高碘酸钾氧化偶氮胭脂红B动力学光度法测定微量钌

在 Ru( )催化高碘酸钾氧化偶氮胭脂红 B的褪色反应基础上 ,提出了测定钌的新催化光度法。钌质量浓度在 0～ 2 .8μg/ 2 5 m L范围内符合比尔定律 ,检出限为 3.83× 1 0 -4 μg/ m L。对 1 .0 μg/ 2 5 m L Ru( )测定的相对标准偏差为 3.8% ( n=1 1 )。催化反应的表观活化能为 5 1 .9k J/ mol,为假一级反应     

高碘酸钾氧化中性红催化光度法测定痕量铱

在稀硫酸介质中 ,铱催化高碘酸钾氧化中性红 (NR)褪色 ,据此建立了测定痕量铱的新催化光度法。本法线性范围为 0～2 4× 1 0 -3 μg mL ,检出限为 9.2× 1 0 -5μg mL。对 0 .0 50 μgIr(Ⅳ )测定的相对标准偏差为 1 .3% (n =1 0 )。考察了 40多种共存离子的影响 ,允许 50倍量的Ru(Ⅲ ) ,50 0倍量的Au(Ⅲ ) ,2 50 0倍量的Pt(Ⅳ )、Pd(Ⅱ )及Rh(Ⅲ )存在。本法已用于冶金产品及岩矿中铱的测定 ,其相对标准偏差为 1 .1 %～2 .4% ,标准加入回收率为 97.8%～1 0 2 .6%。     

甲苯胺蓝指示反应动力学光度法测定痕量钌

在磷酸和热水浴中 ,钌 (Ⅲ )对高碘酸钾氧化甲苯胺蓝的反应具有催化作用 ,据此建立了测定钌的新催化光度法。钌在 0～ 0 .0 5 0 μg/ 2 5ml范围内与催化反应速率有良好的线性关系 ,检出限为 5 .5 3× 10 - 5μg·ml- 1。对 0 .0 30 μg/ 2 5ml钌 (Ⅲ )测定的相对标准偏差为 2 .0 % (n =11)。该催化反应对钌 (Ⅲ )和甲苯胺蓝分别为一级反应 ,其表观活化能为 5 0 .2 6kJ·mol- 1。试验了 4 0多种共存离子的影响 ,大多数的常见离子不干扰。该方法用于岩矿和冶金产品中钌的测定 ,相对标准偏差为 2 .1%～ 2 .4 % ,标准加入回收率为 10 0 .1%～ 10 5 .4 %。     

钌催化高碘酸钾氧化丽春红G动力学光度法测定微量钌

在硫酸介质和热水浴中，Ru(Ⅲ）催化高碘酸钾氧化丽春红G（间-二甲苯-4，1-偶氮-2-萘酚-3，6-二磺酸基钠盐）褪色，由此建立了测定痕量钌的新催化光度法。钌的质量浓度在0-0.012μg/mL范围内符合比尔定律，线性回归方程为lg(A0/A)=-0.02798 45.7871c(μg/mL）,r=0.9977。对0.01μg/mL Ru（Ⅲ）测定的相对标准偏差为2.5%（n=11)。催化反应的表观活化能为58.55kJ/mol。催化反应对丽春红G和钌（Ⅲ）分别为一级反应。试验了40多种共存离子的影响。该方法已用于岩矿和冶金产品中痕量钌的测定，相对标准偏差为1.2%-2.2%，标准加入回收率为96.0%-106.1%。     

亚甲基蓝-高碘酸钾催化动力学光度法测定痕量钌(Ⅲ)

在稀H_2SO_4介质中及加热85℃的条件下,钌(Ⅲ)对KIO_4氧化亚甲基蓝的褪色反应具有显著的催化作用,建立了一个催化动力学光度法测定痕量钌(Ⅲ)的新分析方法.探讨了该催化反应的最佳实验条件.非催化反应吸光度A_0与催化反应吸光度A之间的差值△A与钌(Ⅲ)质量浓度ρ在0～0.06μg/mL范围内呈良好的线性关系,检出限为2.37×10~(-10)g/mL.测定了动力学参数,反应为准一级反应,表观速率常数为3.63×10~(-4)/s,表观活化能为58.13 kJ/mol.对1.0μg Ru(Ⅲ)测定的相对标准偏差RSD为1.7%(n=11).方法用于分子筛样品中痕量钌(Ⅲ)的测定,回收率98.3%.     

