十二烷基苯磺酸钠与奎尼丁作用的共振光散射研究

研究了表面活性剂十二烷基苯磺酸钠(SDBS)与奎尼丁作用的共振散射光谱特征.实验结果表明在pH1.81的水溶液中,奎尼丁与SDBS作用并产生以278.0 nm和377.0 nm为特征峰的共振散射增强光谱,在上述特征波长下测定的增强共振光散射强度与奎尼丁浓度在一定范围内呈线性关系.当SDBS的浓度为3.0×10-4moL/L时,奎尼丁的检测限可分别达6.71 nmol/L和6.15 nmol/L.据此建立了痕量奎尼丁的共振光散射分析方法.     

共振光散射光谱法测定沙丁胺醇的研究

在B-R缓冲液的酸性条件下,以十二烷基苯磺酸钠作稳定剂,研究了沙丁胺醇的共振光散射光谱,在λex=λem=460 nm处得到一个共振光散射峰,其光谱强度与沙丁胺醇浓度呈线性关系,以此建立了测定沙丁胺醇的共振光散射光谱法。工作曲线的线性回归方程为I_(RLS)=114.67C_(SAL)+39.42,其线性范围为4.18×10~(-7)~5.43×10~(-6)mol·L~(-1),相关系数R为0.9994,以3倍标准偏差(3σ)而计算出的检出限为2.09×10~(-7)mol·L~(-1),相对标准偏差RSD为1.8,用于检测实际样品沙丁胺醇气雾剂得到了令人满意的结果。     

共振瑞利散射光谱法测定利血平的含量

在pH3.96的Tris-盐酸缓冲介质中,利血平的水解产物和质子化的维多利亚蓝B形成离子缔合物,使体系的共振瑞利散射(RRS)急剧增强,在421nm处产生最大散射峰,利血平的质量浓度在0.40～6.40mg·L~(-1)范围内与共振瑞利散射强度(△I_(RRS)=I_(s,RRS)-I_(0,RRS))呈线性关系,检出限(3S_b/k)为18.27μg·L~(-1)。应用此方法测定了市售利血平注射液中利血平含量,并以此试样为基体,用标准加入法做回收率和精密度试验,测得平均回收率为101.0%,相对标准偏差(n=6)为2.1%。     

共振散射光谱法测定水中痕量的过氧化氢

在pH4.3的柠檬酸-磷酸氢二钠缓冲溶液中,以牛血红蛋白为催化剂,加速过氧化氢与过量的KI反应生成I_3~-,I_3~-再与碱性染料乙基紫结合生成离子缔合物颗粒,大大增强了体系的共振散射强度,据此建立了一种测定水中痕量过氧化氢的共振散射光谱法。在659nm处,体系的共振散射强度增加值(ΔI)与过氧化氢的浓度在1.033×10~(-7)~2.272×10~(-6) mol·L~(-1)范围内呈线性关系,检出限(3s/k)为1.64×10-8 mol·L~(-1)。方法用于测定雨水中的过氧化氢,测定值的相对标准偏差(n=5)小于5.0%,加标回收率在104%~105%之间。     

CTMAB增敏荧光光度法测定牛奶中莫西沙星残留量

基于在pH 5.00的柠檬酸盐缓冲溶液中,十六烷基三甲基溴化铵(CTMAB)可使莫西沙星(MXFX)-钇(Ⅲ)反应体系的荧光强度显著增敏,提出了荧光光度法测定牛奶中MXFX残留量的分析方法。在292nm(λ_(ex))及483nm(λ_(em))波长处,所测得的相对荧光强度与MXFX的质量浓度在50～800μg·L~(-1)范围内呈线性关系。方法的检出限(3σ)为46.2μg·L~(-1)。方法用于牛奶中MXFX的测定,测得方法的平均回收率为92.8%,测定值的相对标准偏差(n=5)均小于3%。     

