Microwave‐Assisted Synthesis of Ethyl 1,3‐Disubstituted‐1,6‐dihydropyrrolo[2,3‐c]pyrazole‐5‐carboxylates

A novel series of ethyl 1,3‐disubstituted‐1,6‐dihydropyrrolo[2,3‐c]pyrazole‐5‐carboxylates can be rapidly and efficiently synthesized in excellent yields by condensing a variety of 1,3‐substituted‐4‐formyl‐5‐chloropyrazole with ethyl isocyanoacetate in the presence of 1‐methyl‐3‐butylimidazolium hydroxide under microwave irradiation. The simple experimental procedure, DMSO‐free condition, short period of conversion, and excellent yields are the advantages of the present method. The structures of the novel compounds are confirmed by IR, ¹H NMR, ¹³C NMR, MALDI‐TOF MS, and elemental analysis.     

Syngas production from methane over CeO2-Fe2O3 mixed oxides using a chemical-looping method

A series of mixed oxides Ce_{1 ? x} Fe _x O₂ was prepared by a hydrothermal method. XRD and Raman spectra were measured to study the structure of the prepared materials. The temperature-programmed reduction was undertaken to estimate reducibility of the oxides. Syngas generation from methane using these materials as oxygen carriers/catalysts via a chemical-looping procedure was investigated in detail. This procedure includes catalytic oxidation and decomposition of methane to produce H₂-rich gas at the first step followed by the production of the CO-rich gas by oxidizing the carbon deposited on deactivated catalysts. The results showed that all iron ions were incorporated into the ceria lattice with the formation of oxygen vacancies in the Ce_0.9Fe_0.1O₂ sample, while isolated Fe₂O₃ particles were distributed on the surface of the Ce_0.8Fe_0.2O₂ sample. TPR measurements and the analysis of the two-step chemical-looping reactions indicated a strong interaction between the Ce and Fe species which accounts for an increased activity of the mixed oxides in the syngas generation compared to that of individual oxides. Among the several samples, the Ce_0.8Fe_0.2O₂ catalyst showed the highest activity for methane partial oxidation due to the synergetic effects caused by the interaction of surface iron entities and Ce-Fe solid solution. In addition, selective oxidation of carbon by oxygen to CO can also be found over this material since gaseous products are formed at the carbon oxidation step with the selectivity to CO reaching 91.2%. Evidence is presented that syngas can be feasibly produced from methane with high selectivity via the chemical-looping procedure over the CeO₂-Fe₂O₃ mixed oxides.     

Reductive Coupling of Aldehydes,Ketones and Aroyl Chlorides Induced by LVT Prepared from TiCl4/Al System

Aluminium powder has been used to reduce titanium tetrachloride to generate the low valent titanium (LVT)reagent which can induce the reductive coupling of aldehydes and ketones to form the corresponding pinacols or olefins. However, arylsulfonyl chlorides will give diaryldisulfides under the same condition.     

Diastereoselective Synthesis of γ-Butenolides Catalyzed by Potassium tert-Butoxide

Potassium tert-butoxide (0.1 mol%) catalyzed a vinylogous Mukaiyama aldol reaction between aromatic and aliphatic aldehydes with 2-(trimethylsilyloxy)furan. The corresponding γ-butenolides were obtained in good yields with good diastereoselectivities.     

Improvement in Uranium Adsorption Properties of Amidoxime-Based Adsorbent Through Cografting of Amine Group

Amidoxime (AO)/amine co-functionalized polypropylene fiber adsorbents were prepared. The all-polymeric structures were characterized by using Fourier transform infrared spectroscopy (FTIR), optical microscope, contact angle meter and electron spin resonance (ESR) analysis methods, confirming the grafting, modification, and amidoximation stages gravimetrically, spectroscopically, and visually. The properties for the removal of uranyl(VI) from aqueous solutions were investigated. For amidoxime (AO) fiber, high adsorption rate was observed within the first 30 minutes and the plateau value of 40.6% uranium loading (0.0812 mg/g) was reached at around 30 minutes. The adsorption equilibrium for AO/amine fiber was attained within 20 minutes, resulting in the adsorption of 92.6% uranium loading (0.185 mg/g). The percentage of adsorption increases with increasing pH value (2–6), reaches a maximum at pH 6.0 and then remains almost constant for AO/amine fiber, whereas reduces slightly for AO fiber.     

