Ab initio study of the reaction path of the reaction HNCO+CN

HNCO is a convenient photolytic source of NCO and NH radicals for laboratory kinetics studies of elementary reaction[1] and plays an important role in the combustion and atmosphere chemistry. It can re- move deleterious compounds rapidly from exhausted ga…     

Studies on the cyclization reaction of D-aspartic acid

The cyclization reaction of D-aspartic acid was studied, the carboxyl groups of D-aspartic acid were protected by benzyl alcohol to give compound D-dibenzyl aspartate. Then (4R)-benzyl azetidine-2-one-4-carboxylate and meso-3,6-disubstituted piperazine- 2,5-diones were synthesized via intramolecular cyclization and intermolecular cyclization of D-dibenzyl aspartate, respectively, and their structures were confirmed by 1H NMR and MS. Both cyclization reaction conditions were also investigated in detail.     

Preparation of natural isovaleraldehyde by the Maillard reaction

Isovaleraldehyde possesses malty,fruity,cocoa-like odor and is widely used in fruit,chocolate,coffee flavors.The preparation of natural isovaleraldehyde by the Maillard model reaction was studied in this paper.The effects of the ratio of D-glucose/L-leucine, reaction temperature and pH value on the yield of isovaleraldehyde were explored.The optimum conditions were as follows: n(D-glucose):n(L-leucine)=4,temperature 150℃,reaction time 3 h,pH 5.The highest yield of isovaleraldehyde obtained was about 32%.     

Calculation of the quantum yield of the photochemical isomerization reaction → methoxybutadiene methoxycyclobutene

The methoxybutadiene → methoxycyclobutene photoisomerization process was simulated and the quantum yield of the product was calculated. The validity of the theoretical ideas and model concepts used in the proposed method for the calculation of quantum yields of photochemical reactions was confirmed. It was shown that the empirical parameter used in the model (broadening parameter) is stable in value and has the inherent property of transferability over a series of related molecules and analogous reactions. The cause of a substantial difference between the experimental quantum yields of reactions of the same type for a number of molecules bearing different substituents was revealed: this is a change in the form of vibrations and/or in the magnitude of structural rearrangement that directly involves the substituent.     

Combination of the Claisen-Schmidt reaction,the Michael addition,and the Hantzsch reaction in the synthesis of 2,6′-bis-aryl-3,4′-bipyridines

Russian Chemical Bulletin - Pyridine-3-carbaldehyde reacted with 1-(aryl)ethan-1-ones to give 1,5-diaryl-3-(pyridin-3-yl)pentane-1,5-diones, which were further converted to...     

Synthesis of the integrastatin nucleus using the Ramberg-Bäcklund reaction

[reaction: see text] The first synthesis of the tetracyclic nucleus of the Integrastatins, natural products that have been shown to selectively inhibit HIV-1 integrase, is reported. Key steps of this synthesis involve a novel cis-selective Ramberg-B?cklund reaction and an unusual Lewis acid-promoted cyclization step.     

Systematic study for the stereochemistry of the Atherton–Todd reaction

Under the Atherton–Todd reaction conditions, the stereochemistry on the reaction of H-phosphinates with different nucleophiles (e.g., amines, alcohols, phenols) was investigated. All reactions took place stereospecifically with inversion of configurations at the phosphorus centers. The reaction might proceed via a phosphoryl chloride intermediate with retention of configuration at phosphorus, followed by the attack of nucleophiles from the backside of Cl to give the substitution products with inversion of configuration at the phosphorus center. A plausible mechanism was proposed for these reactions.     

Heterogeneous reaction of NO_2 on the surface of NaCl particles

Sodium chloride is the major constituent of sea salt particles in atmospheric environment, with an esti- mated annual contribution of 1012 kg of sea salt parti- cles to the atmosphere[1]. Many studies have shown a significant chloride deficit in these particles when compared to bulk seawater[2,3]. This deficit has been attributed to reactions with NOx and SO2[4]. Simulta- neously, NO2 is one of the main pollutants of mobile vehicles. Reaction (1) may be particularly important to the atmosph…     

Adapted numerical modelling of the Belousov–Zhabotinsky reaction

Adapted numerical schemes for the integration of differential equations generating periodic wavefronts have reported benefits in terms of accuracy and stability. This work is focused on differential equations modelling chemical phenomena which are characterized by an oscillatory dynamics. The adaptation is carried out through the exponential fitting technique, which is specially suitable to follow the apriori known qualitative behavior of the solution. In particular, we have merged this strategy with the information coming from existing theoretical studies and especially the observation of time series. Numerical tests will be provided to show the effectiveness of this problem-oriented approach.     

