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排序方式: 共有107条查询结果,搜索用时 31 毫秒
41.
Rajkumar Jana 《Journal of organometallic chemistry》2008,693(25):3780-3786
(η5-methylcyclopentadienyl)(η4-tetraphenylcyclobutadiene)cobalt (1) and its derivatives, [(1-acetyl-2-methyl)η5-cyclopentadienyl](η4-tetraphenylcyclobutadiene)cobalt (2) [(1-acetyl-3-methyl)η5-cyclopentadienyl](η4-tetraphenylcyclobutadiene)cobalt (3) [(1-carbomethoxy-2-methyl)η5-cyclopentadienyl](η4-tetraphenylcyclobutadiene)cobalt (4) and [(1-carbomethoxy-3-methyl)η5-cyclopentadienyl](η4-tetraphenylcyclobutadiene) cobalt (5) have been prepared in yields varying from 11% to 28% by introducing the substituents on the cyclopentadienyl ring of methylcyclopentadienyl sodium and then reacting with diphenylacetylene and CoCl(PPh3)3. The carboxylic acids [(1-carboxy-2-methyl)η5-cyclopentadienyl](η4-tetraphenylcyclobutadiene)cobalt (6), [(1-carboxy-3-methyl)η5-cyclopentadienyl](η4-tetraphenylcyclobutadiene)cobalt (7) have been prepared after ester hydrolysis of compounds 4 and 5 using KOH/ethanol. [(1-dimethylaminomethyl-3-methyl)η5-cyclopentadienyl](η4-tetraphenylcyclobutadiene) cobalt (8), was prepared selectively by direct substitution on the cyclopentadienyl ring of (η5-methylcyclopentadienyl)(η4-tetraphenylcyclobutadiene)cobalt in 65% yield. The 1,2-isomer was formed only in traces in this reaction. Reactivity of (η5-methylcyclopentadienyl)(η4-tetraphenylcyclobutadiene)cobalt and its carbomethoxy derivative have been compared with (η5-cyclopentadienyl)(η4-tetraphenylcyclobutadiene)cobalt. All new compounds were characterized by 1H and 13C NMR, FT-IR, mass spectra and CHN analysis. Compounds 2, 4, 6 and 8 have also been structurally characterized by single crystal X-ray structural analysis. 相似文献
42.
Simultaneous and rapid determination of deoxynivalenol and its acetylate derivatives in wheat flour and rice by ultra high performance liquid chromatography with photo diode array detection
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Jiao‐Jiao Xu Jian Zhou Bai‐Fen Huang Zeng‐Xuan Cai Xiao‐Min Xu Yi‐Ping Ren 《Journal of separation science》2016,39(11):2028-2035
A simple and reliable method of ultra high performance liquid chromatography coupled with photo‐diode array detection has been proposed for the simultaneous determination of deoxynivalenol and its acetylated derivatives in wheat flour and rice, especially focusing on the optimization of sample extraction, cleanup, and chromatographic separation conditions. Sample pretreatment consisted of a first step using a quick, easy, cheap, effective, rugged, and safe based extraction procedure and a subsequent cleanup step based on solid‐phase extraction. The method was extensively validated in wheat flour and rice, obtaining satisfactory analytical performance with good linearity (R2 ≥ 0.999), acceptable recoveries (80.0–104.4%), and repeatability (RSDs 1.3–10.7%). The limits of detection (21.7–57.4 μg/kg) and quantitation (72.3–191.4 μg/kg) for deoxynivalenols were lower than those usually permitted by various countries’ legislation in these food matrices. The method was applied to 34 wheat and rice samples. The results were further compared with results of ultra high performance liquid chromatography with electrospray ionization tandem mass spectrometry. 相似文献
43.
N-heterocyclic carbene (NHC) has been employed as an efficient catalyst for cyanation reaction of carbonyl compounds. Under catalysis of 1 mol % NHCs, various aldehydes and 2,2,2-trifluoroacetophenone coupled with ethyl cyanoformate in THF to provide cyanohydrins ethyl carbonates in excellent yields. While in the presence of 10 mol % catalyst, different types of aldehydes and 2,2,2-trifluoroacetophenone reacted with acetyl cyanide in dichloroethane to give acylated cyanohydrins in moderate to high yields. 相似文献
44.
In the past decade, more than 100 different cathinone derivatives slopped over entire Europe due to their enormous popularity. Generally, these novel psychoactive substances are easily available via the internet. This fact leads to various social problems, since cathinones are substances with consciousness‐changing effects and are mainly misused for recreational matters by their consumers. Cathinones possess a chiral center including two enantiomeric forms with potentially different pharmacological behavior. This fact makes analytical method development regarding their chiral separation indispensable. In this study, a chiral capillary zone electrophoresis method for the enantioseparation of 61 cathinone and pyrovalerone derivatives was developed by means of four different β‐cyclodextrin derivatives. As chiral selectors, native β‐cyclodextrin as well as three of its derivatives namely acetyl‐β‐cyclodextrin, 2‐hydroxypropyl‐β‐cyclodextrin, and carboxymethyl‐β‐cyclodextrin were used. The cathinone and pyrovalerone derivatives were either purchased in internet stores or seized by police. As a result, overall 58 of 61 studied substances were partially or baseline separated by at least one of the four chiral selectors using 10 mM of β‐cyclodextrin derivative in a 10 mM sodium phosphate buffer (pH 2.5). Furthermore, the method was found to be suitable for simultaneous enantioseparations, for enantiomeric purity checks and to differentiate between positional isomers. Moreover, an intra‐ and an interday validation was performed successfully for each chiral selector to prove the robustness of the method. 相似文献
45.
