K2 CO3 Research Articles

A Metal-free Approach to 3-Aryl-3-hydroxy-2-oxindoles by Treatment of 3-Acyloxy-2-oxindoles with Diaryliodonium Salts.

A mild, metal-free approach has been realized for the facile construction of highly valuable 3-(hetero)aryl-3-hydroxy-2-oxindoles. Direct arylations of 3-acyloxy-2-oxindoles with diaryliodonium salts as arylation reagents are implemented in the presence of K2 CO3 at room temperature without using an organometallic promoter to deliver an array of 3-(hetero)aryl-3-hydroxy-2-oxindoles in good yields.

Mechanistic Study of a Photocatalyzed C-S Bond Formation Involving Alkyl/Aryl Thiosulfate.

This study presents thioether construction involving alkyl/aryl thiosulfates and diazonium salt catalyzed by visible-light-excited [Ru(bpy)3 Cl2 ] at room temperature in 44-86 % yield. Electron paramagnetic resonance studies found that thiosulfate radical formation was promoted by K2 CO3 . Conversely, radicals generated from BnSH or BnSSBn (Bn=benzyl) were clearly suppressed, demonstrating the special property of thiosulfate in this system. Transient absorption spectra confirmed the electron-transfer process between [Ru(bpy)3 Cl2 ] and 4-MeO-phenyl diazonium salt, which occurred with a rate constant of 1.69×10(9) M(-1) s(-1) . The corresponding radical trapping product was confirmed by X-ray diffraction. The full reaction mechanism was determined together with emission quenching data. Furthermore, this system efficiently avoided the over-oxidation of sulfide caused by H2 O in the photoexcited system containing Ru(2+) . Both aryl and heteroaryl diazonium salts with various electronic properties were investigated for synthetic compatibility. Both alkyl- and aryl-substituted thiosulfates could be used as substrates. Notably, pharmaceutical derivatives afforded late-stage sulfuration smoothly under mild conditions.

Oxidative Amidation of Nitroalkanes with Amine Nucleophiles using Molecular Oxygen and Iodine.

The formation of amides and peptides often necessitates powerful yet mild reagent systems. The reagents used, however, are often expensive and highly elaborate. New atom-economical and practical methods that achieve such goals are highly desirable. Ideally, the methods should start with substrates that are readily available in both chiral and non-chiral forms and utilize cheap reagents that are compatible with a wide variety of functional groups, steric encumberance, and epimerizable stereocenters. A direct oxidative method was developed to form amide and peptide bonds between amines and primary nitroalkanes simply by using I2 and K2 CO3 under O2 . Contrary to expectations, a 1:1 halogen-bonded complex forms between the iodonium source and the amine, which reacts with nitronates to form α-iodo nitroalkanes as precursors to the amides.

A Practical and General Base-Catalyzed Carbonylation of Amines for the Synthesis of N-Formamides.

A highly practical and general base-catalyzed carbonylation of amines to the corresponding N-formamides has been realized. Cheap inorganic bases, including Group IA and IIA metal hydroxides, alkoxides, carbonates, and phosphates, were effective catalysts for the transformation. In the presence of 10-40 mol % of KOH or K2 CO3 , various amines were converted into the corresponding N-formamides in good-to-excellent yields using CO as the formylation reagents.

Base‐Mediated Syntheses of Di‐ and Trisubstituted Imidazoles from Amidine Hydrochlorides and Bromoacetylenes

A new transition metal-free method for the preparation of substituted imidazoles from easy-to-handle amidine hydrochlorides and bromoacetylenes has been developed. The reactions proceed in air and use inexpensive K2 CO3 as base. Additions of 2,2'-bipyridine and water have beneficial effects on the product yields. Various di- and trisubstituted imidazoles have been prepared in good yields (up to 88 %).

Influence of the Base on Pd@MIL-101-NH2 (Cr) as Catalyst for the Suzuki-Miyaura Cross-Coupling Reaction.

