双烯醇酮乙酸酯的极谱催化波及应用研究

采用线性扫描极谱技术,研究了在H2O2存在下双烯醇酮乙酸酯的极谱催化波。结果表明,在pH 4.0±0.5的B-R缓冲溶液、8.0×10-3mol/L H2O2溶液和0.1 mol/L KCl底液中,双烯醇酮乙酸酯于-1.01 V处产生一极谱催化波;其一阶倒数峰电流与双烯醇酮乙酸酯的浓度在1.0×10-8~1.0×10-7mol/L范围内有良好的线性关系,iP′=1.384×1011c 2.374×104(nA/s),相关系数r=0.9991;讨论了极谱催化波的产生机理。     

薯蓣皂甙元的极谱催化波及其应用

采用线性扫描极谱技术,研究了薯蓣皂甙元(C27H42O3,简称皂素)的极谱催化波及应用。结果表明,在pH=5.3±0.5的BR缓冲溶液、0.1mol/LKCl和8×10-3mol/LH2O2的底液中,皂素产生极谱催化波,其一阶导数波的峰电位在-1.05V(vs.SCE)处,峰电流与皂素浓度在1.0×10-8～8.0×10-8mol/L范围内有良好的线性关系,线性回归方程:i′P=7.322×108c+3.919(μA/s),相关系数r=0.9984,检出限为1.0×10-8mol/L;该波为不可逆吸附、平行催化波。建立了测定皂素的新分析方法,并测定了黄姜中皂素的含量。     

过硫酸钾存在下吸附缔合/平行催化波法测定酮洛芬

应用线性扫描极谱法和循环伏安法,在0.10 mol/L NH4C l-NH3.H2O(pH 9.5)-0.01 mol/L K2S2O8底液中,对酮洛芬(KPF)的电化学行为进行了研究。在该底液中KPF于峰电位-1.37 V(vs.SCE)处产生1个灵敏的吸附缔合/平行催化波。该极谱催化波中S2O82-有双重作用:①S2O82-作为配位体与吸附在电极表面的质子化KPF形成缔合物,引起峰电位负移;②S2O82-及其还原中间产物SO4-作为氧化KPF羰基经单电子单质子还原的自由基,产生了极谱催化,使峰电流显著增加。该极谱催化波的二阶导数峰峰电流与KPF浓度在1.97×10-8~3.94×10-6mol/L范围内呈线性关系,检出限为6.57×10-9mol/L(3σ)。对3.94×10-7mol/LKPF溶液进行13次平行测定,RSD为1.24%。该催化波的分析灵敏度比相应还原波提高20倍。该方法已用于药剂中KPF的测定。     

铜( Ⅱ )存在下的催化极谱波检测福美双

报道了在酒石酸-酒石酸钾钠-K2S2O8体系中福美双与Cu2 的极谱催化波。在0.1mol/L酒石酸-酒石酸钾钠(pH=5.5)缓冲液 3.0×10-3mol/LK2S2O8 4.0×10-6mol/LCu2 底液中,极谱催化波峰电位Ep=-0.8V(vs.SCE);福美双的二阶导数峰峰电流Ip″与其浓度在1.0×10-8~1.0×10-6mol/L范围内呈良好的线性关系(r=0.9994),检出限为2.0×10-9mol/L。相对标准偏差(RSD)为1.17%(n=10)。在福美双浓度为1.0×10-6mol/L时,福美双还原波峰电流为12nA,而相应的福美双在Cu2 存在下的催化还原峰电流为1.5μA,即灵敏度提高了125倍。样品的检测回收率为83.8%~91.4%。该方法灵敏、简单、快速。     

