Reductive N‑Alkylation of Nitro Compounds to <i>N</i>‑Alkyl and <i>N</i>,<i>N</i>‑Dialkyl Amines with Glycerol as the Hydrogen Source

As the sustainable and promising hydrogen source, here, glycerol was directly used as the hydrogen source for the reductive amination of alcohol using nitrobenzene as the starting material. The amination of alcohols, especially aliphatic alcohols with different structures, was realized, and mono- or disubstituted amines were synthesized with excellent yields. The reaction mechanism was also explored

Ionic Liquid as an Efficient Promoting Medium for Fixation of CO₂: Clean Synthesis of α-Methylene Cyclic Carbonates from CO₂ and Propargyl Alcohols Catalyzed by Metal Salts under Mild Conditions

Reactions of propargylic alcohols with CO2 in a [BMIm][PhSO3]/CuCl catalytic system to produce the corresponding α-methylene cyclic carbonates were conducted with high yields. Mild reaction conditions, enhanced rates, improved yields, and recyclable ionic liquid catalyst systems are the remarkable features exhibited in this process. Furthermore, the use of large amounts of tertiary amines as well as nitrogen-containing organic solvent as employed in previously studies was avoided

Reductive Amination of Aldehydes and Amines with an Efficient Pd/NiO Catalyst

<div><p></p><p>By applying a simple Pd/NiO catalyst, the reductive amination of amines and aldehydes can progress efficiently under mild reaction conditions, and 24 substituted amines with different structures were synthesized with up to 98% isolated yields.</p> </div

From CO Oxidation to CO₂ Activation: An Unexpected Catalytic Activity of Polymer-Supported Nanogold

A simple, clean, safe, and reproducible catalyst system, polymer-supported nanogold, was successfully developed for the fixation of CO2 to cyclic carbonate and for the carbonylation of amines to disubstituted ureas with unprecedented catalytic activity (TOF > 50 000 mol/mol/h and TOFP ≈ 3000 mol/mol/h, respectively). To the best of our knowledge, it was the first to report that nanogold catalysts have exclusive catalytic activity for activation of carbon dioxide, and that the catalytic activity of the polymer-immobilized nanogold catalysts could be controlled by the particle size of the nanogold

Hydroxyl Ionic Liquids: The Differentiating Effect of Hydroxyl on Polarity due to Ionic Hydrogen Bonds between Hydroxyl and Anions

The polarity of a series of ionic liquids (ILs) based on hydroxyethyl-imidazolium moiety with various anions ([PF6], [NTf2], [ClO4], [DCA], [NO3], [AC], and [Cl]) and their corresponding nonhydroxyl ILs was investigated by solvatochromic dyes and fluorescence probe molecules. Most of the nonhydroxyl ILs exhibit anion-independent polarity with similar ET(30) in the narrow range of 50.7−52.6 kcal/mol, except [EMIm][AC] (49.7 kcal/mol). However, the polarity of the hydroxyl ILs covers a rather wide range (ET(30) = 51.2−61.7 kcal/mol) and is strongly anion-dependent. According to their ET(30) or ET(33) values, the hydroxyl ILs can be further classified into the following three groups: (Ι) acetate-based hydroxyl ILs [HOEMIm][AC] exhibit polarity scale (ET(30) = 51.2 kcal/mol) similar to short chain alcohol and fall in the range of the nonhydroxyl ILs; (II) Hydroxyl ILs containing anions [NO3], [DCA], and [Cl] exhibit comparable polarity (ET(30) = 55.5−56.9 kcal/mol), moderately higher than those of their nonhydroxyl ILs; (III) Hydroxyl ILs containing anions [PF6], [NTf2], and [ClO4] possess unusual “hyperpolarity” (ET(30) = 60.3−61.7 kcal/mol) close to protic ILs and water. Kamlet−Taft parameters and density functional theory calculations indicated that the greatly expanded range of polarity of hydroxyl ILs is correlated to an intramolecular synergistic solvent effect of the ionic hydrogen-bonded HBD/HBA complexes generated by intrasolvent HBD/HBA association between the anions and the hydroxyl group on cations, wherein hydroxyl group exhibits a significant differentiating effect on the strength of H-bonding and thus the polarity. Spiropyran-merocyanine equilibrium acted as a model polarity-sensitive reaction indeed shows obviously polarity-dependent solvatochromism, photochromism, and thermal reversion in hydroxyl ILs

Ionic Liquid as an Efficient Promoting Medium for Fixation of Carbon Dioxide: A Clean Method for the Synthesis of 5-Methylene-1,3-oxazolidin-2-ones from Propargylic Alcohols, Amines, and Carbon Dioxide Catalyzed by Cu(I) under Mild Conditions

