Schiff碱钴(Ⅱ)配合物催化PNPP水解研究

摘要：两种分别带吗啉侧基和氮杂冠醚侧基的Schiff碱钴(Ⅱ)配合物CoL¹ 和CoL²，作为模拟水解金属酶，用于羧酸酯（PNPP）的催化水解。通过对水解反应体系的特性吸收光谱的分析，表明在PNPP催化水解的反应过程中形成了由PNPP和Co(Ⅱ)配合物组成的关键中间体。在分析特性吸收光谱的基础上提出了PNPP的催化水解的机理，由此机理上建立了PNPP催化水解的动力学数学模型。在本文中讨论缓冲溶液酸度、配合物结构以及反应温度对配合物催化PNPP水解速率的影响。     

两种双核配合物催化PNPP水解反应的机理研究

Cu-Cu(Ⅱ)和Cu-Zn(Ⅱ)草酰胺桥联双核配合物被合成和表征．研究了该同核和异核配合物催化PNPP水解的动力学和机理,建立了一种双核配合物催化PNPP水解的动力学数学模型．结果表明：在缓冲溶液中随着溶液pH的增大,草酰胺桥联双核配合物催化PNPP水解速率提高;配合物中的两个金属离子在催化PNPP水解过程中具有协同效应;这两种草酰胺桥联双核配合物在催化PNPP水解中表现出较好的催化活性．     

在CTAB胶束中羟乙基-双胺类Zn(Ⅱ),Ni(Ⅱ)配合物催化PNPP水解反应

本文将合成的三种配体与二价金属离子Zn(Ⅱ)，Ni(Ⅱ)形成配合物，在25℃不同pH值时，研究了它们在CTAB胶束溶液中催化水解PNPP的反应。利用金属胶束催化的三元复合物模型，处理获得了相关的PNPP催化水解反应的动力学参数及热力学参数。结果表明：在PNPP催化水解中，活性物种为配体与金属离子形成l：2的双核金属配合物。不同金属配合物的催化活性与配合物的桥联基团及反应的微环境相关。     

氮杂冠醚或吗啉基取代的单Schiff碱配合物催化α-吡啶甲酸对硝基苯酯水解

两种含5-取代苯并-10-氮杂-15-冠-5的Schiff碱锰(III)、钴(II)配合物( , )及其吗啉基取代的类似物( , ) 用于催化α-吡啶甲酸对硝基苯酯(PNPP)水解。探讨了氮杂冠醚Schiff 碱配合物催化PNPP水解的动力学和机理;提出了配合物催化PNPP水解的动力学模型;考察了配合物结构、反应温度、缓冲溶液pH值等对PNPP水解反应的影响。结果表明,在25℃条件下随着缓冲溶液pH值的增大,催化PNPP水解速率提高;含取代苯并-10-氮杂-15-冠-5的Schiff碱配合物表现出更高的催化活性。根据阿累尼乌斯公式和不同温度下的表观一级常数求出水解反应的表观活化能。     

聚醚桥连二异羟肟酸双核配合物催化PNPP水解的反应动力学

 合成了4种聚醚桥连二异羟肟酸双核配合物,并将其用于催化α-吡啶甲酸对硝基苯酯(PNPP)水解反应,研究了聚醚桥连二异羟肟酸双核配合物催化PNPP水解反应的动力学和机理,提出了配合物催化PNPP水解的动力学模型. 结果表明, 在25 ℃条件下,随着缓冲溶液pH值的增大, 聚醚桥连二异羟肟酸双核配合物催化PNPP水解速率逐渐提高,表现出很高的催化活性. 根据阿累尼乌斯公式和不同温度下的表观一级常数,求出了水解反应的表观活化能.     

氮杂冠醚化双Schiff碱配合物催化羧酸酯水解的研究

将4种氮杂冠醚取代的双Schiff碱钴(H)、锰(m)配合物作为仿水解酶模型催化羧酸酯(PNPP)水解.考察了Schiff碱配合物中氮杂冠醚取代的位置、氮杂冠醚的数目对其仿水解酶性能的影响;探讨了Schiff配合物催化PNPP水解的动力学和机理;提出了配合物催化PNPP水解的动力学模型.结果表明,在25℃条件下随着缓冲溶液pH值的增大,配合物催化PNPP水解速率提高;四种氮杂冠醚取代的双Schiff碱配合物在催化PNPP水解反应中表现出良好的催化活性;氮杂冠醚3-取代的Schiff碱配合物CoL2的催化活性高于5-取代的Schiff碱配合物CoL1,含有2个氮杂冠醚的配合物CoL3的催化活性高于含有1个氮杂冠醚的配合物CoL2.     