The chemical stability of metal-organic frameworks (MOFs) is a major factor preventing their use in industrial processes. Herein, it is shown that judicious choice of the base for the Suzuki-Miyaura cross-coupling reaction can avoid decomposition of the MOF catalyst Pd@MIL-101-NH2 (Cr). Four bases were compared for the reaction: K2 CO3 , KF, Cs2 CO3 and CsF. The carbonates were the most active and achieved excellent yields in shorter reaction times than the fluorides. However, powder XRD and N2 sorption measurements showed that the MOF catalyst was degraded when carbonates were used but remained crystalline and porous with the fluorides. XANES measurements revealed that the trimeric chromium cluster of Pd@MIL-101-NH2 (Cr) is still present in the degraded MOF. In addition, the different countercations of the base significantly affected the catalytic activity of the material. TEM revealed that after several catalytic runs many of the Pd nanoparticles (NPs) had migrated to the external surface of the MOF particles and formed larger aggregates. The Pd NPs were larger after catalysis with caesium bases compared to potassium bases.

Synthesis of pyrimido[4′,5′:2,3][1,4]thiazepino[7,6-b]quinolines, derivatives of a novel ring system

Abstract Several derivatives of the novel pyrimido[4′,5′:2,3][1,4]thiazepino[7,6-b]quinoline ring system have been synthesized through cyclocondensation of 5-amino-6-methylpyrimidine-4-thiols 5a,b and 2-chloroquinoline-3-carbaldehydes 6a–c in the presence of K2 CO3 in DMF.

Analysis of K+ release kinetics of biomass ash with different pH

试验选取4种生物质灰渣(玉米灰渣、水稻灰渣、锯木灰渣和谷壳灰渣)为研究材料, 以不同pH(4、7、9)的NH₄Ac为交换液, 采用渗透交换法, 研究了生物质灰渣中K⁺的释放动力学特征。结果表明, 在pH为4、7和9条件下, 供试生物质灰渣中K+释放量在20~80 min达到平衡, 平衡释放量分别为14.77~255.17 cmol·kg^-1、4.83~106.71 cmol·kg^-1和12.11~224.33 cmol·kg^-1。相关分析表明, K⁺释放量与生物质灰渣中全钾含量极显著相关, 说明受生物质灰渣中全钾含量影响, 其K+释放平衡时间和释放量存在显著差异。方差分析显示, 同一生物质灰渣中K+释放速率在不同pH条件之间存在极显著差异。由此可见, 受交换液pH和全钾含量的影响, 不同生物质灰渣中K+的释放量和平衡时间均存在较大差异。不同pH条件下, 水稻灰渣和玉米灰渣 K⁺释放量(<i>Q</i>)表现为<i>Q</i>₄><i>Q</i>₉><i>_Q</i>₇, 锯木灰渣和谷壳灰渣的释放量表现为<i>Q</i>₉><i>Q</i>₄><i>Q</i>₇; 在3种pH条件下, 4种生物质灰渣K+的释放总量均表现为<i>Q</i>_水稻灰渣><i>Q</i>_锯木灰渣><i>Q</i>_谷壳灰渣><i>Q</i>玉米灰渣。平衡前不同时段K⁺的释放率(v)与反应时间的自然对数(lnt)极显著相关。4种生物质灰渣K⁺的释放动力学最适模型均表现为: pH=4时为Elovich方程, pH=7时为双常数方程, pH=9时为Elovich方程; 同一pH条件下, 4种生物质灰渣的模型拟合性最优为Elovich方程, 双常数方程次之, 抛物线扩散方程最差。

Hydrodeoxygenation of the Angelica Lactone Dimer, a Cellulose‐Based Feedstock: Simple, High‐Yield Synthesis of Branched C7–C10 Gasoline‐like Hydrocarbons

Dehydration of biomass-derived levulinic acid under solid acid catalysis and treatment of the resulting angelica lactone with catalytic K2 CO3 produces the angelica lactone dimer in excellent yield. This dimer serves as a novel feedstock for hydrodeoxygenation, which proceeds under relatively mild conditions with a combination of oxophilic metal and noble metal catalysts to yield branched C7 -C10 hydrocarbons in the gasoline volatility range. Considering that levulinic acid is available in >80 % conversion from raw biomass, a field-to-tank yield of drop-in, cellulosic gasoline of >60 % is possible.

