Novel synthesis of 2-isoxazolyl steroids

Novel examples of the reaction of 20-hydroxy-20-isoxazolinyl steroids to 20-isoxazolyl steroids using acetic acid in the presence of hydrobromic acid are reported. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 759–761, May, 2007.     

An entry to new isoxazoline analogues of dideoxynucleosides by bromonitrile oxide 1,3-dipolar cycloaddition

A short and efficient synthesis of new isoxazolinyl nucleosides bearing the nucleobase at the 3-position is reported. The synthetic approach relies upon the 1,3-dipolar cycloaddition of bromonitrile oxide to allyl benzoate and subsequent substitution of the bromine by the nucleobase.     

Novel Method for Soluble‐Polymer‐Supported Synthesis of 3,4,5‐Trisubstituted Isoxazoles

A practical and efficient liquid‐phase synthesis of 3,4,5‐trisubstituted isoxazoles using poly(ethylene glycol) as supported is described. Soluble‐polymer‐supported nitrile oxide generated in situ reacted with chalcones to afford polymer‐supported isoxazolines, which were cleaved by sodium methoxide to generate 3,4,5‐trisubstituted isoxazoles instead of 3,4,5‐trisubstituted isoxazolines. This sequential process provided a novel method to synthesize 3,4,5‐trisubstituted isoxazoles.     

Dimethyl dichloromalonate as a new synthetic equivalent of methyl dichloroacetate in the Darzens condensation

Dimethyl dichloromalonate reacts with aldehydes in the presence of sodium methoxide to form-chloropyruvates,-chloroglycidates, or,-dichlorohydrins, depending on the nature of the aldehyde.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1544–1545, August, 1995.     

Preparation and synthetic application of 2-bromoallyltrimethylsilane as a 1-hydroxymethylvinyl anion equivalent

The 1-trimethylsilylmethylvinyl group, as a 1-hydroxymethylvinyl equivalent, was readily introduced to epoxides with the corresponding Grignard reagent derived from 2-bromoallyltrimethylsilane. Obtained 2-(2-hydroxy-ethyl)-allylsilanes were converted to α-methylene-γ-lactones via diols.     

One-pot synthesis of 5-phenylsulfonyl-3-aroylisoxazolines and 3-aroylisoxazoles from alkynes and (phenylsulfonyl)ethene

1. Download : Download high-res image (29KB)
2. Download : Download full-size image

     

Oxidative desulfonylation. Phenyl vinyl sulfone as a ketene synthetic equivalent

α-Sulfonyl carbanions undergo oxidative desulfonylation to form ketones upon treatment with molybdenum peroxide MoO₅·Py·HMPA (MoOPH) in THF at ?78°C.     

2-Benzoyloxynitroethylene as a cis-2-aminoethenol equivalent

Nitroester 1 reacts readily with dienes to afford trans-nitroesters which are reduced to cis-aminoalcohols.     

Lipase-mediated kinetic resolution of a synthetic equivalent of 2-hydroxymethylcyclopentadien-5-ol

Racemic 3-hydroxy-2-hydroxymethyl-endo-tricyclo[5.2.1.0^2,6]-dec-4,8-diene serving as a synthetic equivalent of 2-hydroxymethylcyclopentadien-5-ol has been resolved by employing lipase-mediated kinetic transesterification with vinyl acetate in an organic solvent.     

Synthesis of spiro-substituted 1,3-oxazines by a new sequence leading to spiroheterocycles

Summary The target compounds, i.e. 1,3-oxazines which are spiro-substituted in position 6 by a piperidine moiety, are derived from 1-oxa-3,9-diaza-spiro[5.5]undecane, a novel heterocyclic parent system. They were all approached by the following three-step sequence: 1,3-dipolar cycloadditions of nitrile oxides and nitrones to piperidines bearing an exocyclic methylene group gave the corresponding spiro-substituted oxazole derivatives3. In a consecutive step these were cleaved by hydrogenolysis to -amino-alcohols4, which in a final step were recyclized by insertions of a C₁-unit to yield the target structures5–10: thus ade facto ring-extension of spiro-oxazoles to spiro-oxazines was accomplished.

---

Synthese von spirosubstituierten 1,3-Oxazinen mittels einer neuen zu Spiroheterocyclen führenden Synthesefolge

Zusammenfassung Die Zielverbindungen, d.h. 1,3-Oxazine mit einem Piperidinring als Spiro-Substituenten in 6-Stellung, leiten sich von 1-Oxa-3,9-diaza-spiro[5.5]undecan, einem neuen heterocyclischen Grundkörper, ab. Sie wurden alle mit Hilfe der folgenden dreistufigen Synthesefolge zugänglich gemacht: 1,3-dipolare Cycloadditionen von Nitriloxiden und Nitronen an Piperidinderivate mit einer exocylischen Methylengruppe gaben die entsprechenden spiro-substituierten Oxazolderivate3. Diese wurden anschließend hydrogenolytisch zu den -Aminoalkoholen4 gespalten, welche schließlich wieder unter Einschub von einem C-Atom zu den Zielstrukturen5–10 cyclisiert wurden: dadurch wurde einede facto-Ringerweiterung von Spiro-Oxazolen zu Spiro-Oxazinen erreicht.

