Search

Pivalic anhydride is shown to be an effective reagent for direct amidation of carboxylic acids with N-alkyl anilines under base-free conditions.

We report a catalyst-free method for the alkylation/annulation of N-arylacrylamides to give the corresponding 3-alkyl-2-oxo-2,3-dihydro-1H-indoles by using alkyl iodides as precursors of alkyl radicals. These reactions occur at moderate temperatures and are mediated by easily accessible K2S2O8 and Bu3N.

Using nitroarenes, sustainable solvents and a solid catalyst to synthesize quinoline compounds through a simple and continuous hydrogen transfer reaction.

The formation of free radicals using visible light as the energy source is of great synthetic value. Despite advances in the photoredox catalysis process using expensive Ir and Ru complexes or organic dyes, the discovery and employment of photocatalysts based on alternative, abundant, and inexpensive metal salts remain highly desired. Herein, the visible-light-induced decarboxylation of α-imino-oxy acids for the generation of iminyl radicals has been accomplished using nontoxic and inexpensive CeCl₃·7H₂O as the photocatalyst via the LMCT process. The iminyl-radical-mediated C–C cleavage/amination and alkene iminoamination have been achieved within this catalyst system.

An iminyl-radical-mediated cyanoalkylarylation of α,β-unsaturated imides with cyclic α-imino oxy acids leading to isoquinoline-1,3(2H,4H)-dione derivatives has been developed. The procedure involves the generation of iminyl radicals through silver-catalyzed oxidative decarboxylation, followed by a C–C bond cleavage, cyanoalkylation, and C–H-functionalization cascade.

Chlorine-containing volatile organic compounds (CVOCs) present in industrial exhaust gas can cause great harm to the human body and the environment. In order to further study the catalytic oxidation of CVOCs, an active site regulated RuOx/Sn0.2Ti0.8O2 catalyst with different Ru precursors was developed. With Dichloromethane as the model molecule, the activity test results showed that the optimization of Ru precursor using Ru colloid significantly increased the activity of the catalyst (T90 was reduced by about 90 °C when the Ru loading was 1 wt%). The analysis of characterization results showed that the improvement of the catalytic performance was mainly due to the improvement of the active species dispersion (the size of Ru cluster was reduced from 3–4 nm to about 1.3 nm) and the enhancement of the interaction between the active species and the support. The utilization efficiency of the active components was improved by nearly doubling TOF value, and the overall oxidation performance of the catalyst was also enhanced. The relationship between the Ru loading and the catalytic activity of the catalyst was also studied to better determine the optimal Ru loading. It could be found that with the increase in Ru loading, the dispersibility of RuOx species on the catalyst surface gradually decreased, despite the increase in their total amount. The combined influence of these two effects led to little change in the catalytic activity of the catalyst at first, and then a significant increase. Therefore, this research is meaningful for the efficient treatment of CVOCs and further reducing the content of active components in the catalysts.

A mild and metal-free procedure is reported for the aerobic oxidation of substituted toluenes to carboxylic acids by using CBr4 as initiator under irradiation from a 400 nm blue light-emitting diode.

An efficient intramolecular iodooxygenation of unsaturated ketoximes has been achieved through the activation of iodine by TBHP, yielding various types of synthetically versatile iodinated isoxazol...

A complementary and general strategy for the oxidative generation of iminyl radicals from the readily available α-imino-oxy acids has been established through silver-catalyzed decarboxylation. To demonstrate its synthesis utility, the direct C-H cyanoalkylation of heterocycles and quinones with cyclic α-imino-oxy acids via the iminyl radical-mediated C-C bond cleavage is developed. This cost-effective method takes place under mild reaction conditions and exhibits a broad substrate scope.

An unexpected regioselective I2/TBHP-mediated 1,2-iodo­oxygenation of alkenes with N-hydroxylamines is described. The reaction proceeds through a radical coupling mechanism or a iodonium mechanism, which is controlled by the structures of both N-hydroxylamines and alkenes, to form vicinal iodo-substituted N-alkoxyamines regioselectively. Both the iodo and alkoxyamine group of the resulting products offer rich possibilities of synthetic manipulations.

