流动注射双安培法测定葛根素

利用不可逆电对的双安培检测原理,建立了流动注射双安培直接检测葛根素的电化学新方法.使用经过恒电位预阳极化处理的双铂电极,通过耦合葛根素在一支电极上的氧化和氧化铂在另一支电极上的还原两个不可逆电极过程,构成流动注射双安培检测体系.在外加电位差为0.2 V时,pH 8.94的碳酸钠-碳酸氢钠缓冲溶液中,测得氧化电流与葛根素浓度在6.0×10-6～1.0×10-3 mol/L范围内呈线性关系(r=0.997 4,n=8),检出限为1.0×10-6 mol/L.连续40次测定6.0 ×10-4 mol/L的葛根素,RSD=1.58%.用该方法对葛根素含量进行了测定,结果令人满意.     

流动注射双安培法测定辛弗林

基于辛弗林在经预阳极化的铂电极上的催化氧化和不可逆电对的双安培检测原理,建立了流动注射双安培直接检测辛弗林的电化学分析新方法.本法使用经过恒电位预阳极化处理的双铂电极,在外加电位差为0 V时,通过偶合辛弗林在一支电极上的氧化和氧化铂在另一支电极上的还原两个不可逆电极过程,构成流动注射双安培检测体系.实验发现,在pH=10.88的BR缓冲溶液中,测得氧化电流与辛弗林浓度在6.0×10-6～1.0×10-3 mol/L范围内呈良好的线性关系(r=0.9990,n=8).检出限为2.0×10-6 mol/L.连续20次测定5.0×10-4 mol/L辛弗林,电流值的相对标准偏差(RSD)为2.2%.方法用于香砂养胃丸中辛弗林含量的测定,结果满意.     

流动注射双安培法测定硫脲

建立了流动注射双安培法检测硫脲的新方法。使用经过恒电位预阳极化处理的双铂电极,在外加电位差为0.30 V时,通过偶合硫脲在一支电极上的氧化和氧化铂在另一支电极上的还原两个不可逆电极过程,构成流动注射双安培检测体系。结果表明,在pH=5.3的HAc-NaAc缓冲液中,测得硫脲氧化电流与其浓度在1.0×10-5~1.0×10-3mol/L范围内呈线性关系(r=0.9989),检出限为5.0×10-6mol/L。对于6.0×10-4mol/L硫脲,测定的相对标准偏差(RSD)为1.80%(n=23)。该法样品处理简单,且有很高的选择性和灵敏度,结果令人满意。     

流动注射双安培法测定尿酸

基于尿酸在预阳极化的铂电极上的催化氧化和不可逆电对的双安培检测原理,使用经过恒电位预阳极化处理的双铂电极,在外加电位差为0 V时,通过偶合尿酸在一支电极上的氧化和氧化铂在另一支电极上的还原两个不可逆电极过程,建立了一种快速准确在线分析测定尿酸的电化学新方法———流动注射双安培检测法。在外加电位差为0 V时尿酸的氧化电流与其浓度在1.0×10-6~8.0×10-3mol/L范围内呈线性关系(r=0.998 5,n=11),检出限为5.0×10-7mol/L。连续28次测定4.0×10-4mol/L尿酸,电流值RSD为2.5%。电极的稳定性良好,常见无机离子和有机离子均不干扰测定。用该方法对尿酸含量进行了测定,样品处理简单,且有很高的选择性和灵敏度,结果令人满意。     

流动注射双安培法测定苯胺

应用苯胺在预阳极化的铂电极上的催化氧化过程,建立了流动注射双安培法直接检测苯胺的电化学新方法.在外加电压差为0.30V时,苯胺在预阳极化处理后铂电极上的和氧化铂在另一支铂电极上的还原为两个不可逆电极过程,在pH=9.94的碳酸钠-碳酸氢钠缓冲溶液中,苯胺的氧化电流与其浓度在4.0×10-6～1.0×10-4 mol/L...     

