Water Reflux Research Articles

The enantioselective hydrogenation of acetophenone over Pd concave tetrahedron nanocrystals affected by the residual adsorbed capping agent polyvinylpyrrolidone (PVP)

One promising way to develop efficient noble-metal catalysts is to induce the exposure of specific catalytically active facets of nanocrystals through shape-controlled syntheses. However, as for the as-prepared noble-metal nanocrystals, there are commonly residual capping agents adsorbed on the metal surfaces, which have complex effects on the catalytic activity and selectivity in different catalytic reactions. In this paper, by taking polyvinylpyrrolidone (PVP), the most commonly used capping agents in the shape-controlled synthesis of noble-metal nanocrystals, as an example, we systematically studied the surface-modification effects of residual capping agents in the enantioselective hydrogenation of acetophenone. It was found for the first time that the residual PVP adsorbed on the Pd concave tetrahedron nanocrystals is detrimental to the enantioselectivity, negative to the activity, while positive to increase the chemoselectivity to the carbonyl group. The loss of enantioselectivity over PVP-stabilized Pd concave tetrahedron nanocrystals is probably due to that the residual PVP adsorbed on the Pd surface can interact with the chiral modifier S-proline and prevent the requisite interaction between S-proline and acetophenone co-adsorbed on the Pd surfaces. Thus, the prochiral interaction complexes which play a significant role in determining the enantioselectivity cannot be formed. KBH4 treatment or hot water reflux offers feasible methods to further reduce the amount of residual PVP adsorbed on the Pd nanocrystals and to achieve enantioselectivity in the enantioselective hydrogenation of acetophenone. This study provides useful information to reveal the essence of enantiodifferentiation in heterogeneous enantioselective hydrogenations, which is beneficial for the design of efficient synthetic protocols and the shape-controlled synthesis of noble-metal nanocrystals to obtain pure enantiomers.

Water Soluble Antioxidative Crude Polysaccharide From Russula senecis Elicits TLR Modulated NF-κB Signaling Pathway and Pro-inflammatory Response in Murine Macrophages.

Russula senecis has recently been reported as a new addition to macrofungal flora of West Bengal. Besides, it also emerged as a seasonal health promoting nutrient to local ethnic people and enlisted for the first time as tribal food in our previous publication. In this context, the present work was designed to establish such usefulness scientifically and to meet the aim, crude polysaccharide, Rusenan, was prepared using conventional heated water reflux. Initially, the polymers were characterized to determine chemical composition and for that spectrophotometry along with Fourier-transform infrared spectroscopy (FT-IR), high-performance thin-layer chromatography (HPTLC), and gas chromatography-mass spectrometry (GC-MS) were performed. Analysis indicated that Rusenan was consisted mainly of carbohydrate conjugated with trace amount of protein. Furthermore, glucose was detected as the major monosaccharide (mainly in β-type glycosidic linkage) while other monomers were presented in the order of galactose > mannose > xylose > rhamnose. Conversely, antioxidant potential was determined following eight in vitro systems where the fraction evidenced strong superoxide, hydroxyl, 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radical scavenging activity, high affinity to Fe2+ as well as instant ability to donate electron with EC50 values ranging from 80 to 3885 μg/ml concentration. In addition, effect on murine macrophages was also investigated where the polysaccharide treatment increased cell proliferation, phagocytic activity, filopodia or lamellipodia formation, nitric oxide (NO) production and reactive oxygen species (ROS) synthesis. Thereafter, through reverse transcriptase polymerase chain reaction (RT-PCR) analysis, significant increase in the expression of Toll like receptor (TLR)-4, TLR-2 and nuclear factor kappa B (NF-κB) was observed; as a result alleviated level of cyclooxygenase (COX)-2, inducible nitric oxide synthase (iNOS), tumor necrosis factor (TNF)-α, IκB-α, and interferon (IFN)-γ were also noticed explaining definite immune-stimulatory activity of the fraction. Thus, overall finding suggests that R. senecis can be considered as a functional food and may be used in preparation of dietary supplement to enhance general health.