Isolation and Characterization of Urethanase from Penicillium variabile and Its Application to Reduce Ethyl Carbamate Contamination in Chinese Rice Wine

A strain with urethanase activity was isolated from mouse gastrointestine. By combination of morphological characterization of the colony, hyphae, and spore and the sequence analysis of its rDNA ITS, the strain was determined as Penicillium variabile and named as P. variabile JN-A525. The enzymatic properties of urethanase from P. variabile JN-A525 were further studied. The optimum temperature and pH value of urethanase are of 50 °C and 6.0, respectively. The enzyme maintains stability when the temperature is below 50 °C and the pH is in the range of 7.0–10.0. The enzyme also exhibits ethanol tolerance. It can remove ethyl carbamate from Chinese rice wine without the change of flavor substances in the wine.     

Assessing the multisite binding properties of multiple sources of dissolved organic matter at nanomolar copper concentrations using piecewise linear regression and parallel factor analysis of fluorescence quenching

This study reports on the development and application of a piecewise linear model for the determination of copper-binding parameters at concentrations in the nanomolar range using fluorescence quenching. l-Tyrosine, Suwannee River natural organic matter, and two leaf leachates with similar fluorescence signatures were used as test compounds, and results were compared with those of the standard Ryan–Weber model. The piecewise model was also applied to and compared with data from an earlier study. Parallel factor analysis (PARAFAC) was used to identify three to five independent fluorophores in each test compound, and copper-binding parameters were estimated for one to three binding sites for each fluorophore. The binding properties of similar and different fluorophores were also compared. The conditional binding strengths (log K′) estimated using the piecewise approach were similar to those obtained using the Ryan–Weber approach (p?>?0.05); however, the piecewise linear model provided superior results compared to models based on the Ryan–Weber equation in several ways, including (1) capable of distinguishing more binding sites for a single fluorophore, (2) capable of extracting binding parameters at environmentally relevant, nanomolar concentrations of copper, where fluorescence changes are often observed as enhancement, (3) greater precision over repeated titrations, and (4) no severe underestimation of complexing capacities. Finally, the copper-binding properties of PARAFAC components with similar optical signatures were found to be similar, both in sources with dramatically different and similar total fluorescence signatures.

SYNTHESES,CRYSTAL STRUCTURES,AND ANTIMICROBIAL ACTIVITIES OF ZINC COMPLEXES DERIVED FROM 2-AMINO-N′- (PYRIDIN-2-YLMETHYLENE)BENZOHYDRAZIDE

Journal of Structural Chemistry - New zinc complexes, [ZnBr2(HL)] (1), [ZnBr(HL)(NCS)]·0.5H2O (2), [Zn(HL)I2] (3), and [ZnL2] (4), where L is the monoanionic form of...     

pH‐controlled reaction divergence of decarboxylation versus fragmentation in reactions of dihydroxyfumarate with glyoxylate and formaldehyde: parallels to biological pathways

The reactions of dihydroxyfumarate with glyoxylate and formaldehyde exhibit a unique pH‐controlled mechanistic divergence leading to different product suites by two distinct pathways. The divergent reactions proceed via a central intermediate (2,3‐dihydroxy‐oxalosuccinate, 3 , in the reaction with glyoxylate and 2‐hydroxy‐2‐hydroxymethyl‐3‐oxosuccinate, 14 , in the reaction with formaldehyde). At pH 7–8, products ( 7 , 8 , and 15 ) exclusively from a decarboxylation of the intermediate are observed, while at pH 13–14, products ( 9 , 10 , and 16 ) solely derived from a hydroxide‐promoted fragmentation of the intermediate are formed. The decarboxylative and fragmentation pathways are mutually exclusive and do not appear to coexist under the range of pH (7–14) conditions investigated. Herein, we employ a combination of quantitative ¹³C NMR measurements and density functional theory calculations to provide a rationale for this pH‐driven reaction divergence. These rationalizations also hold true for the reactions of dihydroxyfumarate produced in situ by the catalytic cyanide‐mediated dimerization of glyoxylate. In addition, the non‐enzymatic decarboxylation and fragmentation transformations of these central intermediates ( 3 and 14 ) appear to have intriguing parallels to the enzymatic reactions of oxalosuccinate and formation of glyceric acid derivatives in extant metabolism – the high and low pH mimicking the precise control exerted by the enzymes over reaction pathways. Copyright © 2016 John Wiley & Sons, Ltd.     

Enhanced superprism effect based on positive/negative lateral shift of reflective beam in a Fabry-Perot filter

It is found that when a light beam is incident obliquely on a thin film Fabry-Perot filter (FPF) from different incident media (air or substrate), the reflective beam will be shifted in both the forward and the backward directions. Based on this inverted spatial dispersion effect, two thin film FPFs with different directional lateral shifts are assembled to get a thin film superprism with a wider dispersion band. The thin film samples are fabricated as well as tested, and the results are in approximate agreement with numerical simulation.