A general and efficient oxyhalogenation of unsaturated ketoximes has been achieved through copper catalysis with diethyl bromomalonate, N-chlorosuccinimide, and N-iodosuccinimide, yielding 5-chloromethyl, 5-bromomethyl, and 5-iodomethyl isoxazolines in good to excellent yields.

For the winemaking bioprocess of jujube wine, the selection of optimal starter cultures is one of the major concerns before fermentation. In this study, we investigated the effects of different winemaking yeasts on the composition of aroma-active compounds in the fermented jujube wine and identified the principal components that determine the flavor quality. It showed that the starter winemaking yeasts produced a total of 43 aroma-active compounds, of which esters (e.g., ethyl caprylate, ethyl decanoate, ethyl hexanoate, and phenethyl acetate) contribute more to the wine quality attributes, especially for the improvement of the aroma. Moreover, the composition of aroma-active compounds, for example, the ratio of the content of esters and alcohols, exerts a great impact on the flavor quality of jujube wine. Different starter winemaking yeasts resulted in significant differences in the composition (both species and content) of aroma-active compounds, and thus formed different flavors in the jujube wine. Thus, we propose that screening of a desirable starter winemaking yeast is essential before the fermentation of jujube wine at a large scale, and more considerations should be taken into the resulting composition of aroma-active compounds.

We report here, for the first time, a simple method to prepare ordered mesoporous carbon containing separate gold, and palladium nanoparticles (AuPd-OMC). Furthermore, the new catalysts were evaluated in the selective hydrogenation of cinnamaldehyde under atmospheric conditions. In comparison with the monometallic catalysts, the AuPd-OMC exhibited excellent catalytic activity (96.2% selectivity for hydro cinnamaldehyde). The observed synergistic effects were ascribed to hydrogen spillover. The Pd nanoparticles possess the main active sites that formed the active hydrogen species, while the Au nanoparticles served as active hydrogen acceptors and diluted the Pd active sites in order to suppress the deep hydrogenation.

A series of gold containing ordered mesoporous carbon (Au–OMC) samples are prepared by using two different hard templates: AuCl4−/SBA-15 as well as gold containing and amino functionalized SBA-15. The hard templates and obtained Au–OMC catalysts were investigated using Fourier transform infrared spectrum, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and nitrogen adsorption/desorption methods. Compared with Au–OMC1 using AuCl4−/SBA-15 as hard template, the Au–OMC2 using modified SBA-15 as hard template had highly dispersed Au nanoparticles with narrow particle size distribution (2.3 ± 0.5 nm) that exhibited much superior activity and selectivity in the liquid phase hydrogenation of nitro aromatic compounds. An important role is played in the post grafting of SBA-15 surface by amino and Au nanoparticles in the preparation of highly dispersed gold nanoparticles that are confined to the walls of an OMC.

A highly active and chemoselective assembled Pt/C(Fe) catalyst was prepared by an adsorption protocol. Pt nanoparticles (∼2.4 nm) in a Pt colloid solution obtained from the decomposition of Pt 2 (dba) 3 (dba = dibenzalacetone) were utilized as Pt precursors and adsorbed by Fe-modified active carbon (AC). The adsorption method makes Pt nanoparticles enriched on the surface of the catalyst, and the enrichment was further enhanced due to the presence of Fe in the active carbon, leading to the formation of more active sites exposed on the surface. XPS analysis revealed that a much more electron-deficient state of the Pt nanoparticles was existed due to the electron transfer between Pt nanoparticles and Fe 2 O 3 . This catalyst was used for the liquid phase hydrogenation of o -chloronitrobenzene ( o -CNB) to o -chloroaniline ( o -CAN) with the highest turnover frequencies (TOF) of 78 (mol o -CNB /(mol Pt s)) and a selectivity of 99.5% at complete conversion of o -CNB. The catalyst was also recycled for five times and the total turnover number was more than 625,000 (mol o -CNB /mol Pt ).

