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11.
Mukherjee A Dhar S Nethaji M Chakravarty AR 《Dalton transactions (Cambridge, England : 2003)》2005,(2):349-353
The ternary iron(II) complex [Fe(L')(L")](PF6)3(1) as a synthetic model for the bleomycins, where L' and L" are formed from metal-mediated cyclizations of N,N'-(2-hydroxypropane-1,3-diyl)bis(pyridine-2-aldimine)(L), is synthesized and structurally characterized by X-ray crystallography. In the six-coordinate iron(ii) complex, ligands L' and L" show tetradentate and bidentate chelating modes of bonding. Ligand L' is formed from an intramolecular attack of the alcoholic OH group of L to one imine moiety leading to the formation of a stereochemically constrained five-membered ring. Ligand L" which is formed from an intermolecular reaction involving one imine moiety of L and pyridine-2-carbaldehyde has an emissive cationic imidazopyridine pendant arm. The complex binds to double-stranded DNA in the minor groove giving a Kapp value of 4.1 x 10(5) M(-1) and displays oxidative cleavage of supercoiled DNA in the presence of H2O2 following a hydroxyl radical pathway. The complex also shows photo-induced DNA cleavage activity on UV light exposure involving formation of singlet oxygen as the reactive species. 相似文献
12.
Anil P. Phadnis Bharati Sinha Bhagbat Nanda Sarita A. Patwardhan J. Venkatesh Rao Ravindra N. Sharma 《Monatshefte für Chemie / Chemical Monthly》1989,120(6-7):581-586
Summary A series of 8-proparglyoxy-3,7-dimethyl-2,6-octadienyl and 8-propargyloxy-3,7-dimethyl-6-octenyl ethers were prepared from 8-hydroxygeranyl and 8-hydroxycitronellyl ethers, respectively. Almost all compounds showed high toxicity toCulex quinquefaciatus larvae at 1 mgl–1 dose level.
Gegen Mücken aktive Produkte, 4. Mitt.: Synthese und biologische Aktivität von 8-Propargyloxy-3,7-dimethyl-2,6-octadienyl/6-octenyl-ethern
Zusammenfassung Eine Reihe von 8-Propargyloxy-3,7-dimethyl-2,6-octadienyl- und 8-propargyloxy-3,7-dimethyl-6-octenyl-ethern wurden aus 8-Hydroxygeranyl- bzw. 8-Hydroxycitronellyl-ethern hergestellt. Fast alle Verbindungen zeigten hoch Toxizität gegenüber Larven vonCulex quinquefaciatus in einer Dosierung von 1 mgl–1.相似文献
13.
Ravindra K. Agrawal 《Journal of Thermal Analysis and Calorimetry》1989,35(3):909-917
In this article, the facts and fictions surrounding the compensation effect is explored. False compensation effect occurs mainly due to: propagation of computational and experimental errors resulting in inaccurate estimates of the Arrhenius parameters; and, the natural compensation between InA andE. Since Arrhenius parameters are sensitive to errors in temperature; the errors due to uncertainty in temperature should be minimized to eliminate false compensation effect. Increasing the experimental temperature range is helpful in minimizing errors due to uncertainty in temperature. A point of concurrence in a plot of Ink and 1/T establishes the occurrence of true compensation effect. True compensation effect has been shown to be a useful tool in chemical research for: identifying the governing reaction mechanism; predicting the effects of various reaction parameters; and, correlating and reducing experimental data.
The author would like to thank the reviewer for his constructive criticisms. 相似文献
Zusammenfassung In dieser Mitteilung werden Fakten und Vorstellungen betreffs des Kompensationseffektes untersucht. Falsche Kompensationseffekte werden hauptsächlich verursacht durch: eine ungenaue Ermittlung der Arrheniusparameter durch die Fortpflanzung von rechnerischen und experimentellen Fehlern sowie dem natürlichen Kompensationseffektes zwischen InA undE. Das Arrheniusparameter gegenüber Fehler im Temperaturwert sehr empfindlich sind, sollten Temperaturungenäuigkeitsfehler zur Vermeidung eines falschen Kompensationseffektes minimalisiert werden. Zur Verminderung der aus der Temperaturungenauigkeit resultierenden Fehler ist es von Nutzen, den Temperaturbereich des Experimentes zu erweitern. Ein wahrer Kompensationseffekt wird durch einen Schnittpunkt in einem Ink-1/T Diagramm angezeigt. Es wird gezeigt, daß der wahre Kompensationseffekt ein nutzvolles Mittel in der chemischen Forschung darstellt: zur Feststellung des dominierenden Reaktionsmechanismus, zur Vorhersage der einflüsse verschiedener Reaktionsparameter und zur Aufarbeitung und Schlußfolgerung von bzw. aus experimentellen Daten.
, . , , lnA E. , , . . Ink-1/T . , , , .
The author would like to thank the reviewer for his constructive criticisms. 相似文献
14.
15.
Microwave-activated solvent-free Michael addition of 3-imino-1,4,2-dithiazoles to 4-arylidene-5(4H)-oxazolones furnished isolable adducts regio- and diastereoselectively, which underwent ring transformation to yield the target dithiazolopyrimidines. Alternatively, the similar conjugate addition of methanesulfinylmethylisothioureas to 4-arylidene-5(4H)-oxazolones diastereoselectively afforded Michael adducts, which underwent ring transformation followed by heterocyclization via deoxygenative demethylation with thionyl chloride to yield the same products dithiazolopyrimidines regio- and diastereoselectively. 相似文献
16.