Synthesis of β-substituted tetrahydrofurans by the prins reaction

Mixtures of 3-trif uoroacetoxy- and 3-chloro-4-alkyltetraliydrofurans were synthesized by the reaction of a series of-olefins with formaldehyde in trifuoroacetic acid and trimethylchlorosilane.The characteristics of the mixtures of cis and trans isomers are given, and the n_D ²⁰ values are given for the trans isomers.Bashkir State University, Institute of Fine Organic Synthesis. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 605–608, May, 1995. Original article submitted November 4, 1994; revision submitted May 10, 1995.     

On the study of nonlinear dynamics of complex chemical reaction systems

When driven far from equilibrium,nonlinear chemical reactions often show a variety of self-organization behavior,including chemical oscillations,waves,chaos and patterns[1].Recently,the study of such nonlinear phenomena in‘complex’systems,such as the li…     

Rearrangement reaction of the hydroxyl group of ω-hydroxy-alkyltriphenyl phosphonium bromides

No molecular ion peak from the Electron Impact lonization of eight co-hydroxyalkyltriphenyl phosphonium bromides(Ph3P (CH2)nOHBr-,n=2-6,8-10)can be found,except a part of some relative powerful fragment ions can be observed only.Each compound forms a very characteristic ion(O=PPbj-1) at m/z 277 through hydroxyl rearrangement reaction.The intensity of this ion is closely related with the size of the carbon chain of hydroxyalkyl and with temperature of ion source and temperature of sample probe.The above rearrangement reaction and the reaction to form ion at m/z 262 take place simultaneously,thus leading to strong competition.At n=2,ion at m/z 277 is the most powerful and becomes continuously the base peak.At n=3 and n=4,the intensity of ion at m/z 262 reaches the maximum,and is always the base peak,and the relative abundance of m/z 277 is only around 2%.At n=5,6,8,9,10,m/z 277 becomes base peak when the temperature of probe is below 300℃.But,when the temperature increases from 300℃to 350℃,m/z 262 sud     

Modification of the Pictet–Spengler reaction in the synthesis of fused 2,3-benzodiazocines

A new strategy for the synthesis of the eight-membered heterocyclic skeleton of tetrahydro-quinazolino[3,2-c][2,3]benzodiazocin-15-ones, based on the Pictet–Spengler reaction of 3-amino-2-[2-(3,4-dimethoxyphenyl)ethyl]quinazolin-4(3H)-one with carbonyl compounds in acidic media, is proposed.     

Addition of γ-silyloxyallyltins on ethyl glyoxylate: evaluation of the influence of the experimental conditions on the stereochemical course of the reaction

Ethyl glyoxylate was reacted with α-substituted γ-(t-butyldimethylsilyloxy)-allyltributyltin in order to obtain selectively each diastereomer of ethyl 3-(t-butyldimethylsilyloxy)-2-hydroxyhex-4-enoate and subsequently the corresponding diols. Diastereomers syn-E, anti-E and anti-Z were obtained in good yields with good to high selectivities and the obtained results were rationalized by consideration of cyclic or open transition states in agreement with the experimental conditions and with the structure of the starting reagents.     

On the probable mechanism of the complex formation reaction of metal salts with the β-substituted corroles

The kinetics of the complex formation reaction of the β-hexamethyldiethylcorrole, [H₃(β-Me₆Et₂)Cor], with zinc and cobalt acetates and with zinc acetylacetonate in DMF was studied. The rate of the complexation process between H₃(β-Me₆Et₂)Cor and Zn(OAc)₂ was shown to decrease in the following series of the solvents as DMF < AN < benzene and to suggest elevated chemical activity of the NH bonds in a molecule of corrole. The destruction of β-octaalkylcorrole in the basic solvents (DMF and DMSO) was discovered for the first time, and the kinetic parameters of this process were determined. With account for the structural distinctions between corroles H₃Cor and porphyrins H₂P, the probable mechanism of their reactions with metal salts was discussed and the transition state structure, which noticeably differ from the analogous reactions with porphyrins in the formation of the [H₃Cor · Zn(OAc)₂(Solv) _n?3] intermediate.     