Hydroxyalkylation and Polyether Polyol Grafting of Graphene Tailored for Graphene/Polyurethane Nanocomposites

Graphene functionalization by hydroxyalkylation and grafting with polyether polyols enables polyurethane (PU) nanocomposites formation by in situ polymerization with isocyanates combined with effective covalent interfacial coupling. Functionalized graphene (FG) hydroxylation is achieved either by alkylation, transesterification, or grafting of thermally reduced graphite oxide. In the presence of K2 CO3 as catalyst the reaction of FG-OH with ethylene carbonate at 180 °C affords hydroxyethylated FG, whereas transesterification with castor oil produces riconoleiate-modified FG polyols. In the "grafting-from" process, FG-alkoholate macro initiators initiate the graft polymerization of propylene oxide to produce hybrid FG polyols containing 38 and 59 wt% oligopropylene oxide. In the "grafting-to" process 3-ethyl-3-hydroxymethyl-oxetane is cationically polymerized onto FG-OH, producing novel hyperbranched FG-based polyether polyols. Whereas hydroxylation and grafting of FG greatly improve FG dispersion in organic solvents, polyols and even PU, as confirmed by transmission electron microscopy, matrix reinforcement of FG/PU is impaired by increasing alkyl chain length and polyol graft copolymer content.

Optimization of the radiosynthesis of [18F]MEFWAY for imaging brain serotonin 1A receptors by using the GE TracerLab FXFN‐Pro module

The aim of this study was to develop a highly reliable radiofluorination method for the preparation of N-{2-[4-(2-methoxyphenyl)piperazinyl]ethyl}-N-(2-pyridyl)-N-(4-(18) F-fluoromethylcyclohexane)carboxamide ([(18) F]Mefway) by using a fully automated system. The optimal condition is composed of two parts. The extraction system of the trapped F-18 in the anion exchange resin (i.e., quaternary methylamine cartridge) is a complex of Kryptofix 2.2.2. (K222, 4 mg/0.9 mL methanol) and K2 CO3 (1 mg/0.1 mL H2 O). After removing the solvents, the trans-tosylated Mefway precursor (1 mg/0.5 mL acetonitrile) was reacted with dried K222-K[(18) F] at 100°C for 5 min. After purification and formulation, [(18) F]Mefway was obtained with 38 ± 2.4% (decay corrected, n = 34) radiochemical yield, a total synthesis time of 52 ± 3.4 min, specific activity was 120.6 ± 8.7 GBq/µmol at the end of synthesis and a radiochemical purity of 99%. According to the quality control tests, formulated [(18) F]Mefway is suitable to apply parenteral clinical application.

An improved synthesis of [11C]MENET via Suzuki coupling with [11C]methyl iodide

[(11) C]MENET, a promising norepinephrine transporter imaging agent, was prepared by Suzuki cross coupling of 1 mg N-t-Boc pinacolborate precursor with [(11) C]CH3 I in DMF using palladium complex generated in situ from Pd2 (dba)3 and (o-CH3 C6 H4 )3 P together with K2 CO3 as the co-catalyst, followed by deprotection with trifluoroacetic acid. This improved radiolabeling method provided [(11) C]MENET in high radiochemical yield at end of synthesis (EOS, 51 ± 3%, decay-corrected from end of (11) CH3 I synthesis, n = 6), moderate specific activity (1.5-1.9 Ci/µmol at EOS), and high radiochemical (>98%) and chemical purity (>98%) in a synthesis time of 60 ± 5 min from the end of bombardment.