Ordered mesoporous ruthenium containing carbon (Ru-OMC) catalyst with semi-embedded uniform Ru particle distribution was synthesized by using RuCl3/SBA-15 as a hard template. The sucrose both acts as the carbon precursor and Ru3+ stabilizer. The use of RuCl3/SBA-15 makes more exposed Ru surface available for reactants. The turnover frequency of the Ru-OMC catalyst for hydrogenation of benzene reaches ca. 35,000 h− 1 at 4 MPa, 110 °C, which is 12 times improvement compared with that of Ru/OMC catalyst prepared by impregnation. The Ru-OMC catalyst can be recycled more than 9 times without much loss of performance and aggregation of Ru nanoparticles.

Carbon nanotubes (CNTs), γ-alumina (γ-Al 2 O 3 ) and silica (SiO 2 ) supported Pt and Pd catalysts were produced by laser vaporization deposition of respective bulk metals. The catalysts were characterized by inductive coupled plasma emission spectrometer (ICP), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The catalytic properties of the catalysts were investigated in the liquid phase hydrogenation of o -chloronitrobenzene ( o -CNB) to o -chloroaniline ( o -CAN) under 333 K and 1.0 MPa hydrogen pressure. The results show that the catalytic properties are greatly affected by the supports. Pt/CNTs catalyst exhibits the best catalytic performance among the Pt-based catalysts, producing o -CAN with 99.6% selectivity at complete conversion. Pd/CNTs catalyst exhibits the best catalytic performance among the Pd-based catalysts, giving o -CAN with 95.2% selectivity at complete conversion. For Pt-based catalysts, geometric effect and the textures and properties of the supports play important roles on catalytic properties. On the other hand, geometric effect, electronic effect and the textures and properties of the supports simultaneously influence the catalytic properties of the Pd-based catalysts. In addition, hydrogenolysis of the C–Cl bond can be well inhibited over all catalysts prepared by laser vaporization deposition.

In the novel catalytic transfer hydrogenation, 12 active hydrogen (H*) can be transferred from water/ethanol system as the efficient hydrogen donor and used directly for the hydrogenation of halogenated nitrobenzene over Ru–Fe/C catalyst, obtaining o-chloroaniline (o-CAN) with 98.0% selectivity at 99.8% conversion without hydrodehalogenation. Most other halogenated nitrobenzenes were reduced with selectivity >98%, and conversion >99.0%. Moreover, the Ru–Fe/C catalyst was still active after reaction for 480 h.

A pressing problem in supported-metal-nanoparticle heterogeneous catalysis—despite the long history and considerable fundamental as well as industrial importance of such heterogeneous catalysts—is how to monitor such catalysts’ formation more routinely, rapidly, and in real time. Such information is needed to better control the size, shape, composition, and thus resultant catalytic activity, selectivity, and lifetime of these important catalysts. To this end, a study is reported of the formation of supported Pt(0)n nanoparticles by H2 reduction of H2PtCl6 on Al2O3 (or TiO2) to give 6 equivalents of HCl plus supported Pt(0)n/Al2O3 (or Pt(0)n/TiO2), all while in contact with a solution of EtOH and cyclohexene. The HCl and Pt(0)n products were confirmed, respectively, by the stoichiometry of HCl formation using pHapparent measurements, appropriate standards, and by TEM and EDX measurements. The hypothesis of this research is that the kinetics of formation of this supported heterogeneous catalyst could be suc...

An efficient metal-free oxidative arylsulfonylation of α,β-unsaturated imides with sulfonylhydrazides leading to isoquinoline-1,3(2H,4H)-dione derivatives has been developed. The procedure involves the generation of sulfonyl radicals via cleavage of the S–N bond of sulfonylhydrazides with sulfonylation and C–H functionalization. The protocol uses the economical and environmentally friendly TBAI–TBHP catalytic system, and the corresponding isoquinoline-1,3(2H,4H)-diones with various functional groups were obtained in moderate to good yields.

