石斛碱与新石斛碱的构型

我国四川、云南等地出产的兰科植物金石斛(Dendrobium nobile)中含植物碱.Suzuki等^[1]及陈克恢等^[2]自其中分离出石斛碱(dendrobine,C₁₆H₂₅O₂N);最近Yamamura等^[3]又分离出一种新植物碱——nobiline(建议译为新石斛碱),C₁₇H₂₇O₃N.Inubushi等^[4]与Yamamura等^[3]分别独立提出石斛碱(Ⅰ)的部分相对构型式;后者尚测定了新石斛碱(Ⅱ)的部分相对构型式.它们的结构与天然有机物苦毒宁(picrotoxinin)^[5](Ⅲ)很相似.     

一系列Ru(II)配合物电致化学发光性质的比较研究

比较研究了以C₂O₄^2－为共反应物时5个结构相关的Ru(II)配合物[Ru(bpy)₂L¹]^2＋, [Ru(bpy)₂L²]^2＋, [Ru(bpy)₂L³]^2＋, [Ru(phen)₂L¹]^2＋和[Ru(phen)₂L²]^2＋(其中bpy＝2,2′-联吡啶, phen＝1,10-邻菲啰啉, L¹＝4-羧基苯基咪唑[4,5-f][1,10]邻菲啰啉, L²＝3-羧基-4-羟基苯基咪唑[4,5-f][1,10]邻菲啰啉, L³＝3,4-二羟基苯基咪唑[4,5-f][1,10]邻菲啰啉)的电致化学发光(ECL)性质. 结果表明, 酚羟基的存在能有效地淬灭Ru(II)配合物[Ru(bpy)₂L²]^2＋, [Ru(bpy)₂L³]^2＋和[Ru(phen)₂L²]^2＋的ECL, 其它Ru(II)配合物的ECL量子效率与[Ru(bpy)₃]^2＋相差不大.     

质子化甜菜碱阳离子与双三氟甲磺酰亚胺阴离子相互作用的理论研究

利用密度泛函理论(DFT)方法, 在B3LYP/6-311＋G(d,p)水平下, 对质子化甜菜碱阳离子与双三氟甲磺酰亚胺阴离子形成的气态阴阳离子对([Hbet][Tf₂N])进行理论研究, 通过几何结构优化和频率分析得到势能面上的六个稳定构型. 计算结果表明[Hbet]^＋和[Tf₂N]^－之间能够形成较强的氢键相互作用, 氢键相互作用的稳定化能主要来源于[Tf₂N]^－中O, N原子的孤对电子和[Hbet]^＋中参与形成氢键的O-H, C-H反键轨道之间的相互作用. 自然布局分析(NPA)给出气态[Hbet][Tf₂N]离子对中阴阳离子间的电荷转移比传统离子液体中电荷转移的数值小. AIM (atoms in molecules)分析得到[Hbet]^＋和[Tf₂N]^－之间的氢键相互作用以静电作用为主. 通过实验和理论结果相比较, 初步探讨影响离子液体熔点及其对金属离子选择性溶解的结构因素.     

吸收液采样-高效液相色谱法测定室内空气中甲醛的含量

<正>甲醛是一种无色有刺激性气味的气体，被世界卫生组织(WHO)定为致畸和致癌的物质之一^[1]。我国规定室内空气甲醛的限值为0.10 mg·m-3^[2]。目前监测环境中甲醛的国家标准测定方法很多^[3],常用的有4-氨基-3-联氨-5-巯基-1,2,4-三氮杂茂(Ⅰ)(AHMT)分光光度法^[4]、3-甲基-2-苯并噻唑啉酮腙盐酸盐水合物(MBTH)酚试剂分光光度法^[5]、乙酰丙酮分光光度法^[6]、气相色谱法(GC)^[7]、     

NiTi过渡金属团簇的结构和芳香性的理论研究

在B3PW91/6-311+G(d)计算水平上, 计算并讨论了Ni₄Ti₂, [Ni₄Ti₂]²⁺, [Ni₄Ti₂]^2-与Ni₄Ti₄, [Ni₄Ti₄]²⁺, [Ni₄Ti₄]^2-团簇的几何结构和芳香性. 在构型优化过程中得到了Ni₄Ti₂(D_4h), [Ni₄Ti₂]²⁺(D_4h), [Ni₄Ti₂]^2-(D_4h)和Ni₄Ti₄(D_2h)4个稳定构型, 发现当引入上下2个Ti原子后, Ni₄环成为了平面正方形构型. 核无关化学位移(NICS)计算结果表明, Ni₄Ti₂(D_4h)与Ni₄Ti₄(D_2h)的NICS值为正, 而[Ni₄Ti₂]²⁺(D_4h)和[Ni₄Ti₂]^2-(D_4h)的NICS值为负, 且[Ni₄Ti₂]^2-(D_4h)的NICS值更负. 同时还发现, 由s与d轨道参与形成的反磁性环流是引起[Ni₄Ti₂]²⁺(D_4h)和[Ni₄Ti₂]^2-(D_4h)具有较大芳香性的主要原因; 其中Ti原子主要提供d_z²与s轨道, 而Ni原子主要利用其d_z²与d_x²-y²轨道形成正方形环, 它们之间构成了球状的d轨道环流, 且[Ni₄Ti₂]²⁺(D_4h)和[Ni₄Ti₂]^2-(D_4h)中还有非常明显的π轨道环流.     