Active components, derived from Kai-xin-san, a herbal formula, increase the expressions of neurotrophic factor NGF and BDNF on mouse astrocyte primary cultures via cAMP-dependent signaling pathway

Ethnopharmacological relevanceKai-Xin-San (KXS), an ancient formula composed of Ginseng Radix et Rhizoma, Polygalae Radix, Acori Tatarinowii Rhizoma and Poria, was frequently applied for Alzheimer's disease and major depression disorders for thousands of years. However, its active components and molecular mechanism have not clearly been investigated. Aim of the studyWe aimed to reveal the active components of KXS on regulating neurotrophic factor NGF and BDNF expressions and its mechanisms on mouse astrocyte primary cultures. Materials and methodsExtracts of KXS had been prepared by water reflux and chemical standardization was carried out by HPLC-MS/MS. Various ethanol elution components were prepared by eluting ethanol on macro pore resin column and compound identification was carried out by high-resolution mass spectrometry. KXS extract, elution components and identified chemicals were applied on mouse astrocytes and expressions of NGF and BDNF and related metabolic enzymes were analyzed by qPCR and western blotting analysis. ResultsOne compatible ratio of KXS named D-652 exerted the best effect on stimulation of NGF and BDNF expressions on mouse astrocytes. 70% ethanol elution fraction of D-652 exerted the highest increase tendency on expressions of NGF and BDNF by activating cAMP-dependent signaling pathway as well as stimulating enzymes accounting for neurotrophic factor synthesis. Combined with compound identification by high-resolution mass spectrometry, ginsenoside Rg1 and Rb1 might be the active compounds of this fraction on increasing NGF and BDNF expressions. ConclusionsThe active compounds of KXS on increasing NGF and BDNF expressions might be the ginsenosides via activating cAMP-dependent signaling pathway as well as stimulating enzymes accounting for neurotrophic factor synthesis, which partly reveal the target of this formulae supported the clinically usage of this decoction.

Alkaline extractive crude polysaccharide from Russula senecis possesses antioxidant potential and stimulates innate immunity response.

Over past decades, investigation on bioactive polysaccharides extracted from mushroom by heated water reflux has been an emerging field of biomedicine especially in the area of immune stimulation. While studies with macromolecules isolated from remainder residue of aqueous extraction are scarce. In this context, crude polysaccharide from a traditionally edible macrofungus, Russula senecis, was prepared (RuseCap) by alkaline solvent using leftover residue of that conventional process and its structural along with therapeutic properties were evaluated. Investigation by FT-IR, HPTLC, GC-MS and spectrophotometry showed that the fraction was mainly consisted of carbohydrate with backbone of xylose, rhamnose, mannose and glucose (mostly β-glucan). Besides, RuseCap exhibited strong antioxidant activity evident by radical scavenging (superoxide, hydroxyl, DPPH, ABTS), chelating ability and reduction power where EC50 values ranged from 257 to 4068 μg/ml concentration. In addition, it also exhibited immune-boosting potentiality as the treatment effectively induced proliferation, phagocytosis, nitric oxide production, intracellular reactive oxygen species generation, morphological changes and increased transcription level of iNOS, COX-2, TNF-α, IL-6 genes in macrophage cells. Overall, the study provided blueprint for extended utilization of R. senecis basidiocarps beyond hot water process and defined use of RuseCap as potent therapeutic agent against free radicals as well as deprived immunity.

Early dolomitization in the Lower Cretaceous shallow-water carbonates of Southern Apennines (Italy): Clues about palaeoclimatic fluctuations in western Tethys

