A conversion route towards tubular SiO2 using rod-like BaSiF6 as a novel template

A simple hydrothermal reaction between Ba(NO₃)₂ and K₂SiF₆ results in the formation of 1D rod-like BaSiF₆. The BaSiF₆ rods can act as efficient precursors for production of tubular SiO₂ by hydrothermal reaction in alkaline solutions. Powder X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), transmission electron microscopy (TEM), high resolution electron microscopy (HRTEM), and field emission scanning electron microscopy (FESEM) were used to characterize the phase and morphology of the final product. The experiments indicated the amount of NaOH, reaction temperature, and reaction time played important roles in the transformation process. A possible growth mechanism of tubular silica was proposed.     

Hydrothermal Synthesis and Properties of Controlled α‐Fe2O3 Nanostructures in HEPES Solution

A facile, template‐free, and environmentally friendly hydrothermal strategy was explored for the controllable synthesis of α‐Fe₂O₃ nanostructures in HEPES solution (HEPES=2‐[4‐(2‐hydroxyethyl)‐1‐piperazinyl]ethanesulfonic acid). The effects of experimental parameters including HEPES/FeCl₃ molar ratio, pH value, reaction temperature, and reaction time on the formation of α‐Fe₂O₃ nanostructures have been investigated systematically. Based on the observations of the products, the function of HEPES in the reaction is discussed. The different α‐Fe₂O₃ nanostructures possess different optical, magnetic properties, and photocatalytic activities, depending on the shape and size of the sample. In addition, a novel and facile approach was developed for the synthesis of Au/α‐Fe₂O₃ and Ag/α‐Fe₂O₃ nanocomposites in HEPES buffer solution; this verified the dual function of HEPES both as reductant and stabilizer. This work provides a new strategy for the controllable synthesis of transition metal oxide nanostructures and metal‐supported nanocomposites, and gives a strong evidence of the relationship between the property and morphology/size of nanomaterials.     

Morphology-controlled nonaqueous synthesis of anisotropic lanthanum hydroxide nanoparticles

The preparation of lanthanum hydroxide and manganese oxide nanoparticles is presented, based on a nonaqueous sol-gel process involving the reaction of La(OiPr)₃ and KMnO₄ with organic solvents such as benzyl alcohol, 2-butanone and a 1:1 vol. mixture thereof. The lanthanum manganese oxide system is highly complex and surprising results with respect to product composition and morphology were obtained. In dependence of the reaction parameters, the La(OH)₃ nanoparticles undergo a shape transformation from short nanorods with an average aspect ratio of 2.1 to micron-sized nanofibers (average aspect ratio is more than 59.5). Although not directly involved, KMnO₄ plays a crucial role in determining the particle morphology of La(OH)₃. The reason lies in the fact that KMnO₄ is able to oxidize the benzyl alcohol to benzoic acid, which presumably induces the anisotropic particle growth in [0 0 1] direction upon preferential coordination to the ±(1 0 0), ±(0 1 0) and ±(−110) crystal facets. By adjusting the molar La(OiPr)₃-to-KMnO₄ ratio as well as by using the appropriate solvent mixture it is possible to tailor the morphology, phase purity and microstructure of the La(OH)₃ nanoparticles. Postsynthetic thermal treatment of the sample containing La(OH)₃ nanofibers and β-MnOOH nanoparticles at the temperature of 800 °C for 8 h yielded polyhedral LaMnO₃ and worm-like La₂O₃ nanoparticles as final products.     

Solvothermal synthesis and characterisation of La1−xAxMnO3 nanoparticles

The synthesis of La_1−xA_xMnO₃ (A=Ca, Sr, Ba) nanoparticles in nonaqueous solvents has been studied. For this solvothermal procedure benzyl alcohol and acetophenone were chosen as reaction media. After this treatment in mild conditions a precipitate was obtained, which, however, can be annealed to the crystalline perovskite structure. Our results show that acetophenone is more suited to obtain the clean pervoskite phase than benzyl alcohol.     

Synthesis and Characterization of Water Soluble Gold Nanoclusters of Varied Core Size

A series of water soluble gold nanoclusters of variable core size were prepared and characterized. The clusters were synthesized using a ligand substitution reaction between CH₃(OCH₂CH₂)₃SH and hexanethiol encapsulated gold nanoclusters, and characterized using NMR, FTIR, and UV/Vis spectroscopy, as well as TGA, DSC, and TEM. Conductivity values were obtained for the clusters and increased as expected along with the gold core size. The substitution reaction used in the synthesis was followed by ¹H NMR and found to produce only partial ligand substitution after 24 h, consistent with solubility observations and necessitating use of a two-step preparation scheme.     

