Synthesis of 8-Bromo-N-benzylpurines via 8-Lithiated Purines: Scope and Limitations

9-Benzylpurines have been lithiated in the 8-position and subsequently brominated when trapped with BrCCl₂CCl₂Br. The 8-bromopurines were isolated in excellent yields when the benzyl group carried an alkoxy or alkyl group in the ortho or para position. Without these substituents, the conversion was generally less, and formation of 8,8′-purinyl dimers was observed. There was also evidence of debenzylation in some instances. Bromination of 7-benzylpurines employing the same set of reaction conditions has also been achieved.     

镧与8-羟基喹啉配合物固相化学合成与表征

近年来，固相配位化学反应研究取得许多进展，但大多集中于Cu、Co、Ni、Zn、Fe等d电子组元素[1，2]，用室温或低热温度下的固相化学反应合成稀土配合物尚未见报道，我国稀土资源丰富，稀土配合物在材料科学和生命科学中占有独特的地位，因此开展稀土配合物的室温及低热温度下的固相合成有重要意义．我们在60℃利用La（Ac）3·3／2H2O与8-羟基喹啉的固相反应合成了La（Oxine）3，并对产物进行了表征．1实验部分1．1试剂与仪器根据文献[3]用液相合成法制备出对照的标准样品La（Oxine）3。按文献[4]的方法合成La（Ac）3·3／2H2O．8-羟…     

Synthesis of 3-Aminopyrocatechol via Lithiated Intermediates

We report the synthesis of 3-aminopyrocatechol (7) through electrophilic amination of lithiated pyrocatechol, protected in the form of a ketal. For this purpose the lithiation reaction of protected pyrocatechol (1) was studied. The synthesis of compounds (3) was achieved by the reaction of organolithium derivative (2) and a series of electrophilic reagents. Lithium-t-butyl-N-tosyloxycarbamate (5) was used as the electrophilic aminating reagent. With the cupro derivative (4) the protecting groups in compound (6) are removed in an acid medium by heating in ethanol-HCl solution (4:1).     

Purines. XIV. Synthesis and properties of 8-nitroxanthine and its N-methyl derivatives

Xanthine ( 1 ) and its N-methyl derivatives 2–16 have been nitrated to the corresponding 8-nitro derivatives 17–32 under different reaction conditions. Nitration in glacial acetic acid with nitric acid works well with the N-7 unsubstituted and some of the 9-methylxanthines, respectively, whereas the 7-methylxanthine derivatives react best with nitronium tetrafluoroborate in sulfolane or glacial acetic acid. The 8-nitro group can be displaced nucleophilically to form 8-chloro-, 33, 34 , 8-ethoxy-, 35,36 , and uric acid derivatives 37–40 , respectively. The newly synthesized 8-nitroxanthines have been characterized by elemental analyses, pK-determinations and uv and ¹H-nmr spectra.     

Crystal Engineering with Multipoint Halogen Bonding: Double Two-Point Donors and Acceptors at Work

The combination of singly or doubly bidentate halogen-bond donors with double bidentate acceptors was investigated as a supramolecular synthon in crystal engineering. The crystal topologies obtained feature novel halogen-bonding motifs like double two-point recognition and infinite chains or networks based on two-point interactions. Induced conformational changes in the double bidentate halogen-bond donors could be exploited to obtain different 1D and 2D networks. All solid-state studies were accompanied by DFT calculations to predict and rationalize the outcome.     

卤代苯丙氨酸衍生物的合成与拆分

以苯胺类化合物为起始原料,经重氮化、丙烯酸加成、氨解等过程合成了5种消旋苯环取代苯丙氨酸衍生物,并采用α-糜蛋白酶和枯草杆菌蛋白酶对所有氨基酸进行了拆分,通过IR,¹HNMR,元素分析和旋光等技术进行表征.其中4种氨基酸未见文献报道.     

