The electrochemical oxidation of silver and tetraethylammonium salts of formamides and imides. N,N-Coupling of formanilidyl radicals

Abstract

The electrochemical oxidation of [amide-Ag-amide]Ag, [amide-Ag-amide]Et4N, and [amide]Et4N salts of imides and formanilides, in acetonitrile containing tetraethylammonium tetrafluoroborate, at platinum and vitreous carbon electrodes, is a one-electron and irreversible (αn < 1) process leading to an amidyl radicals that preferentially abstracts hydrogen from the medium to give the parent amide. N,N-Coupling (formation of hydrazine derivatives) was observed in the oxidation of the amide-Ag-amide anions of formanilide and p-methoxyformanilide. No coupling was observed in the oxidation of the amide-Ag-amide anion of p-cyanoformanilide and of imides, and in the oxidation of any of the tetraethylammonium salts (amidyl anions) studied. The formanilidyl radical was trapped by N-tert-butyl-α-phenylnitrone. Attempts to trap the succinimidyl radical by addition to olefins were unsuccessful.