由1,1-二溴烯烃一锅法合成1,4-二取代-1,2,3-三氮唑

以1,1-二溴乙烯和芳基叠氮化合物为原料,碘化亚铜为催化剂,室温下通过一锅法合成了1,4-二取代-1,2,3-三氮唑衍生物。考察了催化剂用量、反应溶剂、反应温度对产品收率的影响。通过IR,MS,_¹H NMR及_¹³C NMR等对目标产物结构进行确证,并提出了可能的反应机理。该合成方法具有环境友好、条件温和、操作简单、收率高等特点。     

Reaction Mechanisms of Strontium Ferrites Synthesis

The reactions between strontium and iron nitrates have been studied in an open atmosphere system using three different molar ratios, 1:1 (I), 1:2 (II) and 2:1 (III) at different temperatures as pointed out from the DTA data. The reaction mechanism was discussed based on the chemical composition characterized by means of thermal analysis, X‐ray diffraction patterns, infrared spectra and magnetic susceptibility. It was found that the reaction products depend on both temperature of reaction and the ratio between reactants. The reaction products were found to be composed of a variety of iron compounds that possess different valences: SrFeO_2.86, SrFeO_2.97, SrFe₂O₄, SrFe₁₂O₁₉, Sr₂Fe₂O₅ and Sr₇Fe₁₀O₂₂ in addition to some accessory reaction products namely α‐Fe₂O₃ and FeO(OH).     

KCC-1 aminopropyl-functionalized supported on iron oxide magnetic nanoparticles as a novel magnetic nanocatalyst for the green and efficient synthesis of sulfonamide derivatives

A new magnetic nanocatalyst (Fe₃O₄@KCC-1-npr-NH₂) was synthesized directly through the reaction of Fe₃O₄@KCC-1 with (3-aminopropyl) triethoxysilane (APTES) using a hydrothermal protocol. Prepared nanocomposite was used as a magnetically reusable nanocatalyst for an efficient synthesis of a broad range of sulfonamide derivatives in water as a green solvent at room temperature and the products are collected by filtration with excellent yields (85–97%). The nanocatalyst could be remarkably recovered and reused after ten times without any significant decrease in activity. This mild and simple synthesis method offers some advantages including short reaction time, high yield and simple work-up procedure.     

Convenient Synthesis of Dicyclohexyldithiophosphinic Acid

Dicyclohexyldithiophosphinic acid was synthesized by a three-step strategy through the Grignard reaction of PSCl₃ with cyclo-C₆H₁₁MgBr and the P-P bond-cleavage reaction of the intermediate. The ¹H NMR data of ammonium dicyclohexyldithiophosphinate 4 and dicyclohexyldithiophosphinic acid 5 were characterized by ¹H-¹H correlation spectra.     

氯化亚锡催化“一锅法”合成N1-取代的3,4-二氢嘧啶-2(1H)-酮

以芳香醛、乙酰乙酸乙酯(甲酯)、单取代脲为原料,氯化亚锡为催化剂,在无溶剂、80℃条件下,通过三组分"一锅法"合成了一系列N1-取代的3,4-二氢嘧啶-2(1H)-酮衍生物。考察了催化剂用量和反应温度对产品收率的影响。通过IR、~1H NMR、~(13)C NMR和元素分析对目标产物结构进行确证,提出了可能的催化作用机理。本文的合成方法具有催化剂活性高、廉价易得和反应时间短、条件温和、产率高、绿色环保等优点。     

Indium(III)chloride catalyzed synthesis of novel 1H-pyrazolo[1,2-b]phthalazine-5,10-diones and 1H-pyrazolo[1,2-a]pyridazine-5,8-diones under solvent-free condition

An efficient, inexpensive and environmentally friendly synthesis of novel 3-amino-2-benzoyl-1-aryl-1H-pyrazolo[1,2-b]phthalazine-5,10-dione and 3-amino-2-benzoyl-1-aryl-1H-pyrazolo[1,2-a]pyridazine-5,8-dione derivatives has been developed via one-pot three-component reaction of phthalhydrazide or maleic hydrazide, aldehydes and arylacetonitrile in the presence of catalytic amount of InCl₃ as a Lewis acid catalyst under solvent-free conditions. The most important features of the present protocol are mild reaction conditions, short reaction times, high yields, and a wide range of functional group tolerance.     

