取代芳基重氧盐及其冠醚配合物的XPS研究

本文用XOS 研究了十四种芳基重氮盐及其与18-c-6(1)和二苯并-24-c-8(2)的配合物.结果表明, 重氮盐中α-N1s 结合能的化学移大小与R有关. 重氮盐与冠醚以β-N向醚氧提供电子(β-N→O)而配位的, 而醚氧O1s 结合能降低多少似可反映配合物的稳定性.     

取代芳基重氮盐及其冠醚配合物的 XPS 研究

本文用 XPS 研究了十四种芳基重氮盐及其与18-c-6(1)和二苯并-24-c-8(2)的配合物.结果表明,重氮盐中α-N1s 和β-N1s 结合能的化学位移大小与 R 有关.重氮盐与冠醚以β-N 向醚氧提供电子(β-N→O)而配位的,而醚氧 O1s 结合能降低多少似可反映配合物的稳定性.     

稀土冠醚类配合物的研究——Ⅶ.二价及三价铕氯化物与二环己基-24-冠-8和二价及三价钐、镱氯化物与18-冠-6固体配合物的合成及性质

在THF介质中合成了2:1型固体配合物2EuCl_3·DCH-24-c-8·2THF·2H_2O和4:3型团体配合物4SmCl_3·3(18-c-6)·4H_2O及4YbCl_3·3(18-c-6)·4H_2O。在氩气氛中用锂-萘使Ln~(3+)还原,制得了三种相应的二价稀土氯化物与DCH-24-c-8和18-c-6的固体配合物2EuCl_2·DCH-24-c-8·2H_2O、4SmCl_2·3(18-c-6)·4H_2O及4YbCl_2·3(18-c-6)·4H_2O。元素分析、红外光谱、电子自旋共振谱、差热-热重分析、还原性实验及偏光显微镜下的光性研究不但证实了冠醚与稀土离子的配位作用,而且说明Ln~(2+)及Ln~(3+)的冠醚配合物在物理及化学性质上存在着差别。     

单-马来二腈基二硫烯-β-环糊精异构体在溶液中的不同组装行为

通过单-2-对甲苯磺酰基-β-环糊精(1)与马来二腈基二硫烯钠盐的取代反应制得单-2-马来二腈基二硫烯-β-环糊精(2),并经红外光谱、紫外光谱、热重分析、1H和13C NMR等手段对产物进行了表征.虽然化合物2的异构体--单-6-马来二腈基二硫烯9-β-环糊精在溶液中因为相互包合作用而在圆二色性光谱中产生分裂的Cot...     

环糊精包结谷胱甘肽的机理

使用分子动力学模拟结合自由能计算的方法在原子水平上研究了谷胱甘肽与α-,β-和γ-环糊精的包结模式,计算了谷胱甘肽与3种环糊精之间6种可能包结过程的自由能变化.结果表明,谷胱甘肽的谷氨酸残基从α-环糊精大口端进入空腔最终形成的包结复合物最稳定;在该复合物中,谷氨酸残基的亚甲基链部分被完全包结在疏水空腔中,其氨基与羧基位于与α-环糊精的小口端,并与环糊精的伯羟基形成了氢键,同时半胱氨酸中的巯基位于环糊精的大口端,得到了有效的保护.因此,疏水相互作用和氢键相互作用构成了包结的主要驱动力.β-环糊精的优势包结模式与α-环糊精类似,但形成复合物的稳定性次之,而γ-环糊精由于空腔较大,优势的包结模式是谷氨酸残基从γ-环糊精小口端进入空腔,但所形成的复合物结构的稳定性最弱.     

