长光程薄层紫外-可见光谱电化学法测定多巴胺

利用一种长光程薄层光谱电化学池,建立了在抗坏血酸存在下测定多巴胺的紫外-可见光谱电化学法。测定条件为：在pH=6．0的PBS介质中,电极电位在0．6V（vs.Ag/AgCl）,测定波长为300nm多巴胺电氧化产物的吸光度,吸光度与多巴胺浓度在4×10－6～2．4×10－4mol/L范围内呈线性关系,检测限为1．0×10－6mol/L。用于多巴胺针剂的测定,结果令人满意。     

新显色剂1-羟基-2-(5-NO2-2-吡啶偶氮)-8-氨基-3,6-萘二磺酸与铜显色反应的研究

探讨了新显色剂 1-羟基-2-(5-NO2-2-吡啶偶氮)-8-氨基-3,6-萘二磺酸(简称5-NO2-PAH)与铜离子显色的适宜条件及其共存离子的影响,建立了 5-NO2-PAH测定铜的新显色反应体系.在 pH 7.0～10.0 范围内,铜与试剂形成稳定的 1∶2 配合物,其最大吸收峰位于 653 nm, 表观摩尔吸光系数εCu=4.68×104 L·mol-1·cm-1,铜的浓度在 0 μg/10 mL～14 μg/10 mL 范围内遵守比尔定律.方法已用于合金中铜的测定.     

偶氮胂Ⅲ分光光度法测定人血清中蛋白质

偶氮胂Ⅲ是测定无机离子的灵敏显色剂 ,研究发现该试剂能在pH 2 1的缓冲介质中 ,与牛血清白蛋白形成复合物 ,最大吸收波长 60 2nm ,比试剂本身红移 5 9nm ,表观摩尔吸光系数 5 6× 1 0 5L·mol- 1·cm- 1,线性范围 0～ 45 0 μg/mL。方法用于人血清样品中蛋白质的测定 ,结果可靠     

曲利本蓝-氨基糖苷类抗生素的显色反应及其分析应用

曲利本蓝 (TB)与硫酸卡那霉素 (KANA)和硫酸妥布霉素 (TOB)等氨基糖苷类抗生素在pH 2 .0～ 7.0的条件下反应生成蓝色离子缔合物。其最大显色波长位于 680nm(TOB)和 686nm(KANA) ,线性范围分别是 0～ 1 1 .0 μg mL(TOB)和0～ 1 3.0 μg mL(KANA) ,摩尔吸光系数 (ε)分别为 5 .32× 1 0 3(TOB)和 3.64× 1 0 3(KANA)L·mol-1·cm-1;最大褪色波长位于 5 88nm(TOB)和 5 90nm(KANA) ,线性范围均为 0～ 1 1 .0 μg mL ,摩尔吸光系数 (ε)分别为 1 .84× 1 0 4 (TOB)和 1 .1 1× 1 0 4(KANA)L·mol-1·cm-1。当用双波长叠加法时 ,ε值分别为 2 .37× 1 0 4 (TOB)和1 47× 1 0 4 (KANA)L·mol-1·cm-1。探讨了适宜的反应条件及主要的分析化学性质。该方法用于市售药物中氨基糖苷类抗生素的测定。     

磺硝酚偶氮若丹宁固相萃取光度法测定环境样品中的铅

在pH 4.5的HAc NaAc缓冲介质中 ,吐温 - 80存在下 ,磺硝酚偶氮若丹宁 (NSPAR)与铅反应生成 2∶1稳定络合物 ,该络合物可被WatersSep PakC1 8小柱固相萃取 ,用氮 氮二甲基甲酰胺 (DMF)洗脱后用光度法测定。在洗脱液介质中 ,λmax=5 5 5nm ,体系摩尔吸光系数ε=1 .0 2× 1 0 5L·mol- 1 ·cm- 1 。铅质量浓度在 0 .0 5～ 4.0 μg/mL内符合比尔定律 ,本方法可用于环境样品中铅的测定     

新显色剂2,4,4''''-三硝基苯基重氮氨基偶氮苯的合成及其与汞的显色反应

合成了新试剂2,4,4'-三硝基苯基重氮氨基偶氮苯(简称TNBDAA),并研究了在Triton X-100存在下其与汞的显色反应. 在pH 9.0的Na2B4O7-HCl缓冲介质中,Hg(Ⅱ)与试剂形成12的红色络合物,最大吸收波长为553 nm,表观摩尔吸光系数为1.69×105 L·mol-1·cm-1,汞质量浓度在0～0.7 μg/mL范围内服从比尔定律. 方法已用于废水中微量汞的直接测定.     

