Oxidative activation reaction partners

The catalytic activity of MePc depends on the nature of the ligand in the apical position and should therefore be solvent dependent.[56] From the chromatographic determination of the respective adsorption coefficients of the reaction partners in pre-catalytic conditions, a very pronounced activity difference is found depending on the nature of the solvent used.[64] However, the sequence of the adsorption coefficients is of zeolitic origin and reflects a sorption effect rather than a coordination effect. The respective values of the adsorption coefficients indicate that for the oxidation of alkanes, cyclohexane, with organic peroxide for example, in acetone the oxidant is enriched in the intracrystalline voids, resulting preferentially in peroxide decomposition. In excess cyclohexane, the substrate is enriched in the pores, so that every adsorbed peroxide molecule results in an efficient oxygenation. 

In case of dAMP and dGMP-8 OH, there is redox ambivalence. This is a general property of radicals since they are in-between two stable oxidation states Therefore, they can be oxidized or reduced depending on their reaction partner. The proportion repaired, depends not only on the reducing activities of PPGs but also on their concentration in the repaired system. 

The most severe drawback of this kind of approach is obvious The Fukui function describes reactivity against an isotropic, abstract reactivity bath . If a drug is positioned in a specific orientation within the active site of a cytochrome, the oxidation will not take place at the same site of the ligand as it would in an isotropic situation (e.g., in solution, with a small, sterically less demanding reaction partner). This is a common drawback of any ligand based approach. Combinations of docking approaches and estimations of reactivity like MetaSite... 

Alkylation Using Alkanes. Direct alkylation of pyridines and quinolines using simple alkanes and terf-butyl peroxide as oxidant was developed. This C-C bond forming reaction was carried out by using Sc(OTf)3 as a Lewis acid to increase the reactivity of pyridine and quinoline derivatives (eq 37). Scandium triflate demonstrated the best catalytic activity among the Lewis acids tested. While bis-alkylation product was obtained using quinoline, only mono-alkylation products were afforded when isoquinoline was used. Cycloheptane, cyclohexane, and norbornane were determined to be suitable reaction partners. 

Archier et al. [227] noted that the side chain alkylation of toluene required the simultaneous presence of CS2O bulk oxide and dispersed Cs cations. Addition of boron was found to attenuate the basicity of CS2O. However, too strong basic sites would enhance the decomposition of formaldehyde, formed by dehydrogenation of methanol on the basic sites. This exemplifies the fact that not only the surface species have to be present in the ratios outlmed above. It is also important that the reaction partners are both activated in the same temperature interval aroimd 400 °C. Because the boron-modified zeolites had sites with lower basic strength, decomposition of formalde-hyde/methanol was more retarded and formaldehyde was available for the side chain alkylation, enhancing the activity of these catalysts for side chain alkylation. 

The boronic acid 2 is first converted to an activated species 8 containing a tetravalent boron center by reaction with a base. Halides or triflates (OTf = trilluoromethanesulfonate) are used as coupling partners R-X for the boronic acids. In many cases the rate-limiting step is the oxidative addition. With respect to the leaving group X, the rate decreases in the order ... 

The experiments using Sn adatoms are Intended to test for a correlation between the activity of these species as promoters for CO oxidation kinetics and their influence on the CO vibrational spectrum. Watanabe et. al. have proposed an "adatom oxidation" model for the catalytic activity of these adatoms (23). They propose that the function of the Sn adatoms is to catalyze the generation of adsorbed 0 or OH species at a lower potential than would be required on unpromoted Pt (23). The latter species then react with neighboring adsorbed CO molecules to accomplish the overall oxidation reaction. One implication of this proposed mechanism is that the adsorbed adatom is expected to have little, if any, direct interaction with the adsorbed CO reactant partner. Vibrational spectroscopy can be used to test for such an interaction. 

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