Jun-ichi Yoshida

Electrochemical oxidation of organosilicon compounds. I: Oxidative cleavage of carbon-silicon bond in allylsilanes and benzylsilanes

Abstract Electrochemical oxidation of allylsilanes and benzylsilanes in the presence of alcohol, carboxylic acid, or water resulted in cleavage of the carbon-silicon bond and formation of the corresponding ether, ester, or alcohol, respectively.

Electrochemical oxidation of α-silylcarbamates1

Abstract α-Silyl group activates carbamates toward electrochemical oxidationwhich results in facile cleavage of carbon-silicon bond and regioselective introduction of methanol at α-carbon.

New one carbon homologation reagents utilizing electrochemical oxidation of organosilicon compounds

Abstract Phenylthio(trimethylsilyl)methane, phenylthiobis(trimethylsilyl)methane, methoxy(trimethylsilyl)methane, and methoxybis(trimethylsilyl)methane are deprotonated and the resulting anions are alkylated with electrophiles such as organic halides. The alkylation products are readily converted into the corresponding dimethyl acetals or methyl esters by electrochemical oxidation in methanol.

Electrochemical oxidation of α-alkoxystannanes

Abstract The introduction of tin on the carbon adjacent to the oxygen of aliphatic ethers results in significant decrease in the oxidation potentials. The effect of tin is much larger than that observed for silicon. Preparative electrochemical oxidation of α-alkoxystannanes results in selective cleavage of the carbon-tin-bond and introduction of a nucleophile such as an alcohol onto the carbon.

Anodic cyclization of unsaturated α-stannyl ethers. Termination by bromide derived from dibromomethane

Anodic oxidation of unsaturated α-stannyl ethers in Bu4NClO4–CH2Br2 results in effective cyclization and the introduction of bromide into one of the original olefinic carbons; a mechanism involving the coupling between the cyclized carbocation and Br– generated by cathodic reduction of CH2Br2 is suggested.

Electrochemical Reactions of Organosilicon Compounds

Although the electrochemical reactivity of unfunctionalized tetraalkylisilanes is low, organosilicon compounds containing π-systems and heteroatoms exhibit unique electrochemical activitv. Upon α-substitution, silyl groups have electron-accepting effects and upon β-substitution, silyl groups have electron-donating effects to π systems. Silyl groups also have electron-donating effects to β-situated heteroatoms such as oxygen, nitrogen, and sulfur. It is also noteworthy that silyl groups control the regiochemistry of the electrochemical reactions of these compounds. On the basis of such silicon effects, various types of electrochemical reactions of organosilicon compounds have been developed and some of them are utilized as useful tools in organic synthesis. The electrochemical behaviour of organosilicon compounds containing Si-Si bonds is also interesting. Si-Si bonds are susceptible to both anodic oxidation and cathodic reduction. Halosilanes are rather inert to electrochemical redox reactions and are often used as effective trapping agents of carbanion intermediates generated by cathodic reduction of organic halides. However, in the absence of other reducible substrates, halosilanes can be reduced cathodically to form Si-Si bonds.

Oxygenation of γ,δ-unsaturated ketones in the presence of thiophenol. Efficient formation of cyclic peroxides.

Abstract γ,δ-Unsaturated ketones were found to be oxygenated in the presence of thiophenol to give the corresponding cyclic peroxides. The electrochemical initiation accelerated the reaction markedly.

Electrochemical oxidation of 1-trimethylsilyl-1,3-dienes☆

Abstract Electrochemical oxidation of 1-trimethylsilyl-1,3-dienes in methanol afforded 1,1,4-trimethoxy-2-butene derivatives, which were readily hydrolyzed to the corresponding α,β-unsaturated aldehydes. By combination of this electrochemical reaction with the synthesis of 1-trimethylsilyl-1,3-dienes from carbonyl compounds, 1,3-bis(trimethylsilyl)propene provides a β-formylvinyl anion equivalent.

Methoxy(trimethylsilyl)methane and methoxybis(trimethylsilyl)methane as new reagents for homologation

Abstract New synthons of formyl anion (methoxy(trimethylsilyl)methane ( 1 )) and alkoxylcarbonyl anion (methoxybis(trimethylsilyl)methane ( 2 )) have been developed using oxidative cleavage of the carbon-silicon bond by anodic oxidation.

Electrooxidative coupling of α-heteroatom-substituted organostannanes and organosilanes

Anodic oxidation of α-heteroatom-substituted organostannanes in the presence of organosilanes such as allylsilanes and silyl enol ethers results in the facile cleavage of the carbon–tin bond and introduction of allyl and acyl groups onto the carbon, respectively.