Ming Lu

An Efficient Procedure for Chloromethylation of Aromatic Hydrocarbons Catalyzed by PEG1000‐Dicationic Ionic Liquids in Aqueous Media

Chloromethyl-substituted aromatic compounds are very important intermediates which have been widely applied in synthesis of a variety of fine or special chemicals, such as pharmaceuticals, agrochemicals, dyes, flavors, fragrances, polymers, and additives. The oldest method for the synthesis of this class of compounds involves the chloromethylation of aromatic hydrocarbons with hydrochloric acid and the use of trioxane or paraformaldehyde in the absence of any catalyst; however, the reaction rate is very slow. Other classic methods for chloromethylation employ various Lewis acids, such as zinc chloride, stannic chloride, aluminum chloride, and boron trifluoride as the catalysts. Zinc chloride has been found to be an effective catalyst in a hydrochloric acid solution. 7–9] The use of Lewis acids is very important to improve the reactive activity. However, these catalysts, in general, are invariably associated with one or more disadvantages, such as tedious workup procedures, corrosiveness, high susceptibility to water, difficulty of catalyst recovery, environmental hazards, and waste control. Therefore, it is important to develop environmentally conscious catalysts that are active under mild conditions and can be easily recovered after the reaction for reuse. To attain these goals in the chloromethylation of aromatic hydrocarbons, our research project group proposed surfactant micelles, particularly cetyltrimethylammonium bromide (CTAB), as catalyst to synthesize chloromethylated hydrocarbons. Kishida et al. recently reported the use of rare earth metal triflates in the chloromethylation of aromatic hydrocarbons. 15, 16] However, the use of surfactant micelles suffers from difficulties encountered in their handling and separation after the reaction and also can not be reused for new reactions. Rare earth metal triflates are very expensive, which impeded their use for practical chemical processes. Ionic liquids (ILs) are a special class of molten salts composed of organic cations and inorganic or organic anions. Ionic liquids, with their unique properties, including low volatility, high polarity, good thermal stability over a wide temperature range, and selective dissolving capacity by a proper choice of cations or anions, have attracted increasing interest in the organic transformations as reaction medium and catalyst (ligand). Up to now, examples of their application as catalysts in the chloromethylation of aromatic hydrocarbons were seldom reported. 27] However, these ILs are inevitably associated with one or more disadvantages, such as low recovery ratio, high cost or difficulty of synthesis. In view of both the advantages and disadvantages of homogeneous and heterogeneous catalysts, and to improve catalyst recovery, multiphase systems, such as phase-transfer catalysis, thermoregulated phasetransfer catalysis, and liquid–liquid biphasic catalysis, have been studied. Some novel temperature-dependent ionic liquid biphasic catalytic systems have been reported recently, and found that they showed some advantages, such as high conversions and selectivity, stability at high temperatures, and reusability in the reaction, which provide a novel route for the separating and recycling of the catalysts. We now report an efficient and convenient procedure for the chloromethylation of aromatic hydrocarbons catalyzed by PEG1000-based dicationic ionic liquid (PEG1000-DIL) in aqueous media (Scheme 1). We found that the PEG1000-DIL/methylcyclohexane temperaturedependent biphasic system is active for chloromethylation and that it is an environmentally conscious catalytic system. The chloromethylation of ethylbenzene was initially carried out in an oil–water biphasic system in the presence and absence of PEG1000-DIL at 75 8C. In the absence of PEG1000-DIL,

Oxidation of Benzyl Halides to Aldehydes and Ketones with Potassium Nitrate Catalyzed by Phase-Transfer Catalyst in Aqueous Media

Abstract The catalytic oxidation of benzyl halides to aldehydes and ketones in aqueous media was studied under relatively mild reaction conditions by using phase-transfer catalyst combined with potassium nitrate and 10% aqueous potassium hydroxide solution. As a result, a simple high-yield procedure has been developed.

Pd Nanoparticles Immobilized on Fe3O4 @ Poly(ethylene glycol) Bridged Amine Functionalized Imidazolium Ionic Liquid: A Magnetically Separable Catalyst for Heck in Water

AbstractnA palladium-based catalyst supported on novel Fe3O4 @ Poly(ethylene glycol) bridged amine functionalized imidazolium ionic liquid (Fe3O4@PEG–AIm–NH2–IL) was successfully prepared by a facile method. The catalyst was characterized by FT-IR, TEM, VSM, XRD, XPS and TGA-DSC, which showed high activity and stability for the Heck reaction in pure water. Furthermore, the catalyst could be recovered in a facile manner from the reaction mixture and recycled five times without any loss in activity.Graphical AbstractA novel magnetically separable Fe3O4@PEG–AIm–NH2–IL–Pd was designed and synthesized, which was used as outstanding palladium catalyst for the Heck reaction in pure water. The supported catalyst could be recycled and reused with the simple application of an external magnetic field, while keeping similar catalytic activity for five successive reactions.

