ELECTROCHEMICAL OXIDATION OF ACYLSILANES AND THEIR TOSYLHYDRAZONES

Oxidation potentials of acylsilanes were found to be much less positive than those of ketones and aldehydes. The effect of silicon is attributed to the rise of the HOMO level by the interaction between the C-Si sigma-orbital and the nonbonding p orbital of the carbonyl oxygen which in turn favors the electron transfer. Preparative electrochemical oxidation of acylsilanes proceeded smoothly, giving rise to facile cleavage of the C-Si bond and the introduction of nucleophiles such as alcohols, water, and carbamates onto the carbonyl carbon. Electrochemical properties of tosylhydrazones of acylsilanes were also investigated. A decrease in oxidation potential of tosylhydrazones caused by silyl substitution was found to be smaller than that for carbonyl compounds. Preparative electrochemical oxidation of tosylhydrazones of acylsilanes gave the corresponding nitriles with consumption of a catalytic amount of electricity.