Silica-Gel-Supported Dual Acidic Ionic Liquids as Efficient Catalysts for the Synthesis of Polyoxymethylene Dimethyl Ethers

The supported ionic liquids were prepared by anchoring 3-sulfobutyl-1-(3-propyltriethoxysilane) imidazolium hydrogen sulfate onto silica gel of different types. The properties of the catalysts were characterized by elemental analysis, Fourier transform infrared (FT-IR) spectra, scanning electron microscopy (SEM), thermogravimetry/differential scanning calorimetry (TG/DSC), and X-ray photoelectron spectroscopy (XPS). The catalytic activities of both the immobilized ionic liquids and the free one (1-butylsulfonate-3-methylimidazolium bisulfate, [MIM-BS]­[HSO4–]) were investigated by the synthesis of polyoxymethylene dimethyl ethers (DMMn) from methylal (DMM) and trioxane (TOX), which suggested that all covalently anchored ionic liquids have better catalytic effects than [MIM-BS]­[HSO4–]. The optimization experiment of catalyst dosage demonstrated that the acid amount of ionic liquid is a major factor for the catalytic activity

Palladium-Catalyzed Oxidative Aminocarbonylation: A New Entry to Amides via C–H Activation

A novel palladium-catalyzed oxidative aminocarbonylation reaction via C(sp3)–H activation was established, which provides a convenient and general method for the construction of arylacetamides via the carbonylation reaction of alkyl aromatics and amines. By using this protocol, the marketed drug ibuprofen could be easily obtained

Upgrading Ethanol to Higher Alcohols via Biomass-Derived Ni/Bio-Apatite

Acquiring value-added chemicals from renewable ethanol instead of fossil resources has special significance under the background of carbon neutrality. In this work, a heterogeneous recyclable biomass-derived Ni/bio-apatite catalyst was developed for upgrading ethanol to higher alcohols (C6+-OH). Catalysts were prepared employing calcined porous natural bone and analyzed by various characterizations of thermogravimetric analysis–differential thermal analysis, X-ray diffraction, high-angle annular dark field scanning transmission electron microscopy, X-ray photoelectron spectroscopy, H2-temperature-programmed reduction, and CO2-temperature-programmed desorption. The ethanol upgrading reaction can be achieved in the liquid phase without alkali additives, ligands, and extra hydrogen. The selectivity for C6+-OH reached as high as 67.7% at the single pass 55.6% ethanol conversion, substantially higher than the Anderson–Schulz–Flory distribution. Research shows that the porous structure and coordination between metal and alkaline sites could play key roles in C6+-OH selectivity. The catalyst recycles and reaction pathway of ethanol upgrading to higher alcohols were also discussed

Nickel-Catalyzed Alkynylation of a C(sp²)–H Bond Directed by an 8‑Aminoquinoline Moiety

An efficient nickel catalyst system for the direct ortho C–H alkynylation of the amides has been successfully developed with the directing assistance of 8-aminoquinoline. It was found that the flexible bis­(2-dimethylaminoethyl) ether (BDMAE) ligand was critical to achieve the optimized reactivity. This protocol showed good tolerance toward not only a wide range of (hetero)­aryl amides but also the rarely studied α,β-unsaturated alkenyl amide. The directing amide group could be easily transformed to aldehyde or ester in high yields. Meanwhile, the removable TIPS substituent on the resultant aryl/alkenyl alkynes could be further converted to an aryl moiety through a Sila–Sonogashira coupling reaction. This Ni-catalyzed alkynylation procedure provides an alternative approach to construct a C­(sp²)–C­(sp) bond

Iridium-Catalyzed Asymmetric Transfer Hydrogenation of Quinolines in Biphasic Systems or Water

An asymmetric transfer hydrogenation (ATH) of quinolines in water or biphasic systems was developed. This ATH reaction proceeds smoothly without the need for inert atmosphere protection in the presence of a water-soluble iridium catalyst, which bears an easily available aminobenzimidazole ligand. This ATH system can work at a catalyst loading of 0.001 mol % (S/C = 100 000, turnover number (TON) of up to 33 000) under mild reaction conditions. The turnover frequency (TOF) value can reach as high as 90 000 h–1. A variety of quinoline and N-heteroaryl compounds are transformed into the desired products in high yield and up to 99% enantiomeric excess (ee)

Synergistic Acid-Catalyzed Synthesis of <i>N</i>‑Aryl-Substituted Azacycles from Anilines and Cyclic Ethers

