共查询到20条相似文献,搜索用时 31 毫秒
1.
以1-肼羰亚甲基-2-三氟甲基苯并[d]咪唑(1)为原料, 与芳基异硫氰酸酯在无水乙醇中反应得酰氨基硫脲2a~2d, 继而在氢氧化钠水溶液中合环得4,5-二氢-3-(2-三氟甲基苯并[d]咪唑-1-亚甲基)-4-芳基-1,2,4-三唑-5-硫酮(3a~3d), 然后分别采用超声辐射法和常规加热法与四种胺反应合成了16个未见报道的Mannich碱4a~4d, 5a~5d, 6a~6d和7a~7d. 与常规加热法对比, 超声辐射法具有操作简单, 反应时间短, 条件温和, 产率高, 副反应少等优点, 为此类化合物的合成提供了一种有效的新方法. 目标化合物的结构经元素分析, IR和1H NMR确证. 相似文献
2.
Bing Tian Zhao Tae In Kim Young Ho Kim Jong Seong Kang Byung Sun Min 《Natural product research》2018,32(2):239-242
We have developed a new method to simultaneously determine five marker compounds in Menthae Herba via HPLC/PDA – including hesperidin (1), rosmarinic acid (2), diosmin (3), didymin (4) and buddleoside (5). The newly developed method was successfully used to analyse for two species (Mentha arvensis L. and Mentha haplocalyx Briq.) of Menthae Herba, and the satisfactory results were obtained from the validation of developed method. The pattern analysis could greatly discriminate between M. arvensis L. and M. haplocalyx Briq. In conclusion, the proposed HPLC/PDA method is suitable for quality evaluation of Menthae Herba. 相似文献
3.
V. N. Emel’yanenko S. P. Verevkin E. N. Stepurko G. N. Roganov M. K. Georgieva 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2010,84(8):1301-1308
The values of combustion and formation enthalpy for glycolic acid (I) and glycolide (II) were determined by calorimetry. The temperature dependence of vapor pressures of I and II was obtained using the transpiration method, and the sublimation enthalpies were obtained. The enthalpy of melting of I was found by differential scanning calorimetry. Stable conformers were determined by the ab initio (DFT) method, and combinations
of the fundamental oscillations and inertia momenta of I and II conformers were calculated. The full and relative energies of the compounds most stable conformers were found by a composite
G3MP2 method, and the enthalpies of formation of I and II in the gaseous state were estimated. The values of the thermodynamic properties in the ideal gas state were determined over
the range of 0–1500 K. A thermodynamic analysis was performed for the process of preparation of II from I and the formation of polyglycolide (III) from I and II. 相似文献
4.
An improved method for the synthesis of 3,5-difluorosalicylic acid (3b) and 3,5-difluorosalicylaldehyde (3a) is described. 2,4-Difluorophenol (4) undergoes a formylation reaction to afford aldehyde 3a which is oxidized to the desired acid 3b. This method avoids the use of the highly corrosive HF and fluorine gas and requires no special laboratory apparatus. 相似文献
5.
Mahmure Ü. Özgür Güzin Alpdoğan Bürge Aşçi 《Monatshefte für Chemie / Chemical Monthly》2002,133(2):219-223
Summary. A simple and rapid derivative spectrophotometric assay procedure is described for the analysis of caffeine (1), acetaminophen (2), and propyphenazone (3) in tablet formulations. The concentration range of application is 5.0–25.0 μg·cm−3 for 2 and 3 and 1.0–5.0 μg·cm−3 for 1. The method involves the extraction of the drugs from tablets with 0.1 N H2SO4, filtration, appropriate dilution, and measurement of the fourth derivative absorbance values at zero crossing wavelengths
of 230.0, 263.2, and 256.6 nm for 1, 2, and 3. As a reference method, a reversed phase HPLC procedure was developed. Commercially available tablets were analyzed; statistical
comparison of the results with those obtained from the reference method showed good agreement. The derivative spectrophotometric
method has the advantage of being simple, rapid, inexpensive, and easy to perform.
Received April 18, 2001. Accepted (revised) June 5, 2001 相似文献
6.
M. Srinivasan Jang Bahadur Rampal 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-3):105-107
Abstract A novel two-step synthetic method to prepare 4-(thienyl)quinazolines (8a and 8b) is described. The method is based on the simultaneous reductive cyclization of a nitro group β to the carbonyl group in ketones under Leuckart reaction conditions. The method has been found useful for the syntheses of the 4-substituted quinazolines. 相似文献
7.
