荷移光度法测定依诺沙星

依诺沙星与茜素红在水-乙醇介质中发生电荷转移反应,其中依诺沙星是电子给予体,茜素红是电子接受体,依据此荷移反应建立了一种快速测定依诺沙星的荷移分光光度法.荷移络合物在 546 nm 波长处有最大吸收,表观摩尔吸光率为 8.04×103L·mol-1·cm-1,相关系数为0.999 9.该络合物的组成为 1:1,表观稳定常数为 2.84×104.依诺沙星的质量浓度在 0～40 mg·L-1范围内服从比耳定律.当依诺沙星的质量浓度为 20 mg·L-1时,测定结果的相对标准偏差(n=6)为 1.2%,回收率在 99%以上.测定了依诺沙星制剂中有效成分的含量,与文献[1]方法结果基本吻合.     

荷移反应分光光度法测定苯巴比妥钠

采用分光光度法研究了电子给体苯巴比妥钠与π电子受体茜素红的荷移反应,建立了荷移分光光度法测定苯巴比妥钠的方法。在水溶液中,苯巴比妥钠与茜素红荷移络合物的最大吸收波长为530 nm,该络合物的组成为1∶1,表观摩尔吸光系数ε为4.43×103L.mol-1.cm-1,稳定常数为2.30×105。药物质量浓度在5~40 mg/L范围内符合比尔定律,相关系数为0.9996。当苯巴比妥钠浓度为20 mg/L时,10次测定结果的相对标准偏差为1.3%。测定了针剂中的苯巴比妥钠,加标回收率在98.9%~105%之间。     

基于与茜素红的荷移反应光度法测定苯妥英钠

采用光度法研究了电子给予体苯妥英钠与电子接受体茜素红之间的荷移反应,据此建立了荷移光度法测定苯妥英钠含量的方法.在水溶液中,苯妥英钠与茜素红荷移络合物的最大吸收波长为530 nm,该络合物的组成为1:1,表观摩尔吸光率为6.54×103L·mol-1·cm-1,稳定常数为2.26×105.苯妥英钠的质量浓度在4～40 mg·L-1叫范围内符合比耳定律.当苯妥英钠质量浓度为20 mg·L-1时,相对标准偏差(n=10)为1.23%.测定了片剂中苯妥英钠的含量,加标回收率在97.7%～101.0%之间.     

甲氧氯普胺与紫色素的荷移反应及其测定

研究了甲氧氯普胺与紫色素之间的荷移反应。确定了反应条件,建立了一种快速简便测定甲氧氯普胺的荷移分光光度法。实验表明,甲氧氯普胺与紫色素在乙醇介质中,室温条件下即可形成稳定的1∶1型荷移络合物,该络合物的λmax=540 nm,表观摩尔吸光系数为4.32×103L.mol-1.cm-1。测定结果的相对标准偏差为0.45%(n=6),回收率为98.3%~105.1%。     

艾司唑仑荷移反应及分析应用

采用紫外分光光度法研究了π电子受体四氯对苯醌 (TCBQ)与电子给予体艾司唑仑的荷移反应 ,结果表明 ,TCBQ与艾司唑仑在pH 8.2的BR缓冲溶液中能形成稳定的荷移反应络合物 ,吸光度显著增强。据此建立了测定艾司唑仑的简单、快速、准确和灵敏的方法。艾司唑仑浓度在 0 .2～ 3 .2mg/L范围内符合比尔定律。r=0 .9992。荷移络合物在 3 1 6nm处的表观摩尔吸光系数为 8.5× 1 0 4L·mol-1·cm-1。方法用于片剂中艾司唑仑含量的测定 ,其回收率为 99.2 %～ 99.7% ;相对标准偏差为 0 .7%～2 .1 %。     

胶束增敏荷移分光光度法测定水中苯胺

用分光光度法研究了苯胺作为电子给体与电子受体茜素红的荷移反应。在pH 5.0乙酸介质中,苯胺与茜素红可形成1∶1的稳定荷移络合物,加入适量的十二烷基硫酸钠,可引起该络合物的吸光度显著增加,最大吸收波长为525 nm,表观摩尔吸光率为3.25×103L.mol-1.cm-1,苯胺的质量浓度在2.0～56.0 mg.L-1范围内呈线性关系。应用此法测定废水样中微量苯胺,并以此水样为基体作回收试验,测得平均回收率在100.3%。     

