共查询到20条相似文献,搜索用时 15 毫秒
1.
Juzo Oyamada 《Tetrahedron》2007,63(51):12754-12762
Hydroarylation of propiolic acid derivatives with arenes in trifluoroacetic acid efficiently proceeded in the presence of PtCl2/AgOTf catalyst to give cis-cinnamic acid derivatives in good to high yields. This PtCl2/AgOTf-catalyzed reaction did not afford any 4-arylbuta-1,3-diene-1,3-dicarboxylic acid derivatives formed by Pd(OAc)2-catalyzed hydroarylation. The specific optimization of the catalytic hydroarylation and application to electron-rich arenes are reported. 相似文献
2.
Juzo Oyamada 《Tetrahedron letters》2005,46(22):3823-3827
PtCl2/AgOTf-catalyzed hydroarylation of ethyl propiolate proceeded effectively to give ethyl (2Z)-cinnamate derivatives in good to high yields, without the formation of diethyl (1E,3Z)-4-arylbuta-1,3-diene-1,3-dicarboxylates that was observed in Pd(OAc)2-catalyzed reaction. Especially, PtCl2/AgOTf-catalyzed hydroarylation of propiolic acids proceeded effectively to give (2Z)-cinnamic acids exclusively. 相似文献
3.
Takuya Hashimoto 《Journal of organometallic chemistry》2011,696(1):99-105
Hydroarylation of propiolic acids with various arenes in TFA proceeded efficiently in the presence of FeCl3/AgOTf catalyst system. In the case of electron-rich arenes, the iron-catalyzed hydroarylation gave cinnamic acids in moderate to high yields. The hydroarylation of phenylacetylene was observed but the catalyst was not effective under the same conditions. 相似文献
4.
Takuya Hashimoto 《Tetrahedron letters》2010,51(4):761-8145
FeCl3/AgOTf-catalyzed hydroarylation of propiolic acid with electron-rich arenes such as mesitylene, tetramethylbenzene, and pentamethylbenzene in trifluoroacetic acid proceeded to give 3-arylpropenoic acids in moderate to high yields. The same reactions with anisole and 1,4-dimethoxybenzene afforded double hydroarylation products, 3,3-diarylpropionic acids. 相似文献
5.
Juzo Oyamada 《Tetrahedron》2006,62(29):6918-6925
Synthesis of coumarins from phenols and propiolic acids was examined by using a Pt catalyst such as PtCl2/AgOTf, K2PtCl4/AgOTf, and K2PtCl4/AgOAc. Propiolic acid reacted even with less reactive phenols in trifluoroacetic acid to give coumarins and dihydrocoumarins. In the case of substituted propiolic acids, phenylpropiolic acid and 2-octynoic acid, the reactions proceeded selectively to afford coumarins in good to high yields. 相似文献
6.
Ivan V. Ogorodnyk Igor V. Zatovsky Vyacheslav N. Baumer 《Journal of solid state chemistry》2006,179(11):3461-3466
New complex phosphates of the general formula K2M0.5Ti1.5(PO4)3 (M=Mn, Co) have been obtained from the melting mixture of KPO3, K4P2O7, TiO2 and CoCO3·mCo(OH)2 or Mn(H2PO4)2 by means of a flux technique. The synthesized phosphates have been characterized by the single-crystal X-ray diffraction and the FTIR-spectroscopy. The compounds crystallize in the cubic system with the space group P213 and cell parameters a=9.9030(14) Å for K2Mn0.5Ti1.5(PO4)3 and a=9.8445(12) Å for K2Co0.5Ti1.5(PO4)3. Both phosphates are isostructural with the langbeinite mineral and contain four formula unit K2M0.5Ti1.5(PO4)3 per unit cell. The structure can be described using [M2(PO4)3] framework composed of two [MO6] octahedra interlinked via three [PO4] tetrahedra. The Curie-Weiss-type behavior is observed in the magnetic susceptibility. 相似文献
7.
