Leiduan Hao

A Protic Ionic Liquid Catalyzes CO2 Conversion at Atmospheric Pressure and Room Temperature: Synthesis of Quinazoline‐2,4(1H,3H)‐diones

The chemical fixation of CO2 under mild reaction conditions is of significance from a sustainable chemistry viewpoint. Herein a CO2-reactive protic ionic liquid (PIL), [HDBU(+)][TFE(-)], was designed by neutralization of the superbase 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) with a weak proton donor trifluoroethanol (TFE). As a bifunctional catalyst for simultaneously activating CO2 and the substrate, this PIL displayed excellent performance in catalyzing the reactions of CO2 with 2-aminobenzonitriles at atmospheric pressure and room temperature, thus producing a series of quinazoline-2,4(1H,3H)-diones in excellent yields.

Selective oxidation of glycerol to lactic acid under acidic conditions using AuPd/TiO2 catalyst

The selective oxidation of glycerol was investigated using AuPd/TiO2 as the catalyst in the presence of AlCl3, and lactic acid was obtained as the predominant product. It was demonstrated that AuPd/TiO2 and AlCl3 played synergistic roles in the production of lactic acid. The possible reaction pathway was proposed, in which glycerol was first oxidized to glyceraldehyde and dihydroxyacetone, catalysed by AuPd/TiO2, followed by the formation of lactic acid, catalyzed by AlCl3.

Azole-Anion-Based Aprotic Ionic Liquids: Functional Solvents for Atmospheric CO2 Transformation into Various Heterocyclic Compounds

The chemical transformation of atmospheric CO2 is of great significance yet still poses a great challenge. Herein, azole-anion-based aprotic ionic liquids (ILs) were synthesized by the deprotonation of weak proton donors (e.g., 2-methylimidazole, 4-methylimidazole, and 2,4-dimethylimidazole) with tetrabutylphosphonium hydroxide, [Bu4 P][OH]. We found that these ILs, such as [Bu4 P][2-MIm], could activate atmospheric CO2 through the formation of carbamates. The resultant carbamate intermediates could further react with various types of substrate, including propargylic alcohols, 2-aminobenzonitriles, ortho-phenylenediamines, and 2-aminothiophenol, thereby producing α-alkylidene cyclic carbonates, quinazoline-2,4(1 H,3 H)-diones, benzimidazolones, and benzothiazoline, respectively, in moderate-to-good yields. Thus, we have achieved the transformation of CO2 at atmospheric pressure, and we expect this method to open up new routes for the synthesis of various oxygen-containing heterocyclic compounds under metal-free conditions.

Au catalyzed synthesis of benzimidazoles from 2-nitroanilines and CO2/H2

The gold-catalyzed synthesis of benzimidazoles from 2-nitroanilines and CO2 in the presence of H2 was reported, and a series of benzimidazoles were obtained under relatively mild conditions. Several supported Au catalysts including Au/TiO2, Au/Al2O3, Au/ZnO, Au/polyurea and Au/hydrotalcite were examined for the synthesis of benzimidazole from the reaction of 2-nitroaniline with CO2 and H2, among which Au/TiO2 displayed the best performance. The reaction mechanism was investigated, and it was found that the production of benzimidazole underwent the formation of o-phenylenediamine via the hydrogenation of 2-nitroaniline, followed by the cyclization of o-phenylenediamine with CO2 and H2. This work provides a CO2-involved route for the synthesis of benzimidazoles, which may widen the applications of CO2 in the chemical synthesis.

Ionic liquid modified montmorillonite-supported Ru nanoparticles: highly efficient heterogeneous catalysts for the hydrodeoxygenation of phenolic compounds to cycloalkanes

The Ru/MMT@IL-SO3H catalyst was prepared by immobilizing Ru nanoparticles onto montmorillonite (MMT) with the assistance of an acidic ionic liquid (1-sulfobutyl-3-methylimidazolium hydrosulfate, IL-SO3H). Transmission electron microscopy examination indicated that the loaded Ru species were distributed uniformly on the MMT support with a particle size of about 1.3 nm, which existed mainly in the form of a metallic state as confirmed by X-ray photoelectron spectroscopy analysis. X-Ray diffraction analysis indicated that the interlayer distance of MMT was increased due to the impregnation of IL-SO3H. The activity of Ru/MMT@IL-SO3H for hydrodeoxygenation (HDO) of various phenolic compounds was investigated. It was demonstrated that the as-prepared catalyst served as a bifunctional catalyst and displayed high efficiency for HDO reactions of a series of phenolic compounds to cycloalkanes.