Water-gas shift reaction over CuO/CeO2 catalysts: Effect of CeO2 supports previously prepared by precipitation with different precipitants

A series of CeO2 supports were firstly prepared by precipitation method with NH3⋅H2O (NH), (NH4)2CO3 (NC) and K2CO3 (KC) as precipitant, respectively, and then CuO/CeO2 catalysts were fabricated by depositing CuO on the as-obtained CeO2 supports by deposition-precipitation method. The effect of CeO2 supports prepared from different precipitants on the catalytic performance, physical and chemical properties of CuO/CeO2 catalysts was investigated with the aid of XRD, N2-physisorption, N2O chemisorption, FT-IR, TG, H2-TPR, CO2-TPD and cyclic voltammetry (CV) characterizations. The CuO/CeO2 catalysts were examined with respect to their catalytic performance for the water-gas shift reaction, and their catalytic activities and stabilities are ranked as: CuO/CeO2–NH > CuO/CeO2–NC > CuO/CeO2–KC. Correlating to the characteristic results, it is found that the CeO2 support prepared by precipitation with NH3⋅H2O as precipitant (i.e., CeO2–NH-300) has the best thermal stability and least surface “carbonate-like” species, which make the corresponding CuO/CeO2–NH catalyst presents the highest Cu-dispersion, the highest microstrain (i.e., the highest surface energy) of CuO, the strongest reducibility and the weakest basicity. While, the precipitants that contain CO32- (e.g. (NH4)2CO3 and K2CO3) result in more surface “carbonate-like” species of CeO2 supports and CuO/CeO2 catalysts. As a result, CuO/CeO2–NC and CuO/CeO2–KC catalysts present poor catalytic performance.

Catalytic Gasification of Coal Using Eutectic Salts: Recovery, Regeneration, and Recycle of Spent Eutectic Catalysts

Catalyst recovery studies were conducted for gasified chars produced from steam gasification of Illinois #6 coal catalyzed with two different catalyst systems. A ternary (43.5 mol% Li2 CO3 –31.5 mol% Na2 CO3 –25 mol% K2 CO3 ) and a binary (29 mol% Na2 CO3 –71 mol% K2 CO3 ) eutectic catalyst system were used for gasifying coal. Various extraction schemes, such as water extraction, H2 SO4 extraction, and acetic acid extraction, were evaluated with respect to their extraction efficiencies. Effects of major process variables, such as solvent-to-char ratio, mixing time, temperature, and concentration, on the extraction efficiency were evaluated. A process schematic for the entire catalyst recovery, regeneration, and recycle scheme was developed and the preliminary process economics were determined based on these extraction schemes. H2 SO4 extraction was found to be the most desirable. It also turned out to be more attractive than a once-through throwaway system.

Kinetics of Dimethyl Carbonate Synthesis From Ethylene Carbonate and Methanol Using Alkali-Metal Compounds as Catalysts

Dimethyl carbonate (DMC) was synthesized by the ester exchange reaction of ethylene carbonate and methanol. K2 CO3 , KOH, LiOH and NaOH were used as catalysts for DMC synthesis and their catalytic abilities were compared in terms of kinetics. LiOH showed the best reaction rate among the catalysts. The rate constant was estimated to be 0.02538 (dm 3 /mol) 0.21 /min at 298 K.

An Improved Method for Extraction and Measurement of the Inorganic Pyrophosphate in Leaves of Crassulacean Acid Metabolism (CAM) Plants

An improved method for extraction and measurement of inorganic pyrophosphate (PPi) in the leaves of crassulacean acid metabolism (CAM) plants, Ananas comosus (pineapple) , Kalanchoë pinnata and K. dotgremontiana is described. Leaf samples were extracted with 5% (w/v) trichloroacetic acid (TCA) dissolved in water. The extracts without neutralizing with KOH or K2 CO3 and those without washing with diethyl ether to remove TCA were directly used to measure PPi with PPi -dependent phosphofructokinase (PPi-PFK, EC 2.7.1.90) coupled with the oxidation of NADH. The method is sensitive and simple, the lower limit of the measurement was less than 1 nmol PPi mL-1 reaction mixture and the recoveries of the PPi added were more than 96%. Moreover, the initial PPi levels in TCA extracts could be maintained for at least one day. This method was advantageous for extracting and measuring a large number of samples at the same time. In addition, we found that neutralizing the extract before determination was disadvantageous to PPi recovery.