One-pot synthesis of substituted indolo[1,2-a]quinolines under transition-metal-free conditions

A simple and efficient one-pot synthesis of substituted indolo[1,2-a]quinolines under transition-metal-free conditions has been developed. When 2-fluorobenzaldehyde was treated with substituted 2-methylindoles in the presence of Cs₂CO₃, the desired products were typically obtained in good to excellent yields. This reaction sequence involves a nucleophilic aromatic substitution and a Knoevenagel condensation reaction. Our mechanistic investigation revealed that both reactions could proceed as an intermolecular reaction in the first step.     

Total synthesis of PGF2α and 6,15-diketo-PGF1α and formal synthesis of 6-keto-PGF1α via three-component coupling

The asymmetric total synthesis of PGF_2α and 6,15-diketo-PGF_1α and formal synthesis of 6-keto-PGF_1α from a common key intermediate are described. The key intermediate, which has a chiral cyclopentane backbone possessing suitable functional groups with required stereochemistry for both side chains, was prepared from (R)-4-silyloxy-2-cyclopentenone through a three-component coupling reaction. The Wittig reaction, Nozaki-Hiyama-Kishi (NHK) coupling and cross metathesis completed the synthesis of PGF_2α, 6,15-diketo-PGF_1α and 6-keto-PGF_1α.     

Chiral Induction by Elimination‐Coupled Lithium–Ene Reaction: Synthesis of (+)‐(3R,4R)‐1,2‐Dihydromultifidene

Cyclization of the alkadienyl carbamates 1 to the cis‐divinylcyclopentanes 2 with high enantioselectivity and diastereoselectivity has been successfully achieved by (−)‐sparteine‐induced asymmetric deprotonation. The conversion may be described as a hybrid of a lithium–ene reaction and an S_n ′ reaction.     

Synthese und Charakterisierung von Fluorenylgallaten und Fluorenylindaten

Synthesis and Characterization of Fluorenyl Gallates and Fluorenyl Indates GaCl₃ reacts with Fluorenyllithium (LiFl) in the ratio 1:4 in Et₂O to [Li(THF)₄][GaFl₄] ( 1 ). The addition of DME (1,2-dimethoxyethane) to solutions of 1 in THF leads to [Li(DME)₃][GaFl₄] ( 2 ) under replacement of THF molecules by DME molecules in the coordination sphere of the Li⁺ ions. Treatment of InCl with LiFl in Et₂O and recrystallization from THF gives [Li(THF)₄][ClInFl₃] ( 3 ), which is formed by an disproportionation reaction. 3 can also be obtained by the reaction of InCl with FlZnCl/LiCl in Et₂O and recrystallization from THF. 1 and 2 crystallize from THF and THF/DME as [Li(THF)₄][GaFl₄] · THF ( 1 · THF) and [Li(DME)₃][GaFl₄] · THF ( 2 · THF), respectively. Crystalline 3 is isolated from the reaction of InCl and FlZnCl/LiCl, while the reaction mixture of InCl and LiFl gives after recrystallization in THF 3 · 1,5 THF. The gallate ions in 1 and 2 differ mainly in the position of the fluorenyl ligands. The unit cells of 3 and 3 · 1,5 THF contain two crystallographic unique ion pairs of [Li(THF)₄][ClInFl₃].     

HAlMCM-41介孔分子筛催化1,3-苯并二噁茂烷合成的研究

研究了HAlMCM-41分子筛催化邻苯二酚与环己酮、丁酮、丙酮、丙醛、丁醛、异丁醛、戊醛、正己醛、正辛醛、苯甲醛、二苯甲酮等十余种醛(酮)的缩合反应. 考察了反应时间、酚与醛(酮)的配比、HAlMCM-41分子筛用量、硅铝比、催化剂重用次数等因素对邻苯二酚与醛(酮)反应的影响. 结果表明, 当邻苯二酚与醛(酮)物质的量比为1∶1.4, 催化剂用量为3.5 g/mol邻苯二酚, 反应4 h, 分子筛n(SiO₂)/n(Al₂O₃)为15时, 选择性一般在99.4%以上, 转化率也一般在85.6%以上, 因此, HAlMCM-41分子筛对邻苯二酚与醛(酮)的反应有较好的催化性能.     

