肾上腺素氧化反应的研究——氧化反应动力学和机理以及自由及中间体

用紫外吸收光谱法结合计算机模拟研究了肾上腺素(Adjn)在Cu(Ⅱ)离子催化下, 用H_2O_2氧化产生肾上腺素红(Adom)的反应动力学, 考查了反应的速率随体系中肾上腺素的初始浓度, Cu(Ⅱ)离子浓度和H_2O_2浓度的变化情况。在流动法或添加自由基稳定剂的条件下, 利用顺磁共振法检测丁肾上腺素自氧化, 光氧化和Cu(Ⅱ)离子催化H_2O_2氧化产生的半醌自由基。考查了Cu(Ⅱ)离子催化下自由基的相对浓度随反应条件的变化情况。在反应动力学和顺磁共振实验的基础上所提出的可能的反应机理, 半定量地解释此反应动力学实验结果和顺磁共振实验中的自由基行为。     

肾上腺素氧化反应的研究——生成肾上腺素红及其进一步氧化反应的研究

利用紫外吸收光谱法结合计算机模拟研究了肾上腺素(Adin)在Cu(Ⅱ)离子催化下,用H₂O₂氧化产生肾上腺素红(Adorn)及其进一步反应的动力学。考察了有关反应的速率随Adin的初始浓度、Cu(Ⅱ)高子浓度和H₂O₂浓度的变化情况。并提出有关反应可能的机理,半定量地解释了相应的动力学行为。     

醇类催化氧化反应的机理研究—半乳糖氧化酶化学模拟体系

本文研究了由Cu(Ⅱ)(PlC)_2、分子氧和碱构成的体系中醇类选择氧化生成相应醛、酮的反应机理,研究结果表明,该催化体系可作为半乳糖氧化酶催化作用的化学模型。根据原位电子光谱,ESR波谱对催化体系的考察,证明催化反应诱导期是Cu(Ⅱ)→Cu(Ⅰ)状态的转变过程,催化过程存在Cu(Ⅱ)/Cu(Ⅰ)价态的循环。相同配体的Cu(Ⅰ)和Cu(Ⅱ)络合物催化氧化反应的性能差异支持了上述结果。动力学研究表明,催化反应符合酶催化米氏方程的一般规律,根据以上结果,提出了一个由底物、双氧、Cu(Ⅱ)络合物形成的三元复合物中间物种的分解而生成产物醛、酮和H_2O_2的反应机理。     

萃取动力学光度法测定痕量铜

本文利用波长接近的两种高灵敏染料缔合形成离子对并萃入有机相,研究了Cu(Ⅱ)催化H_2O_2氧化染料离子对褪色的新指示反应,用萃取平衡控制反应时间和水中有机染料的浓度,弃水相以快速终止反应,在有机相中加人等色剂以准确测定吸光度.经过条件实验,使之成为假一级反应,建立了等色染料离子对测定痕量铜的萃取催化动力学分析方法,为催化动力学的终止反应提供了较为广泛的快速有效的方法.本方法用于直肠癌组织中微量元素铜的测定,有好的选择性,高的准确度,低的检出限.     

四齿配体铜(Ⅱ)络合物对苯甲醇氧化的催化作用——一个模拟半乳糖氧化酶的模型

以Salen-Cu/NaOH/DMF为半乳糖氧化酶的模型,考察了苯甲醇的氧化反应。氧气氛下,笨甲醇被选择性地氧化成苯甲醛,分子氧被还原为H_2O_2。动力学研究结果表明反应对苯甲醇和Salen-Cu均为一级反应,即v=k_表[Salen-Cu][PhCH_2OH],其中k_表=6.1×10~(-3)M~(-1)·min~(-1)。用原位紫外—可见光谱在厌氧和有氧条件下研究了反应过程中d—d跃迁和荷移光谱(MLCT)的变化,结果表明反应诱导过程为Cu(Ⅱ)→Cu(Ⅰ),Cu(Ⅱ)/Cu(Ⅰ)是氧化反应中催化循环的关键,即反应通过两次单电子转移进行。根据实验结果,提出了可能的反应机理。     

催化动力学分析法测定痕量铜——Cu(Ⅱ)-噻嗪红R-H_2O_2体系

研究了在氨性介质中,Cu(Ⅱ)催化H_2O_2氧化噻嗪红R的退色反应,据此建立了催化动力学光度测定Cu(Ⅱ)的新方法,方法的线性范围为0.005～0.5μg/25ml。曾应用于水、猪肝和小麦粉标准物质中痕量铜的测定,获得满意结果。     

