Presumed Mechanism

Little work has been done to confirm the mechanism of the Camps reaction. The presumed mechanism is shown. Deprotonation a to the ketone portion 1 (11) followed... 

Scheme 5. Presumed mechanism of acid-induced epimerization at C-3.

Scheme 4. Presumed mechanism of the CpCo(CO)2-catalyzed cocyclization of 7 with 8.

Scheme 4. Presumed mechanism for the Ni(n)/Cr(ii)-mediated coupling reaction.

One of the possibilities is to study experimentally the coupled system as a whole, at a time when all the reactions concerned are taking place. On the basis of the data obtained it is possible to solve the system of differential equations (1) simultaneously and to determine numerical values of all the parameters unknown (constants). This approach can be refined in that the equations for the stoichiometrically simple reactions can be specified in view of the presumed mechanism and the elementary steps so that one obtains a very complex set of different reaction paths with many unidentifiable intermediates. A number of procedures have been suggested to solve such complicated systems. Some of them start from the assumption of steady-state rates of the individual steps and they were worked out also for stoichiometrically not simple reactions [see, e.g. (8, 9, 5a)]. A concise treatment of the properties of the systems of consecutive processes has been written by Noyes (10). The simplification of the treatment of some complex systems can be achieved by using isotopically labeled compounds (8, 11, 12, 12a, 12b). Even very complicated systems which involve non-... 

For each of these reactions kinetic data were obtained. The reactions were first order in complex concentration, and zero order in isocyanide, as expected. The complex Ni(CNBu )4, and presumably other Ni(CNR)4 complexes as well, undergo ligand dissociation in solution. In benzene solution, a molecular weight determination for this compound gives a low value (110). This is in accord with the presumed mechanism of substitution. 

The presumed mechanism for the transformation of anhydrovobasinediol to koumine is as follows ... 

However, the above presumed mechanism could not explain for all phenomena about redox mediator, which needs to be explored in details. 

Mercuric acetate and thallic acetate have also been used for the oxidative cydiza-tion of vinylallenes (Eq. 13.24) [29]. Exposure of vinylallene 75 to stoichiometric mercuric acetate in acetic acid led to cydopentenone 76 in 75% yield. With thallium acetate as the oxidant, the yield of 76 was 60%. The presumed mechanism of the oxidative cyclization involves a Nazarov cyclization of acetoxymercury intermediate 77. 

First, you will learn about the human nervous system and how it works when it is healthy. This will include an introduction to the structure (anatomy) of the nervous system and the function (physiology) of the nervous system. Next, we ll describe the things that can go wrong. We ll look at how the system breaks down and malfunctions. Then we ll show you how these breakdowns can result in psychiatric illness. Finally, we ll introduce you to the medications used to treat psychiatric illness. You will learn where these medications work and our best guess of how they work. The presumed mechanism of action of many medications is just that, presumed. In contrast to antibiotics, in which we know quite a lot about the ways that they kill bacteria or stop them from reproducing and how these mechanisms ultimately effect a cure for an infectious disease, less is known about how psychotropic medicines work. Oh, we pretty well understand what psychotropic medicines do when they reach the nerve cell. For example, most of the antidepressants used today block the reuptake of serotonin at the nerve cell, but we re still not sure why blocking serotonin reuptake gradually improves mood in someone with depression. This will lead to a tour, if you will, of what happens to a medication from the time the pill is swallowed, until it exerts its therapeutic effect. 

The presumed mechanism of the oxidative ring enlargement is shown for 52 (R = Ph). The first step is the oxidation of the isoxazolidine to the unstable N-oxide 58, which rearranges to the unstable dipolar 59 this yields the methylene nitrone 60 by tautomerization. 60 gives oxazine 53, through ring-chain tautomerization (79JOC1819). 

Optimal therapy of cardiac arrhythmias requires documentation, accurate diagnosis, and modification of precipitating causes, and if indicated, proper selection and use of antiarrhythmic drugs. These drugs are classified according to their effects on the action potential of cardiac cells and their presumed mechanism of action. 

Among the great number of different approaches for the synthesis of phthal-ideisoquinoline alkaloids the application of Reissert compounds, developed first by Kerekes et al. (42,43), proved to be one of the most efficient and suitable methods (Scheme 24). Treatment of isoquinoline Reissert compounds 26 or 28 with sodium hydride in dimethylformamide resulted in the formation of the corresponding Reissert anions, which were reacted with dimethoxy- or meth-ylenedioxy-substituted o-formylbenzoic acid ester derivatives 178 and 179, respectively. The presumed mechanism of this reaction involves an initial reaction... 

As far as the resulting addition patterns of products and the presumed mechanisms are concerned, nucleophilic additions and radical additions are closely related and in some cases it is difficult to decide which mechanism actually operates. Related reactions may be found in Chapter 6. 

These agents are discussed together because their pharmacological properties, clinical indications for the treatment of epilepsy, and presumed mechanisms of action are similar. They differ from each other in several ways, however, and one drug cannot routinely be substituted for another. They differ primarily in their pharmacokinetic properties, their adverse reactions, and their interactions with other drugs. In addition to blocking sodium channels, some possess other therapeutically relevant mechanisms of action as well. 

The ability to monitor the presumed mechanism of action (i.e., monoamine oxidase inhibition) using platelets as a surrogate rather than monitoring the plasma drug level... 

With the preceding issues in mind, the clinician can begin to formulate a logical and systematic approach to antidepressant therapy. At present, several classes of antidepressants are available as defined by the presumed mechanism of action underlying their antidepressant efficacy ( Table 7-16). 

Botanical product Known or presumed mechanism of interaction Description of interaction outcome Comment... 

Oxygen activation has been shown to be important both in the presumed mechanism of attack on DNA by metal complexes of antibiotics, and in the synthesis of dexoyribonucleotides from the corresponding ribonucleotides. Although primarily centered on iron complexes, and thus outside of the scope of this review, some cobalt analogue complexes have been discussed. 

Several reports appear in the more recent literature of syntheses using electrochemical or PIET oxidation of compounds containing >C=N— bonds. These fall into three categories based upon a mechanism or presumed mechanism Cycloadditions, nucleophilic attack on >C=N— + cation radicals and radical annulations. The latter will not be reviewed here179 as none of the annulations appears to involve >C=N— + cation radicals. It should be pointed out that it is by no means certain that the electronic structure of >C=N— + is that of a 7r-cation radical rather than of an iminium cation radical (Figure 5). As will be seen below, reactivity appears sometimes in one guise and sometimes in the other. 

Lee PH, Bang OY, Oh SH et al (2003) Subcortical white matter infarcts. Comparison of superficial perforating artery and internal borderzone infarcts using diffusion-weighted magnetic resonance imaging. Stroke 34 2630-2635 Leys D, Mounier-Vehier F, Lavenu I et al (1994) Anterior choroidal artery territory infarcts. Study of presumed mechanisms. Stroke 25 837-842... 

Another frequently presumed mechanism appropriates the classical S 2 pathway and interprets the halogenation as a simple nucleophilic substitution reaction, the displacement of Y in a direct attack by Nu on X of Y—X (equation 2). The precedence for this mecha-... 

TABLE 3.5. Classification of Antidepressants According to Their Presumed Mechanism of Action ... 

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