固绿FCF催化动力学光度法测定痕量钌

研究了钌(Ⅲ)催化高碘酸钾氧化固绿FCF褪色反应的反应条件, 测定了该反应的反应级数和表观活化能, 并建立了测定钌的新动力学光度法. 在选定实验条件下, 非催化反应体系与催化反应体系在633 nm波长处的吸光度差值与钌(Ⅲ)的质量浓度在0～0.001 μg/mL及0.001～0.0025 μg/mL范围内有良好的线性关系, 检出限为 9.53×10-11 g/mL. 对0.001 μg/mL钌(Ⅲ)测定11次标准偏差为1.7%, 方法的选择性好, 灵敏度高, 可用于钌精矿及合成样中痕量钌的测定.     

铱催化偶氮胭脂红B氧化高碘酸钾体系的研究及其分析应用

在稀硫酸介质中 ,基于铱对高碘酸钾氧化偶氮胭脂红B(ABX)褪色反应的催化作用 ,建立了一个测定铱的动力学光度分析方法。非催化体系与催化体系在 5 1 0mm波长处的吸光度差值与铱的浓度在 0～ 1 2 μg 2 5mL范围内有良好的线性关系 ,检出限为 7 83× 1 0 -10 g mL。对 0 5 μg 2 5mLIr(Ⅳ )测定 1 1次的相对标准偏差为 1 3 0 %。考察了 3 0多种共存离子的影响 ,允许 2 0 0倍的Ag+ ,2 0倍的Pt(Ⅳ ) ,1 0倍的Au(Ⅲ )、Pd(Ⅱ )和Rh(Ⅲ )存在 ,方法有较好的选择性。用于冶金产品及岩矿中铱测定的相对标准偏差为 1 40 %～ 1 68% ,加标回收率为 98 2 %～ 1 0 3 3 %。     

甲基红-高碘酸钾催化光度法测定铱

在稀硫酸介质中 ,铱可催化高碘酸钾氧化甲基红褪色 ,据此建立了一个测定铱的催化光度新方法。铱的浓度在 0～ 2 .0μg/ 2 5 m L范围内与催化反应速率呈线性关系 ,检出限为 6.44× 1 0 - 4μg/ m L。对 0 .1 μg Ir( )及 1 .0 μg Ir( )独立测定 1 0次的相对标准偏差分别为 1 .98%和 1 .82 %。本法对冶金产品和岩矿中铱测定的相对标准偏差为 0 .64%～ 2 .30 %,标准加入回收率为 98.8%～ 1 0 3.8%。     

橙黄G催化动力学光度法测定痕量钌

研究了钌(Ⅲ)催化KIO4氧化橙黄G(OG)褪色反应的反应条件,测定了该反应的反应级数和表现活化能,并建立了一个测定钌的新动力学光度法。在选定的实验条件下,非催化反应体系与催化反应体系在470nm波长处的吸光度差值与钌(Ⅲ)的质量浓度在0 50～6 0ng/mL范围内有良好的线性关系,检出限为4.4×10-8g/L。对2 0ng/mL钌(Ⅲ)测定11次的相对标准偏差为1 4%。方法可用于冶金产品及岩矿中痕量钌的测定。     

孔雀石绿-KIO4催化动力学光度法测定痕量钌

在H2SO4介质中及80 ℃的条件下, 钌对KIO4氧化孔雀石绿的褪色反应有明显催化作用, 探讨了反应的最佳条件, 据此建立了催化动力学光度法测定钌的新方法. 非催化反应吸光度A0与催化反应吸光度A之间的差值ΔA与Ru(Ⅲ)质量浓度在0.1～1.5 μg/25 mL范围内具有良好的线性关系, 检出限为4.31×10-10 g/mL. 测定了动力学参数, 反应为准一级反应, 表观速率常数为3.52×10-4 s, 表观活化能为46.97 kJ/mol. 该方法用于分子筛样品及活性炭样品中痕量钌的测定, 其回率在98.6%～104.8%之间, 符合痕量分析的要求.     

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.     

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.     

Synthesis of N-substituted carbazolones from α-iodo enaminones via Pd(0)-catalyzed intramolecular coupling under microwave irradiation

A variety of N-aryl and N-alkyl carbazolones were conveniently achieved in good to high yields via Pd₂(dba)₃-mediated intramolecular coupling of N-substituted α-iodo enaminones under microwave irradiation. The Pd(0)-catalyzed cyclization was found to proceed favorably with the more electron-deficient phenyl ring during the reactions involving unsymmetrical N,N-diaryl α-iodo enaminones. This unique property enables the construction of carbazolone skeleton containing nitro substituted benzenoid ring.     

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.