荷移分光光度法测定酒石酸美托洛尔

研究了酒石酸美托洛尔与紫色素之间的荷移反应。确定了反应条件,建立了一种测定酒石酸美托洛尔的荷移分光光度法。酒石酸美托洛尔与紫色素在乙醇介质中,室温条件下即可形成稳定的1∶1型荷移络合物,该络合物的最大吸收波长为540 nm,表观摩尔吸光率为6.83×103L.mol-1.cm-1。酒石酸美托洛尔质量浓度在10~80 mg/L范围内服从比耳定律,相关系数为0.9991。相对标准偏差为1.3%(n=11),回收率为99.3%~102.7%。     

依诺沙星的荷移分光光度法测定

研究了电子给体依诺沙星(Enoxacin,ENX)与电子受体茜素红(Alizarin Red,AR)之间的电荷转移反应,确定了反应的最佳条件。实验结果表明:ENX与AR在水溶液中,于室温下即可生成稳定的1∶2络合物。该络合物的λmax=524 nm,表观摩尔吸光系数是6.96×103L.mol-1.cm-1,依诺沙星浓度在0~20 mg/L范围内符合比耳定律,相对标准偏差为0.25%(n=11)。方法用于测定药物制剂中依诺沙星的含量,其回收率为99.4%~100.5%。     

阿替洛尔与紫色素的荷移反应研究

采用光度法研究了电子给予体阿替洛尔与电子接受体紫色素之间的荷移反应,据此建立了荷移光度法测定阿替洛尔含量的方法。实验表明,阿替洛尔与紫色素在乙醇介质中,室温条件下即可形成稳定的1∶1型荷移络合物,该络合物的最大吸收波长为542nm,表观摩尔吸光系数为6.17×103L.mo-l1.cm-1。阿替洛尔的质量浓度在0~35 mg.L-1范围内符合比尔定律,相关系数为0.9993。当阿替洛尔的质量浓度为20 mg.L-1时,测定结果的相对标准偏差(n=6)为0.78%。采用本法测定片剂中阿替洛尔的含量,平均回收率在98.9%~101.6%之间。     

茜素红荷移分光光度法测定阿米卡星

采用分光光度法研究了阿米卡星和茜素红在水溶液中的电荷转移反应,室温条件下二者在水溶液中可形成结合比为1∶1荷移络合物,其最大吸收波长位于520nm处,表观摩尔吸光系数为1.44×103L·mol-1.cm-1。阿米卡星在5×10-5～6×10-4mol/L范围内符合比尔定律,线性回归方程为A=0.23+1439.5c(mol/L),相关系数r=0.9992,相对标准偏差为0.31%(n=6),加标回收率为97.6%～101.6%,据此建立了阿米卡星的测定新方法,可用于药品中阿米卡星的测定。     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.     

A carbanion induced synthesis of highly congested pyrazole and imidazole containing heterocycles

An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions.     

Synthesis of pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles by Curtius reaction in Morita-Baylis-Hillman derivatives

Synthesis of substituted pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles from the Morita-Baylis-Hillman derivatives of acrylates via saponification followed by Curtius reaction is described.     

Cu0-catalysed 1,3-dipolar cycloadditions of α-amino acid derived N,N-cyclic azomethine imines to ynones

A series of 20 CuAIAC reactions between eight 4-acylamino substituted pyrazolidine-3-one-1-azomethine imines and four terminal ynones were performed using Cu⁰ as catalyst. The corresponding fluorescent cycloadducts were obtained in very high yields upon simple workup. Thus, Cu-metal turned out to be a better catalyst than Cu^I in terms of yield and ease of isolation. Availability of azomethine imines, mild reaction conditions, and simple workup enable a “click” access to libraries of densely substituted 2,3-dihydro-1H,5H-pyrazolo[1,2-a]pyrazol-1-ones. Reactivity of differently substituted dipoles was evaluated experimentally and by quantum chemical methods (DFT).     

Selective synthesis of 4,5-dihydroimidazo- and imidazo[1,5-a]quinoxalines via modified Pictet–Spengler reaction

An efficient tandem approach for the selective synthesis of 4,5-dihydroimidazo[1,5-a]quinoxalines 6a–g and imidazo[1,5-a]quinoxalines 7a–h by the reaction of 2-imidazolyl anilines 4a–c with aryl aldehydes 5a–k under mild reaction conditions is described. Introduction of electron releasing alkyl groups in substrates 4a–b was found to be instrumental for the success of the reaction.