Transient Stabilization Effect of CO2 in the Electrochemical Hydrogenation of Azo Compounds and the Reductive Coupling of α-Ketoesters.

The carbon dioxide (CO2 ) capture and utilization has attracted a great attention in organic synthesis. Herein, an unpresented transient stabilization effect (TSE) of CO2 is disclosed and well applied to the electrochemical hydrogenation of azo compounds to hydrazine derivatives. Mechanistic experiments and computational studies imply that CO2 can capture azo radical anion intermediates to protect the hydrogenation from potential degradation reactions, and is finally released through decarboxylation. The promotion effect of CO2 was further demonstrated to work in the preliminary study of electrochemical reductive coupling of α-ketoesters to vicinal diol derivatives. For the electrochemical reductive reactions mentioned above, CO2 is indispensable. The presented results shed light on a different usage of CO2 and could inspire novel experimental design by using CO2 as a transient protecting group.

CF3CO2H-Catalyzed Synthesis of 3-Alkynylpyrrole Derivatives and Their Controlled Reduction.

A transition-metal-free methodology employing nitroenynes and enaminones has been developed to access 3-alkynylpyrrole derivatives. This mild cyclization reaction might proceed through the nucleophilic addition, intramolecular cyclization, and the subsequent elimination processes. The protocol features a broad substrate scope, good selectivity, and functional group tolerance. Notably, the advantage of this method is also highlighted by the controlled reduction to generate alkenyl- or alkylpyrrole derivatives in good to excellent yields.

Hydrosilane-Assisted Synthesis of Urea Derivatives from CO2 and Amines.

A methodology employing CO2, amines, and phenylsilane was discussed to access aryl- or alkyl-substituted urea derivatives. This procedure was characterized by adopting hydrosilane to promote the formation of ureas directly, without the need to prepare silylamines in advance. Control reactions suggested that FeCl3 was a favorable additive for the generation of ureas, and this 1,5,7-triazabicyclo[4.4.0]dec-5-ene-catalyzed reaction might proceed through nucleophilic addition, silicon migration, and the subsequent formal substitution of silylcarbamate.

Synthesis of fused-tetrahydropyrimidines: one-pot methylenation-cyclization utilizing two molecules of CO2.

A methylenation-cyclization reaction, employing cyclic enaminones with primary aromatic amines and two molecules of CO2, furnishing fused-tetrahydropyrimidines, is discussed. In this Cs2CO3 and ZnI2 catalyzed one-pot two-step procedure, two molecules of CO2 were selectively converted to methylene groups. The multi-component reaction might proceed through the formation of bis(silyl)acetal which was followed by condensation and further aza-Diels-Alder reaction. Hydroquinazoline, hydrocyclopenta[d]pyrimidine and hydroindeno[1,2-d]pyrimidine derivatives could be prepared with CO2 as the C1 source, effectively.

A Mini Review of S-Nitrosoglutathione Loaded Nano/Micro-Formulation Strategies.

As a potential therapeutic agent, the clinical application of S-nitrosoglutathione (GSNO) is limited because of its instability. Therefore, different formulations have been developed to protect GSNO from degradation, delivery and the release of GSNO at a physiological concentration in the active position. Due to the high water-solubility and small molecular-size of GSNO, the biggest challenges in the encapsulation step are low encapsulation efficiency and burst release. This review summarizes the different nano/micro-formulation strategies of a GSNO related delivery system to provide references for subsequent researchers interested in GSNO encapsulation.

Investigating the Rheology and Stability of Heavy Crude Oil-in-Water Emulsions Using APG08 Emulsifiers.

This work investigates the performance of isooctyl glucoside (APG08) as an emulsifier for the preparation of a Karamay heavy crude oil-in-water emulsion to facilitate its pipeline transportation. First, various factors affecting the rheology and stability of prepared emulsions were studied. The results revealed that the viscosity and stability of emulsions increased with increasing oil content, surfactant concentration, mixing speed, mixing time, and pH of the aqueous phase. Emulsion viscosity was initially unchanged with the increase in homogenization temperature and then increased while emulsion stability decreased. Meanwhile, the optimal values of key parameters were 75 wt % oil content, 0.5 wt % surfactant concentration, temperature of 30 °C, mixing speed of 750 rpm, mixing time of 10 min, and aqueous phase pH of 11.14, resulting in a viscosity reduction of 88.82% and emulsion stability up to 48 h at 96.27%. In addition, a qualitative relationship between the stability and rheology of emulsions was elaborated by analyzing the experimental results. The findings showed that an increase in emulsion stability was accompanied by an increase in emulsion viscosity. Therefore, emulsion viscosity cannot become very high while improving emulsion stability to ensure proper transportation.

Components Interaction of Cotton Stalk under Low-Temperature Hydrothermal Conversion: A Bio-Oil Pyrolysis Behavior Perspective Analysis.