46.
Dong Gyun Shin 《Tetrahedron letters》2005,46(12):1985-1987
Lewis acid induced C-O bond cleavage of a bicyclic ketal compound using AcCl-NaI produced a mixture of δ,ε-enone, allylic acetate and diacetate derivatives via a common 5-membered acetoxonium intermediate. A selective method to the synthesis of δ,ε-enone in high yield was introduced and applied to the synthesis of Douglas-fir tussock moth pheromone. 相似文献
47.
Georgia Tsolomiti 《Tetrahedron letters》2004,45(51):9353-9355
The unexpected synthesis of N-substituted 2-acetoxy-5-arylpyrroles, from the reaction of 3-aroyl-propionamides with a large excess of refluxing acetyl chloride, and their alkaline hydrolysis to 3- and 4-pyrrolin-2-ones, is described. 相似文献
48.
Summary A fully automated method, based on continuous ultrasound-assisted derivatization coupled with pervaporation before gas chromatographic
separation and flame ionization detection, has been developed for the determination of phenol and cresols in water. Spiked
water samples were doped with acetic anhydride and dipotassium hydrogen phosphate, before introduction into the flow system,
to achieve catalytic acetylation of the target compounds. A multivariate study was performed to optimize the main factors
affecting the derivatization process. The correlation coefficients, r, of the calibration plots obtained were better than
0.999 for cresols and better than 0.99 for phenol. Detection limits were 0.02 μg mL1 for phenol, o-cresol, andp-cresol, and 0.05 μg mL1 form-cresol. Reproducibility and repeatability, expressed as relative standard deviation, ranged from 2.0–3.9% and from 1.0–3.5%
respectively. 相似文献
49.
对乙酰基的基态(X12A′)和激发态进行了理论和实验研究。通过采用MRSDCI和MP2方法计算,获得了CH3CO自由基的四个电子激发态(A12A″,B22A′,C32A′,D22A″),其垂直激发能分别为250.8kJ·mol-1,472.3kJ·mol-1,645.8kJ·mol-1和674.7kJ·mol-1。运用时间分辨付里叶红外光谱仪(TR-FTIR)分别研究了CH3CO自由基的热解和光解反应,观察到初生产物CO(V)的红外发射光谱.势垒仅为75.2kJ·mol-1的基态CH3CO极易热解.532um的激光只能将CH3CO激发到束缚态A12A″,故未观察到CO信号;而248nm或266nm的激光可使CH3CO发生B22A′←X12A′跃迁,生成高振动激发的CO(V8)产物. 相似文献
50.
W. Franek 《Monatshefte für Chemie / Chemical Monthly》1996,127(8-9):895-907
Summary In a new, feasible procedure five symmetricalpara-substituted diaroylmethanes ((4-X-C6H4-CO)2-CH2;X=F, Cl, Br, CH3, and CH3O) are prepared, in most cases in very good yields. For purification and activation, they are converted into the copper(II) complexes of their enolates. Subsequently, three reaction steps with disulfur dichloride (S2Cl2), chlorine, and ethanethioic acid yield new CH-acidic dithio-bis-(diaroylmethanes), -chlorosulfenic acid chlorides, and acetyl diaroyl-chloromethyl disulfides. The latter compounds are of interest for the liberation of highly reactive dithiirane/thiosulfine species. With thiomorpholine, -chlorosulfenic acid chlorides give -chlorosulfenic acid amides.
Neue Dithio-bis-(diaroylmethane) und Acetyl-diaroylchlormethyl-disulfide: attraktive Synthone und Vorläufer zur Freisetzung hochreaktiver Dithiirane oder Thiosulfine
Zusammenfassung In einem neuen, gut handhabbaren Verfahren werden in meist sehr guter Ausbeute fünf symmetrischepara-substituierte Diaroylmethane ((4-X-C6H4-CO)2-CH2;X=F, Cl, Br, CH3 und CH3O) und daraus zur Reinigung und Aktivierung die Kupfer(II)komplexe ihrer Enolate dargestellt. Drei Reaktionsschritte mit Dischwefeldichlorid (S2Cl2), Chlor und Thioessigsäure führen der Reihe nach anschließend zu neuen CH-aciden Dithio-bis-(diaroylmethanen), -Chlorsulfensäure-chloriden und Acetyl-diaroylchlormethyl-disulfiden. Die letzteren Verbindungen sind zur Freisetzung von hochreaktiven Dithiiran/Thiosulfin-Spezies von Interesse. Mit Thiomorpholin geben -Chlorsulfensäurechloride -Chlorsulfensäureamide.相似文献