氨基酸基咪唑离子液体氧化萃取脱硫研究

通过离子交换法制备以天冬氨酸(Asp)、组氨酸(His)、甘氨酸(Gly)、色氨酸(Try)为阴离子的氨基酸咪唑离子液体,与H_2O_2协同深度去除模拟汽油中的二苯并噻吩(DBT)。对合成的氨基酸咪唑离子液体进行了FT-IR、1H NMR表征,并优化氧化脱硫工艺条件。结果表明,与以组氨酸、甘氨酸和色氨酸作为离子液体的阴离子相比,天冬氨酸作为阴离子时,离子液体与H_2O_2体系的催化萃取脱硫效果最好。通过对反应温度、H_2O_2/模拟油体积比和反应时间的工艺优化,探讨了[C_8mim]Asp和H_2O_2催化萃取脱硫的效果,最优工艺条件下,脱硫率可达96.5%。[C_8mim]Asp离子液体再生循环7次后脱硫率仍能保持在93.7%。对[C_8mim]Asp和H_2O_2协同催化脱硫机理的研究发现,[C_8mim]Asp的羧基与双氧水反应成过氧化羧基,将二苯并噻吩氧化成为二苯并噻吩砜,从而达到脱硫的目的。     

钴(Ⅱ)催化过氧化氢氧化5-Br-TAMB的褪色反应动力学及其应用

研究了NaAc-HAc介质中钴(Ⅱ)催化H_2O_2氧化5-Br-TAMB的褪色的反应,测定了反应动力学参数,探讨了反应机理,并建立了测定痕量钴的新方法。本法检出限为1.8×10~(-10)g/mL,钴(Ⅱ)浓度在0～124.7 ng/12.5 mL范围内与1g(A_0/A)呈良好的线性关系。该体系已用于人发、茶叶中钴的测定,结果满意。     

金属离子与卟啉的嵌入反应动力学研究 IV.Cu(Ⅱ)T_(β-N-EAES)PyP~(4+)生成反应中的动力学盐效应

在不同离子强度的高氯酸钠水溶液中,用分光光度法测量自由卟啉H_2T_(β-N-EAES)PyPBr_4(简记为H_2P~(4+))与Gu(Ⅱ)离子的配位反应动力学,探讨高氯酸钠对Cu(Ⅱ)离子嵌入自由卟啉反应的催化本质.在给定条件下,高氯酸根与自由卟啉的缔合数n为1;缔合平衡常数K_0=3.70±0.42dm~3.mol~(-1).配位反应实验动力学方程为d[Cu(Ⅱ)P~(4+)]/dt=5.55×10~5γCu~2+γH_2P~4+γ(3)[ClO_4~-]~3[Cu~(2+)][H_2P]_总/(1.00+10~(2.02{H+}+10~(4.36{H~+}~2)、反应的活化能E=53.30kJ·mol~(-1),活化焓变△H~ =50.31kJ·mol~(-1),活化熵变△S~ =-77.65J·mol~(-1)·K~(-1).提出了金属卟啉生成反应中的ClO_4~-催化卟啉环变形的反应机理.     

Mn(Ⅱ)催化硝酸氧化草酸反应动力学及机理

为明确反应机理和反应历程,优化反应工艺条件,开展了在硝酸体系中以草酸为还原剂、Mn~(2+)为催化剂催化硝酸氧化草酸的动力学研究。通过考察草酸浓度、硝酸浓度等反应条件对反应过程的影响,确定了该反应的初始动力学速率方程为:-dc(H_2C_2O_4)/dt=kc~(0.7840)(H_2C_2O_4)c~(0.3192)(HNO_3),在393 K时,反应速率常数k=3.0×10~(-3)(mol/L)~(-0.1032)/min。研究了Mn~(2+)和亚硝酸钠浓度对反应速率的影响,结果表明,Mn~(2+)浓度在0.008～0.020 mol/L范围内,Mn~(2+)的反应级数为0.6742,Mn~(2+)和亚硝酸钠浓度的增加对初始草酸消耗速率有促进作用,并在此基础上推测了可能的反应机理,认为Mn~(2+)促进了亚硝酸的生成,产物亚硝酸与草酸发生次级氧化还原反应从而促进了草酸的分解。     

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.     

正丁胺对激光染料荧光谱影响的研究

用正丁胺作为碳源,采用射频辉光放电制备碳膜,选用激光染料R6G和聚乙二醇混合液作为蒸气源,采用单源热蒸发,在蒸发室与染料同时沉积得到混合膜,用拉曼光谱和红外光谱分析了碳膜的结构和键合方式,分析表明:碳膜中存在胺基团和氢原子.混合膜的荧光谱测量结果表明,认为正丁胺对染料荧光谱的影响是因为胺基和氢原子的存在.     

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.