The conversion of agricultural and forestry waste biomass materials into bio-oil by mild hydro-thermal technology has a positive effect on extending the agricultural industry chain and alleviating the world energy crisis. The interaction investigation of biomass components during bio-oil formation can be significant for the efficient conversion of lignocellulose when different raw materials are fed together. In this paper, a bio-oil pyrolysis behavior (thermogravimetric analysis, TG) perspective component interaction investigation of cotton stalks under low-temperature hydro-thermal conversion (220 °C) was studied. Cellulose, hemi-cellulose, lignin, and protein were used as lignocellulose model components, by their simple binary blending and multi-variate blending and combined with thermo-gravimetric analysis and gas chromatography-mass spectrometry (GC-MS) characterization and analysis. The interaction of different model components and real biomass raw material components in the hydro-thermal process was explored. Results showed that the components of hydro-thermal bio-oil from cotton stalks were highly correlated with the interactions between cellulose, hemi-cellulose, lignin, and protein. During the hydro-thermal process, cellulose and hemi-cellulose inhibit each other, which reduces the content of ketones, aldehydes, ethers, and alcohols in bio-oil. Interaction between cellulose and lignin was obvious, which promotes the formation of oligomers, such as ketones, aldehydes, esters, phenols, and aliphatic, while inhibiting the production of aromatic and multi-hybrid compounds. Otherwise, there was no obvious interaction effect between hemi-cellulose and lignin or between lignin and protein. This research will guide the industrialization of lignocellulose, especially the possible co-feed hydro-thermal conversion technology.

Cotton stalk-derived hydrothermal carbon for methylene blue dye removal: investigation of the raw material plant tissues.

Conversion of the abundant agricultural residual cotton stalk (CS) into useful chemicals or functional materials could alleviate the fossil fuels caused energy shortages and environmental crises. Although some advances have been achieved, less attention has been paid to the plant tissues effect. In this study, the plant tissue of CS was changed by part degradation of some components (hemicelluloses and lignin, for example) with the aid of acid/base (or both). The pretreated CS was transformed into hydrochar by hydrothermal carbonization (HTC) method. Morphological and chemical compositions of CS hydrochar were analyzed by various techniques, including elemental analysis, Fourier transform infrared (FTIR), BET analysis, X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). Methylene blue (MB) removal of prepared CS hydrochar was used to evaluate CS hydrochar pollutions adsorption capacity. Results reveal acid/base (or both) pretreatment is beneficial for CS raw material to prepare high-quality CS hydrochar. The effects of some parameters, such as initial MB concentration, temperature, pH value and recyclability on the adsorption of MB onto both acid and base-pretreated CS hydrochar (CS-H2SO4 + NaOH-HTC) were studied. The present work exhibits the importance of agricultural waste biomass material plant tissues on its derived materials, which will have a positive effect on the direct utilization of waste biomass.

PhB(OH)2-Promoted Electrochemical Sulfuration-Formyloxylation of Styrenes and Selectfluor-Mediated Oxidation-Olefination.

We report a PhB(OH)2-promoted electrochemical sulfuration-formyloxylation reaction of styrenes employing commercially available thiophenols/thiols as thiolating agents. Specifically, metal catalysts and external chemical oxidants are not needed in the reaction for the formation of ß-formyloxy sulfides, and these sulfides can be further converted to (E)-vinyl sulfones via the Selectfluor-mediated oxidation-olefination. Notably, on the basis of this electrochemical oxidation strategy, ß-hydroxy sulfide, ß-formyloxy sulfoxide, ß-formyloxy sulfone, and (E)-vinyl sulfoxide can also be easily prepared.

The Effect of Temperature and Sputtered Particles on the Wettability of Al/Al2O3.

Two kinds of Al2O3 ceramic samples with and without Al film deposited were designed respectively. The influences of temperature and high kinetic energy sputtering particles on the wettability and interface strength of Al/Al2O3 were studied by comparing the wetting behavior of molten aluminum on two samples. The results show that molten aluminum does not wet the Al2O3 sample without Al film deposited at 700 °C, the contact angle is 165°, and the interfacial shear strength is 28 MPa. With the increase of temperature, the contact angle decreases continuously, and the interface shear strength gradually increases. The fracture of the brazed joint is transferred from the interface to the brazing seam. In comparison, the sample deposited with Al film is wetted by molten aluminum at 700 °C, and the contact angle is only 12°. The interface shear strength is about 120 MPa and is less affected by temperature. The shear fracture of the joint occurs in the brazed seam of Al metal. Therefore, the high energy generated by either the temperature increase or the particle sputtering enable the Al atoms to overcome the energy barrier to form Al-O bonds with the O atoms on the Al2O3 ceramic surface, thereby improving the wettability of Al/Al2O3.

Reductive CO2 Fixation via the Selective Formation of C-C Bonds: Bridging Enaminones and Synthesis of 1,4-Dihydropyridines.

Herein, a selective tandem C-C bond-forming reaction with CO2 was developed to realize the bridging of enaminones and synthesis of 1,4-dihydropyridines, respectively. n-Butylamine significantly promoted this CO2 deoxymethylenation procedure catalyzed by 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) and ZnCl2. The mechanism involving the formation of bis(silyl)acetal, nucleophilic addition, and amine elimination was also interpreted to clarify the bridging of two molecules of enaminones with CO2 and the generation of dihydropyridine derivatives.