Xu-Lu Luo Na Li Min Xu Hong-Tao Zhu Peng He Yong Ding 《Natural product research》2015,29(20):1963-1965
Arbutin (1), chlorogenic acid (2) and 6′-O-caffeoylarbutin (3) are three major components in Vaccinium dunalianum Wight with various promising bioactivities. A reliable, reproducible and accurate method for simultaneous and quantitative determination of 1–3 is developed by RP-HPLC analysis. This method should be appropriate for the quality assurance of unprocessed and processed materials of V. dunalianum. The contents of 1–3 in different parts of V. dunalianum from different origins were analysed. The content of 3 was much higher than those of 1 and 2, accounting for up to 31.76% in the dried leaf buds. Moreover, the leaf buds, flower buds and leaves showed a tendency towards higher contents of 1–3 than the other plant parts. 相似文献
8.
《Monatshefte für Chemie / Chemical Monthly》2002,19(1):219-223
A simple and rapid derivative spectrophotometric assay procedure is described for the analysis of caffeine (1), acetaminophen (2), and propyphenazone (3) in tablet formulations. The concentration range of application is 5.0–25.0 μg·cm−3 for 2 and 3 and 1.0–5.0 μg·cm−3 for 1. The method involves the extraction of the drugs from tablets with 0.1 N H2SO4, filtration, appropriate dilution, and measurement of the fourth derivative absorbance values at zero crossing wavelengths of 230.0, 263.2, and 256.6 nm for 1, 2, and 3. As a reference method, a reversed phase HPLC procedure was developed. Commercially available tablets were analyzed; statistical comparison of the results with those obtained from the reference method showed good agreement. The derivative spectrophotometric method has the advantage of being simple, rapid, inexpensive, and easy to perform. 相似文献
9.
The O-H bond dissociation energies (D
OH) in the molecules of 2,5-dimethylhydroquinone (1) and 2,5-di-tert-butylhydroquinone (2) and in the corresponding semiquinone radicals (5 and 8, respectively) were estimated by the method of intersecting parabolas (IP) from experimental data on the rate constants for
the reactions of these compounds with N-phenyl-1,4-benzoquinonemonoimine (3) and using the density functional B3LYP/6-31+G* quantum chemical calculations. When calculating the D
OH values by the IP method, solvation of reactants and transition states should be taken into account. The energies of solvation
of quinones, semiquinone radicals, and hydroquinones were evaluated by the PCM method. The results of quantum chemical calculations
obtained with inclusion of the effects of solvation and the D
OH estimates obtained by the IP method are in good agreement, being equal to 337.9±1.6, 242.5±1.4, and 242.7±3.4 kJ mol−1 for molecule 1 and radicals 5 and 8, respectively.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2244–2251, October, 2005. 相似文献
10.
We have obtained dihydrofurans 3a–j in the radical cyclization of 4‐hydroxycoumarin 1a and 2‐hydroxy‐1,4‐naphtoquinone 1b with electron rich alkenes 2a–i by manganese(III) acetate. Methods A and B, which have different molar ratios were studied comparatively in these reactions, and we observed that method B (molar ratio 2:1:3) gave the best results. Treatment of 4‐hydroxycoumarin 1a and electron rich alkenes 2a–e gave 2,3‐dihydro‐4H‐furo[3,2‐c]chromen‐4‐ones 3a–e in 36–86% yields by the method B. Under the same conditions, the reactions of 2‐hydroxy‐1,4‐naphtaquinone 1b with conjugated alkenes 2b and 2f–i afforded 2,3‐dihydronaphtho[2,3‐b]furan‐4,9‐diones 3f–j in an excellent yields. 相似文献
11.
《Analytical letters》2012,45(7):1363-1370
ABSTRACT A rapid, sensitive and stability indicating method for the determination of sparfloxacin (SPAR) by RP - HPLC has been developed on a Merck RP - Select B (5 μm; 12.5 cm x 4.0 mm) column using a mobile phase of water: acetonitrile: triethylamine (80 : 20 : 0.2 v/v) pH of which was adjusted to 2.6 with orthrophosphoric acid. The flow rate was 1 ml / min. and the detection was carried out at 304 nm using Waters 486 variable wavelength detector. The retention time for SPAR was 7.2 min. Linearity range was from 8 - 1000 ppm. The method showed good precision and accuracy when applied to two brands of tablets containing SPAR. In alkaline media SPAR is stable where as it undergoes degradation in acidic and oxidising conditions generating different degradation products the nature of which is required to be established. The proposed method nicely separates the degraded products from SPAR and hence can be used as stability indicating method for the assay of SPAR. 相似文献
12.
