Reaction ofo-aminobenzohydroxamic acid with aldehydes

The reaction of o-aminobenzohydroxamic acid with aliphatic, aromatic, or heterocyclic aldehydes leads to the formation of derivatives of 3-hydroxy-1,2-dihydroquinazolin-4-one. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 115–117, January, 1997.     

Ozone as an oxygen source for alkene ene-reactions

Summary A strategy was developed which uses the adduct of ozone and triphenyl phosphite as a substitute for photochemically generated singlet oxygen in ene reactions of olefins. The resulting allylic hydroperoxide can be conveniently reduced by a second mole of phosphite to yield the corresponding allylic alcohol. The aryl phosphate produced as the by-product can either be recycled by reduction or used itself as a commodity. As an example, the two key steps of the rose oxide synthesis involving singlet oxygen can thus be reduced to a one pot procedure. With respect to the reaction mechanism, additional arguments for the direct reaction of the olefin with the phosphite ozonide were gathered. A simple decomposition of the ozonide to produce singlet oxygen was made rather unlikely.

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Ozon als Sauerstoffquelle für En-Reaktionen von Olefinen

Zusammenfassung Es wurde eine Strategie zum Ersatz von photochemisch erzeugtem Singlett-Sauerstoff durch das Addukt aus Ozon und Triphenylphosphit zum Einsatz in En-Reaktionen von Olefinen entwickelt. Das entstehende allylische Hydroperoxid kann durch ein zweites Molekül Phosphit einfach zum entsprechenden allylischen Alkolhol reduziert werden. Das als Nebenprodukt entstehende Arylphosphat kann entweder durch Reduktion recycliert oder direkt als Handelsware weiterverwendet werden. Auf diese Weise können zum Beispiel die beiden Stufen der Rosenoxidsynthese, an denen Singlett-Sauerstoff beteiligt ist, zu einer Eintopfreaktion vereinfacht werden. Bezüglich des Reaktionsmechanismus wurden zusätzliche Hinweise auf die direkte Reaktion des Phosphitozonids mit dem Olefin gefunden. Eine Zersetzung des Ozonids unter Bildung von Singlettsauerstoff ist nicht wahrscheinlich.

     

Experimental and theoretical studies of Diels-Alder dimerization of 1,2,3,4,5-pentachlorocyclopentadiene and of Diels-Alder cycloaddition of polychlorinated cyclopentadienes to norbornadiene

Diels-Alder cyclodimerization of 1,2,3,4,5-pentachlorocyclopentadiene (1) affords 2a as the exclusive reaction product. Diels-Alder cycloaddition of 1 to norbornadiene also proceeds stereoselectively to produce a single [4+2] cycloadduct, 4c. The structures of 2a and 4c were established unequivocally via application of single crystal X-ray crystallographic techniques. The origins of the observed diastereofacial selectivity in each of these cycloaddition processes have been investigated by application of semiempirical (AM1 Hamiltonian) and ab initio (Hartree-Fock 3-21G*) calculations. The computational results thereby obtained, which are based upon consideration of the kinetically favored transition state for each of the two cycloaddition reactions studied, are consistent with experiment. These semiempirical and ab initio methods also have been used to investigate the mechanisms of the Diels-Alder reactions that have been used to prepare aldrin and isodrin (7 and 8, respectively). The results thereby obtained suggest that isodrin formation via Diels-Alder cycloaddition of cyclopentadiene to 1,2,3,4,7,7-hexachloronorbornadiene proceeds with kinetic control of product stereochemistry.     

A straightforward preparation of a polystyrene thiol resin

A mild and efficient two-step synthesis of a polystyrene thiol resin is reported. Firstly, a polystyrene resin was reacted with an activated sulfoxide to afford the resin bound bis-(2-methoxy-carbonylethyl)-sulfonium trifluoromethanesulfonate. Smooth β-elimination based dealkylations afforded the polystyrene thiol resin with good and controlled loading. Its reactivity was assessed through a derivatisation step.     

