Reactions of bicyclic phosphonates with halides of α-halocarboxylic acids

Novel types of substituted framework phosphonates have been synthesized via functionalization of bicyclic compounds obtained in the reaction of 2-ethoxyvinyl dichlorophosphonate with different phenols. The reactions of functionalized bicyclic phosphonates with triphenyl phosphine have been studied; antimicrobial activity of the prepared compounds has been investigated.     

Computer-assisted reaction prediction and synthesis design

The design of organic syntheses requires deep insight into chemical reactivity. Methods have been developed to calculate important electronic and energy effects and use them for the modelling of reaction mechanisms. The approach is illustrated by the haloform reaction. The procedures have been incorporated into different versions of the EROS system. A study of the synthesis of fredericamycin illustrates the use of these EROS procedures in synthesis design and reaction prediction. Recent work on synthesis design for aromatic compounds is highlighted and new definitions of the similarity of chemical compounds are discussed.     

脱氢醋酸与氨的反应

脱氢醋酸(1)与氨反应生成2,6-二甲基-4-羟基吡啶(2)^[1]。IguChi等^[2]曾用纸层析法定性地研究了这反应的过程。为进一步了解(1)与氨反应的历程及影响反应的因素,我们用HPLC研究了在不同反应条件下得到的中间体和产物,研究了相互转变关系,并进行了分离和鉴定。初步提出了该反应的可能历程。     

Studies on ylides: generation and reactions of new 2-naphthylmethylenetriphenylarsenanes

Two new semistabilized arsonium ylides have been generated and treated with carbonyl compounds. In reaction with carbonyl compounds, the carbanionic centres of both the ylides attack the carbonyl carbon to form similar cyclic intermediates. These intermediates, however, decompose to give different reaction products. The structures of the products are indicated by IR and NMR spectroscopy.     

Effect of sodium naphthalenide, a key SET reagent, on trifluoroacetyl derivatives

Aromatic trifluoroacetyl derivatives on treatment with single electron transfer (SET) reagent, sodium naphthalenide, yield symmetrical defluorinated dimers, whereas for aliphatic trifluoroacetyl compounds the reaction usually fails. Investigations have been made for different substituents as well as for similar types of chloro and bromo compounds to establish the scope of the reaction.     

Density Functional Study on the Mechanism of Amadori Rearrangement Reaction

The reaction mechanism of amadori rearrangement in the initial stage of Maillard reaction has been investigated by means of density functional theory calculations in the gaseous phase and aqueous solution.Cyclic ribose and glycine were taken as the model in the amadori rearrangement.Reaction mechanisms have been proposed,and possibility for the formation of different compounds has been evaluated through calculating the relative energy changes for different steps of the reaction by following the total mass balance.The calculations reveal that the amadori rearrangement initialized via the intramolecular rearrangement,transferring one proton from N(3) to O(4) atom.In the next step,the second proton is also transferred from N(3) to O(4) atom,corresponding to the cleavage of C(4)-O(4) bond and the release of one water molecule.Then another proton is transferred from N(3) to C(5) atom via TS3 with the reaction barrier of 58.3 kcal·mol-1 after tunneling the effect correction calculated at the B3LYP/6-31+G(d) level of theory,and this step is rate limiting for the whole catalytic cycle.Ultimately,the product is generated via keto-enolic tautomerization.Present calculation could provide insights into the reaction mechanism of Maillard reaction since experimental evaluation of the role of intermediates in the Maillard reaction is quite complicated.     

SYNTHESIS AND APPLICATION OF SOME NEW 5-SULPHONYL-N-HETEROCYCLO-8-HYDROXYQUINOLINE DERIVATIVES AS POTENTIAL DRUGS

Abstract

Some new sulphonyl-N-heterocyclo-8-hydroxy quinolines have been synthesised by the reaction of 8-hydroxyquinoline-5-sulphonyl hydrazide with different active methylene compounds. The pyrazole, pyrazoline, pyrazolidine and pyridazine derivatives were reacted with some metal cations to give the corresponding chelates. All synthesized compounds have been screened in vitro for their biological activities.     

Untersuchungen der Reaktionsprodukte von Isocyanaten mit Hydroxylamin

Investigations of the Products of Isocyanates with Hydroxylamine The reactions of isocyanates with hydroxylamine give rise to several compounds according to the different conditions involved when starting with the primary reaction products, the hydroxy-ureas. The pure compounds have been isolated. An interesting reaction of N-phenyl-N′-phenylcarbamoyloxyurea with sodium hydroxide has been observed. This compound is converted to 3-hydroxy-1, 5-diphenylbiuret under conditions described.     

Use of allylzinc halide as a source of halide: Differential addition of nucleophiles to Ts-aziridines and aldehydes under similar reaction conditions

We have observed that the allylic zinc halide under identical reaction conditions acts in different modes for different electrophiles. For Ts-aziridines the halide part of the allylic halide has been introduced as a nucleophile and for the carbonyl compounds the simple allylation reaction occurs. To the best of our knowledge this is the first report where the allylic zinc halide is the source of halide acting as nucleophile. The main advantages of the present procedure are easy to handle, no need of inert atmosphere, mild reaction conditions, and applicability to a wide variety of substrates for aziridines and carbonyl compounds.     

Efficient One-Step Synthesis of N,N′-Bis(2-Hydroxy-5-Bromobenzylidene) Arylmethamediamines

The tittle compounds have directly been synthesized by one-step reaction of two different aldehydes in the presence of ammonia in good to excellent yields.     