The La2CuO4 crystal nanofibers were prepared by using single-walled carbon nanotubes as templates under mild hydrothermal conditions. The steam reforming of methanol (SRM) to CO2 and H2 over such nanofiber catalysts was studied. At the low temperature of 150 °C and steam/methanol=1.3, methanol was completely (100%, 13.8 g/h g catalyst) converted to hydrogen and CO2 without the generation of CO. Within the 60 h catalyst lifespan test, methanol conversion was maintained at 98.6% (13.6 g/h g catalyst) and with 100% CO2 selectivity. In the meantime, for distinguishing the advantage of nanoscale catalyst, the La2CuO4 bulk powder was prepared and tested for the SRM reaction for comparison. Compared with the La2CuO4 nanofiber, the bulk powder La2CuO4 showed worse catalytic activity for the SRM reaction. The 100% conversion of methanol was achieved at the temperature of 400 °C, with the products being H2 and CO2 together with CO. The catalytic activity in terms of methanol conversion dropped to 88.7% (12.2 g/h g catalyst) in 60 h. The reduction temperature for nanofiber La2CuO4 was much lower than that for the La2CuO4 bulk powder. The nanofibers were of higher specific surface area (105.0 m2/g), metal copper area and copper dispersion. The in situ FTIR and EPR experiments were employed to study the catalysts and catalytic process. In the nanofiber catalyst, there were oxygen vacancies. H2-reduction resulted in the generation of trapped electrons [e] on the vacancy sites. Over the nanofiber catalyst, the intermediate H2CO/HCO was stable and was reformed to CO2 and H2 by steam rather than being decomposed directly to CO and H2. Over the bulk counterpart, apart from the direct decomposition of H2CO/HCO to CO and H2, the intermediate H2COO might go through two decomposition ways: H2COO=CO+H2O and H2COO=CO2+H2. 相似文献
8.
The reaction of single crystals and powders of K2PtCl4 with hydrogen is studied by means of thermogravimetry (TG) at temperatures between 175 and 225°C and by optical microscopy. Two different mechanisms are observed. The rate of decomposition of single crystals is determined by the displacement of the reaction interface, which is similar in every crystallographic direction.The rate of decomposition of the powders is limited by the rate of nucleation in the powder particles. For both mechanisms the kinetic parameters are calculated. The activation energy for the displacement of the interface is much higher than the one necessary for nucleation. 相似文献
9.
The chemical fixation of CO2 with mono-substituted terminal epoxides or cyclohexene oxide to form cyclic carbonates under the ZnCl2/[BMIm]Br catalyst system without using additional organic solvents was achieved in excellent selectivity (>98%) and TOF (5410 h−1) and the catalyst could be used six times almost without losing its catalytic activity and selectivity. Besides, the pure cis-cyclic carbonate of cyclohexene oxide was obtained in this catalyst system. 相似文献
10.
采用恒pH法和非恒pH法制备了Al2O3掺杂的Pt/WO3/ZrO2催化剂,并用N2吸附-脱附、X射线衍射、紫外-可见漫反射、CO化学吸附、X射线光电子能谱、27Al魔角旋转核磁共振和吡啶吸附红外等技术对催化剂进行了表征.结果表明,相比于非恒pH法制备的催化剂,恒pH法制备的催化剂具有较高的比表面积和Pt分散度,在H2气氛中产生更多的B酸位,从而表现出更高的催化正庚烷临氢异构化反应活性; 在200℃和质量空速0.9h-1的反应条件下,正庚烷转化率达70.0%,明显高于非恒pH法制备的催化剂(43.5%). 相似文献
11.
