Herein, we report CO₂-mediated metathesis reactions between amines and DMF to synthesize formamides. More than 20 amines, including primary, secondary, aromatic, and heterocyclic amines, diamines, and amino acids, are converted to the corresponding formamides with good-to-excellent conversions and selectivities under mild conditions. This strategy employs CO₂ as a mediator to activate the amine under metal-free conditions. The experimental data and in situ NMR and attenuated total reflectance IR spectroscopy measurements support the formation of the N-carbamic acid as an intermediate through the weak acid–base interaction between CO₂ and the amine. The metathesis reaction is driven by the formation of a stable carbamate, and a reaction mechanism is proposed.

The first enantioselective copper-catalyzed decarboxylative propargylic alkylation has been developed. Treatment of propargyl β-ketoesters with a catalyst, prepared in situ from [Cu(CH₃CN)₄BF₄] and a newly developed chiral tridentate ketimine P,N,N-ligand under mild reaction conditions, generates β-ethynyl ketones in good yields and with high enantioselectivities without requiring the pregeneration of ketone enolates. This new process provides facile access to a range of chiral β-ethynyl ketones in a highly enantioenriched form.

The production of chemicals directly from sugars is an important step in biomass conversion. Herein, tetrahydro-2,5-furandimethanol (THFDM), obtained from fructose, is formed by using a combination of acid and hydrophobic Ru/SiO₂ in a water/cyclohexane biphasic system. Two key factors enable the high selectivity towards THFDM: modifying the hydrogenation catalyst so that it has hydrophobic properties, and the continuous hydrogenation of generated 5-(hydroxymethyl)furfural in the cyclohexane phase. Moreover, the selectivity towards THFDM is found to depend strongly on the acid catalyst used.

The first enantioselective copper-catalyzed decarboxylative propargylic alkylation has been developed. Treatment of propargyl β-ketoesters with a catalyst, prepared in situ from [Cu(CH₃CN)₄BF₄] and a newly developed chiral tridentate ketimine P,N,N-ligand under mild reaction conditions, generates β-ethynyl ketones in good yields and with high enantioselectivities without requiring the pregeneration of ketone enolates. This new process provides facile access to a range of chiral β-ethynyl ketones in a highly enantioenriched form.

Au nanoclusters with an average size of approximately 1 nm size supported on HY zeolite exhibit a superior catalytic performance for the selective oxidation of 5-hydroxymethyl-2-furfural (HMF) into 2,5-furandicarboxylic acid (FDCA). It achieved >99 % yield of 2,5-furandicarboxylic acid in water under mild conditions (60 °C, 0.3 MPa oxygen), which is much higher than that of Au supported on metal oxides/hydroxide (TiO₂, CeO₂, and Mg(OH)₂) and channel-type zeolites (ZSM-5 and H-MOR). Detailed characterizations, such as X-ray diffraction, transmission electron microscopy, N₂-physisorption, and H₂-temperature-programmed reduction (TPR), revealed that the Au nanoclusters are well encapsulated in the HY zeolite supercage, which is considered to restrict and avoid further growing of the Au nanoclusters into large particles. The acidic hydroxyl groups of the supercage were proven to be responsible for the formation and stabilization of the gold nanoclusters. Moreover, the interaction between the hydroxyl groups in the supercage and the Au nanoclusters leads to electronic modification of the Au nanoparticles, which is supposed to contribute to the high efficiency in the catalytic oxidation of HMF to FDCA.

Complexation was innovatively utilized to design a novel catalytic system for the selective oxidation of toluene, which runs contrary to the traditional definition of organic metal complex catalysis. In the present system, an N-heteroaromatic ring-containing N-hydroxy compound acts as the catalytically active component. Through an electron-withdrawing effect produced by the occurring complexation with proper metal salts, which was characterized by real-time in situ Fourier transform infrared spectra, the activity of the organic molecule could be remarkably improved. The combination of copper(II) chloride with 6-hydroxy-pyrrolo[3,4-b]pyrazine-5,7-dione showed the best activity, and an inert hydrocarbon such as toluene could be efficiently transformed with 70.9% conversion and 93.5% selectivity to benzoic acid at 90 °C within 2 h.

The substituents of quinones play an important role in modulating the kinetics of the electron- and proton-transfer reaction. In this paper, the steric effects of substituents of quinones on their catalytic performance were studied in the oxidation of ethylbenzene and ascorbate. The substituents limited the addition of the free radicals to the CC double bonds of the quinone ring because of the steric hindrance. On the other hand, too many substituents hindered the contact between the active site (CO) of quinone and the reactant. So, the quinones with two substituents presented better catalytic performance than those with more or less substituents. These results will be helpful in designing the quinone compounds for drugs and in understanding the catalytic behavior of quinones in biochemistry. Copyright © 2010 John Wiley & Sons, Ltd.

BACKGROUND: Catalytic oxidation of toluene with dioxygen is a fundamental industrial technology because the oxidized products are important intermediates for many fine chemicals. In this study, phenyl modification was utilized to alter catalyst surface characteristics in order to enhance activity.