An efficient metal-free oxidative arylsulfonylation of α,β-unsaturated imides with sulfonylhydrazides leading to isoquinoline-1,3(2H,4H)-dione derivatives has been developed. The procedure involves the generation of sulfonyl radicals via cleavage of the S–N bond of sulfonylhydrazides with sulfonylation and C–H functionalization. The protocol uses the economical and environmentally friendly TBAI–TBHP catalytic system, and the corresponding isoquinoline-1,3(2H,4H)-diones with various functional groups were obtained in moderate to good yields.

The Fe-doped Ni–P amorphous alloy catalyst was prepared by the chemical reduction of the aqueous solution containing NiCl 2 and FeCl 3 with NaH 2 PO 2 at 343 K and characterized by EDS, XRD, SAED, TEM, XPS and DTA. It was used as a catalyst for the liquid phase hydrogenation of m -chloronitrobenzene (CNB) and p -chloronitrobenzene (CNB) to corresponding chloroaniline (CAN) in alcohol at 383 K under 1.0 MPa of hydrogen. At a suitable Fe content ( X Fe ), the Ni–Fe–P amorphous alloy catalyst exhibited much higher activity and selectivity than the Ni–P, Fe–P, and Raney Ni catalysts in the hydrogenation reaction. With the increase of X Fe , the activity first increased and then decreased. The optimum X Fe was 0.25, at which the conversions of CNB could reach 99.9% and the yields of m - and p -CAN could reach 97.3% and 98.1%, respectively. The promoting effect of the Fe-dopant could be attributed to both a dispersing effect that resulted in the higher stability and the electron donation of the metallic Fe to the metallic Ni that was favorable for the hydrogenation. The structure of amorphous alloy and the alloying P were also favorable for the hydrogenation. Very high contents of the Fe-dopant ( X Fe > 0.25) resulted in the decrease of the hydrogenation activity because Ni active sites were mostly covered by the inactive Fe.

The Ni-Co-B bimetallic amorphous alloy with Co/(Co+Ni) molar ratio varying from 0 to 1 was prepared by chemical reduction of Ni(NO3)2 and Co(NO3)2 with KBH4 in solution. Its amorphous structure was verified by X-ray powder diffraction and selected area electron diffraction. The thermostability of the amorphous alloy was characterized by thermogravimetry-differential thermal analysis. Scanning electron microscopy and transmission electron microscopy were used to determine its morphology and particle size. The Ni-Co-B amorphous catalyst with a Co/(Co+Ni) molar ratio of 0.5 exhibits a much higher activity and selectivity than the Ni-B and Co-B catalysts in the liquid-phase hydrogenation of chloronitrobenzene to chloroaniline. The maximum conversion of both o-chloronitrobenzene and 3,4-dichloronitrobenzene reaches 99.9%, whereas the dechlorinations of chloroaniline are 1.12% and 0.42%, respectively, showing a good potential for industrial applications. The higher activity and selectivity of the Ni-Co-B catalyst can be attributed to the electron donation from the alloying B and metallic Co to the metallic Ni. By following this, the B and Co atoms become electron-deficient whereas the Ni atom becomes electron-rich, which can activate the N=O bond, inhibit the hydrodechlorination of chloronitrobenzene, and increase the thermostability of the amorphous alloy.

Quinoxaline derivatives are widely used in dyes, electroluminescent materials and organic semiconductors. An economic and convenient strategy for the synthesis of 2-phenyl-quinoxaline is described. The approach relies on the oxidation of acetophenones by [hydroxy(tosyloxy)iodo]benzene, followed by tandem nucleophilic substitution with o-phenylenediamines, dehydration cyclisation and dehydrogenation. The method was performed in two stages as a one-pot reaction.

Carotenoid content analysis in wolfberry processed products has mainly focused on the determination of zeaxanthin or zeaxanthin dipalmitate, which cannot indicate the total carotenoid content (TCC) in wolfberries.We have exploited an effective approach for rapid extraction of carotenoid from wolfberry juice and determined TCC using UV-visible spectrophotometry. Several solvent mixtures, adsorption wavelengths of carotenoid extracts and extraction procedures were investigated. The optimal solvent mixture with broad spectrum polarity was hexane-ethanol-acetone (2:1:1) and optimal wavelength was 456 nm. There was no significant difference of TCC in wolfberry juice between direct extraction and saponification extraction.The developed method for assessment of TCC has been successfully employed in quality evaluation of wolfberry juice under different processing conditions. This measurement approach has inherent advantages (simplicity, rapidity, effectiveness) that make it appropriate for obtaining on-site information of TCC in wolfberry juice during processing.