Some K2O-TiO2-GeO2 glasses with a large amount of TiO2 contents (15-25 mol%) such as 25K2O-25TiO2-50GeO2 have been prepared, and their electronic polarizability, Raman scattering spectra, and crystallization behavior are examined to clarify thermal properties and structure of the glasses and to develop new nonlinear optical crystallized glasses. It is proposed that the glasses consist of the network of TiO6 and GeO4 polyhedra. The glasses show large optical basicities of Λ=0.88-0.92, indicating the high polarizabity of TiOn (n=4-6) polyhedra in the glasses. K2TiGe3O9 crystals are formed through crystallization in all glasses prepared in the present study. In particular, 20K2O-20TiO2-60GeO2 glass shows bulk crystallization and 18K2O-18TiO2-64GeO2 glass exhibits surface crystallization giving the c-axis orientation. The crystallized glasses show second harmonic generations (SHGs), and it is suggested that the distortion of TiO6 octahedra in K2TiGe3O9 crystals induces SHGs. 相似文献
12.
An efficient and economical protocol for the synthesis of 5-substituted-1H-tetrazoles from various nitriles and sodium azide is reported using nano TiO2/SO42− as an effective heterogeneous catalyst. A wide variety of aryl nitriles underwent [3 + 2] cycloaddition to afford tetrazoles in good to excellent yields. 相似文献
13.
A study of the catalytic activity of V2O5/C catalyst for the oxygen oxidation of glyoxal has been made, showing that glyoxylic acid can be formed without control of
pH value and there is little oxalic acid from the excessive oxidation of glyoxylic acid. The studies of XRD and TEM have shown
that V2O5 diffraction peaks gradually strengthen with the increase of the content of V2O5. With the content of 3% V2O5 and the calcination temperature of 573 K, V2O5/C catalyst displayed the best activity and selectivity. The conversion of glyoxal and the selectivity of glyoxylic acid reached
18.76% and 77.70% after 5 h, respectively. Moreover, V2O5/C catalyst showed small deactivation after recycling three times, which indicates that V2O5/C has a higher stability than noble metal catalysts in the reaction medium.
Supported by the Technology Research and Development Project for University of Shanxi Province of China (Grant No. 20051272) 相似文献
14.
A new procedure for the deprotection of carboxylic tert-butyl and 1-adamantyl esters, and N-Boc-amines using H2SO4 in CH2Cl2 is described. The proposed method is simple, cheap, eco-friendly and represents a valid alternative to existing ones, with special significance in large scale applications. 相似文献
15.
采用热扩散法(TS)和等体积浸渍法制备了MoO3/SiO2催化剂用于草酸二甲酯和苯酚酯交换反应.结果表明,热扩散法制备的10%MoO3/SiO2-TS催化剂较等体积浸渍法制备的10%MoO3/SiO2-C催化剂具有更好的催化性能.运用X射线衍射、Raman光谱、X射线光电子能谱分析、吡啶吸附红外光谱、NH3程序升温脱附等手段对催化剂进行了表征,发现虽然两种方法制备的催化剂都只有弱Lewis酸中心,钼均以氧化钼单体形式存在,未形成解离和聚合,但是10%MoO3/SiO2-TS催化剂较10%MoO3/SiO2-C催化剂表面钼含量更高且MoO3分散得更好.在苯酚用量为0.2mol,10%MoO3/SiO2-TS催化剂用量为1.2g,反应温度为180℃,草酸二甲酯与苯酚的摩尔比为2,反应时间为4h的优化条件下,苯酚转化率可达70.9%,甲基苯基草酸酯和草酸二苯酯的收率分别达63.1%和7.7%. 相似文献
16.
