盐酸氯丙嗪-卤代荧光素体系的光度法测定

在NaAc HCl缓冲介质中,盐酸氯丙嗪可与曙红Y、赤藓红、乙基署红等卤代荧光素染料反应,形成离子缔合物,溶液颜色发生明显改变,可用光度法测定。盐酸氯丙嗪的浓度在0～1.6×10-5mol·L-1(曙红Y)、0～1.3×10-5mol·L-1(赤鲜红)、0～1.5×10-5mol·L-1(乙基曙红)范围内遵守比耳定律,其表观摩尔吸光系数分别为4.63×104L·mol-1·cm-1、2.50×104L·mol-1·cm-1、为4.32×104L·mol-1·cm-1。方法用于片剂和针剂中盐酸氯丙嗪的测定,结果满意。     

曙红Y褪色光度法测定微量铈

研究了在氨-氯化铵介质中Ce(Ⅳ)催化高碘酸钾氧化曙红Y的褪色反应及其动力学条件,测定了反应级数和表观活化能,建立了测定痕量铈的新方法.曙红Y的最大吸收波长为515 nm,该方法的检出极限为2.0×10-10 g·ml-1,线性范围为0～400 ng·ml-1,可用于发样中痕量铈的测定.     

乙基曙红光度法测定西地那非的含量

在pH3.5～4.0的NaAc HCl缓冲介质中,西地那非与乙基曙红反应,形成离子缔合物,使乙基曙红溶液颜色发生明显改变,最大吸收波长在550nm,比乙基曙红红移了30nm,并在520nm处产生最大褪色作用,从而建立测定西地那非(Sild)的光度法。在最大褪色波长520nm处,西地那非浓度在0.2～2.0×10-5mol·L-1范围内遵守比耳定律,表观摩尔吸光系数ε520为2.44×104L·mol-1·cm-1,检出限为9.3×10-7mol·L-1,若用双波长叠加,则表观摩尔吸光系数ε520+550达4.53×104L·mol-1·cm-1,检出限达5.0×10-7mol·L-1。本法操作简便,体系稳定,灵敏度较高,选择性好,用于柠檬酸西地那非片(万艾可)中西地那非含量的测定,结果满意。     

阻抑褪色光度法测定水样中阴离子表面活性剂

在弱酸性的HCl-NaOAC缓冲介质中,溴化十六烷基吡啶(CPB)和曙红Y(EY)染料的混合溶液发生褪色,在该褪色的溶液中分别加入十二烷基硫酸钠(SDS)及十二烷基苯磺酸钠(SDBS)等阴离子表面活性剂(AS),溶液颜色发生改变,最大吸收波长都在514 nm处,并分别在548、546 nm处产生明显褪色。在吸收或褪色波长处,阴离子表面活性剂的浓度与增色或褪色程度呈良好线性关系,从而建立测定阴离子表面活性剂的光度法。在最大吸收波长处,SDBS体系、SDS体系中AS的浓度在0~2.06×10-5mol/L、0~2.63×10-5mol/L范围内遵守比尔定律,表观摩尔吸光系数分别为1.30×104、1.01×104L.mol-1.cm-1,检出限分别为8.14×10-7、9.96×10-7mol/L。若用双波长叠加,表观摩尔吸光系数达2.07×104、1.78×104L.mol-1.cm-1,检出限为4.82×10-7、8.34×10-7mol/L。方法具有较高的灵敏度和良好的选择性,用于水样中AS的测定。     

曙红B与盐酸洛美沙星相互作用的分光光度法研究

在pH=1.2的Clark Lubs缓冲溶液条件下,曙红B与盐酸洛美沙星复合物的最大吸收峰位于535nm,比曙红B本身红移30nm,复合物的表观摩尔吸光系数为5.82×103L·mol-1·cm-1。方法的线性范围为10～40mg·L-1,检出限为2.2mg·L-1。实验考察了反应条件的影响,初步讨论了反应机理。     

