Synthesis of 2-Substituted and 2,3-Disubstituted Quinazolin-4-ones Containing a Sterically Hindered Phenol Residue

A series of 2-substituted and 2,3-disubstituted quinazolin-4-ones containing a 3,5-di(tert-butyl)-4-hydroxyphenyl group has been synthesized. They were prepared by the condensation of carboxylic acid imino ester hydrochlorides containing the indicated fragment with ethyl anthranilate and also by the reaction of azomethines, N-acylhydrazones, or the 4-phenylthiosemicarbazone of 3,5-di(tert-butyl)-4-hydroxybenzaldehyde with 2-methyl-4H-2,1-benzoxazin-4-one.     

Synthesis of Sterically Hindered Heteroaromatic Ketones under Phase-transfer and Metal-complex Catalysis Conditions. (Review)

We have correlated data on methods for obtaining sterically hindered ketones, derivatives of furan, thiophene, pyrrole, and pyridine. We examine routes to arylation of chroman-4-ones and synthesis of sterically hindered unsaturated and silicon-containing heteroaromatic ketones.     

微波作用下大位阻氨基酸与H-Pro-CTC树脂的高效缩合

微波反应下, 运用新型固相肽合成反应器, 深入研究了五种大位阻氨基酸与H-Pro-CTC树脂(CTC树脂, 2-氯三苯甲基氯树脂)的缩合反应. 使用三次缩合的策略, 分别在DMF/NMP/THF (V∶V∶V＝1∶1∶1), NMP/DMSO/THF (V∶V∶V＝4∶1∶1), DMF/DMSO/THF (V∶V∶V＝4∶1∶1)混合溶剂中缩合一次, 每次缩合反应的最优条件为: 缩合试剂HBTU、氨基酸浓度7 mmol/L、微波辐射3 min、反应温度35 ℃、维持时间3 min, 与传统方法相比, 氨基酸的用量大大减少, 其过量倍数从5倍降低为2倍, 缩合反应速率提高了16倍以上. 五种大位阻氨基酸与H-Pro-CTC树脂的缩合率都提高到80%以上.     

Greener Ullmann-Type Coupling of Aryl Halides for Preparing Biaryls Using Reusable Pd/ZrO2 Catalyst

Biaryls with excellent yields can be prepared by the Ullmann-type coupling of aryl halides in the presence of potassium carbonate (as a base) and dimethylformamide (as a solvent), at 140 °C, using a reusable Pd (2.5 wt%)/ZrO₂ catalyst. The product yield of 4-iodoanisole coupling is strongly influenced by the catalyst preparation method, solvent, and base.     

Highly Stereoselective Cyclopropanation of Olefins Catalyzed by a Novel C 3-Symmetric Arsine

A novel C ₃-symmetric arsine was employed in the one-pot cyclopropanation of olefins with carbonyl-stabilized arsonium ylides formed in situ from phenacyl bromide in the presence of NaHCO₃. This new arsine demonstrates good stereoselectivity and activity in the one-pot cyclopropanation of arylidenemalononitrile.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]     

熔融盐法制备LiMn2O4材料的合成条件研究

采用熔融盐法制备锂离子电池正极材料LiMn₂O₄,对制备过程中熔融盐种类、焙烧时间和焙烧温度等影响因素进行了系统研究。通过XRD、SEM和充放电测试,研究了产物的组成结构、形貌及电化学性能。研究结果表明,合成的LiMn₂O₄样品具有完整的尖晶石结构;样品的粒径分布范围小,平均粒径为几百纳米;优化实验条件之后制备得到的材料,在电压范围3.3～4.3 V,充放电电流值为60 mA·g^-1(0.5C)时     

1-Ethyl-2-Fluoro Pyridinium Salt: A Highly Efficient CouplingReagents for Sterically Hindered Peptide Synthesis

Moreand"loreattentionfortheincorporationof,\l'-methylorC'.,(;'.-dialkylaminoacidresiduesintopeptideshasbeenpaidinviewoftheincreasingnumberofisolatednaturally-occurrillgpeptidebearingstericallyhinderedanlinoacidunits.suchasMeValalldAib.However.thechainelongationofsuchpeptideisotienineftlcientusillgconventionalpeptidecouplingreagents,suchasHOBt-basedphosphonium'.uronium:andimmoniUm;typereagents.Recently,HOAt-derivedoniumsalts'and11alogeneratedoniumsalts'wereshowntobeeffectiveforthesynthesiso…     

