OXIDATIVELY INDUCED NUCLEOPHILIC CAPTURE VS DEGRADATION OF CYCLOPENTADIENYL IRON DERIVATIVES OF SIMPLE CARBOXYLIC-ACIDS AND OF ALPHA-AMINO-ACIDS - A COMPARATIVE-STUDY

The electrochemical behaviour and the chemical oxidation of various cyclopentadienyl iron complexes of simple carboxylic acids and of amino-protected alpha-amino acids have been studied in relation to several factors including the nature of the ligands on the metal (CP, Cp(star), CO, PPh3), the nature of the oxidizing agent (one-electron oxidants such as Cu(OTf)2, FcOTf and CAN or a two-electron oxidant such as NBS) and the medium effects (especially the presence or absence of nucleophilic species). With simple carboxylic acid derivatives either homolytic dissociation (leading to alkyl radicals) or nucleophilic capture of the first-formed iron radical cations is observed, depending on the reaction conditions. With alpha-amino acid derivatives, an oxidative degradation to aldehyde is observed invariably, which is likely to proceed through the successive and transient formation of N-acyl alpha-amino radicals and N-acyl iminium ions.