Mechanistic Observations

There are no reports of detailed mechanistic studies on the Petasis borono-Mannich reaction. Nevertheless, some experimental observations have been made that provide a basic understanding of the reaction. These observations also provide some useful guidelines as to the types of substrates that are suitable for participation in the Petasis borono-Mannich reaction. 

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Mechanistic observations on formation of hydrocarbons in Cp2Fe2(C0K with LAH. There is little doubt that the initial step in the reaction of Cp2Fe2(C0K with LAH involves formation of a formyl complex by addition of a hydride to coordinated CO. 

Balthazor, T.M. and Grabiak, R.C., Nickel-catalyzed Arbuzov reaction mechanistic observations, /. Org. Chem., 45, 5425, 1980. 

Winkler, J.D., Harrison, S.J., Greaney, M.F., and Rouse, M.B. (2002) Mechanistic observations on the unusual reactivity of dioxenone photosubstrates in the synthesis ofingenol. Synthesis, 2150-2154. 

Singleton, D. A. Merrigan, S. R. Resolution of conflicting mechanistic observations in ester aminolysis. A warning on the qualitative prediction of isotope effects for reactive intermediates, 7. Am. Chem. Soc. 2000,122, 11035-11036. 

The application of the basic ideas to real combustion systems is then taken up in Chapters 6 and 7. In Chapter 6, experimental and modelling studies are described which link the mechanistic observations of Chapter 1 to combustion characteristics of fuels studied under laboratory conditions. The experimental emphasis is initially on global combustion phenomena - ignition and oscillatory cool-flames - for a range of hydrocarbons. Section 6.5 then addresses the distribution of products in hydrocarbon oxidation this discussion differs from that in Chapter 1 where the conditions were optimized to allow the investigation of specific reactions. The focus is now on studies of oxidation products over a range of isothermal and non-isothermal conditions, the interpretation of the results in terms of elementary reactions and the use of the experimental data as a detailed test of combustion models. The chapter provides an overview of the success of detailed models in describing combustion phenomena and combustion... 

This is an indirect statement of the common mechanistic observation that the more electropositive (electrophilic) atom (or part) of the polar molecule becomes attached to the end of the multiple bond that would result in the more stable carbenium ion (whether or not a carbenium ion is actually formed as a reaction INTERMEDIATE in the addition reaction). Addition in the opposite sense is commonly called anti-Markow-nikoff addition. 

In another early example Periana and Bergman made an important mechanistic observation by reacting the unsaturated Rh complex with cyclopropane [Eq. (6.108)]. At -60°C C-H insertion resulted in complex 127, which is the kinetically favored product. This underwent direct rearrangement to the thermodynamically favored 128 rhodacyclobutane. 

When propylene is used as the feed, acrolein is observed as the major primary oxidation product. These are significant mechanistic observations, since it follows therefrom that all higher oxidized products, when starting with propane as feed must derive from the first formed propylene or a subsequently formed intermediate. A reaction network (Scheme 1) consistent with these observations portends that propane is first oxidized to propylene, which... 

This chapter is concerned with mechanistic observations on hydride-transfer processes in non-enzymic systems, but under conditions and with structures such that the observations are considered relevant to enzyme-catalyzed reactions. Even... 

This compound undergoes rearrangement to 6-O-demethylsalutaridine (139) in the presence of Claisen s alkali.147 The product has been correlated with salutari-dine and a mechanism involving SN2 attack by base on the allylic bromide function to form the intermediate (140 X = OH) has been proposed. Compound (139) has also been obtained independently by treatment of 7-bromoneopinone (140 X = Br) perchlorate with sodium acetate-acetic acid and several pertinent mechanistic observations on this reaction have been presented.149 Attempts to prepare the proposed intermediate (140 X = OH) from (140 X = Br) perchlorate by treatment with aqueous silver nitrate at room temperature gave no reaction, while under reflux a quantitative yield of (139) perchlorate was obtained. Compound (140 X = Br) perchlorate was stable to base in the cold while at reflux temperature a Hofmann degradation product was obtained.150 It is interesting to... 

The formic acid arena reflects both, the classical chemical attempts to equate surface species with simple bulk compounds of chemistry, as well as the viewing of the solid as a new electronic (and therefore chemical) species. Importantly, the authors of that review point to the danger of generalizing mechanistic observations made with one reaction to heterogeneous catalysis. To us such a step would indeed be analogous to the expectation that the reactivity of an acid with a base would supply the answer to chemical reactions, generally. 

Cerebral Blood Flow during Isovolemic Hemodilution Mechanistic Observations Michael M. Todd... 

The addition of carbon monoxide to (/x,-dpm)2Rh2(jLt-Cl)(CO)2 (Equation 6) is one of the few reactions of these binuclear complexes where any mechanistic observations have been made. By following the introduction of into this complex by infrared and C-NMR... 

The early phosphoramides 21.9 and 21.10 (Figure 21.1), developed by Denmark, exhibited modest enantioselectivity in the allylation reaction but played an important role in the mechanistic elucidation and development of the second generation of catalysts. Thus, kinetic measurements and the observation of a nonlinear relationship between the enantiopurity of 21.9/21.10 and the product 21.7 indicated that two molecules of the catalyst are coordinated to the silicon centre.However, when the concentration of the catalyst is low, a second mechanism may compete, namely that with only one molecule of the catalyst coordinated, which apparently attenuates the enantioselectivity. As a logical progression from these mechanistic observations, bidentate catalysts, such as 21.12 and 21.13, were designed. The latter exhibited higher enantios-electivities and also was more reactive, so that the loading could be reduced from 10-20 to 5 Excellent diastereoselectivity was... 

Tius MA, Kawakami JK (1995) The reaction of XeFj with trialkylvinylstannanes scope and some mechanistic observations. Tetrahedron 51 3997-4010... 

A key mechanistic observation in support of an excimer mechanism is the dependence of the quantum yield of reaction upon the aryl halide concentration a[ArX]. Inferential evidence is provided when... 

Zard SZ. The genesis of the reversible radical addition-fragmentation-transfer of thi-ocarbonylthio derivatives from the Barton-McCombie deoxygenation a brief account and some mechanistic observations. Aust J Chem. 2006 59 663-668. 

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