Analysis of the Volmer–Krishtalic mechanism for the chlorine electrode reaction

The dependencies of the current density and surface coverage of the adsorbed intermediates on overpotential were established without kinetic approximations for the chlorine electrode reaction under the Volmer–Krishtalic mechanism. Tafelian regions were obtained which slope values cannot be derived from the use of the rate determining step criteria, such as 2.3026(2RT/3F) and 2.3026(RT/F), as well as two or three Tafel regions with different slopes in the same anodic or cathodic curve. The existence of limiting kinetic current densities was also demonstrated. Finally, the results obtained were analysed and discussed, comparing them with those obtained by the usual methods.     

Do reaction conditions affect the stereoselectivity in the Staudinger reaction?

The stereochemistry is one of the critical issues in the Staudinger reaction. We have proposed the origin of the stereoselectivity recently. The effects of solvents, additives, and pathways of ketene generation on the stereoselectivity were investigated by using a clean Staudinger reaction, which is a sensitive reaction system to the stereoselectivity. The results indicate that the additives, usually existed and generated in the Staudinger reaction, and the pathways of the ketene generation do not generally affect the stereoselectivity. The solvent affects the stereoselectivity. The polar solvent is favorable to the formation of trans-beta-lactams. The addition orders of the reagents affect the stereoselectivity in the Staudinger reaction between acyl chlorides and imines. The addition of a tertiary amine into a solution of the acyl chloride and the imine generally decreases the stereoselectivity, which is affected by the interval between additions of the acyl chloride and the tertiary amine, and the imine substituents. Our current results provide further understanding on the stereochemistry of the Staudinger reaction between acyl chlorides and imines and on the factors affecting the stereochemistry and also provide a method to prepare beta-lactams with the desired relative configuration via rationally tuning the stereoselectivity-controlling factors in the Staudinger reaction.     

A study of the color reaction of iron with “TTA”

Summary TTA, or 2-Thenoyltrifluoroacetone, gives with ferric ion, in various concentrations colorations ranging from blood red to light pink. The advantages of this test are that it is simple to perform, that it is applicable in different acid media of fairly high concentrations, and that it is somewhat sensitive in the presence of ions that usually interfere with such tests. The sensitivity (limit of identification) was found to be 0,5 and the limit of concentration 1 : 100000 when a benzene solution of the reagent was reacted with a slightly acid solution of ferric ion on spot paper.

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Zusammenfassung TTA (2-Thenoyltrifluoraceton) gibt mit Ferriionen je nach Konzentration der letzteren eine blutrote bis blaßrosa Färbung. Die Probe ist einfach ausführbar und wird durch die Gegenwart von Säuren bis zu ziemlich hohen Konzentrationen sowie durch die Gegenwart störender Ionen wenig beeinträchtigt. Wenn eine Lösung des Reagens in Benzol zu einer leicht angesäuerten Ferrisalzlösung zugesetzt wird, beträgt die Erfassungsgrenze 0,5 bei einer Grenzkonzentration von 1 : 100000.

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Résumé Le TTA, thénoyl-2 trifluoracétone, donne avec les ions ferriques, suivant leur concentration, une coloration rouge sang à rose pâle. L'essai est simple à effectuer et à peine troublé par la présence des acides jusqu'à des concentrations passablement élevées et par la présence des ions gênants. Quand on ajoute une solution du réactif dans le benzène à une solution peu acide de sel ferrique, on observe une limite de sensibilité de 0,5 pour une limite de dilution de 1 : 100000.

     

The Wittig–Horner reaction for the synthesis of neratinib

The Wittig–Horner reaction is a classic method to get alkenes by reaction phosphonates with carbonyl compounds. In this study, it was used for the synthesis of the anticancer drug neratinib. In this method, ethyl diethoxyphosphinylacetate and dimethylaminoacetaldehyde diethylacetal, replacing (E)-4-(dimethylamino)but-2-enoyl acid hydrochloride and oxalyl chloride, were used to synthesize the 6-position side chain of neratinib.     

Catalase-like catalytic reaction of the dinuclear manganese–salen complex

Catalase-like activity of a dinuclear manganese-salen (Mn–salen) complex, [Mn(salen)(H₂O)]₂(ClO₄)₂ (salen = N,N ′-bis(salicylidene)-1,2-diaminoethane), was investigated. The dinuclear Mn–salen complex exhibits higher catalase-like activity than that of the mononuclear Mn–salen compound, and its activity can be enhanced by an external base. Different reaction intermediates in the presence and absence of an external base were observed, and the catalytically active species was dimeric as evidenced by UV-Vis spectroscopic studies and mass spectrometry data.