Synthesis and structure of C2-symmetric N-heterocyclic carbene complexes of palladium

The first 9- and 11-membered cis and trans C₂-symmetric benzimidazol-2-ylidene palladium(II) complexes based on a trans-2,2-dimethyl-1,3-dioxalane backbone were synthesised and the configuration of the complexes was elucidated via NMR and X-ray crystallography.     

ZnBr2-Catalyzed and Microwave-Assisted Synthesis of 2,3-Unsaturated Glucosides of Hindered Phenols and Alcohols

Zinc bromide (ZnBr₂) under microwave irradiation efficiently catalyzed the Ferrier reaction of hindered phenols and alcohols to afford the corresponding α-2,3-unsaturated glucoside acetates in good yields and with good stereoselectivity. The reaction affords a facile access to new 2,3-dideoxyglucosides of important phenolic and alcoholic constituents of spices.     

Synthesis of Gels in the System Na2O-ZrO2-SiO2

Gels have been synthesized in the SiO₂-Na₂O-ZrO₂ system and calcined at various temperatures up to 700°C. They have been studied by infrared absorption spectroscopy. The position of the asymmetric stretching frequency of the SiO₄ unit is used as a tracer of the homogeneity. It is shown that sodium increases the solubility of zirconium in the silica matrix as already observed in fused glasses.     

熔盐法合成LiTaO3粉体

LiTaO3由于其突出的电光、压电和热释电效应,以及居里温度高、介电常数低,介电损耗小、老化速率低等特点,已成为广泛应用的功能材料[1,2]。而且,LiTaO3还可以与其他陶瓷材料如(K0.5Na0.5)NbO3等复合制成新型压电陶瓷[3]。另外,与陶瓷材料PZT相比较,该种压电材料不含铅,不会造成环境污染,属环境协调性绿色材料。LiTaO3的熔点很高(1630℃)[4],目前合成这类材料的常规方法有固相法、质子交换法和溶胶-凝胶法等[5￣9]。其中固相法采用Li2O和Ta2O5为原料,高温煅烧(往往高于1000℃),由于Li2O在高温下易挥发,使化学计量比较难控制[6],且在…     

Practical Organocatalytic Synthesis of Functionalized Non‐C2‐Symmetrical Atropisomeric Biaryls

An organic acid catalyzed direct arylation of aromatic C(sp²)? H bonds in phenols and naphthols for the preparation of 1,1′‐linked functionalized biaryls was developed. The products are non‐C₂‐symmetrical, atropoisomeric, and represent previously untapped chemical space. Overall this transformation is operationally simple, does not require an external oxidant, is readily scaled up (up to 98 mmol), and the structurally diverse 2,2′‐dihydroxy biaryl (i.e., BINOL‐type), as well as 2‐amino‐2′‐hydroxy products (i.e., NOBIN‐type) are formed with complete regioselectivity. Density‐functional calculations suggest that the quinone and imino‐quinone monoacetal coupling partners are exclusively arylated at their α‐position by an asynchronous [3,3]‐sigmatropic rearrangement of a mixed acetal species which is formed in situ under the reaction conditions.     

Interaction Between Two Similar Plane Parallel Double Layers for (NH4)2Fe(SO4)2 or (NH4)2Cu(SO4)2 Type Complex Salt Electrolytes at Positive Surface Potential

Interaction energies between two similar plane parallel double layers for (NH₄)₂Fe(SO₄)₂ or (NH₄)₂Cu(SO₄)₂ type complex salt electrolytes at positive surface potential were expanded in a power series and accurate numeral results were given for 0.1 ≤ y _e  < y ₀ ≤ 20. The general expressions were given for the interaction energies of A _ν +B _ν′ +C_ν? type complex salt electrolytes at y > 0. The interaction energies for simple salts NaCl, CaCl₂, Na₂SO₄, FeCl₃, Na₃PO₄, Mg₃(PO₄)₂, Al₂(SO₄)₃, and complex salts (NH₄)₂Fe(SO₄)₂ or (NH₄)₂Cu(SO₄)₂ at y ₀ = 1 were compared. There was hardly difference between these simple salts and this complex salt for the interaction energies. The interaction energy for complex salt (NH₄)₂Fe(SO₄)₂ was close to that for simple salt Na₃PO₄.