RESULTS: Phenyl groups were successfully immobilized on the surface of Mn-containing hexagonal mesoporous silica (HMS) through a one-step synthesis route, as demonstrated by detailed characterization. As a result, the surface of the catalyst PhMnHMS was more hydrophobic with a water droplet contact angle of 96°. In the oxidation of toluene to benzoic acid with dioxygen under solvent-free conditions, this new catalyst showed higher activity and selectivity than non-organomodified MnHMS, and the conversion and selectivity increased by a factor of 40% and 9%, respectively.

CONCLUSION: Modification of the catalyst surface with phenyl groups was an effective strategy to increase activity in the oxidation of toluene. Both conversion and selectivity were improved and this is linked to the hydrophobic character of the surface. This organic modification strategy may also be extended for oxidation of other hydrocarbons. Copyright © 2009 Society of Chemical Industry

An embedded catalyst for the oxidative dehydration of glycerol, featuring iron oxide (FeO_x) domains on the surface of an iron orthovanadate (FeVO₄) phase, is developed. Catalytic reactions are conducted in a fixed-bed reactor at 300 °C with a feed composition N₂/O₂/H₂O/glycerol=66.6:1.7:30.3:1.5. Catalytic results show that the catalyst exhibits a better performance than an FeO_x catalyst prepared by impregnation and than a mixture of FeVO₄ and Fe₂O₃. The best yield for acrylic acid was 14 %. The presence of FeO_x domains on the surface of FeVO₄ catalyzes the oxidation of acrolein to acrylic acid. The catalysts are characterized by a range of techniques. The interaction between the nanometer-sized FeO_x domains and the FeVO₄ phase is strong enough to stabilize the FeO_x and retain its high activity. The proximity of the two phases provides an environment for the dehydration of glycerol and the oxidation of acrolein to acrylic acid.

BACKGROUD: Direct oxidation of alkylaromatics to the corresponding aromatic ketone is an important process in the manufacture of perfumes, pharmaceuticals, flavors, dyes and agrochemicals. For example, tetralin is oxidized to produce 1-tetralinone, which is a key intermediate in the commercial production of 1-naphthol, 2-hydroxy-1-tetralone, aureolic acid antibiotics and other pharmaceuticals.

RESULTS: In this investigation, it was found that alkylaromatics could be efficiently and selectively oxidized to the corresponding aromatic ketones when methyl violet was employed as a promotor in the presence of N-hydroxyphthalimide (NHPI); tetralin was oxidized with 89% conversion and 76% selectivity to 1-tetralinone under 0.3 MPa of O₂ at 75 °C for 2.5 h. The effects of temperature, oxygen pressure, reaction time and additive inclusion were studied in detail. A possible reaction mechanism for tetralin oxidation has been proposed.

CONCLUSION: It was demonstrated that methyl violet could efficiently promote the aerobic oxidation of alkylaromatics in the presence of NHPI under mild conditions. Further investigations indicated that the nitrogen cation had a crucial promotion effect in the oxidation process. Copyright © 2009 Society of Chemical Industry

Reducing regents, such as ascorbic acid, are needed for vanadium-containing catalysts to catalyze the direct oxidation of benzene to phenol by dioxygen. Quadrivalent vanadium species, reduced from quinquevalent vanadium species, can activate dioxygen to produce active oxygen species, which is important for the reaction. The key step is to prepare more V⁴⁺-containing catalysts. Here, VO_X-C₁₆-A was prepared in an acidic medium to produce more V⁴⁺ species. The results of XPS and XRD studies confirmed that the vanadium species in VO_X-C₁₆-A was mainly V⁴⁺ ions. The results of XRD and electron diffraction patterns revealed that VO_X-C₁₆-A consisted of tetragonal VO₂ and monoclinic VO₂. Morphology observations display that the VO_X-C₁₆-A is made of nanorod. Investigations into the performances of the catalysts showed that VO_X-C₁₆-A was reusable, producing a 1.9% conversion of benzene without reducing agent.

BACKGROUND: Hydrocarbon oxidation reactions are central to numerous processes that convert bulk chemicals into useful and higher-value products. In this investigation, an efficient metal-free catalytic system for aerobic oxidation of aromatic hydrocarbons was successfully established by synthesizing a series of aryl-tetrahalogenated N-hydroxyphthalimides and applying these compounds with 1,4-diamino-2,3-dichloroanthraquinone (DADCAQ).

RESULTS: Ethylbenzene was oxidized with 82.3% conversion and 86.9% selectivity to acetophenone catalyzed by the system of TCNHPI/DADCAQ under 0.3 MPa of molecular oxygen at 100 °C for 5 h. Other hydrocarbons were oxidized with high efficiency using this catalytic system. For example, indane can be converted completely to indan-1-one with 98.0% selectivity.

CONCLUSION: A highly efficient metal-free catalytic system consisting of TCNHPI and DADCAQ was developed for the oxidation of aromatic hydrocarbons with molecular oxygen. Aryl-halogen substituents served to significantly increase the activities of the catalytic system. The results in this study can form the basis for the design of an efficient hydrocarbon oxidation process. Copyright © 2008 Society of Chemical Industry