β-丙氨酸-银复合膜修饰电极用于循环伏安法测定对乙酰氨基酚

制备了β-丙氨酸-银复合膜修饰电极(Ag-Ala/GCE),采用循环伏安法研究了对乙酰氨基酚在修饰电极上的电化学行为。结果表明:在pH 4.0的磷酸盐缓冲液中,对乙酰氨基酚在修饰电极上呈现一对灵敏的氧化还原峰,提出了用循环伏安法测定对乙酰氨基酚的含量。对乙酰氨基酚浓度在6.0×10-7～7.0×10-4 mol.L-1范围内与氧化峰电流呈现线性关系,检出限(3S/N)为2.0×10-7 mol.L-1。修饰电极用于药剂中对乙酰氨基酚的测定,并用标准加入法测得方法的回收率在95.1%～101.6%之间。     

对乙酰氨基酚在多壁碳纳米管修饰电极上的电化学行为

制备了多壁碳纳米管修饰玻碳电极,研究了对乙酰氨基酚在多壁碳纳米管修饰电极上的循环伏安行为,并建立了测定对乙酰氨基酚含量的电化学分析方法。在pH为6.89的磷酸盐缓冲液中,多壁碳纳米管修饰电极对对乙酰氨基酚有明显的电催化作用,其氧化峰电流与对乙酰氨基酚浓度在1.0×10-6～1.0×10-4mol·L-1范围内呈良好的线性关系,检测限为2.0×10-7mol·L-1。     

岩白菜素在多壁碳纳米管修饰碳糊电极上的电化学行为及其测定

采用循环伏安法研究了岩白菜素在多壁碳纳米管(MWCNTs)修饰碳糊电极(CPE)上的伏安行为,建立了测定岩白菜素含量的电化学分析新方法.MWCNTs修饰碳糊电极对岩白菜素有明显的电催化作用,在pH 7.0磷酸盐缓冲溶液中,氧化峰电流与岩白菜素浓度在6.0×10-7～1.0×10-5mol·L-1范围内呈良好的线性关系,检出限为7.0 X10-8～mol·L-1(S/N=3,n=10).MWCNTs修饰电极可有效消除制剂中其它组分对岩白菜素测定的干扰,用于实际样品中岩白菜素含量的直接测定,回收率在99.8%～100.2%之间.     

二茂铁修饰碳糊电极示差脉冲伏安法测定槲皮素

制备了二茂铁修饰碳糊电极,并采用循环伏安法研究了槲皮素在该修饰电极上的电化学行为。研究发现:在pH 6.2磷酸盐缓冲溶液中,修饰电极对槲皮素有良好的电催化作用,得到了一对氧化还原峰,其氧化反应是受吸附控制的两电子、两质子电极过程。并在此基础上提出了一种测定槲皮素的示差脉冲伏安法。试验结果表明:槲皮素的氧化峰电流与其浓度在8×10-4～2×10-6 mol.L-1范围内呈线性关系,检出限(3S/N)为7×10-6 mol.L-1。     

银掺杂聚L-精氨酸修饰电极同时测定芦丁和抗坏血酸

用循环伏安法制备银掺杂聚L-精氨酸修饰玻碳电极(Ag-PA/GCE),研究了芦丁和抗坏血酸在该修饰电极上的电化学行为,建立了芦丁和抗坏血酸同时测定的新方法。在pH=2.5的磷酸盐缓冲溶液(PBS)中,于140mV·s-1的扫速下,芦丁产生一对氧化还原峰,其氧化峰电位为0.552V,还原峰电位为0.491V;抗坏血酸产生一个氧化峰,峰电位为0.281V。芦丁和抗坏血酸的△Epa=0.271V,用氧化峰不需分离可直接对芦丁和抗坏血酸进行同时测定,在最佳条件下,芦丁和抗坏血酸的线性范围分别5.0×10-7~2.0×10-5 mol·L-1和2.5×10-5~5.0×10-3 mol·L-1,检出限分别为1.0×10-7 mol·L-1和1.0×10-5 mol·L-1。方法可用于复方芦丁片中芦丁和抗坏血酸的同时测定。     