Untersuchungen zur Umsetzung von [Lithium(trimethylsilyl)amido]-methyl-trimethylsilylamino-silan Me(Me3SiNLi)(Me3SiNH)SiH mit verschiedenen Elektrophilen

Investigations of the Reaction between the [Lithium(trimethylsilyl)amido]-methyl-trimethyl-silylamino-silane Me(Me₃SiNLi)(Me₃SiNH)SiH and different Electrophiles The lithium silylamide Me(Me₃SiNLi)(Me₃SiNH)SiH 1 reacts with chlorotrimethylsilan in the nonpolar solvent n-hexane to the N-substitution product Me[(Me₃Si)₂N](Me₃SiNH)SiH 2 and to the cyclodisilazane [Me(Me₃SiNH)Si—N(SiMe₃)]₂ 3 nearly in same amounts. The reaction of 1 with chlorotrimethylstannane gives besides small amounts of the cyclodisilazane 3 the N-substitution product Me[(Me₃Si)(Me₃Sn)N](Me₃SiNH)SiH 4 . By the reaction of 1 with trimethylsilyltriflate the cyclodisilazane 3 is obtained as the main product. Furthermore 2 and the cyclodisilazane 5 are formed. Ethylbromide shows no reaction with 1 under the same conditions. These results indicate the existence of an equilibrium of the lithium silylamide 1 , the silanimine Me(Me₃SiNH)Si?N(SiMe₃) and lithium hydride.     

Synthesis of carboxylic esters from aldehydes using metal carbonyl anions,part 2. Dimerization of aldehydes to carboxylic esters catalyzed by disodium pentacarbonylchromate,na2[cr(co)5]

Na₂[Cr(CO)₅] (1) was found to be an efficient catalyst for the dimerization of aldehydes to carboxylic esters. Several aromatic aldehydes including furfural gave the corresponding esters in good yields. This reaction also proceeded intramolecularly to give phthalide from phthalaldehyde. Compared with M₂[Fe(CO)₄] (M = Na, K), 1 was found to be a more efficient catalyst for this reaction. However, aliphatic aldehydes gave aldolcondensation products instead of the corresponding esters. In the reactions of p-substituted benzaldehydes with 1, the reactivity decreased with the increase of the electron-releasing ability of the substituents. However, even p-anisaldehyde, which hardly reacted with M₂[Fe(CO)₄], reacted with 1 to give the ester in moderate yield. The reaction mechanism, including the nucleophilic attack of the pentacarbonylchromate dianion on the carbonyl carbon, is discussed.     

“Instant Methylide” Modification of the Corey–Chaykovsky Epoxide Synthesis

Abstract

We report that Me₃S(O)⁺I^? (1) and Me₃S⁺I^? (2) form stable, dry mixtures with KOt-Bu and NaH, respectively, which remain stable upon prolonged storage (>1 year). The corresponding methylides (Me₂SO=CH₂ and Me₂S=CH₂) are generated upon addition of DMSO or DMSO/THF solutions of carbonyl compounds, cleanly affording epoxides via the Corey–Chaykovsky reaction in good yields and short reaction times (as short as 20 min when 1–2 mmol of various ketones and aldehydes were treated with a mixture of 1 and KOt-Bu at 50–60°C).     

SO42-/SnO2-硅藻土型固体酸的制备及其对正丁酸与异戊醇的催化酯化

采用质量比为1∶3的SnCl₄·5H₂O和硅藻土制备的硅藻土Sn(OH)₄溶胶,70 ℃老化12 h,90 ℃干燥12 h、3.0 mol/L硫酸浸渍3 h、550 ℃焙烧3.5 h,制备了SO₄^2-/SnO₂硅藻土型固体酸催化剂。 利用IR、 XRD、TG测试技术表征了催化剂的理化性质。 用于催化正丁酸与异戊醇的酯化反应,当n（异戊醇）∶n（正丁酸）=1.4∶1、催化剂用量为反应物总质量的2.5%、10 mL苯、反应时间70 min时,酯收率为97.7％。 结果表明,该催化剂兼具多元氧化物型固体酸和硫酸酸化改性天然粘土固体酸催化剂的优点,催化活性高,成本低廉、制备方法简单并可适当回收循环使用。