大环中性配体用作大块液膜载体分离金属离子的研究

本文报道以大环中性配体作为大块液膜载体时,冠醚结构对金属离子的传质选择性,以及迁移速度与配合物稳定常数之间的关系。实验结果表明,在一定的配合物稳定常数范围,其稳定常数越高,迁移速度也越快。对于4-取代苯并-15-冠-5类型的冠醚与Na~+的配合物,其配合物的稳定常数顺序与取代基的给电子或吸电子效应的强弱一致,而迁移速度与稳定常数的大小顺序一致。在影响着冠醚醚氧碱度的取代基效应的Hammett常数(δm+δ_P)同配合物稳定常数logk及离子迁移通量logJ之间存在着线性关系。对于其空腔直径与N_a~+相匹配的苯并-15-冠-5及空腔直径与K~+相匹配的苯并-18冠-6,当冠醚中的一个或两个1,2-亚乙基被1,3-亚丙基所代替而变成苯并-17-冠-5及苯并-19-冠-6时,其配合物的稳定常数减小,迁移速度也相应减小。     

修饰β-环糊精／4-（N，N-二甲氨基）-苯甲酸-2′-乙基己基酯笼型包结物研究

用分子光谱法研究了甲基-β-环糊精(M-CD)和羟丙基-β-环糊精(HP-CD)与4-(N,N-二甲氨基)-苯甲酸-2′-乙基己基酯(EHDAB)分子间的包结作用.结果表明,柔性的2′-乙基己基和刚性的芳香端都包结在M-CD和HP-CD空腔中,形成了2∶1笼型主-客体包结物.疏水性2′-乙基己基在包结物的热力学稳定性中起重要作用,亲水性M-CD和HP-CD将EHDAB增溶在水中,提高了EHDAB分子的紫外吸收程度,M-CD和HP-CD空腔抑制了光诱导EHDAB分子内扭转电荷转移,显著提高了EHDAB的光化学稳定性,增强了其抗氧化性,降低了酸碱性水解程度,包结物的热稳定性与所用主体环糊精相当.     

修饰β-环糊精/4-(N,N-二甲氨基)-苯甲酸-2''''-乙基己基酯笼型包结物研究

用分子光谱法研究了甲基-β-环糊精(M-CD)和羟丙基-β-环糊精(HP-CD)与4-(N,N-二甲氨基)-苯甲酸-2'-乙基己基酯(EHDAB)分子间的包结作用.结果表明,柔性的2'-乙基己基和刚性的芳香端都包结在M-CD和HP-CD空腔中,形成了21笼型主-客体包结物.疏水性2'-乙基己基在包结物的热力学稳定性中起重要作用,亲水性M-CD和HP-CD将EHDAB增溶在水中,提高了EHDAB分子的紫外吸收程度,M-CD和HP-CD空腔抑制了光诱导EHDAB分子内扭转电荷转移,显著提高了EHDAB的光化学稳定性,增强了其抗氧化性,降低了酸碱性水解程度,包结物的热稳定性与所用主体环糊精相当.     

β-环糊精与莨菪类药物包结反应的热力学研究

研究了β-环糊精与四种莨菪类药物的包结反应.微量量热法研究表明,反应中均生成1:1包结配合物,并测出各反应的热力学参数K,△G°,△H°与△S°.~1H NMR谱表明,药物分子被包结在β-环糊精分子疏水性空穴内.初步讨论了反应作用力的性质、客体分子的手征性及其分子空间环境对包结反应的影响.     

稀土冠醚配合物的研究XV. 稀土硝酸盐与臂型冠醚配合物的合成 和性质研究

本工作以6-羟基-2,3,9,10-二苯并-1,4,8,11,14-五氧杂-环十六-2,9-二烯(1)及其衍生物(2,3和4)为配体,在乙腈中合成了十八种新的稀土硝酸盐配合物。其中羧酸冠醚4与稀土硝酸盐[Ln(NO~3)~3]分别形成2:1型(Ln=La,Ce,Pr,Nd)、4:3型(Ln=Sm)和3:4型(Ln=Eu,Gd,Tb,Dy,Ho,Er,Tm,Yb,Lu,Y)配合物;冠醚1与La(NO~3)~3形成1:1型配合物;冠醚2,3与La(NO~3)~3均形成2:1型配合物。对所得配合物进行了元素分析、紫外光谱、红外光谱、^1H核磁共振、X射线光电子能谱等性质研究。对臂型冠醚中边臂的配位作用进行了初步讨论。     

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.     

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.     

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.     

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.