Fading Spectrophotometric Method for the Determination of Polyvinylpyrrolidone with Eosin Y

在弱酸性HC1-NaAc缓冲介质中,曙红Y（EY）在可见光区有强烈的光吸收,其最大吸收波长(lmax)位于517 nm处,而聚乙烯吡咯烷酮(PVP)在250-700 nm之间无光吸收,当EY与PVP反应形成结合产物时,EY发生明显的褪色作用,最大褪色波长仍位于517 nm,并在545 nm处出现一个较小的吸收峰。其褪色程度（DA）与PVP浓度在0.40~3.20 µg mL-1范围成线性关系,此褪色反应的灵敏度高,摩尔吸光系数(ε)是6.4 × 106 L mol-1 cm-1,对PVP的检出限为0.12 µg mL-1。并研究了反应的影响因素,结果表明方法具有较好的选择性,据此发展了一种曙红Y褪色分光光度法测定PVP的新方法。方法简便快速,可用于啤酒中PVP的定量测定。     

维多利亚蓝B双波长叠加吸光光度法测定微量亚硝酸根

在稀盐酸介质中 ,维多利亚蓝B(VBB)的最大吸收峰位于 6 13nm ,当与NO- 2 反应后发生颜色变化 ,最大吸收峰红移 ,以试剂空白为参比 ,可观察到在 6 39nm处出现一新的最大吸收峰 ,同时在 5 6 0nm处发生褪色反应 ,最大褪色波长和最大吸收波长处吸光度均与溶液中NO- 2 的浓度成正比 ,其线性范围在 0～ 2 0 μg/ 2 5mlNO- 2 ,摩尔吸光系数分别为ε56 0 =2 .96× 10 4 L·mol- 1·cm- 1,ε6 39=3.2 3× 10 4 L·mol- 1·cm- 1,用双波长叠加法ε56 0 +6 39=6 .19× 10 4 L·mol- 1·cm- 1,相关系数为 0 .9999。由于显色反应在较强的酸性介质中进行 ,方法具有良好的选择性 ,用于环境水中微量NO- 2 的测定 ,结果满意。     

曙红B共振光散射法测定微量的盐酸异丙嗪

研究了染料曙红B与盐酸异丙嗪的结合反应.在pH=3.50的Walpole介质中,曙红B本身的共振光散射信号较弱,与盐酸异丙嗪结合形成离子缔合物后,体系的共振光散射明显增强,并且光散射增强强度与盐酸异丙嗪在一定浓度范围内成正比,据此建立了一种高灵敏测定盐酸异丙嗪的方法.在体系的最大散射波长363 nm处,测得盐酸异丙嗪的线性范围为7.5×10-8～4.5×10-6 g/mL,检测限为1.8×10-8 g/mL,用于盐酸异丙嗪片剂、针剂、人血清及尿样中盐酸异丙嗪的测定,结果令人满意.     

钙羧酸钠褪色光度法测定微量碘的研究

提出了以钙羧酸钠褪色光度法测定微量碘的新方法。在盐酸介质中 ,表面活性剂十六烷基三甲基溴化铵 (CTMAB)存在下 ,碘酸根离子定量氧化钙羧酸钠褪色。最大吸收波长λmax=5 95nm ,表观摩尔吸光系数ε =3.1× 10 4 L·mol-1·cm-1。碘浓度在 0～ 5 0 μg 2 5ml范围内服从比耳定律。方法用于加碘食盐中碘的测定 ,结果满意     

甲基红氧化褪色光度法测定食盐中碘

基于在盐酸介质中 ,碘酸根在溴化钾的催化作用下使甲基红氧化褪色的反应 ,建立了测定微量碘的新方法。方法的线性范围为 8μg/2 5mL～ 2 2 μg/2 5mL ,表观摩尔吸收系数为 6 .5× 1 0 4 L·mol- 1 ·cm- 1 ,已用于食盐中碘的测定。     

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.