4-(2-噻唑偶氮)-苯二甘氨酸的合成及其与钯显色反应的研究

报道了水溶性 4 ( 2 噻唑偶氮 ) 苯二甘氨酸 (TAPC)新试剂的合成。该试剂对钯具有较高灵敏度和选择性。在 0 .5mol/LHNO3介质中 ,TAPC与Pd(Ⅱ )形成 2∶1蓝色配合物 ,最大吸收波长 632nm。钯浓度在 0 μg/mL～ 1 .6μg/mL范围内符合比耳定律 ,表观摩尔吸光系数ε632 =5× 1 0 4 L·mol- 1 ·cm- 1 。可允许许多离子共存 ,可直接用于含钯分子筛样中微量钯的测定     

双波长吸光光度法同时测定多巴和酪氨酸的研究

研究了双波长吸光光度法同时测定多巴和酪氨酸。在 pH 1 2 .0 0的硼砂 氢氧化钠缓冲介质中 ,多巴和酪氨酸的含量分别在 0～ 2 0 .0 μg·ml-1和 0～ 1 9.0 μg·ml-1范围内呈良好线性关系 ,方法检出限和摩尔吸光系数 :多巴为 0 .2 3 μg·ml-1和 1 .2 0× 1 0 4L·mol-1·cm-1,酪氨酸为 0 .2 7μg·ml-1和 1 .48× 1 0 4L·mol-1·cm-1,方法的灵敏度和和选择性均较好 ,应用于尿液中多巴和酪氨酸的测定。     

1-(偶氮苯基)-3-(3,5-二溴-2-吡啶)-三氮烯的合成及其与镉的显色反应

报道了 1 (偶氮苯基 ) 3 ( 3,5 二溴 2 吡啶 ) 三氮烯的合成及其与镉的显色反应。在TritonX 1 0 0存在下 ,于pH 1 0 .9的Na2 B4O7 NaOH缓冲介质中 ,镉与ABDBPDT形成摩尔比 1∶3型红色配合物。试剂及配合物的最大吸收波长分别为 430nm和 5 30nm。表观摩尔吸光系数为 1 .75× 1 0 5L·mol- 1 ·cm- 1 。镉含量在 0 μg/2 5mL～ 1 2 μg/2 5mL范围内符合比耳定律     

钒与新显色剂 1,4-双肼酞嗪显色反应的研究及应用

研究了钒与新显色剂 1,4-双肼酞嗪的显色反应.在 pH 5.8 的 HAc-NaAc 缓冲溶液中,加入溴化十六烷基三甲铵于 60℃加热 10 min,钒与 1,4-双肼酞嗪形成稳定的螯合物,λmax=422nm,ε422=1.32×104 L·mol-1·cm-1,钒的浓度在 0 μg/25 mL～20 μg/25 mL 范围内符合比耳定律,检出限为 15 ng/mL,已用于测定钢样中的微量钒.     

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.     

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.     

Understanding the Diels-Alder reactivity of 1,2-azaborine analogues

The Diels-Alder reactivity of 1,2-heteroborines (H₄C₄B(H)X, X?=?NH, PH, AsH; O, S, Se) has been computationally explored by means of Density Functional Theory (DFT) calculations. The influence of the HB?=?X fragment on the reactivity of the system has been quantitatively analyzed in detail by means of the so-called Activation Strain Model (ASM) of reactivity. It is found that the interaction between these species and the dienophile is significantly stronger than that computed for their all-carbon isoelectronic counterpart, benzene. In addition, the strain energy plays a key role in the observed reactivity trends. The role of the aromaticity strength of these heteroarenes on the reactivity is also assessed.