A multidisciplinary study of the dolomitized bodies present in the Lower Cretaceous platform carbonates of Mt. Faito (Southern Apennines – Italy) was carried out in order to explore the connection between early dolomite formation and fluctuating climate conditions.The Berriasian-Aptian investigated succession is 466m thick and mainly consists of shallow-water lagoonal limestones with frequent dolomite caps. The dolomitization intensity varies along the succession and reaches its peak in the upper Hauterivian-lower Barremian interval, where it is present a completely dolomitized interval about 100-m-thick. Field relations, petrography, mineralogy, and geochemistry of the analyzed dolomite bodies allowed identifying two populations of early dolomites, a fine-medium crystalline (FMdol) and a coarse crystalline dolomite (Cdol), both interpreted as the product of mesohaline water reflux. According to our interpretation, FMdol precipitated from concentrated brines in the very early stage of the reflux process, producing typical sedimentary features as dolomite caps. In the successive step of the process, the basin-ward ‘latent’ reflux precipitated Cdol from less concentrated brines.A peculiar feature of the studied succession is the great consistency between stratigraphic distribution of dolomite bodies and their geochemical signature. The completely dolomitized Hauterivian-Barremian interval, in fact, is characterized by geochemical values suggesting an origin from distinctly saltier brines. Considering that the observed near-surface dolomitization process is controlled by physical and chemical parameters reflecting the paleoenvironmental and paleoclimatic conditions during dolomite formation, we propose that the stratigraphically controlled dolomitization intensity reflects periodic fluctuations in the salinity of dolomitizing fluid, in turn controlled by long-term climate oscillations.The present work highlights that the stratigraphic distribution of early diagenetic dolomite may be used as proxy to define the climatic fluctuations that have influenced the sedimentary dynamics in the Early Cretaceous. Moreover, considering that a comparable early dolomite distribution is present also in the Dinaric Platform, we suggest that a regional scale climate control acted on early dolomite formation and distribution. Refining the knowledge of such a key control may have a significative impact on hydrocarbon reservoir characterization and exploration in the Periadriatic area.

Are Water-lean Solvent Systems Viable for Post-Combustion CO2 Capture?

We present here an overview of water-lean solvents that compares their projected costs and performance to aqueous amine systems, emphasizing critical areas of study needed to evaluate their performance against their water-based brethren. The work presented here focuses on bridging these knowledge gaps. Because the majority of water-lean solvents are still at the lab scale, substantial studies are still needed to model and assess their performance at full scales. This presents a significant challenge as each formulation has different physical and thermodynamic properties and behavior, and quantifying how these different properties manifest themselves in conventional absorber-stripper configurations, or identifying new configurations that are specific for a solvent's signature behavior. We identify critical areas of study that are needed, and our efforts (e.g. custom infrastructure, molecular models) to predict, measure, and model these behaviors. Such findings are critical for determining the rheology required for heat exchanger design; absorber designs and packing to accommodate solvents with gradient changes (e.g. viscosity, contact angle, surface tension), and stripper configurations without direct steam utilization or water reflux. Another critical area of research need is to understand the molecular structure of the liquid interface and bulk as a function of CO2 loading, and to assess whether conventional film theories accurately quantify solvent behavior, or if thermodynamic models adequately quantify activity coefficients of ions in solution. We conclude with an assessment of our efforts to aid in bridging the knowledge gaps in understanding water-lean solvents, and suggestions of what is needed to enable large-scale demonstrations to meet the United States Department of Energy's goals.

Oxidative Esterification of Methacrolein to Methyl Methacrylate over Supported Gold Catalysts Prepared by Colloid Deposition

AbstractEsterification is one of the most pivotal organic transformations. Au catalysts were prepared by using a colloid deposition method with poly(vinyl alcohol) (PVA) as a protective agent. The catalyst was used for the oxidative esterification of methacrylate (MAL) to methyl methacrylate (MMA). Three pre‐treatments were used to remove the PVA, which is unfavorable for catalytic activity. It is found that the catalyst pre‐treated at 300 °C showed substantially improved activity owing to the lower PVA loading compared with catalysts treated with hot water washing and water reflux. Surprisingly, it is also found that the distribution and loading content of Au particles was closely related to the pH of the colloid solution. We demonstrate that the deposition process is controlled by the different charge of the support surface at different colloid solution pH. Further, the catalysts with similar size Au particles loaded on TiO2, SiO2, Al2O3, CeO2, ZrO2, and ZnO were successfully prepared by controlling the colloid solution pH. The Au/ZnO catalyst presented the best performance, which may be a result of the strong basic surface sites that improved the formation of the intermediate and the strong interaction between Au and ZnO. This interaction caused an anchoring effect and changed the geometries of Au particles, which could enhance the stability of catalysts and promote the mobility of oxygen, respectively.