The reactions of propargylic alcohols, aliphatic primary amines, and CO2 were conducted in CuCl/[BMIm]BF4 system to produce the corresponding 5-methylene-1,3-oxazolidin-2-ones under relatively mild conditions. The products could be conveniently isolated by means of liquid−liquid extraction. The solvent ionic liquid as well as CuCl catalyst can be recovered and reused three times without appreciable loss of activity. By this green approach, several new 5-methylene-1,3-oxazolidin-2-ones were prepared in excellent yields and purity and were well-characterized

Investigation of Physicochemical Properties of Lactam-Based Brønsted Acidic Ionic Liquids

Novel lactam-cation-based Brønsted acid ionic liquids (ILs) were prepared through a simple and atom-economic neutralization reaction between a lactam, such as caprolactam and butyrolactam, and a Brønsted acid, HX, where X is BF4-, CF3COO-, phCOO-, ClCH2COO-, NO3-, or H2PO4-. The density, viscosity, acidic scale, electrochemical window, temperature dependency of ionic conductivity, and thermal property of these ILs were measured and investigated in detail. The results show that protonated caprolactam tetrafluoroborate (CPBF) has a relatively strong acidity with −0.22 of Hammett acidic scale H0 and caprolactam trifluoroacetate (CPTFA) and pyrrolidonium trifluoroacetate (PYTFA) ILs possess very low viscosities, that is, 28 cP and 11 cP, respectively. An investigation of thermal property showed that a wide liquid range (up to −90 °C), moderate thermal stability (up to 249 °C for 10% of decomposition), and complex polymorphism were observed in these ILs. In comparison to imidazolium-cation-based ILs, the lactam-cation-based Brønsted acid ILs have a relatively lower cost, lower toxicity, and comparable ion conductivity and heat storage density (more than 200 MJ/m3). They have wide applicable perspectives for fuel cell devices, thermal transfer fluids, and acid-catalyzed reaction media and catalysts as replacements of conventional inorganic acids

Novel Ionic Liquid Crystals Based on <i>N</i>-Alkylcaprolactam as Cations

A novel series of ionic liquids (ILs) based on N-alkyl-ε-caprolactam as cations [Cn−CP]+ (Cn = alkyl with different numbers of C atoms; n = 6, 8, 10, 12, 16, or 18) containing toluene-p-sulfonate [TS]- and methanesulfonate [MS]- as anions have been synthesized via a one-step atom-economic reaction. Characterizations of these ILs by differential scanning calorimetry, polarizing optical microscopy, variable-temperature powder X-ray diffraction, etc., were conducted. The results showed that the caprolactam-based ILs (n ≥ 8) were enantiotropic thermotropic liquid crystals, except for C18−CPMS (monotropic), and displayed smectic A phases. Some properties, such as higher transition enthalpies (e.g., ΔH = 83.1 kJ/mol for C18−CPTS), higher specific heat capacities (e.g., Cp = 2.85 J/g·K for C16−CPTS) and higher heat storage densities (e.g., sensible heat storage density Es = 262.8l MJ/m3 for C16−CPTS; latent heat storage density El = 146.0 MJ/m3 for C18−CPTS), were observed. Fluorescence measurements showed that the homologous Cn−CPTS ILs exhibited strong fluorescence behavior. Finally, the test of acute toxicity toward rats showed that these new ILs were less toxic than the popular [BMIm]BF4 IL

Benzonitrile as a Probe of Local Environment in Ionic Liquids

Because of its sensitivity to chemical and electrostatic characteristics, nitrile group as an infrared (IR) probe to monitor the local structure, folding kinetics, and electrostatic environment of protein, or solvation of molecular solvents, has attracted increasing attention. Herein, by choosing benzonitrile and imidazolium ionic liquids (ILs) as the IR probe and model ILs, respectively, we report that the nitrile stretching vibration (νCN) could be utilized as a simple and substantial IR probe to monitor the local environment of ILs such as hydrogen bonding (H-bonding) as well as intrinsic electric field. In 1-alkyl-3-methylimidazolium-based non-hydroxyl ILs, the νCN is in a “free” state, and is less affected by the alkyl chain, while it significantly decreases with the effective anion charge. In 1-(2-hydroxyethyl)-3-methylimidazolium-based hydroxyl ILs, however, a distinct anion-dependent νCN forming H-bonding with the hydroxyl is also observed besides the “free” νCN band. The “free” component of νCN can be further employed to determine the intrinsic electric field in both non-hydroxyl (directly) and hydroxyl (indirectly by subtracting H-bonding contribution) ILs by using vibrational Stark effect. Moreover, the result suggests that benzonitrile is preferentially located in the charge domain in ILs and it could be a more suitable probe to report the ionic network rather than the nonpolar domain in ILs