A Thermoanalytical Study of the Solid State Reactions in the K2CO3-MxOy Systems. Evidence for a kinetic compensation effect

This paper presents the results obtained in the investigation of the reactions of potassium carbonate with some transition metals oxides (TiO2 , V2 O5 , Cr2 O3 , MnO2 , Fe2 O3 ). The reactions were carried out under non-isothermal conditions, and thermogravimetric analysis was used to monitor the transformation degree a. Experimental data indicated that the reaction of potassium carbonate and iron(III) oxide occurs in one stage, whereas the reactions of the oxides of titanium, vanadium, chromium and manganese are more complex, involving two-stage processes. Activation energies and pre-exponential factors were determined for all the processes taking place in the investigated systems. For the second stage of the reaction of K2 CO3 with Cr2 O3 , and V2 O5 the obtained values of activation energy were 59.2 and 512 kJ mol−1 respectively. Based on the values of activation energy and pre-exponential factor, the existence of a kinetic compensation effect was postulated for the three homologous series of reactions.

New polymer syntheses. LXXXII. Syntheses of poly(ether‐sulfone)s from silylated aliphatic diols including chiral monomers

AbstractAttempts were made to synthesize poly(ether‐sulfone)s from aliphatic diols or bissilylated diols on the one hand, and 4,4′‐dichlorodiphenylsulfone or 4,4′‐difluorodiphenylsulfone on the other hand. The reaction conditions and the catalyst were varied. Polycondensations of silylated diols with 4,4′‐difluorodiphenylsulfone and powdered K2 CO3 in N‐methylpyr‐rolidone proved to give the best results. Using silylated isosorbide and isomannide as mono‐mers chiral poly(ether‐sulfone)s were prepared. GPC measurements indicate weight‐average molecular weights in the range of 27×103–200×103. © 1995 John Wiley &amp; Sons, Inc.

Effects of Excess Methionine or Lysine for Broilers Fed a Corn-Soybean Meal Diet

Three experiments were conducted to examine the consequences of over-supplementing DL-Met or L-Lys (as L-Lys·HCl) in diets for chicks fed a corn-soybean meal diet (23% CP, 3,200 kcal MEn/kg, .2% supplemental Met) during 1 to 3 wk posthatching. New Hampshire × Columbian male chicks were used in Experiments 1 and 2 and Hubbard × Hubbard males were employed in Experiment 3. The basal diet was supplemented with .5, 1.0, 2.0, or 4.0% DL-Met, or .4, .8, 1.6, or 3.2% L-Lys in Experiment 1. Weight gain, feed intake, and feed efficiency decreased linearly at supplemental levels of DL-Met between 1.0 and 4.0%. Weight gain of chicks fed diets with supplemental L-Lys levels greater than 1.6% was less than that of chicks fed the basal diet, but feed efficiency was not significantly affected. Adding K2 CO3 to the diets containing 1.6 or 3.2% added L-Lys did not improve performance. Experiment 2 evaluated the effect of 1) adding 1.0% Gly or 1.0% L-Thr to the diet supplemented with 2.0% DL-Met; and 2) adding NaHCO3 to the high-Lys diets in order to buffer the excess chloride provided by L-Lys·HCl. Addition of these amino acids or buffer ameliorated but did not totally correct the negative effects of excess Met or Lys. Experiment 3 examined the tolerance of commercial broilers to supplemental DL-Met or L-Lys levels of .5 or 1.0%. Weight gain and feed efficiency were not affected by these excesses, but feed intake was reduced at the 1.0% level of inclusion of either amino acid. These results suggest that .5% excesses of either Met or Lys are not harmful to young broiler chicks fed corn-soybean meal diets.

Surface Tension Around Eutectic Compositions of Molten Alkali Carbonate Mixtures

Abstract The surface tension around the eutectic composition of molten binary and ternary mixtures composed of Li2CO3 with Na2CO3 and/or K2 CO3 has been measured by the maximum bubble pressure method. The surface tensions of all the three systems were represented as functions of temperature