meso-四-(3-N-甲基吡啶)卟啉与钴反应的分光光度研究

水溶性卟啉衍生物作为光度试剂在分析化学中已得到广泛的应用。在测定某些过渡金属元素时具有极高的灵敏度(ε值为2-5×10⁵)^[1]。meso-四-(3-N-甲基吡啶)卟啉[T(3-MPy)P]与铜^[2]、锌^[3]、铅^[4]的反应都已进行研究。本文对T(3-MPy)P与钴的反应进行了初步的研究。T(3-MPy)P的结构如右图。     

N,N,N＇,N＇-四苄基取代方块菁染料LB膜研究

方块菁染料在有机光导材料^[1,2]、有机太阳能存储^[2,3]、光记录^[4、有机光盘中红外吸收器^[4]以及光纤识别功能薄膜等领域中有着广泛应用前景.     

高等植物叶绿体中光诱导生成NO的ESR证据

NO分子在生物细胞体系中是一个十分重要的信使分子,它具有调节细胞凋亡、松弛平滑肌、抑制血小板聚集与黏附、抑制病原体和肿瘤生长等多种生理功能^[1,2],因而备受生物学家的关注.众所周知,动物细胞中NO主要来源于一氧化氮合酶(NOS)的表达^[3];然而,直到最近才有研究证明植物细胞中存在参与调节植物生长和激素信号转导的NOS基因^[4].一般认为植物细胞中NO主要来源于硝酸盐还原酶(NR)^[5].我们曾在高等植物光系统中研究发现了与电子传递相关的活性氧生成机制^[6～8],但其间是否也会通过光诱导电子传递产生NO尚不清楚.Kozlov等^[9]曾报道在小鼠线粒体内存在与亚硝酸盐还原酶功能类似的还原型烟酰胺腺嘌呤二核苷酸(NADH)诱导电子传递生成NO的反应,本文采用电子自旋共振(ESR)方法验证了高等植物叶绿体内光诱导电子传递可产生NO的设想.     

双(O,O-二芳基硫代磷酰基)多硫物的合成

双(O,O-二芳基硫磷酰基)多硫物(Ⅰ)具有杀虫作用^[1]、增效作用^[2,3]、杀菌作用^[4],亦可用作橡胶硫化剂^[5]。R为芳基的I,除几个双二硫物(I,n=2)^[6,7]外,文献中尚未有记载,为探索它们的杀菌活性,我们用下列反应由(Ⅱ)或(Ⅲ)合成了17个行为2,3和4,R为芳基、卤代芳基的I。     

对称群表的系统校验(续)——论证P42/nnm总公式B的错误

最近我们应用结构因子类型定理^[1,2],对《X-光结晶学国际表》(第一卷)进行了系统校验^[3]。并以最简明的列表方式扼要地报导了全部结果^[4]。在文献^[4]中最引人注目的是No.134(P4₂/nnm,原点在42m)空间群.它的结构因子总公式有错误。可见,关于这个空间群的其它推论,只要以总公式为基础,就不可能正确。本文将论证这一重要问题,关于文献^[4]中指出的其它14个空间群的错误,可以用类似的方法论证。     

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.     

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.     

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.     

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.     

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.     

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.     

Microwave-assisted copper-catalyzed stereoselective ring expansion of three-membered heterocycles with α-diazo-β-dicarbonyl compounds

Microwave-assisted copper-catalyzed ring expansions of three-membered heterocycles with α-diazo-β-dicarbonyl compounds were investigated. Thiiranes generated 3-acyl-5,6-dihydro-1,4-oxathiines in the presence of copper sulfate and trans-3-acyl-5,6-dihydro-1,4-oxathiines as stereospecific products for 1,2-disubstituted cis-thiiranes through an intramolecular S_N2 process. Oxiranes gave rise to 2-acyl-5,6-dihydro-1,4-dioxines under the catalysis of copper hexafluoroacetylacetonate and cis-3-acyl-5,6-dihydro-1,4-dioxines as stereospecific products for 1,2-disubstituted cis-oxiranes via an intimate ion-pair mechanism. The current method provides a direct and simple strategy in efficient preparation of 3-acyl-5,6-dihydro-1,4-oxathiines and 2-acyl-5,6-dihydro-1,4-dioxines, important agents in medicinal and agricultural chemistry, from readily available thiiranes and oxiranes, respectively.     

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.