基于硫堇反应的共振瑞利散射光谱法测定阴离子表面活性剂

在pH 2.36的B-R介质中,一定量的3种阴离子表面活性剂十二烷基苯磺酸钠(SD-BS)、十二烷基硫酸钠(SDS)和十二烷基磺酸钠(SLS)可与1.0×10-4 mol·L-1硫堇溶液1.0mL在总体积10mL中反应生成离子缔合物,产生共振瑞利散射光谱,在其最大共振光散射峰655nm波长处测定共振瑞利散射强度IRRS。SDBS、SDS和SLS的质量浓度分别在0.05～3.0,0.5～3.0,1.0～5.0mg·L-1范围内与样品及空白溶液的IRRS值之差ΔIRRS呈线性关系,方法的检出限(3S/N)分别为0.017,0.166,0.571mg·L-1。方法用于两个标准样品和两个环境水样中SDBS的测定,测定结果与认定值和亚甲蓝光度法测得结果相符。     

硫酸卡那霉素-固绿体系的共振瑞利散射光谱及其分析应用

提出了共振瑞利散射法(RRS)测定硫酸卡那霉素(KANA)的方法。在p H为4.56~6.09的B-R缓冲溶液中,固绿与KANA结合生成离子缔合物,使溶液共振瑞利散射(RRS)增强,其最大散射峰位于709 nm,另在463 nm、370 nm有两个较弱的散射峰。KANA的浓度在0.08~1.6 mg·L~(-1)范围内,与RRS强度有良好的线性关系,对KANA的检出限(3σ)达0.024 mg·L~(-1)。研究了适宜的反应条件和影响因素,表明该方法灵敏、稳定。用于硫酸卡那霉素注射液的测定,回收率为96.5%~103.0%。     

过氧化氢-钴-纳米银体系共振散射法测定痕量过氧化氢

基于纳米银与Co~(2+)的络合反应及H_2O_2与Co~(2+)的类Fenton反应,建立了一种测定H_2O_2的共振散射方法。在pH=5.2的柠檬酸-磷酸氢二钠缓冲液中,530nm处,H_2O_2浓度在0.02~0.4μmol·L~(-1)范围内与共振散射强度降低值△I呈良好的线性关系,相关系数r为0.9966,检出限为1.07×10~(-8)mol·L~(-1)。该法用于池塘水和雨水中过氧化氢的测定,回收率分别为104.26%和97.63%,同时探讨了反应机理。     

镍(Ⅱ)-1-(1吡啶偶氮)-2-萘酚-十二烷基苯磺酸钠体系共振光散射法测定痕量镍

在pH 8.0的Tris-盐酸缓冲介质中,利用十二烷基苯磺酸钠(SDBS)增敏镍(Ⅱ)和1-(2-吡啶偶氮)-2-萘酚(PAN)形成离子缔合物体系,使体系共振光散射增强.体系最大散射波长545 nm,在15～500μg·L-1范围内共振散射增强强度(△I)与镍(Ⅱ)质量浓度呈线性关系.检出限(3S/N)为4.57μg·L-1,分别对50,200,400 μg·L-1镍(Ⅱ)标准溶液进行11次平行测定,测定值的相对标准偏差(n=6)依次为3.5%,3.0%,1.7%.据此提出了一种简单而快速的测定镍的方法.应用于测定水样中镍量,测得其平均回收率为98.5%.     

硫氰化亚铜共振散射光谱法测定药物中卡托普利

在pH为4.8的乙酸-乙酸钠缓冲溶液中,卡托普利能将Cu(Ⅱ)还原为Cu(Ⅰ),Cu(Ⅰ)与SCN-反应生成硫氰酸亚铜粒子后体系呈现较强的共振光散射信号,反应体系在波长398nm处的共振散射信号增强程度(ΔIRS)与卡托普利的质量浓度在一定范围内呈线性关系,据此采用硫氰化亚铜共振散射光谱法测定药物中卡托普利的含量。优化的试验条件如下:①0.50g·L~(-1)硫酸铜溶液的用量为1.50mL;②0.50g·L~(-1)硫氰化钾溶液用量为2.00mL;③反应时间为10min。卡托普利的线性范围为0.40～24.00mg·L~(-1),检出限(3σ)为0.14mg·L~(-1)。在1.00mg·L~(-1)浓度水平进行加标回收试验,回收率为97.0%～104%,测定值的相对标准偏差(n=5)为1.6%～2.7%。     

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.     

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.     

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.