Chitosan–graphene oxide films and CO2-dried porous aerogel microspheres: Interfacial interplay and stability

The intimate interplay of chitosan (CS) and graphene oxide (GO) in aqueous acidic solution has been explored to design upon casting, nanostructured “brick-and-mortar” films (CS-GO-f) and by acidic-to-basic pH inversion, porous CO2-dried aerogel microspheres (CS-GO-m). Owing to the presence of oxygenated functional groups in GO, good-quality crack-free hybrid films were obtained. Mechanical properties were improved independently of the GO content and it was found that a 20wt% loading affords hybrid film characterized with a Young modulus three times superior to that reached with the same loading of layered clay. The presence of graphene oxide was found to be detrimental for the thermal stability of the polysaccharide at T <350°C, a fact attributed to the well-established decomposition of the oxygenated functional groups of the graphene sheets. Irrespective to the graphene oxide loading, chitosan-graphene oxide mixture preserves the gelation memory of the polysaccharide. Supercritical drying of the resulting soft hydrogels provides macroporous network with surface areas ranging from 226m2g−1 to 554m2g−1. XPS and RAMAN analyses evidenced the selective reduction of GO sheets inside of these microspheres, affording the hitherto unknown macroporous chitosan-entangled-reduced graphene oxide (CS-rGO-m) aerogels. Improvement in both hydrothermal stability (under water reflux) and chemical stability (under acidic conditions) have been noticed for chitosan-graphene oxide microspheres with respect to non-modified chitosan and chitosan-clay bio-hybrids, a result rooted in the substantial hydrophobic character imparted by the addition of graphenic material to the polysaccharide skeleton. In essence, this contribution demonstrates that graphene oxide loading do not disturb neither the filmogenicity of chitosan nor its gelation ability and constitutes a promising route for novel chitosan-based functional hybrid materials.

Chemical and microbiological studies on Kenyan and Gabali Egyptian tea

The present study was designed to compare the quality of Gabali Egyptian tea and Kenyan tea locally cultivated in Egypt. Gabali, black and green Kenyan teas were laboratory processed, then analyzed chemically and microbiologically for their quality evaluation. Representative results show that all samples of the 3 types were contaminated with aerobic mesophilic plate counts of the tea types varied from 6.1x103 to 2.2x108 cfu/g, spore-forming bacteria 1.1x102 to 1.6x104 cfu/g, coliforms (MPN) 0.36- 1.5 x101 cell/g, molds 2.3x102 to 3.0x104 and yeasts 1.2x102 to 5.8x103 cfu/g, in which gabali tea was the highest and black Kenyan tea was the lowest microbial count. Pathogenic bacteria were not in detectable level. The black Kenyan tea had the highest antibacterial activity followed by the green Kenyan tea with all solvents, but extraction of Gabali tea had antibacterial activity only by distilled water and water reflux. Total aflatoxin in concentration range of 6.1, 9.8 and >50 μg/kg in black and green Kenyan tea and Gabali tea, respectively. Phytochemical analysis of the tea samples revealed the presence of tannin in high level in black Kenyan tea (14.33%). Considering the results obtained, only black and green Kenyan tea had acceptable levels for all microbial factors in comparison with the Egyptian standards. It was concluded that Gabali tea may be high risk product and therefore, more studies are necessary to find methods of decontamination.

不同提取方法对山药多糖提取率及抗氧化活性的影响

本文研究不同提取方法对山药多糖提取率及抗氧化活性的影响。采用热水回流、超声波辅助、热水–酶联合以及超声波–酶联合四种方法提取山药多糖。通过提取率测定、电镜扫描、抗氧化测定对四种提取方法的提取效果和样品活性进行评价。上述四种提取方法的提取率分别为0.465%、0.851%、0.443%、1.929%。超声波–酶联合方法提取获得多糖抗氧化活性强于其他三种方法。结果表明，超声波–酶联合法为最佳提取方法，同时山药多糖表现出较强的抗氧化能力，这些都为后续相关药物或功能性食品的开发奠定了重要基础。 In this paper, the effects of different extraction methods on yield and antioxidant activity of polysaccharides from Rhizoma dioscoreae were investigated. Four different extraction methods, including hot water reflux, ultrasonic assisted, hot water enzyme combination and ultrasonic en-zyme combination, were used to extract Rhizoma dioscoreae polysaccharides. The extraction efficiency and antioxidant activity of the four extraction methods were evaluated by extraction rate, electron microscopy and antioxidant. The yields of the above four extraction methods are 0.465%, 0.851%, 0.443%, 1.929% respectively. The antioxidant activity of polysaccharide extracted by ultrasonic enzyme combination method was better than that of the other three methods. The results showed that ultrasonic enzyme combination is the best extraction method, and the Rhizoma dioscoreae polysaccharides have strong antioxidant activity, which lay an important foundation for the development of the follow-up related drugs or functional foods.