Oxidative Coupling of o-Phenylenediamine with Arylmethylamines to Synthesize Aryl-Substituted Benzimidazoles Under Catalyst-Free and Solvent-Free Conditions

Abstract Solvent-free oxidative synthesis of benzimidazoles from arylmethylamines and o-phenylenediamine has been achieved under catalyst-free conditions. This reaction can use tert-butyl hydroperoxide (TBHP) as the oxidant, and a wide variety of derivatives were obtained in good yields. The reaction mechanism was proposed and this method provides a direct and practical approach for the preparation of substituted benzimidazoles. GRAPHICAL ABSTRACT

Stabilization of the Pentazolate Anion in Three Anhydrous and Metal-Free Energetic Salts

According to previous reports, metal cations or water molecules are necessary for the stabilization of pentazolate anion (cyclo-N5- ) at ambient temperature and pressure. Seeking a new method to stabilize N5- is a big challenge. In this work, three anhydrous, metal-free energetic salts based on cyclo-N5- 3,9-diamino-6,7-dihydro-5u2009H-bis([1,2,4]triazolo)[4,3-e:3,4-g][1,2,4,5] tetrazepine-2,10-diium, N-carbamoylguanidinium, and oxalohydrazinium (oxahy+ ) pentazolate were synthesized and isolated. All salts were characterized by elemental analysis, IR spectroscopy, 1 H, 13 C, and (in some cases) 15 N NMR spectroscopy, thermal analysis (TGA and DSC), and single-crystal XRD analysis. Computational studies associated with heats of formation and detonation performance were performed by using Gaussianu200509 and Explo5 programs, respectively. The sensitivity of the salts towards impact and friction was determined, and overall the real N5 explosives showed promising energetic properties.

Green and Efficient Methods for One-Pot Aerobic Oxidative Synthesis of Benzimidazoles from Alcohols with TEMPO-PEG4000-NHC-Cu(II) Complex in Water

Abstract In this article, an amphiphilic catalyst TEMPO-PEG4000-NHC-Cu(II) [2,2,6,6-tetramethylpiperidine-1-oxyl/polyethylene glycol/N-heterocyclic carbene] complex was synthesized and used as a highly efficient catalyst for one-pot aerobic oxidative synthesis of benzimidazoles from alcohols. The reactions were applicable in water with good yields in the presence of catalyst (5 mol%). Moreover, the catalyst was easily recovered from the reaction mixture and reused with almost consistent activity. GRAPHICAL ABSTRACT

Aerobic Oxidation of Benzylic Halides to Carbonyl Compounds with Molecular Oxygen Catalyzed by TEMPO/KNO2 in Aqueous Media

Benzylic halides were successfully oxidized to the corresponding aldehydes and ketones in good to excellent yields in aqueous media with molecular oxygen as oxidant in the presence of catalytic amounts of TEMPO (2,2,6,6-tetramethylpiperidyl-1-oxy) and potassium nitrite (KNO2).

Theoretical studies on high energetic density nitramine explosives containing pyridine

The insensitive property of explosives containing pyridine is combined with the high energy of nitramine explosives, and the concept of new nitramine explosives containing pyridine is proposed, into which nitramine group with N-N bonds is introduced as much as possible. Based on molecular structures of nitramine compounds containing pyridine, density functional theory (DFT) calculation method was applied to study designed molecules at B3LYP/6–31+G(d) level. The geometric and electronic structures, density, heats of formation (HOF), detonation performance and bond dissociation energies (BDE) were investigated and comparable to 1,3,5-trinitro-1,3,5-triazinane (RDX) and 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX). The simulation results reveal that molecules B and D perform similarly to traditionally used RDX. Molecule E outperform RDX, with performance that approach that of HMX and may be considered as potential candidate of high energy density compound (HEDC). These results provide basic information for molecular design of novel high energetic density compounds.

Syntheses, Crystal Structures and Properties of a Series of 3D Metal-Inorganic Frameworks Containing Pentazolate Anion

Pentazolate anion (cyclo-N5- ), and/or N3- , NO3- were used as the ligands to obtain a series of nitrogen-rich energetic three-dimensional (3D) frameworks [Cu(N5 )(N3 )]n , [Ag(N5 )]n , [Ba(N5 )(NO3 )(H2 O)3 ]n , and [NaBa3 (N5 )6 (NO3 )(H2 O)3 ]n by self-assembly. These frameworks were characterized by single-crystal X-ray diffraction, SEM, IR and Raman spectroscopy, elemental analysis, and thermal analysis. All the frameworks exhibited regular supramolecular structures and excellent stabilities at room temperature which can be attributed to the strong coordination bonds between cyclo-N5- anions and metal ions. The successful stabilization of the cyclo-N5- in more 3D multi-ligand metal-N5- frameworks after Na-N5- frameworks has been demonstrated. This breakthrough offers new opportunities for the future of metal-pentazolate frameworks and polynitrogen chemistry.

Synthesis of Benzimidazoles via Iron-Catalyzed Aerobic Oxidation Reaction of Imine Derivatives with o-Phenylenediamine

Abstract A simple and efficient protocol for preparing benzimidazoles via Fe(NO3)3 · 9H2O-catalyzed aerobic oxidation reaction of imine derivatives with o-phenylenediamine. This process uses air as an economical and green oxidant, tolerates a wide range of substrates, and affords the targeted benzimidazoles in moderate to excellent yields. GRAPHICAL ABSTRACT