金属胶束催化: 二氧环胺Ni(Ⅱ)配合物催化羧酸酯水解

 合成了单核二氧大环四胺镍(Ⅱ)配合物,对该配合物在不同胶束体系中催化对硝基苯基α-吡啶甲酸酯(PNPP)的水解进行了动力学研究,用三元复合物动力学模型处理得到了相关的动力学和热力学参数. 结果表明,该配合物对PNPP水解反应有显著的催化作用,配合物在两性离子表面活性剂正月桂酸肌氨酸钠(LSS)和非离子表面活性剂聚氧乙烯(23)十二烷基醚(Brij35)胶束溶液中对PNPP水解的催化活性高于在阳离子表面活性剂十六烷基三甲基溴化铵(CTAB)胶束溶液中的催化活性; 配合物的空间构型对反应速率有较大影响,具有四面体结构的配合物更有利于PNPP的水解.     

大环钴(Ⅱ)配合物模拟水解酶催化羧酸酯水解的比较研究

在Brij35胶束溶液中,比较研究了四氮大环席夫碱(5,7,7,12,14,14-六甲基-1,4,8,11-四氮杂十四环-二烯,L)的钴(Ⅱ)配合物1催化对硝基苯酚吡啶甲酸酯(PNPP)及对硝基苯酚乙酸酯(PNPA)水解的动力学.结果表明:配合物1对PNPP及PNPA的催化作用具有酸碱催化的特征,催化活性物种为与金属离子结合的氢氧根离子CoL-OH-;配合物1催化PNPP水解的速度远远大于其催化PNPA水解的速度,在pH 7.40、30℃时,表观二级速率常数kc分别为0.997mol-1@L@s-1和1.12×10-3mol-1@L@s-1,这种反应速率的差异可归因于反应机理的不同;Brij35胶束对PNPP及PNPA的水解均有抑制作用.     

氮杂冠醚化单Schiff碱锰(III)配合物催化PNPP水解研究

将4种氮杂冠醚或吗啉取代的单Schiff碱锰(III)配合物作为仿水解酶模型催化α-吡啶甲酸对硝基苯酯(PNPP)水解。考察了单Schiff碱配体中取代基类型、氮杂冠醚取代的位置对其仿水解酶性能的影响;探讨了Schiff配合物催化PNPP水解的动力学和机理;提出了配合物催化PNPP水解的动力学模型。结果表明,在25℃条件下随着缓冲溶液pH值的增大,配合物催化PNPP水解速率提高,氮杂冠醚化单Schiff碱锰(III)配合物在催化PNPP水解反应中表现出良好的催化活性,Schiff碱配体结构显著影响配合物催化活性。     

2-氨基吡啶金属配合物对羧酸酯水解的催化作用

 合成了2-氨基吡啶(2-AP)为配体的Zn(2-AP)2(OAc)2,Ni(2-AP)2(OAc)2和Cu(2-AP)2(OAc)2三种金属配合物,并将其用于催化2-吡啶甲酸对硝基苯酚酯(PNPP)和乙酸对硝基苯酚酯(PNPA)的水解反应. 研究了金属配合物催化PNPP水解的动力学,提出了可能的催化机理. 结果表明,Zn(2-AP)2(OAc)2和Ni(2-AP)2(OAc)2金属配合物对PNPP水解反应有显著的催化作用,且Ni(2-AP)2(OAc)2的催化活性大于Zn(2-AP)2(OAc)2,而对PNPA无催化活性. Cu(2-AP)2(OAc)2对PNPP和PNPA均无催化活性. 这可能源自底物本身的特性以及配合物结构的差异. 同时,实验结果也说明合成的Zn(2-AP)2-(OAc)2和Ni(2-AP)2(OAc)2是水解金属酶的良好模型.     

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.     

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.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

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.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

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.