A metal-free and efficient approach to <i>N</i>-aryl-substituted azacycles from arylamines and cyclic ethers is described. In this synthesis, the synergistic effect between Lewis and Brønsted acids is crucial to the ring-opening of cyclic ethers and the subsequent cyclization. The use of B­(C₆F₅)₃ enabled the formation of frustrated Lewis pairs (FLPs) from the reactants, and the resulting FLPs allowed ready access to the <i>N</i>-arylazacycles in moderate to good yields via further cyclization. Water is the sole waste resulting from the reaction, thereby making it an environmentally benign process

Nitrogen-Functionalized Ordered Mesoporous Carbons as Multifunctional Supports of Ultrasmall Pd Nanoparticles for Hydrogenation of Phenol

N-functionalized ordered mesoporous carbons could be readily obtained by post-synthesis treatment with nitrogen containing molecules to achieve materials with a nitrogen loading as high as 8.6 wt % and well preserved mesopore structure. Using NH₃ as nitrogen source dramatically increased the Brunauer–Emmett–Teller (BET) surface area and pore volume of the resultant hybrid material; however, N-doping with melamine as a source resulted in the contrary results. The N-doped carbons were used as supports to immobilize small-sized Pd nanoparticles (PdNPs), which provided a unique platform to investigate the influence of metal nanoparticle size, mesostructural properties, and N-functionalized supports on the selective hydrogenation of phenol to cyclohexanone, an important intermediate in the production of nylon 6 and nylon 66 in the chemical industry. The catalyst with ultrasmall (about 1.2 nm) PdNPs gave the best reaction activity and selectivity under mild conditions. In addition, the present multifunctional catalyst demonstrated excellent catalytic stability and could be used 6 times without loss of product yields. This outstanding catalytic performance could be attributed to the synergetic effects of mesoporous structure, N-functionalized supports, and the stabilized ultrasmall PdNPs. This work might open new avenues for the development of functionalized catalysts with supported ultrasmall metal nanoparticles and hybrid porous support as well as their clean catalyses

CO₂ as a C1 Source: B(C₆F₅)₃‑Catalyzed Cyclization of <i>o</i>‑Phenylene-diamines To Construct Benzimidazoles in the Presence of Hydrosilane

The catalytic construction of benzimidazoles using CO₂ as a carbon source represents a facile and sustainable approach to obtaining these valuable compounds. Herein, we describe the B­(C₆F₅)₃-catalyzed synthesis of benzimidazoles via cyclization of <i>o</i>-phenylenediamines with CO₂ and PhSiH₃. This metal-free catalytic route achieves the desired products in high yield under convenient reaction conditions and is applicable to a broad substrate scope. A plausible mechanism for the reaction involving a frustrated Lewis pair pathway is proposed based on spectroscopic characterization (e.g., ¹³C NMR) of the reaction intermediates

Direct Oxidative Coupling of Enamides and 1,3-Dicarbonyl Compounds: A Facile and Versatile Approach to Dihydrofurans, Furans, Pyrroles, and Dicarbonyl Enamides

An efficient manganese­(III)-mediated oxidative coupling reaction between α-aryl enamides and 1,3-dicarbonyl compounds has been developed. A series of dihydrofurans and dicarbonyl enamides were synthesized in moderate to good yields. Moreover, these dihydrofurans could be readily transformed into the corresponding furans and pyrroles via the Paal–Knorr reaction

Corrosion Behavior of Metallic Materials in Acidic-Functionalized Ionic Liquids

This paper describes the influence of temperature, water content, and anionic type of acidic-functionalized ionic liquids (ILs), 1-(4-sulfobutyl)-3-methylimidazolium hydrogen sulfate ([BsMIM]­[HSO₄]) and 1-(4-sulfobutyl)-3-methylimidazolium toluenesulfonate ([BsMIM]­[OTs]), on the corrosion behavior of Fe, Ni, and 304 stainless steel (304SS). Electrochemical methods including electrochemical impedance spectroscopy (EIS) and Tafel plots were used to investigate it. Also, scanning electron microscopy (SEM) was used to characterize the nature of the corrosion morphology. The obtained electrochemical results indicated that increasing temperature accelerates the corrosion, while decreasing IL concentration retards the corrosion. The corrosion process is controlled by charge transfer. Moreover, the bisulfate anion (HSO₄^–) has an effect on the corrosion rate more significantly than the <i>p</i>-toluenesulfonate anion (OTs^–) does. The SEM spectrum showed that the corrosion situation of Fe is more serious than Ni and 304SS performed in IL-based solutions, especially in [BsMIM]­[HSO₄]. Also, the protective layer formed on the 304SS surface is more uniform. On the basis of these consistent finds, the corrosion mechanism is assumed