多取代芳香族化合物的合成 5.卤素-苯硒基取代的丁二烯和丁炔二酸二甲酯的环加成-芳构化串连反应

本文报道用环加成－芳构化串连反应制备多取代芳香族化合物的方法。将１－氯－２－卤－３－苯硒基－１，３－丁二烯（５）与丁炔二酸二甲酯进行Ｄｉｅｌｓ－Ａｌｄｅｒ反应时，能直接生成多取代的芳香族化合物４－苯硒基－５－卤代邻苯二甲酸二甲酯（４）。若用２－卤素－３－苯硒基－１，３－丁二烯（１）与丁炔二酸二甲酯进行Ｄｉｅｌｓ－Ａｌｄｅｒ反应，只得到正常的加成产物４－苯硒基－５－卤素－１，４－环己二烯－１，２－二甲酸二甲酯（３），需再用ＤＤＱ处理，才得到多取代芳香族化合物（４）。     

Comparison between Hydrogen and Halogen Bonds in Complexes of 6-OX-Fulvene with Pnicogen and Chalcogen Electron Donors

Quantum chemical calculations are applied to complexes of 6-OX-fulvene (X=H, Cl, Br, I) with ZH₃/H₂Y (Z=N, P, As, Sb; Y=O, S, Se, Te) to study the competition between the hydrogen bond and the halogen bond. The H-bond weakens as the base atom grows in size and the associated negative electrostatic potential on the Lewis base atom diminishes. The pattern for the halogen bonds is more complicated. In most cases, the halogen bond is stronger for the heavier halogen atom, and pnicogen electron donors are more strongly bound than chalcogen. Halogen bonds to chalcogen atoms strengthen in the order O<S<Se<Te, whereas the pattern is murkier for the pnicogen donors. In terms of competition, most halogen bonds to pnicogen donors are stronger than their H-bond analogues, but there is no clear pattern with respect to chalcogen donors. O prefers a H-bond, while halogen bonds are favored by Te. For S and Se, I-bonds are strongest, followed Br, H, and Cl-bonds in that order.     

Theoretical Investigation of Reverse Water Gas Shift Reaction Catalyzed by Ruthenium Halogen Carbonyl Complexes

In this paper we present theoretical study of the reverse water gas shift (RWGS) reaction catalyzed by ruthenium halogen carbonyl complexes. Three mechanisms, including hydrogen chloride, formic acid and oxidation–reduction mechanism, have been explored by density functional theory. The calculations indicate that the oxidation–reduction mechanism contributes to the TDI and TDTS in the ESM TOF calculations. Bimetallic catalysts would be likely to be more highly active than monometallic catalyst for the RWGS reaction. Among bimetallic catalysts studied, both bimetallic catalysts [Ru(μ-Cl)Cl(CO)₃]₂ and [Ru(μ-CO)Cl(CO)₃]₂ shows higher activity than [Ru(μ-Cl)(CO)₄]₂ catalyst with [Ru(μ-CO)Cl(CO)₃]₂ considering as the most efficient catalyst for RWGS reaction.     

Spectral Study of the Reaction of Functionally Substituted Enehydrazides with Proton Donors

Reactions of new enehydrazides, N',N'-dimethyl-N-vinylpropenohydrazide and N',N'-dimethyl-N-vinylbenzohydrazide with chloroform, phenol, and hydrogen chloride in carbon tetrachloride were studied by IR spectroscopy. In the first two cases, molecular complexes are formed between the hydrazide and proton donor. The reaction of N',N'-dimethyl-N-vinylpropenohydrazide with HCl results in formation of dihydropyrazole derivative which exists as a tautomeric mixture of the major lactam and minor lactim forms. N',N'-dimethyl-N-vinylbenzohydrazide reacts with hydrogen chloride to give protonated form in which proton is localized on the amino nitrogen atom. The structure of the initial compounds and the products was analyzed in terms of AM1 quantum-chemical calculations.     

