Mediated homogeneous reductive

Transition Metal-Mediated Homogeneous Reductive Amination... 

Eranen, K., Lindfors, L.E., Klingdted, F. et al. (2003) Continuous reduction of NO with octane over a silver/alumina catalyst in oxygen-rich exhaust gases combined heterogeneous and surface-mediated homogeneous reactions, J. Catal. 219, 25. 

A key step in the macrocyclic-mediated homogeneous electrocatalytic reduction of dioxygen involves encounters between the two species within the electrolyte region immediately adjacent to the electrode surface (see step a in Scheme 3.3). Hence, the course of the process will depend on the relative concentrations, or, more precisely, the fluxes, to be denoted hereafter as njp/Oj" of the mediator and dioxygen. 

In this chapter, we do not attempt to give a comprehensive overview of the field, but we would rather concentrate on results where both enantioselectivity and catalyst activity are relevant to preparative application. In the first section, results obtained with cinchona-mediated homogeneous systems for the reduction of ketones are briefly reviewed. Then, heterogeneous cinchona-modified Pt catalysts applied to the hydrogenation of a-functionalized ketones and cinchona-modified Pd catalysts for the hydrogenation of activated C=C bonds are discussed from a synthetic point... 

Fig. 1.94. Catalytic cycles for the homogeneous reduction of nitrogen oxides by carbon monoxide mediated by various atomic transition metal cations M+. The ions Fe+, Os+, and lr+ were found to be most effectively performing the outhned reaction cycles out of 29 investigated transition metal elements. Adapted from [462]...

Mediator-facilitated reduction/oxidation of a protein requires a rapid turnover of the reduced and the oxidised form of the mediator for both the heterogeneous electron transfer at the electrode and homogeneous electron transfer... 

Aspects featured in a review of asymmetric reductive aminations have included transition metal-mediated homogeneous-, enantioselective organocatalytic-. 

When an outer-sphere aromatic electron donor. Red in Equation 8.9, is used to mediate homogeneously the RBr reduction, an exchange of two electrons and one proton yields the corresponding debrominated and hydrogenated molecule, RH. 

S.3.3 Electrocatalytic Modified Electrodes Often the desired redox reaction at the bare electrode involves slow electron-transfer kinetics and therefore occurs at an appreciable rate only at potentials substantially higher than its thermodynamic redox potential. Such reactions can be catalyzed by attaching to the surface a suitable electron transfer mediator (45,46). Knowledge of homogeneous solution kinetics is often used to select the surface-bound catalyst. The function of the mediator is to facilitate the charge transfer between the analyte and the electrode. In most cases the mediated reaction sequence (e.g., for a reduction process) can be described by... 

Glod G, W Angst, C Holliger and RP Schwartzenbach (1997) Corrinoid-mediated reduction of tetrachloro-ethene, trichloroethene, and trichlorofluoroethene in homogeneous solution reaction kinetics and reaction mechanisms. Environ Sci Technol 31 253-260. 

Schwarzenbach RP, R Stierliu, K Lanz, J Zeyer (1990) Quinone and iron porphyrin mediated reduction of nitroaromatic compounds in homogeneous aqueous solution. Environ. Sci. Technol. 24 1566-1574. 

An elegant example of a paired mediated reaction has been reported by Chaussard and Lahitte [69] EDF (Electricite de France), who use Cr(VI) generated at the anode of a divided cell to oxidize the methyl side chain of a nitro-aromatic and Ti(III) generated at the cathode to reduce the nitro group. The reduction step, due to the faster homogeneous rate can be performed within the cell, whereas the oxidation has to be performed in a stirred tank reactor. 

Two-Electron Catalytic Reactions In a number of circumstances, the intermediate C formed upon transformation of the transient species B is easily reduced (for a reductive process, and vice versa for an oxidative process) by the active form of the mediator, Q. This mechanism is the exact counterpart of the ECE mechanism (Section 2.2.2) changing electron transfers at the electrode into homogeneous electron transfers from Q, as depicted in Scheme 2.9. In most practical circumstances both intermediates B and C obey the steady-state approximation. It follows that the current is equal to what it would be for the corresponding EC mechanism with a... 

Schwarzenbach, R. P., R. Stierli, and J. Zeyer (1990), "Quinone and Iron Porphyrine Mediated Reduction of Nitroaromatic Compounds in Homogeneous Aqueous Solution , Env. Sci. Technol. 24/10, 1566-1574. 

Buschmann, J., W. Angst, and R. P. Schwarzenbach, Iron porphyrin and cysteine mediated reduction of ten polyhalogenated methanes in homogeneous aqueous solution Product analyses and mechanistic considerations , Environ. Sci. Technol., 33, 1015-1020 (1999). 

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