An Efficient and General Method for Formylation of Aryl Bromides with CO2 and Poly(methylhydrosiloxane)

The formylation of aryl halides with CO2 to generate aryl aldehydes is challenging. Herein, we report a novel synthesis of aryl aldehydes by formylation of aryl bromides with CO2 and a waste silane, poly(methylhydrosiloxane) (PMHS). It has been discovered that a simple combination of 1,3-bis(diphenyphosphino)propane (DPPP)-chelated Pd catalyst, Pd(DPPP)Cl2 , with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) is able to effectively catalyze the reaction, leading to aryl aldehydes in moderate to excellent yields, and without any by-products in most cases. Moreover, this route could be extended to the formylation of aryl iodides with high efficiency. This approach is simple, less costly, and environmentally friendly, and also widens the applications of CO2 to form value-added chemicals by the construction of new C-C bonds.

Ti3+ self-doped TiOx@anatase core–shell structure with enhanced visible light photocatalytic activity

Ti3+ self-doped TiOx@anatase core–shell structures were prepared via hydrolysis of Ti2(SO4)3 around TiO particles, followed by post-calcination at temperatures from 723 to 823 K. The as-prepared TiOx@anatase was examined by means of transmission electronic microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. It was demonstrated that the samples displayed core–shell structures with the shell in the anatase form and the core in the anatase and rutile phases, and a large number of Ti3+ ions were present. Electron paramagnetic resonance analysis indicated that the Ti3+ ions were located throughout the whole sample, including the shell, the core and the interface between the core and the shell. The as-prepared TiOx@anatase core–shell catalysts can absorb visible light and showed good activity for catalyzing the degradation of Rhodamine B under visible light irradiation. In particular, the TiOx@anatase obtained at 773 K showed the best performance, due to the high concentration of well-dispersed Ti3+ ions in the sample.

Atmospheric CO2 promoted synthesis of N-containing heterocycles over B(C6F5)3 catalyst

B(C6F5)3 combined with atmospheric CO2 was found to be highly effective for the cyclization of ortho-substituted aniline derivatives with N,N-dimethylformamide (DMF), and a series of N-containing heterocycles including benzothiazoles, benzimidazoles, quinazolinone and benzoxazole were obtained in good to excellent yields.

Hydrosilane-promoted cyclization of 2-aminothiophenols by CO2 to benzothiazoles

A new route is presented to synthesize benzothiazoles via cyclization of 2-aminothiophenols by CO2 in the presence of diethylsilane catalyzed by 1,5-diazabicyclo[4.3.0]non-5-ene, and a series of benzothiazoles were obtained in good yields.

Polyurea-supported metal nanocatalysts: synthesis, characterization and application in selective hydrogenation of o-chloronitrobenzene.

Polyurea (PU) spheres with size of 2-10 μm were derived through the polymerization of CO2 with 1,4-butanediamine, and characterized by FTIR spectroscopy, scanning electron microscopy and TG analysis. It was demonstrated that the PU spheres displayed flower-like morphology with the betel thickness around 30 nm, and they had high thermal stability. The resultant PU spheres were used to immobilize metal particles, and a series of PU-supported metal nanocatalysts including Pt/PU, Au/PU, Pd/PU were prepared via just mixing the metal precursors with the PU spheres in water, followed by the reduction of metal ions by NaBH4. Transmission electron microscopy examination indicated that the metal nanoparticles were distributed uniformly on the surface of the PU spheres with mean particle size less than 3.0 nm, and the Pt particles existed mainly in the form of metallic state as confirmed by the X-ray photoelectron spectroscopy analysis. The performance of the Pt/PU catalyst was tested in the catalytic hydrogenation of o-chloronitrobenzene, and a high selectivity of 99.5% toward o-chloroaniline at complete conversion of o-chloronitrobenzene was obtained at room temperature.