Bimolecular reactions of electrogenerated cation radicals of arylmethylselenides

Electrochemical oxidation of arylmethylselenides in acetonitrile in the presence of a strong proton donor follows an E+C2 scheme contrariwise to E+C1+E scheme for the oxidation of alkylarylselenides under non-protic conditions. The reaction constants of first and second order potential determining reactions of electrogenerated cation radicals have different signs which, given the electron transfer reaction constant being the same in both cases, determines different sensitivity of the apparent oxidation potential E1/2 towards the ring substitution

Chemical structure and electrochemical reactivity of organic arylselenides

Factors of chemical structure of arylselenides are considered in relation with their reactivity in the electrooxidation processes following stepwise or dissociative electron transfer (ET) mechanism. The reactivity of electrogenerated cation radicals (CRs) is determined by electronic and stereoelectronic effects affecting the charge distribution. Compensation of the charge on Se and lowering of the energy of the CRs favour the radical properties as compared to the ionic properties of these species. © 1998 OPA (Overseas Publishers Association) N. V. Published by license under the Gordon and Breach Science Publishers imprint

Electrochemical synthesis of cyclic alkylsilanes

The electrochemical reduction of aliphatic α,ω-dibromides in the presence of polychlorosilanes of the formula RnSiCl4-n(n = 0, 2) was shown to afford heterocyclic silicon compounds in good yield (up to 91%). In contrast to non-electrochemical methods of synthesis of silacycloalkanes, based on the ring closure of terminal unsaturated compounds, the electrochemical route does not produce α-methylated byproducts and the heterocycle formation occurs quite selectively. The yield of cyclic organosilicon compounds goes through a maximum for 1,1-dimethyl-1-silacyclopentane (91%) and roughly decreases for 1,1-dimethyl-1-silacyclobutane (18%) and 1,1-dimethyl-1-silacycloheptane (57%). The formation of 5-silaspiro[4,4] nonane by the electrochemical process occurs with high selectivity despite the multitude of possible reaction pathways and the high probability of polymer formation due to the high functionality of the silicon. The relatively high selectivity of the electrochemical ring closure is suggested to be due to the orientating effect of an electrode in the course of an irreversible reduction of a CHal bond in the monosilylated intermediate. A possible mechanism for the process is discussed. © 1995

Electrochemical reactions of organosilicon compounds

Data on the processes of electrochemical reduction and oxidation of organosilicon compounds of various classes as well as on the interaction of these compounds with electrically generated reagents are generalised and surveyed systematically. The electrochemical reactivity of organic derivatives of silicon is considered taking into account their structures and reaction conditions. © 1997 Russian Academy of Sciences and Turpion Ltd

Electrochemical reactions of organosilicon compounds

Data on the processes of electrochemical reduction and oxidation of organosilicon compounds of various classes, as well as of interaction of these compounds with electrogenerated reagents, are generalised and surveyed systematically. The electrochemical reactivity of organic derivatives of silicon is considered with regards to their structure and reaction conditions

The electrochemical oxidation of β-silyl-substituted arylsulfides and arylselenides

The oxidation of ring-substituted aryl(timethylsilylmethyl)sulfides and aryl(trimethylsilylmethyl)-selenides (R = H, Me, MeO, Cl, Br) in MeCN consists of a reversible electron transfer followed by the dimerization of the primary cation radicals and the rupture of the Csp3-chalcogenide bonds of the dicationic intermediate (E + C2 + C1 + E scheme). In MeOH, the oxidation leads to PhSCH2OMe and PhSeCH2OMe resulting from the cleavage of the C - Si bond. The diaryldichalcogenides, which are the main products in MeCN, are practically absent. The electrochemical reactivity of arylchalcogenides is determined by their electronic structure. The specificity of the latter is a decrease in the role of the transmission of the electronic effects through the aromatic ring and an increase in the susceptibility of the heteroatom to direct electronic effects when going from ArSMe to ArSeMe and to their silylated derivatives. © 1998 Elsevier Science Ltd. All rights reserved

Field-effect in electrochemical reactivity of alkylarylselenides

The anchimeric assistance of some substituents bearing the carbonyl group alters the nature of the potential-determining reaction of the cation radicals of alkylarylselenides,-instead of a charge-controlled fragmentation of the first order characteristic for these kinds of particles, the orbital-controlled second order disproportionation of dimerization take place. © 1995

Electrochemical silylation of phenylacetylene

Electrochemical reduction of chlorotrimethylsilane and dichlorodimethylsilane in the presence of phenylacetylene results in silylated ethynyl and ethenyl derivatives - phenyl(trimethylsilyl)acetylene and trimethylsilylstyrene. Under similar conditions, phenyl(trimethylsilyl)acetylene gives a product which corresponds to the addition of Me3Si- anion to the triple bond. By varying the conditions of the electrolysis (the ratio of the reagents, quantity of electricity passed and on carrying out the electrolysis in ECE-mode), either mono-(up to 82% yield) or disilylated (up to 61% yield) products were obtained. The use of the bifunctional chlorosilane as a silylating reagent results in dimethyl bis(phenylethynyl) silane (20% yield). The active silylating species of the process was shown to be the Me3Si--anions, though some assistance from secondary silyl-radicals cannot be ignored. A mechanism of silylation is discussed. Copyright © 1996 Elsevier Science Ltd

Effect of concentration on oxidation potentials of alkylarylselenides

For the processes of electrochemical oxidation of alkylarylselenides, implying the reversible electron transfer followed by potential-determining 1st order or 2nd order reaction (taking into account the concentration dependence of E 1 2 due to consecutive kinetics), an extrapolation of oxidation potentials to infinite diluted solution (C → O) allows the elimination of a non-specific adsorption contribution into the effective E 1 2 value. © 1995