Georgia Tsolomiti 《合成通讯》2013,43(4):501-507
A simple and efficient method is described for the synthesis of new functionalized 2‐aminothiazoles, the 2‐aminothiazole‐4‐phenyl‐5‐acetamides 5, in 67–96% yields based on an application of the Hantzsch synthesis. The method involves the reaction of thiourea with 3‐benzoyl‐3‐bromo‐propionamides 4 prepared from the corresponding 3‐benzoylpropionamides 3. The tautomeric structure of the γ‐keto amides 3 and 6 is directly related to the present study, because 2‐aminothiazoles 5 are readily obtained from the corresponding open chain γ‐keto amides 3. 相似文献
13.
Sanjeev Kumar V. Vernekar Paul Kipke Hartmut Redlich 《Journal of carbohydrate chemistry》2013,32(1):10-31
A convenient method for the syntheses of non‐1‐ynitols 8a–8d, by chemoselective addition of (trimethylsilyl)‐propargylmagnesium bromide at the anomeric center of a 1‐unprotected sugar, in the presence of 3‐C′‐halide and 3‐C′‐silyl functions in the side chain is described. In addition, an efficient method for the synthesis of 3‐C′‐hydroxymethyl sugar 3 via the addition of C1 silyl Grignard reagents to ulose 1 and subsequent oxidation by the Fleming‐Tamao method in excellent yields is reported. Also, a suitable acid‐catalyzed isomerization of the 1,2‐O‐isopropylidene group to the 2,3‐O‐isopropylidene group (5a–5f), to get access to the anomeric center, in good to excellent yields has been depicted. 相似文献
14.
Arslane-Larbi Haouchine Youssef Kabri Saléha Bakhta Christophe Curti Bellara Nedjar-Kolli 《合成通讯》2018,48(17):2159-2168
A simple and general method for the synthesis of new imidazopyridines bearing an aminopyridinyl, chromenyl, or quinolinyl moiety in the C2 position was developed. The Knoevenagel reaction between imidazo[1,2-a]pyridine-2-carbaldehyde 1 and malononitrile resulted in the formation of starting material 2. Subsequently, intramolecular cyclization between the cyano group of 2 and acetophenones, naphtols, hydroxyquinolines, or phenols, gave 3, 4, 5, and 6 compounds, respectively. This is a simple, reproducible, and environmentally friendly method of synthesizing substituted imidazopyridines using water as a solvent or under solvent-free conditions. 相似文献
15.
16.
Dieter Binder Christian R. Noe Johannes Nußbaumer Bernhard C. Prager 《Monatshefte für Chemie / Chemical Monthly》1980,111(2):407-411
The positionsselective synthesis of the title compounds5 is described and the structure established by reduction of5c to8 and synthesis of the latter by an unambiguous method. 相似文献
17.
以5-氨基-1H-1,2,4-三唑-3-羧酸(HAtca)为配体,通过水热法和溶液扩散法分别合成了2个新的配合物[Zn(Athy) Br]n(1,HAthy=5-氨基-1H-1,2,4-三唑-3-醇)和[Mn(Atca)2(H2O)2](2)。单晶结构分析表明配合物1和2分别属于正交和单斜晶系,结晶于Pbca和P21/c空间群。配合物1为2D层状结构,2是单核配合物。在配合物1中不存在氢键,而配合物2中含有丰富的氢键作用,并且通过氢键的作用形成了一个三维的网格结构。同时在固态下,配合物1和2分别在360、462 nm和382、402 nm处有较强的荧光发射峰。 相似文献
18.
A convenient method for the synthesis of various azafluorenones (2a-f & 4a-d) by cyclization of substituted arylpyridines (1a-f & 3a-d) using zeolites are described. 相似文献
19.
A spectrophotometric method for the determination of methimazole (MT), D-penicillamine (PA), captopril (CA), and disulfiram (DM) was proposed. The method is based on the reaction of sulfur compound with N,N-dimethyl-p-phenylenediamine (DMPD) in acidic solution, in the presence of Fe3+ ions as oxidizing agent. The Beer’s law was obeyed in the range 16–110 mg of MT, 19–260 mg of PA, 29–160 mg of CA, and 36–110
mg of DM. The method was successfully applied to the quantification of these compounds in pharmaceuticals. 相似文献
20.
描述了一种方便的合成甲硫芳炔化合物的新方法. 利用亲核硫试剂甲硫甲基苯基砜(methylthiomethyl phenyl sulfone, MP-S)与芳香醛的“一锅反应”, 成功地合成了一系列甲硫芳炔化合物1a~1h.通过对各阶段形成的中间体的分析, 探讨了1的形成机制.实验结果表明, 一锅反应经历了双离去基中间体2的形成和后续的两次消除过程.该方法原料易得, 操作简单, 可得到较好的产率(>70%). 此外, 反应还具有副产物少、容易分离和纯化的优点. 相似文献