流动注射双安培法测定没食子酸

基于没食子酸在经预阳极化的铂电极上的催化氧化和不可逆电对的双安培检测原理,使用经过恒电位预阳极化处理的双铂电极,在外加电位差为0V时,通过偶合没食子酸在一支电极上的氧化和氧化铂在另一支电极上的还原两个不可逆电极过程,构建流动注射双安培检测体系,建立了一种流动注射双安培直接检测没食子酸的新方法。常用药物赋形剂、无机离子以及生化样品中一些共存物均不干扰没食子酸测定。没食子酸的氧化电流与其浓度在1.0×10-5～1.0×10-3mol/L范围内有良好的线性关系。检出限为5.0×10-6mol/L。连续20次测定2.0×10-4mol/L没食子酸,电流值的RSD为1.7%。该方法有很高的选择性和灵敏度,样品处理方法简单快速,适于在线分析。     

流动注射双安培法测定环境水样中苯酚

基于苯酚在铂电极上的氧化和不可逆电对的双安培检测原理,建立了流动注射双安培测定环境水样中苯酚的新方法。通过偶合苯酚在一支铂电极上的氧化和KMnO4在另一支铂电极上的还原这两个不可逆电对,构建双安培检测体系,在外加电位差为0V时,苯酚的氧化电流与其浓度在1.0×10-6～1.0×10-4mol/L范围内呈线性关系,检出限为5.0×10-7mol/L,连续30次测定2.0×10-5mol/L苯酚,电流值RSD为1.4%。用本方法分别对几种含酚废水样品中苯酚含量进行测量,并与4 氨基安替比啉比色法进行了对照。     

流动注射双安培法测定盐酸苯肼

使用经过恒电位预阳极化处理的双铂电极,在外加电压差为0.20 V时,通过偶合盐酸苯肼在一支电极上的氧化和氧化铂在另一支电极上的还原两个不可逆电极过程,建立快速准确分析测定盐酸苯肼的流动注射双安培检测法.结果表明:在pH为2.36的B-R缓冲溶液中,外加电位差为0.20 V时测得盐酸苯肼的氧化电流与其浓度在1.0×10~(-6)～1.0×10~(-4)mol/L范围内呈线性关系(r=0.9949,n=9),检出限为1.0×10~(-7)mol/L.对1.0×10~(-5)mol/L的盐酸苯肼溶液的连续23次测定,电流值的相对标准偏差为2.26%.常见离子均不干扰测定.样品处理方法简单,且有较高的选择性和灵敏性,结果令人满意.     

流动注射双安培法测定柚皮苷

基于柚皮苷的不可逆氧化和氧化铂的不可逆还原构成双安培检测体系应用于柚皮苷的直接检测。使用两支经阳极化预处理的铂电极,在外加电压为0 V时,通过偶合柚皮苷在一支电极上的氧化和氧化铂在另一支电极上的还原两个不可逆电极过程,构成流动注射双安培检测体系。实验发现,在pH 9.62BR(Briton Robinson)缓冲溶液中,测得柚皮苷氧化电流与其浓度在6.0×10-5~1.0×10-3mol/L范围内呈良好的线性关系(r=0.9953,n=8),检出限为1.0×10-5mol/L。连续20次测定6.0×10-4mol/L柚皮苷,其峰电流相对标准偏差(RSD)为3.3%。常用药物赋形剂和无机离子均不干扰柚皮苷的测定。方法用于模拟样品中柚皮苷的测定。     

流动注射双安培法测定橙皮甙

基于橙皮甙的不可逆氧化和氧化铂的不可逆还原体系构成了双安培法直接检测橙皮甙的新方法。在外加电压为0.2 V时,通过偶合橙皮甙在一支电极上的氧化和氧化铂在另一支电极上的还原两个不可逆电极过程,构成流动注射双安培检测体系。在pH 8.95的B-R缓冲溶液中,测得橙皮甙的氧化电流与其浓度在6.0×10-6~8.0×10-4mol/L范围内呈良好的线性关系(r=0.9997,n=11),检出限为1.0×10-6mol/L。连续30次测定6.0×10-4mol/L橙皮甙,其峰电流相对标准偏差(RSD)为3.2%,常用药物赋形剂和无机离子均不干扰橙皮甙的测定。方法已用于江中健胃消食片中橙皮甙含量的测定。     

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%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.     

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.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.     

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%).     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

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.