碘酸钾存在下萘丁美酮的极谱催化波法测定

本文报道了灵敏、快速测定萘丁美酮的新方法。在0.10 mol.L-1HAc-NaAc(pH 4.7)支持电解质中,萘丁美酮产生一极谱波,峰电位Ep=-1.12 V(vs.SCE)。加入KIO3后,该极谱波被催化,峰电流增加约30倍,峰电位基本不变,产生一灵敏的极谱催化波。其二阶导数峰峰电流ip″与萘丁美酮浓度在2.0×10-7~4.0×10-5mol.L-1范围内呈线性关系(r=0.9970,n=8),检出限为1.0×10-7mol.L-1。该方法可用于药物制剂中萘丁美酮含量的测定。     

防晒剂2，2’，4，4＇-四羟基二苯甲酮在B—R缓冲体系中的极谱行为

用线性扫描极谱法系统研究了2,2′,4,4′-四羟基二苯甲酮(简称BP-2)在不同缓冲体系中的极谱行为.实验表明,在pH=2.25的B-R缓冲溶液中,BP-2的一阶导数峰电位为-1.12 V,其峰电流与浓度在5.0×10-6～9.0×10-5mol/L范围内的对数值有良好的线性关系,线性方程为ip′(nA/s)=11 457 2 133×lgc(mol/L),相关系数为0.9998.BP-2的微分循环伏安研究表明,该极谱波为不可逆还原波;初步讨论了电极反应机理.     

防晒剂2,2′,4,4′-四羟基二苯甲酮在B-R缓冲体系中的极谱行为

用线性扫描极谱法系统研究了2,2′,4,4′-四羟基二苯甲酮(简称BP-2)在不同缓冲体系中的极谱行为。实验表明,在pH=2.25的B-R缓冲溶液中,BP-2的一阶导数峰电位为-1.12 V,其峰电流与浓度在5.0×10-6~9.0×10-5mol/L范围内的对数值有良好的线性关系,线性方程为ip′(nA/s)=11 457 2 133×lgc(mol/L),相关系数为0.9998。BP-2的微分循环伏安研究表明,该极谱波为不可逆还原波;初步讨论了电极反应机理。     

直接快速极谱法测定生物样品中的痕量铬

报道了在亚硝酸钠-2,2′-联吡啶-溴化十六烷基三甲铵(CTMAB)中铬(Ⅵ)的极谱催化波。在0.24mol/LNaNO2-4×10-5mol/L2,2′-联吡啶-1.6×10-5mol/LCTMAB(pH8.0)底液中,极谱催化波峰电位EP=-1.39V(vs.SCE),其峰电流与铬(Ⅵ)浓度在0～20ng/mL范围内有良好的线性关系。方法可用于测定生物样猪肝及猪肾中痕量铬(Ⅵ)。对极谱波的性质进行了初步探讨。     

极谱催化波法测定中草药中的芦丁

基于芦丁在K2S2O8存在下产生的极谱催化波,拟定了测定中草药中芦丁的方法。在0.1 mol/L HAc-NaAc(pH 3.60±0.05),8×10-3mol/L K2S2O8支持电解质中,芦丁催化波峰电位为-1.37 V(vs.SCE),它的二阶导数峰电流与其浓度在1.6×10-6~1.6×10-5mol/L范围内呈线性关系(r=0.9960,n=6)。检出限为9.013×10-11mol/L,回收率为96.18%~102.66%。样品可不经分离,直接测定。采用该方法测得山楂和川明参中芦丁的质量分数分别为1.78%和1.60%。     

雷公藤内酯酮的极谱行为研究

在不同pH值的相关体系中,雷公藤内酯酮可产生两个还原波,其峰电流和峰电位两者均受酸度的影响;然而,在B-R缓冲体系中,虽然峰电流受溶液酸度的影响,但峰电位基本上保持不变。在pH=5.4的B-R缓冲体系中,雷公藤内酯酮的两峰的峰电位分别为-0.06 V和-1.05 V(vs.SCE);两峰的峰电流与雷公藤内酯酮的浓度在3.16×10-6~3.16×10-5mol/L的范围内成良好的线性关系。循环伏安研究表明,两波都是不可逆吸附波。     

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.     

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.     

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%).     

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.