Synthesis of Li-ion Battery Cathode Materials Based on Lithiated Transition Metal Oxides by Spray Method

The parameters of synthesis by the spray method of cathode materials Li_1.2Ni_0.13Co_0.13Mn_0.54O₂ and Li_1.25Ni_0.12Co_0.12Mn_0.51O₂, differing in lithium content were studied. The phase and granulometric composition, the morphology of the powder particles obtained, as well as an influence of temperature, total metal concentration, and pH of the solution on the properties of powders of cathode materials were studied. The discharge capacities of the obtained materials reached 260 mAh g^?1 in the range of 2.5?4.8 V.     

Synthesis of Arylhydrazines by Reaction of Arylbromides with DEAD via Sonochemical Barbier Reaction

A series of arylhydrazines was synthesized from the reaction mixture of Mg powder, 1,2‐dibromoethane, aryl bromide and DEAD (diethyl azodicarboxylate) in THF under ultrasound. This sonochemical Barbier reaction provides an efficient and inexpensive preparation method for synthesis of arylhydrazines.     

一类新型多取代嘌呤类化合物的合成及生物活性

以4-氯-5硝基嘧啶(3)为起始物, 经胺解、还原和环合等反应, 构建了新型的多取代嘌呤-8-硫酮(6)结构. 通过化合物6与卤代物的反应, 获得了该杂环的8位巯基衍生物7a-1~7, 7b-1~5和8, 其结构经元素分析, 1H NMR, IR及MS确证. 生物活性测试结果表明,  化合物6和7具有一定的除草和抗烟草花叶病毒活性.     

Purines. LII. Synthesis and biological evaluation of 8-methylguanine 7-oxide and its 9-arylmethyl derivatives.

The synthesis of 8-methylguanine 7-oxide (3) was accomplished via a "phenacylamine route", which started from condensation of alpha-(4-methoxybenzylamino)propiophenone (6), prepared by coupling of alpha-bromopropiophenone (4) and 4-methoxybenzylamine (5), with 2-amino-6-chloro-5-nitro-4(3H)-pyrimidinone (7) and proceeded through cyclization of the resulting phenacylaminopyrimidinone (8) and removal of the 4-methoxybenzyl group. The N-oxide 3 and its 9-arylmethyl derivatives 9 and 11 showed only very weak antileukemic activity and no antimicrobial activity.     

Benchmarking of Halogen Bond Strength in Solution with Nickel Fluorides: Bromine versus Iodine and Perfluoroaryl versus Perfluoroalkyl Donors

The energetics of halogen bond formation in solution have been investigated for a series of nickel fluoride halogen bond acceptors; trans-[NiF(2-C₅NF₄)(PEt₃)₂] ( A1 ), trans-[NiF{2-C₅NF₃(4-H)}(PEt₃)₂] ( A2 ), trans-[NiF{2-C₅NF₃(4-NMe₂)}(PEt₃)₂] ( A3 ) and trans-[NiF{2-C₅NF₂H(4-CF₃)}(PCy₃)₂] ( A4 ) with neutral organic halogen bond donors, iodopentafluorobenzene ( D1 ), 1-iodononafluorobutane ( D2 ) and bromopentafluorobenzene ( D3 ), in order to establish the significance of changes from perfluoroaryl to perfluoroalkyl donors and from iodine to bromine donors. ¹⁹F NMR titration experiments have been employed to obtain the association constants, enthalpy, and entropy for the halogen bond formed between these donor-acceptor partners in protiotoluene. For A2 – A4 , association constants of the halogen bonds formed with iodoperfluoroalkane ( D2 ) are consistently larger than those obtained for analogous complexes with the iodoperfluoroarene ( D1 ). For complexes formed with A2 – A4 , the strength of the halogen bond is significantly lowered upon modification of the halogen donor atom from I (in D1 ) to Br (in D3 ) (for D1 : 5≤K₂₈₅≤12 m ⁻¹, for D3 : 1.0≤K₁₉₃≤1.6 m ⁻¹). The presence of the electron donating NMe₂ substituent on the pyridyl ring of acceptor A3 led to an increase in −ΔH, and the association constants of the halogen bond complexes formed with D1 – D3 , compared to those formed by A1 , A2 and A4 with the same donors.