The core structure of the complex pentacyclic 5,11-methanomorphanthridine alkaloids is constructed stereospecifically in one step employing an intramolecular [3 + 2]-cycloaddition of nonstabilized azomethine ylide as the key step. The strategy is demonstrated by accomplishing the formal total synthesis of (+/-)-pancracine. [reaction: see text] 相似文献
17.
We study the long-time relaxation of magnetization in a disordered linear chain of Ising spins from an initially aligned state. The coupling constants are ferromagnetic and nearest-neighbor only, taking valuesJ
0 andJ
1 with probabilitiesp and 1–p, respectively. The time evolution of the system is governed by the Glauber master equation. It is shown that for large timest, the magnetizationM(t) varies as [exp(–0
t](t), where 0 is a function of the stronger bond strengthJ
0 only, and (t) decreases slower than an exponential. For very long times, we find that ln (t) varies as –t
1/3. For low enough temperatures, there is an intermediate time regime when ln (t) varies as –t
1/2. The results can be extended to more general probability distributions of ferromagnetic coupling constants, assuming thatM(t) can only increase if any bond in the chain is strengthened. If the coupling constants have a continuous distribution in which the probability density varies as a power law near some maximum valueJ
0, we find that ln (t) varies as –t
1/3(lnt)2/3 for large times. 相似文献
18.
The axial aqua bound copper(II) complex [Cu(dpq)2(H2O)](ClO4)2, having a planar NN-donor heterocyclic base dipyridoquinoxaline (dpq) as the DNA minor groove binder, shows efficient hydrolytic cleavage of supercoiled DNA in the dark and in the absence of any external reagents, as evidenced from T4 ligase experiments, with a rate of 5.58 +/- 0.4 h(-1) and a rate enhancement of 1.55 x 10(8). 相似文献
19.
The reaction of nucleophilic and non-nucleophilic bases wtih 2-carbamoyl-3-(γ-chloropropyl)-1-indenone ( 5 ) have been investigated. Condensation of γ-chlorobutyrophenone with malono-nitrile afforded α-cyano-β-(3-ehloropropyl)cinnamonitrile which was cyclized in concentrated sulfurie acid to produce 5 . Two other products obtained from the cyclization reaction were 2-carbamoyl-3-(γ-ehloropropylidene)-1-indanone ( 4 ) and α-carbamoyl-β-(3-chloropropyl)cinnam-amide. Treatment of a solution of 4 in ethyl acetate with piperidine resulted in cyclization of the γ-chloropropyl side chain to give 2-carbamoyl-3-cycIopropyl-1-indanone. The same compound was obtained in improved yield by the treatment of 4 or 5 with sodium hydroxide solution. The reaction of dirnethylamine with 5 in benzene gave initial Michael addition of the amine followed by internal alkylation of the carbanion so formed to yield 3a-dimethylamino-2,3,3a,8-tetrahydro-8-oxoeyclopent[a]indene-8a(lH)earboxamide ( 7a ). Similarly addition of ammonia, pyrrolidine, piperidine, benzenethiol, p-toluenethiol, 2-naphthalenethiol and nitromethane to the indenone I gave respective analogs of type 7 . Treatment of 5 with sodium cyanide in aqueous t-butyl alcohol resulted in a similar Michael addition followed by internal alkylation. In addition, cyclization between the nitrile and the carbamoyl functions occurred in the same step to give 2-oxo-4-imino-7,8-benzo-3-aza[3.3.3]-propellan-6-one ( 13a ). Hydrolysis of the iminopyrrolido ring in 13a to the corresponding suecin-irnide gave 2,4-dioxo-7,8-benzo-3-aza[3.3.3]propellan-6-one ( 13b ). Reactión of 13b with methyl iodide, allyl bromide, benzyl bromide, and diethyluminoethyl chloride afforded the corresponding N-alkylated products. A similar sequence starling with δ-ehlorovalerophenone led to 5,6-fused ring systems, including a [4.3.3]propellane. 2,9-Dioxo-4-methyl-7,8-benzo-3-aza[4.3.3]propell-4-ene was obtained by the reaction of 5 with acetone in dilute alkali. 相似文献
20.
The analysis of dehydration of the complexes, [La(C8H8NO3)3.2H2O] and [Yb(C8H8NO3)3.3H2O] for the evaluation of kinetic parameters (Z, E &S
*) and mechanism of dehydration by non-isothermal methods are reported. The complexes decompose in three well defined steps involving random nucleation mechanism. First two steps involving the dehydration and the third step the loss of the ligand moiety. The intermediates formed during decomposition were found to be unstable for carrying out any significant studies.
Zusammenfassung Zwecks Ermittlung der kinetischen Parameter (Z, E undS *) und des Mechanismus der Dehydratierung durch nichtisotherme Verfahren wird die Analyse der Dehydratierung der Komplexe [La(C8H8NO3)3·2H2O] und [Yb(C8H8NO3)3·3H2O] beschrieben. Die Komplexe zersetzen sich in drei gut definierten Schritten mit Random-Keimbildungsmechanismus. Die ersten zwei Schritte beinhalten die Dehydratierung, der dritte Schritt den Verlust der Liganden. Die wÄhrend der Zersetzung entstandenen Zwischenprodukte erwiesen sich für jegliche signifikante Untersuchung als zu unstabil.相似文献