Novel process of bio-chemical ammonia removal from air streams using a water reflux system and zeolite as filter media

A novel biofilter that removes ammonia from air streams and converts it to nitrogen gas has been developed and operated continuously for 300 days. The ammonia from the incoming up-flow air stream is first absorbed into water and the carrier material, zeolite. A continuous gravity reflux of condensed water from the exit of the biofilter provides moisture for nitrifying bacteria to develop and convert dissolved ammonia (ammonium) to nitrite/nitrate. The down-flow of the condensed water reflux washes down nitrite/nitrate preventing ammonium and nitrite/nitrate accumulation at the top region of the biofilter. The evaporation caused by the inflow air leads to the accumulation of nitrite to extremely high concentrations in the bottom of the biofilter. The high nitrite concentrations favour the spontaneous chemical oxidation of ammonium by nitrite to nitrogen (N2). Tests showed that this chemical reaction was catalysed by the zeolite filter medium and allowed it to take place at room temperature. This study shows that ammonia can be removed from air streams and converted to N2 in a fully aerated single step biofilter. The process also overcomes the problem of microorganism-inhibition and resulted in zero leachate production.

INFLUENCE OF SOME TRADITIONAL CHINESE MEDICINES (TCMS) ON CYTOKINE-INDUCED KILLER CELLS PROLIFERATION AND ANTI-TUMOR FEATURES IN VITRO

Some traditional Chinese medical (TCM) formulations shown to have anti - tumor actions in patients with various solid tumours. However, the mechanisms of the potential anticancer actio n are rarely reported. In the present study, we found that extracts from pharmaceutical raw materials consisting of ROR (Red ginseng, Ophiopogon japonicus, Radix Astragali) could significantly improve the proliferation rate and cytotoxic activity of cytoki ne - induced kil ler (CIK) cells, which is a heterogeneous population of polyclonal T lymphocytes sharing NK (Natural Killer) phenotype and functional properties. The extracts were prepared using modified ethanol - water reflux method. Pharmacodynamic test resu lts showed that 5% ROR - adding CIK Cells group performs 2.8 folds proliferation multiples than that of no ROR - adding CIK cells group, meanwhile the cytotoxic activity to K562 tumor cell has also a significant difference between them. In conclusion, ROR - addi ng CIK cells group exhibits stronger proliferation and cytotoxicity than no ROR - adding CIK cells group, and the results provided a new experimental evidence for TCM’s application in CIK - immunotherapy.

The Study of Physiological Activities from Chelidonium majus var asiaticum Extract

This research is to useful physiological activities data of the aerial part of the Chelidonium majus var asiaticum, analyzed contents of polyphenol and flavonoid compound, nitrite scavenging, superoxide dismutatse (SOD)-like activity, electron donating, tyrosinase inhibition and xanthine oxidase inhibition. The RW (Reflux water extract of C. majus var asiaticum) showed the highest value of nitrite scavenging ability of 73.13% at pH 1.2, 2.0 mg/mL. The RE (Reflux 70% ethanol extract of C. majus var asiaticum) showed the highest of SOD-like activity of 78.67% at 2.0 mg/mL and electron donating ability of 86.07% at 0.3 mg/mL. The tyrosinase inhibitory of RW was 38.71%, it was significantly 2.5 higher compared to the RE (15.18%). The xanthine oxidase inhibitory of RW and RE were over 97% at 2.0 mg/mL. The both extracts were higher than ascorbic acid (55.36%) at 0.05 mg/mL. This suggests that C. majus var. asiaticum can be useful materials as functional healthy product, medicine, and cosmetic products.