甲巯咪唑基于血红素修饰碳糊电极的电化学测定

制备了一种血红素修饰碳糊电极,用循环伏安法研究了甲巯咪唑在该修饰碳糊电极上的电化学响应特征,并对各实验参数进行了优化.相对于裸碳糊电极,甲巯咪唑在血红素修饰碳糊电极上的氧化峰电位明显负移,氧化峰电流大大提高,说明血红素对甲巯咪唑的氧化具有一定的促进作用.微分脉冲伏安实验结果表明,甲巯咪唑的氧化峰电流与其浓度在4×10-7 ～2×10-4 mol/L范围内呈良好的线性关系,检出限(S/N=3)为2×10-7 mol/L.该修饰碳糊电极显示了较好的抗干扰能力,尿酸几乎不干扰测定.用于实际尿样中甲巯咪唑的加标回收测定,结果满意.     

氨基硅油修饰碳糊电极阳极伏安法测定叶酸

在pH 6.8的B-R缓冲溶液中,采用氨基硅油修饰碳糊电极做工作电极,线性扫描伏安法对叶酸进行测定。伏安图上出现一灵敏的氧化峰,其峰电位EPa=+0.84 V,峰电流与叶酸的浓度在1.6×10-7~6.5×10-6mol.L-1范围内呈线性关系,检出限(3S/N)为7.2×10-8mol.L-1。富集时间为100 s,同时采用循环伏安法研究叶酸在氨基硅油修饰碳糊电极上的氧化还原反应,结果表明此电极反应为一不可逆的吸附过程。     

SMV在SDBS自组装膜与RGO复合修饰碳糊电极上的电催化氧化及电分析研究

研究了辛伐他汀(SMV)在表面活性剂十二烷基苯磺酸钠(SDBS)自组装膜与石墨烯(RGO)复合修饰碳糊电极(SDBS-RGO/CPE)上的电催化氧化和电化学动力学性质。实验结果表明,SDBS-RGO/CPE对SMV电化学氧化具有良好的催化作用。同时用循环伏安法(CV),计时电流法(CA)测定了SMV在SDBS-RGO/CPE上的电极反应动力学参数,用方波伏安法(SWV)测得SMV氧化峰电流(I pa)与其浓度在6.0×10-5～4.5×10-4mol·L-1范围内呈良好线性关系,检测限(S/N=3)为5.0×10-6mol·L-1,同时运用该方法对市售辛伐他汀片剂中SMV含量进行了电化学定量测定,测定结果符合定量测定要求。     

对乙酰氨基酚在聚刚果红修饰电极上的伏安测定

应用循环伏安法于玻碳电极修饰聚刚果红薄膜,并研究对乙酰氨基酚(ACOP)在该修饰电极上的电化学行为.实验表明,聚刚果红修饰电极对ACOP具有良好的电催化性能.在2.0×10-7~2.0×10-6mol.L-1ACOP浓度范围内,其差示脉冲伏安峰电流随浓度变化呈良好的线性关系,检测限为4.0×10-8mol.L-1.该法可用于实际样品的含量测定.     

6-羟基烟酸修饰电极的制备及应用研究

采用循环伏安法制备了6-羟基烟酸膜修饰炭糊电极(6-HNC/CPE),研究了多巴胺(DA)和肾上腺素(EP)在该修饰电极的电化学行为,结果表明该修饰电极对DA及EP具有明显的电催化效果。其电化学信号与DA的浓度在9.52×10-7~7.28×10-5mol·L-1和8.67×10-5~3.72×10-4mol·L-1范围内呈良好的线性关系。检出限为1.9×10-7mol·L-1(S/N=3),氧化峰电流与EP的浓度在1.74×10-6~4.41×10-5mol·L-1和5.58×10-5~1.01×10-4mol·L-1范围内呈良好的线性关系。检出限为3.6×10-7mol·L-1(S/N=3),利用差示脉冲伏安法(DPV),研究DA,UA和Trp的混合溶液电催化效果,结果该发现三者氧化峰电位在6-HNC/CPE上的能够完全分开,该方法操作简单,灵敏度高,可用于三者的选择性测定及实际样品中DA含量的测定。     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

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.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

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.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.