Density functional computational studies on the glucose and glycine Maillard reaction: Formation of the Amadori rearrangement products

Theoretical energy changes of various intermediates leading to the formation of the Amadori rearrangement products (ARPs) under different mechanistic assumptions have been calculated, by using open chain glucose (O‐Glu)/closed chain glucose (A‐Glu and B‐Glu) and glycine (Gly) as a model for the Maillard reaction. Density functional theory (DFT) computations have been applied on the proposed mechanisms under different pH conditions. Thus, the possibility of the formation of different compounds and electronic energy changes for different steps in the proposed mechanisms has been evaluated. B‐Glu has been found to be more efficient than A‐Glu, and A‐Glu has been found more efficient than O‐Glu in the reaction. The reaction under basic condition is the most favorable for the formation of ARPs. Other reaction pathways have been computed and discussed in this work. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008     

Germanium/phosphorus cage compounds with germanium in three different oxidation states

Novel germanium/phosphorus cage compounds with new structural motifs have been synthesized containing germanium in three different oxidation states. The key to obtain this new class of compounds is the use of monolithiated primary phosphine LiHPtBu in the reaction with GeX(2).     

An efficient synthesis of 2,6-disubstituted benzobisoxazoles: new building blocks for organic semiconductors

2,6-Disubstituted benzobisoxazoles have been synthesized by a highly efficient reaction of diaminobenzene diols with various orthoesters. The scope of this new reaction for the synthesis of substituted benzobisoxazoles has been investigated using four different orthoesters. The utility of these compounds as building blocks for the synthesis of conjugated polymers is demonstrated.     

稀土－铌(钽)复合溴氧化物的结构与光谱特性

用高温固相法合成了系列化合物RE_0.06La_0.94M₂O₆Br(M=Nb,Ta;RE=Eu,Tb,Pr,Sm),并测定了其激发和发射光谱,室温下Eu³⁺、Tb³⁺、Pr³⁺、Sm³⁺在稀土-铌(钽)复合溴氧化物中呈现特征激发谱线,但Nb和Ta的光谱特性稍有不同。     

羟基喹啉偶氮类化合物的互变异构与顺反异构的研究

本工作合成了数种带不同取代苯基的羟基喹啉偶氮类化合物。对它们在不同溶剂。不同酸碱度溶液中的偶氮式及腙式间互变异构平衡进行了研究。苯环上不同取代基的引入可引起平衡发生变化。拉电子基的引入有利于腙式结构的形成,而推电子基的引入则对偶氮的生成影响不大。此外,工作中还发现:羟基喹啉偶氮化合物在光照下存在着以偶氮顺-反异构化反应为主的变化过程。     

Maleimide-dimethylfuran exo adducts: effective maleimide protection in the synthesis of oligonucleotide conjugates

The reaction of maleimide-containing compounds with 2,5-dimethylfuran gives a mixture of exo and endo isomers from which the exo cycloadduct can be easily isolated taking advantage of its stability in concentrated aqueous ammonia. Bifunctional compounds incorporating a dimethylfuran-protected maleimide (exo adduct) have been attached to resin-linked oligonucleotide chains. Removal of protecting groups masking oligonucleotide functionalities followed by retro-Diels-Alder maleimide deprotection affords maleimido-oligonucleotides suitable for conjugation, as assessed by their reaction with different thiols.     

Thiophene chemistry—IX Preparation and dealkylation of 5-substituted 2-t-butoxythiophenes

Different substituents have been introduced into the 5-position of 2-t-butoxythiophene and by subsequent acid-catalyst dealkylation the corresponding hydroxythiophenes (or their different tautomeric forms) have been isolated in high yields. By NMR, IR and UV-spectroscopy the constitution and the composition of the different tautomeres have been determined. The reaction between carbonyl compounds and 5-t-butoxy-2-thiophenelithium gives carbinols, which upon heating with p-toluenesulphonic acid yielded 5-methylene-3-thiolen-2-ones.     

Thermal and Photolytic Transformation of NHC–B,N‐Heterocycles: Controlled Generation of Blue Fluorescent 1,3‐Azaborinine Derivatives and 1H‐Imidazo[1,2‐a]indoles by External Stimuli

NHC–B,N‐heterocyclic compounds have been found to act as convenient precursors for obtaining either 1,3‐azaborinine or 1H‐imidazo[1,2‐a]indole derivatives, which are two different and rare classes of compounds. The formation of these two classes of compounds from the NHC–B,N‐heterocycles is highly selective depending on the external stimuli employed, and the resulting products have been studied for their interesting chemical and photophysical properties. The mechanism and possible reaction pathways of the unusual transformation are established by computational studies.     

Nickel-catalyzed cycloadditions of thiophthalic anhydrides with alkynes

Nickel-catalyzed cycloadditions have been developed where thiophthalic anhydrides react with alkynes to afford substituted sulfur-containing heterocyclic compounds. Selective formations of thioisocoumarins, benzothiophenes, and thiochromones were accomplished with three different reaction conditions.     

具有光致变色和发光性能的有机化合物的合成及其性能研究

以吲哚啉螺苯并吡喃与香豆素衍生物为原料,用D_cC缩合酯化法在温和条件下合成了8种新的具有光致变色和发光性能的化合物,确定了结构,研究了紫外光谱、荧光光谱及光致变色性.所得化合物同时具有光致变色和发荧光的双重特性,而且荧光光谱中有两个激发波长,每一个波长对应产生一个不同的荧光发射峰.