The Effect of Cr, Ni, Fe, and Mn Dopants on the Performance of Hydrothermal Synthesized Vanadium Phosphate Catalysts for n-Butane Oxidation

Vanadium phosphorus oxide (VPO) catalysts synthesized via hydrothermal method were introduced with some different dopants, Cr, Ni, Fe, and Mn during the preparation of the precursors, VOHPO4 · 0.5H2O. All modified precursors were subsequently transformed under reaction conditions to give the active phase, (VO)2P2O7. Several techniques were used to characterize the physicochemical properties of the catalysts, such as X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), H2-temperature programmed reduction (TPR), laser Raman spectroscopy (LRS), and chemical analysis. The catalytic performance of the catalysts for selective oxidation of n-butane to maleic anhydride has been carried out by using a fixed bed microreactor (673 K, gas hourly space velocity [GHSV] = 2,400 hr−1). The results show that the addition of dopants into the VPO catalysts increased the surface area of the catalysts and induced the formation of V5+ phases as shown in XRD and LRS spectra that promoted the catalytic performance. A further water reflux treatment to all the precursors gave catalysts with only (VO)2P2O7 phase. However, the activity and selectivity of these catalysts were reduced markedly.

Palladium-Catalyzed Cross-Coupling Reactions of Potassium Alkenyltrifluoroborates with Organic Halides in Aqueous Media

Potassium vinyl and alkenyltrifluoroborates are cross-coupled with aryl and heteroaryl bromides using 1 mol % Pd loading of 4-hydroxyacetophenone oxime derived palladacycle or Pd(OAc)2 as precatalysts, K2CO3 as base, and TBAB as additive and water reflux under conventional or microwave heating to afford styrenes, stilbenoids, and alkenylbenzenes. These borates can be cross-coupled diastereoselectively with allyl and benzyl chlorides using KOH as base in acetone-water (3:2) at 50 degrees C and 0.1 mol % Pd loading, giving the corresponding 1,4-dienes and allylarenes, respectively. These simple phosphine-free reaction conditions allow the palladium recycling from the aqueous phase during up to five runs by extractive separation of the products, which contain 58-105 ppm of Pd.

Kaiser oxime resin-derived palladacycle: A recoverable polymeric precatalyst in Suzuki–Miyaura reactions in aqueous media

Abstract Representative cross-coupling reactions of aryl bromides with different types of aryl-, alkyl, trivinylboroxine–pyridine complex, and alkenylboronic acids are performed using a polymer-bonded palladacycle derived from Kaiser oxime resin as precatalyst and potassium carbonate as base under water reflux. These processes afford biphenyls, alkylbenzenes, styrenes, and stilbenes, respectively. The same boronic acids can be cross-coupled with representative allyl and benzyl chlorides using KOH as base in aqueous acetone at 50 °C providing allylbenzenes, diarylmethanes, and 1,4-pentadienes. The palladated polymer can be recovered by filtration and reused during 3–9 cycles with up to 5% of Pd leaching in each run. Very low Pd leaching levels in the crude product can be determined by ICP–OES analyses. The reaction does not work when Hg(0) is added. TEM analyses from the solution indicate the formation of Pd nanoparticles.

Direct Coupling Reactions of Alkynylsilanes Catalyzed by Palladium(II) Chloride and a Di(2‐pyridyl)methylamine‐Derived Palladium(II) Chloride Complex in Water and in NMP

AbstractSymmetrical internal alkynes can be prepared either by diarylation of mono‐ and bis(trimethylsilyl)acetylene (TMSA and BTMSA) catalyzed by ligand‐less palladium(II) chloride or by a di(2‐pyridyl)methylamine‐derived palladium(II) chloride complex 1 (typical 0.1–1 mol % of Pd loading) in water using pyrrolidine as base and tetra‐n‐butylammonium bromide as additive. Alternatively, this same process is performed in NMP in the presence of tetra‐n‐butylammonium acetate (TBAA) as base with even lower Pd loadings (0.001–1 mol % Pd). The same reaction conditions are applied to the synthesis of unsymmetrical internal alkynes by monoarylation of silylated terminal alkynes. Aryl iodides can be coupled with TMSA, BTMSA and silylated terminal alkynes under heating or at room temperature, whereas for aryl bromides couplings are performed under water reflux or at 110 °C in the case of NMP. Complex 1 can be reused during several cycles either in water or in NMP without loss of catalytic activity. These simple reaction conditions allow the preparation of internal alkynes without secondary products, most probably by succesive protiodesilylation‐Sonogashira coupling.