The assembled Pt catalyst was prepared using activated carbon as support to capture “unprotected” Pt nanoparticles obtained from the decomposition of Pt 2 (dba) 3 (dba = dibenzene acetone). Transmission electron microscopy showed that the size of the Pt nanopar-ticles depended on the decomposition pressure. The catalytic activity was evaluated by the liquid-phase hydrogenation of o -chloronitrobenzene. The Pt/C catalyst exhibited high conversion and selectivity. When the Pt nanoparticles were prepared at 2.0 MPa of hydrogen pressure and 30°C, the average size of the Pt nanoparticles was 2.8 nm with 0.5% Pt loading. Under the hydrogenation conditions of 60°C and 1.0 MPa hydrogen pressure, the dehalogenation rate was less than 1.67% while the TOF was 39.8 s −1 .

Phenyl- and naphthyl-substituted substrates (I) and (III) undergo tandem rearrangement—cyclization under identical conditions.

A pressing problem in supported-metal-nanoparticle heterogeneous catalysis--despite the long history and considerable fundamental as well as industrial importance of such heterogeneous catalysts--is how to monitor such catalysts' formation more routinely, rapidly, and in real time. Such information is needed to better control the size, shape, composition, and thus resultant catalytic activity, selectivity, and lifetime of these important catalysts. To this end, a study is reported of the formation of supported Pt(0)(n) nanoparticles by H(2) reduction of H(2)PtCl(6) on Al(2)O(3) (or TiO(2)) to give 6 equivalents of HCl plus supported Pt(0)(n)/Al(2)O(3) (or Pt(0)(n)/TiO(2)), all while in contact with a solution of EtOH and cyclohexene. The HCl and Pt(0)(n) products were confirmed, respectively, by the stoichiometry of HCl formation using pH(apparent) measurements, appropriate standards, and by TEM and EDX measurements. The hypothesis of this research is that the kinetics of formation of this supported heterogeneous catalyst could be successfully monitored by a fast cyclohexene hydrogenation catalytic reporter reaction method first worked out for monitoring transition-metal nanoparticle formation in solution (Watzky, M. A. and Finke, R. G. J. Am. Chem. Soc. 1997, 119, 10382-10400). Significantly, sigmoidal kinetics of Pt(0)(n)/Al(2)O(3) catalyst formation were in fact successfully monitored by the catalytic hydrogenation reporter reaction method and then found to be well fit to the Finke-Watzky (hereafter F-W) 2-step, slow continuous nucleation and then autocatalytic surface growth mechanism, A --B (rate constant k(1)) and A + B --2B (rate constant k(2)), respectively, in which A is the H(2)PtCl(6) and B is the growing, catalytically active Pt(0) nanoparticle surface. The finding that the F-W mechanism is applicable is significant in that it, in turn, suggests that theor = 8 insights from studies of the mechanisms of soluble nanocluster formation can likely also be applied to supported heterogeneous catalyst synthesis, including a recent equation that gives nanocluster size vs time in terms of k(1), k(2), [A](o) and other parameters (Watzky, M. A., Finney, E. E. and Finke, R. G. J. Am. Chem. Soc. 2008, 130, 11959-11969 ). Also presented are the use of the catalytic reporter reaction to reveal H(2) gas to-solution mass-transfer-limitations (MTL) in the system of H(2)PtCl(6) on TiO(2), results relevant to a recent communication in this journal. The use of the F-W 2-step nucleation and autocatalytic growth kinetic model to fit 3 literature examples of heterogeneous catalyst formation, involving H(2) reduction of both supported or bulk M(x)O(y) (i.e., and in gas-solid reactions), are also presented as part of the Supporting Information. A conclusion section is then provided summarizing the insights and caveats from the present work, as well as some needed future studies.