorus-containing intumescent flame retardant

A novel phosphorus-containing triazine oligomer poly(2-morpholinyl-4-penta-erythritol phosphate-1,3,5-triazine) (PMPT) was synthesized as a kind of tri-component intumescent flame retardant (IFR). The chemical structure of PMPT was characterized by FTIR, 1H-NMR and 31P-NMR, and the mechanical and flammability properties of FR-PP were measured. The FTIR results showed that the expected chemical reactions had happened at each step. The 1H-NMR and 31P-NMR spectra also agreed with the chemical structure of PMPT. The slight effect of PMPT on the mechanical properties of FR-PP suggested that PMPT and PP are compatible. The high limited oxygen index (LOI) values of FR-PP revealed that PMPT was an efficient IFR and there was the synergistic effect between PMPT and ammonium polyphosphate/ pentaerythritol (APP/PER).