Synthesis, Characterization and Photocatalytic Activity of TiO2 Powders Prepared Under Different Gelling and Pressure Conditions

Homogeneous TiO2 gel powders were prepared by hydrolysis and condensation of titanium(IV) isopropoxide with HCl or SnCl2 catalysts, by working under reduced pressure or in air. Ti(IV) alkoxide was previously modified by reaction with formic or acetic acid, used as chelating ligands, when gelation was performed in acidic catalysis. Crude TiO2 xerogels were purified by water reflux treatment in order to induce a low temperature crystallisation to the anatase phase. Both crude and purified TiO2 samples were characterised by XRD, FT-IR, SEM, and N2 adsorption analysis. Thermoanalyses (TG, DTA, DTG, TG-MS, TG-GC-MS) were carried out to quantify the residual organic components in the crude TiO2 gels and to obtain stoichiometric formulas to describe their chemical compositions. XRD data of purified TiO2 powders were processed by means of a Rietveld refinement procedure to determine TiO2 polymorphs, crystallite sizes and cell parameters, before their use in photocatalytic tests. The photoactivity of the purified TiO2 anatase powders was studied by using 4-nitrophenol degradation as “probe” reaction carried out in a batch and/or a membrane photoreactor. Samples prepared by using formic acid or SnCl2 were the most photoactive, whereas specimens gelled under vacuum treatment showed detrimental effects.

Suzuki–Miyaura and Related Cross‐Couplings in Aqueous Solvents Catalyzed by Di(2‐pyridyl)methylamine‐Palladium Dichloride Complexes

AbstractDi(2‐pyridyl)methylamine‐based palladium dichloride complexes 4 are versatile catalysts for different types of cross‐coupling reactions in water or aqueous solvents under aerobic conditions. The Suzuki–Miyaura reaction of arylboronic acids can be performed with bromoarenes under water reflux using K2CO3 as base or at room temperature or 60 °C in aqueous methanol using KOH as base. For aryl chlorides the corresponding cross‐couplings with arylboronic acids can be carried out in refluxing water with K2CO3 as base and TBAB as additive to provide biaryls and heterobiaryls. Arylboronic acids react with benzylic chlorides and allylic substrates such as chlorides, acetates or carbonates also in refluxing water with K2CO3 as base or at room temperature in aqueous acetone and KOH as base, to give diarylmethanes and arylpropenes. Trimethylboroxine and alkylboronic acids are coupled with bromo‐ and chloroarenes under water at reflux with K2CO3 as base and TBAB as additive to furnish methyl‐ and butylarenes. These cross‐couplings have also been performed in shorter times under microwave irradiation. Several important intermediates such as, 4′‐methylbiphenyl‐2‐carbonitrile, 4‐biphenylacetic acid, 3‐(3‐methylphenyl)benzoic acid, 4,5‐diphenyl‐2‐methyl‐3(2H)pyridazinone and 2‐(4′‐fluorobenzyl)thiophene have been prepared under aqueous and aerobic conditions in good yields.

Generation of ginsenosides Rg3 and Rh2 from North American ginseng

Rg3 and Rh2 ginsenosides are primarily found in Korean red ginseng root (Panax ginseng C.A. Meyer) and valued for their bioactive properties. We quantified both Rh2 and Rg3 ginseng leaf and Rg3 from root extracts derived from North American ginseng (Panax quinquefolius). Quantification was obtained by application of HPLC with ion fragments detected using ESI-MS. Ginseng leaf contained 11.3±0.5 mg/g Rh2 and 7.5±0.9 mg/g Rg3 in concentrated extracts compared to 10.6±0.4 mg/g Rg3 in ginseng root. No detectable Rh2 was found in root extracts by HPLC, although it was detectable by ESI-MS analysis. Ginsenosides Rg3 and Rh2 were detected following hot water reflux extraction, but not from tissues extracted with 80% aqueous ethanol at room temperature. Therefore ginsenosides Rg3 and Rh2 are not naturally present in North American ginseng, but are products of a thermal process. Using ESI-MS analysis, it was found that formation of Rg3 and Rh2, among other compounds, were a function of heating time and were breakdown products of the more abundant ginsenosides Rb1 and Rc. Our findings that heat processed North American ginseng leaf is an excellent source of Rh2 ginsenoside is an important discovery considering that ginseng leaf material is obtainable throughout the entire plant cycle for recovery of valuable ginsenosides for pharmaceutical use.