     

Polystyrene-graphene oxide modified glassy carbon electrode as a new class of polymeric nanosensors for electrochemical determination of histamine

A simple and rapid protocol for the synthesis of polystyrene-graphene oxide nanocomposite(PS/GONC)was achieved for first time using an in situ polymerization method.PS/GONC modified glassy carbon electrode(PS/GONC/GCE) has been employed as an efficient nanosensor for the electrooxidation of histamine.The PS/GONC/GCE is used as an electrochemical nanosensors for monitoring histamine using differential pulse voltammetry techniques(detection limit 0.03 μmol/L).In addition,the prepared nanosensor was successfully applied to determine histamine in fish samples,yielding satisfactory results.The spiked recoveries were in the range of 98.2%-103.1%.     

Synthesis of carbamoylformhydroxymoyl chlorides and study of their reactivities

Carbamoylformhydroxymoyl chlorides were synthesized by the reactions of carbamoylformamide oximes with sodium nitrite in the presence of hydrochloric acid, and their reactivities were examined.     

A useful synthetic equivalent of a hydroxyacetone enolate

Indium promoted allylation of carbonyl compounds with 4-(bromomethyl)-1,3-dioxol-2-one diastereoselectively affords anti-α,β-dihydroxyketones, protected as enol carbonates. These initial products can be deprotected to free dihydroxyketones or transformed under mild conditions into the corresponding cyclic carbonates, which constitutes a useful approach to hydroxyacetone aldols.     

Iodomethyl group as a hydroxymethyl synthetic equivalent: application to the syntheses of D-manno-hept-2-ulose and l-fructose derivatives

The one-carbon elongation of aldoses to ketoses using iodomethyllithium as the key reagent in the homologation step is exemplified by the preparation of two carbohydrates of chemical and biological interests: d-manno-hept-2-ulose from d-mannose and l-fructose from l-arabinose.     

Carbamic acid 2-trimethylsilylethyl ester as a new ammonia equivalent for palladium-catalyzed amination of aryl halides

Carbamic acid 2-trimethylsilylethyl ester (Teoc-NH₂) serves as an ammonia equivalent in the palladium-catalyzed amination of aryl bromides and aryl chlorides. Anilines with sensitive functional groups can be readily prepared using these amine derivatives.     

三维二硫化钼/还原氧化石墨烯气凝胶用作宏观可见光催化剂

近年来,光催化技术在解决环境污染和能源短缺方面展现出巨大潜力.二硫化钼(MoS2)作为一种二维层状光催化材料受到广泛关注.MoS2具有可调的带隙(1.2–1.9 eV)、低的成本和高的存储量,是一种可替代铂的理想助催化剂.然而,MoS2本身光催化活性较低.理论和实验已经证明,MoS2只有暴露的边缘具有催化活性,并且MoS2的光生电子-空穴对容易复合,导致其光催化效率低.增加暴露的活性边缘以及有效分离电子-空穴对是提高MoS2光催化活性的关键.而石墨烯气凝胶是一种理想的催化剂载体,其高比表面积和高空隙率可以有效提高催化剂利用率.同时,其高导电性可以促进光生电子-空穴对分离.因此,将MoS2负载到石墨烯气凝胶上制备宏观可回收光催化材料具有广阔的应用前景.然而,目前尚未见到有关MoS2/石墨烯气凝胶光催化产氢以及还原Cr(VI)的报道.本文以钼酸铵为钼源,硫脲为硫源和还原剂,同时加入氧化石墨烯及其还原剂氨水,通过一步水热法制备出二硫化钼/还原氧化石墨烯(MoS2/RGO)水凝胶.最后通过冷冻干燥得到MoS2/RGO气凝胶.经光催化测试发现其产氢达到38.9μmol/g,光还原Cr(VI)达到92%,明显高于MoS2粉体.采用X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、X射线光电子能谱(XPS)、紫外-可见-近红外吸收光谱(UV-Vis-NIR)及红外光谱(FTIR)等手段研究了其光催化性能提高的原因.XRD测试显示,过量的NH4+离子插入到MoS2层与层之间增加了(002)面的晶面间距;SEM观察到在形成气凝胶后,MoS2从粉末的片状转变成花状,这是因为氧化石墨烯上的含氧官能团促进MoS2成核同时限制其生长导致的;TEM观察到MoS2上存在大量的脱节和扭曲,这是由于过量硫脲阻碍了MoS2晶体的取向生长而产生缺陷;XPS发现,除了形成MoS2之外,还形成了MoO2,同时大量的暴露边缘导致不饱和硫产生;FTIR表明MoS2与RGO之间通过氢键链接在一起;UV-Vis-NIR吸收光谱显示,MoS2/RGO气凝胶在可见光区具有很强的吸收,这是黑色的RGO以及光在花状结构的不断反射共同作用导致的.综合以上结果,我们提出了MoS2/RGO光催化性能增强的机理.首先,三维的气凝胶网状结构以及花状结构的MoS2所带来的高比表面积(599.7 m2/g)使得材料对H+和Cr(VI)吸附量增加;其次,黑色的RGO以及入射光在花状结构层片间的不断反射增加了MoS2/RGO气凝胶对可见光的吸收;最后,RGO本身的高导电性促进了光生电子-空穴有效分离,电子通过RGO快速转移到材料表面参与光催化反应.因此,将MoS2负载在RGO上可提高光催化效率.另外,低密度的MoS2/RGO气凝胶(56.1 mg/cm3)可以有效吸附有机溶剂且容易回收.综上所述,本文制备的MoS2/RGO气凝胶光催化材料在环境与能源方面表现出潜在的应用前景.     

The synthesis of new 5-aminoisoxazoles by reaction of thiocarbamoylcyanoacetates with hydroxylamine

The reaction of thiocarbamoylcyanoacetates with hydroxylamine in ethanol under reflux conditions has provided a convenient method for the synthesis of 5-aminoisoxazoles. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 907–912, June, 2008.