Supplemental files are available for this article. Go to the publisher's online edition of the Journal of Dispersion Science and Technology to view the free supplemental file.     

Aminomethylation of hindered 2-propargyl-1,3-diketones

2-Propargyl-substituted methoxy-1,3-diketones react with alkoxymethylamines or paraform and secondary amines in the presence of CuCl at the acetylene group to afford Mannich bases.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1293–1295, May, 1996.     

Stereochemistry of a cubane-like photodimer of methyl 2-naphthoate

A novel type of C₂-symmetric-chiral ligand, based on a cubane-like photodimer 1 of methyl 2-naphthoate, is reported in this work. Crystal analysis reveals that the methyl carboxylate functionality is in an anti-head-to-head conformation and 1 is highly rigid. The optically pure enantiomers of 1 can be obtained simply by HPLC resolution.     

Hindered rotation of ligands in cis-[PtR2Cl2] complexes

The temperature dependence of the¹H NMR spectra ofcis-[Pt(II)R₂Cl₂] complexes was studied in DMSO at 18–100°C (R is 2-methyl and 2,5-dimethylpyridine). The broadening of the signals from the methyl groups or hydrogen atoms in theortho-positions of heteroaromatic ligands is due to the coexistence of two forms of thecis-complexes in solution. These forms arise from the hindered rotation of asymmetrical ligands around the Pt-N bond.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 424–425, February, 1993.     

Synthesis and Characterization of Sol-Gel Cu-ZrO2 and Fe-ZrO2 Catalysts

Fe-ZrO₂ and Cu-ZrO₂ xerogels were prepared by a sol-gel method. The effect of the hydrolysis catalyst during the gelation step, namely H₂SO₄ or NH₄OH, on the properties of the resulting materials was investigated by XRD, BET, TGA/DTA, TPD of ammonia, FTIR, and TPR. Fe-ZrO₂ and Cu-ZrO₂ xerogels, with sulfuric acid introduced as the hydrolysis catalyst, mainly crystallyzed in the tetragonal phase and exhibited larger surface area and acid amount than those obtained with NH₄OH. Ammonia TPD shows that copper promoted sulfated zirconia is the most acidic material. TGA and FTIR reveal that under oxidizing conditions sulfated zirconia promoted with iron and copper retains more sulfate species than unpromoted sulfated zirconia. Regardless of the hydrolysis catalyst employed, copper promoted catalysts calcined at 600°C, contain a large fraction of copper oxide specieseasily reduced at low temperatures. These copper oxide species are believed to have different environment and interactions with the surface oxygen vacancies of the zirconia support. A FeO-like phase appears to be the most probable one after reduction of Fe-ZrO₂ catalysts prepared with NH₄OH as the hydrolysis catalyst. The formation of Fe° species may be hindered by the high dispersion and interaction of Fe²⁺ ions with the zirconia support. On the other hand, the reduction peaks of iron oxide and sulfate species exhibit a considerable overlap in the TPR profiles of sulfated Fe-ZrO₂ samples. Hence, the nature of the supported phase in the latter samples is rather uncertain.     

Pd‐PEPPSI‐IPent: An Active,Sterically Demanding Cross‐Coupling Catalyst and Its Application in the Synthesis of Tetra‐Ortho‐Substituted Biaryls

Incredible Bulk : A series of N‐heterocyclic carbene catalysts (see picture) were prepared and evaluated in the Suzuki–Miyaura reaction. A variety of sterically encumbered tetra‐ortho‐substituted biaryl products were formed from unreactive aryl chlorides using the isopentyl‐substituted catalyst at temperatures ranging from 65 °C to room temperature. The cyclopentyl‐substituted catalyst was virtually inactive, demonstrating that “flexible bulk” is essential to promote these transformations.