A TiCl4/AlCl3/MgCl2 (Cat-B) catalyst containing 5.2 wt.% Al was prepared by the reaction of TiCl4 with ethanol adduct of AlCl3/MgCl2 mixture. A TiCl4/MgCl2 catalyst (Cat-A) without doped AlCl3 was also prepared by the same method. Ethylene-1-hexene copolymerization catalyzed by Cat-B in the presence of hydrogen showed slightly higher efficiency and higher 1-hexene incorporation than Cat-A. Comonomer incorporation was markedly increased when the cocatalyst AlEt3 was replaced by Al(i-Bu)3. Adding Ph2Si(OMe)2 as external donor in the catalyst system caused decrease in polymerization activity and 1-hexene incorporation. Each copolymer sample was fractionated into three fractions: n-heptane insoluble fraction (fraction A), n-heptane soluble and n-hexane insoluble fraction (fraction B) and n-hexane soluble fraction (fraction C). In most cases the amount of intermediate fraction (fraction B) was smaller than the other fractions and did not increase as the total 1-hexene content increase, indicating the presence of two classes of copolymer fractions with greatly different comonomer content and clear bimodality of the copolymer composition distribution. Doping AlCl3 in the catalyst, changing cocatalyst and adding external donor mainly changed the weight ratio of fraction A to fraction C, but exerted little influences on their composition. According to the sequence distribution data of the fractions, doping AlCl3 in the catalyst resulted in slight decrease of product of reactivity ratios (r1r2) in both fraction A and fraction C. 相似文献
17.
Fe2(SO4)3·xH2O can be used as an efficient and reusable catalyst for the synthesis of pyrano- and furanotetrahydroquinolines via one-pot three-component Povarov reaction involving aromatic aldehydes, aromatic amines, and cyclic enol ethers. The catalyst is recyclable, economically viable, and environmentally benign. This protocol provides good yields and diastereoselectivity as well as applicability on a wide range of substrates. 相似文献
18.
K3Na(FeO4)2的电合成及其晶体结构 总被引:2,自引:0,他引:2
本文采用间接法电合成出较高纯度的复盐K3Na(FeO4)2晶体,用粉末XRD结构分析法对其晶体结构作了详细研究。用EDX和AAS确认了其化学式。结构分析表明,K3Na(FeO4)2晶体属三方晶系,具有六方晶胞,空间群为P3m1(No.164),Z=1,晶胞中有6个O位于6(i)位,O,Fe和K各自有2个位于2(d)位,1个K和Na分别位于1(b)位和1(a)位,晶胞参数a=0.583 3(1) nm,c=0.755 9(1) nm,D=2.824 g·cm-3。同时晶胞中各原子间化学键键长得到确定。 相似文献
19.
The results of the X-ray structural study for the K4LiH3(SO4)4 single crystal are presented at a wide temperature range. The thermal expansion of the crystal using the X-ray dilatometry and the capacitance dilatometry from 8 to 500 K was carried out. The crystal structures data collection, solution and refinement at 125, 295, 443 and 480 K were performed. The K4LiH3(SO4)4 crystal has tetragonal symmetry with the P41 space group (Z=4) at room temperature as well as at the considered temperature range. The existence of a low-temperature, para-ferroelastic phase transition at about 120 K is excluded. The layered structure of the crystal reflects a cleavage plane parallel to (001) and an anisotropy of the protonic conductivity. The superionic high-temperature phase transition at TS=425 K is isostructural. Nevertheless, taking into account an increase of the SO4 tetrahedra libration above TS, a mechanism of the Grotthus type could be applied for the proton transport explanation. 相似文献
20.
Fe(Cp)2BF4 is an efficient catalyst for the alcoholysis of aromatic, aliphatic, and cyclic epoxides giving excellent yields of the corresponding β-alkoxy alcohols under ambient conditions. The methanolysis of styrene oxide using Fe(Cp)2BF4 as a catalyst (5 mol %) gave excellent yield of 2-methoxy-2-phenylethanol with complete regio-selectivity. The ring opening of cyclic epoxides gave 77–97% yields of trans-β-methoxy alcohols, in 0.5–6 h. The use of 1,2-epoxyhexane and 1,2-epoxydodecane as substrates gave both regioisomers in excellent yields. The first order rate of reaction with respect to catalyst was observed for the kinetics of ring opening of 1,2-epoxyhexane with methanol. 相似文献