乙炔和甲基二氯硅烷的硅氢加成反应研究：Ⅲ气固相反应规律探讨

比较了铂，铑，钯的氯化物对乙炔和甲基二氯硅烷的气固相硅氢加成反应的催化活性；筛选了铂催化剂中的无机载体；研究了浸渍法和制备的铂催化剂的催化反应行为。结果表明，浸渍法制备的铂催化剂中存在两类稳定性不同的活性中心，铂离子是具有催化活性的组分，甲基二氯硅烷与铂离子间的氧化还原反应是导致催化剂     

HGZ－Ⅱ型自动辉光放电光源的研制

在仔细研辉光放电光源工作过程的基础上，在国内首先设计、制成了ＨＧＺ－Ⅱ型自动辉光放电光源。该光源除换样品外，实现了抽空、进气、对光、预燃、曝光、充气、复位等摄谱全过程的自动控制。有水压、真空度、短路保护措施和醒铃线路。设计合理，性能良好，操作简便，工作安全，可靠。程控部分的编排包括顺序控制。时序控制和条件控制。由于使用了通用执行元、器件，降低了成本，提高了耐用性。为满足表层，逐层分析的需要，还专门设计了计数电路。供电源实现了高压直流供电和脉冲供电。该光源可应用于合金中主成分和少量杂质分析及金属、合金表层，逐层成分分析。     

Astragalus membranaceus ultrafine powder alleviates hyperuricemia by regulating the gut microbiome and reversing bile acid and adrenal hormone biosynthesis dysregulation

Ethnopharmacological relevanceMetabolic syndrome is closely related to the intestinal microbiota and disturbances in the host metabolome. Hyperuricemia (HUA), a manifestation of metabolic syndrome, can induce various cardiovascular diseases and gout, seriously affecting a patient’s quality of life. Astragalus membranaceus has a long history as a commonly used traditional Chinese medicine to treat kidney disease in China and East Asia.Materials and methodsWe compared the therapeutic effect of benzbromarone and two different doses Astragalus membranaceus ultrafine powder (AMUP) in rats with HUA. Ultra-performance liquid chromatography-mass spectrometer was used to analyze the AMUP metabolism in the plasma, urine, and feces. Further, 16S ribosome RNA sequencing and feces metabolomic were performed to capture the variation of the gut microbiota and metabolites changes before and after drug administration.ResultsAMUP had a notable impact on reducing blood uric acid levels while protecting the liver and kidney. Drug metabolism analysis demonstrated that effective constituent flavonoids are distributed in the blood, whereas saponins remain in the intestine. Gut microbiota analysis showed that low-dose AMUP ameliorated HUA-induced gut dysbiosis by reducing the abundance of harmful bacteria and increasing that of some beneficial bacteria with anti-inflammatory properties, such as Clostridia, Lachnospiraceae, and Muribaculaceae. In addition, HUA-induced changes in metabolite contents in bile acid and adrenal hormone biosynthesis pathways were restored after treatment with AMUP.ConclusionLow-dose AMUP exerts remarkable therapeutic effects on HUA by regulating the gut microbiome and mediating gut metabolism pathways associated with uric acid excretion.     

制备纳米氧化锌的新方法

以草酸和醋酸锌为原料，用室温固相化学反应首先制备前驱物二水合草酸锌，后者在微波场辐射分解得到产物纳米氧化锌。用XRD，TEM和IR等技术对产物的组成，大小及形貌进行了表征。结果表明：产物纳米氧化锌为粒度分布均匀的球形六角晶系结构，平均粒径约为8nm。     

Alkenylation of thiophenes at the 2-position with magnesium alkylidene carbenoids

Treatment of magnesium alkylidene carbenoids, generated from 1-chlorovinyl p-tolyl sulfoxides with isopropylmagnesium chloride at −78 °C in toluene, with 2-lithiothiophenes gave 2-alkenylated thiophenes in good to high yields. The intermediate of this reaction was found to be an alkenylmagnesium, which could be trapped with iodoalkanes and ethyl chloroformate. This procedure offers a novel and efficient one-pot synthesis of thiophenes having a disubstituted or a trisubstituted olefin at the 2-position from thiophenes in good yields.     

Asymmetric lithiation of 2-alkynyl aryl sulfides—Enantio- and diastereoselective formation of allenyl aryl sulfides and their application in nickel-catalyzed cross-coupling reactions

The enantio- and diastereoselective synthesis of allenyl aryl sulfides by asymmetric lithiation of 2-alkynyl (2-hetero)aryl sulfides is described. A dynamic thermodynamic resolution by selective crystallization of the intermediate lithium complexes derived from deprotonation, applying a bis(oxazoline) ligand, was achieved to give enantioselectivities up to 85% ee. Subsequent stereospecific nickel-catalyzed cross-coupling reactions with arylzinc reagents established a versatile access to threefold carbon-substituted allenes.