Redox behaviour of (Z)-2-(5-ethoxycarbonylmethyl-N-methyl-4-oxothiazolidin-2-ylidene)-1-phenylethanone in aprotic medium: Spectroelectrochemical study and theoretical modelling

Electrochemical and spectroelectrochemical study of the reduction of (Z)-2-(5-ethoxycarbonylmethyl-N-methyl-4-oxothiazolidin-2-ylidene)-1-phenylethanone in an aprotic solvent (dimethylsulfoxide (DMSO)) has been presented. The results indicate an ECCEE reaction sequence, whereby the chemical step is a protonation of the anion radical electrogenerated in the first electron transfer step by the enol tautomer of the substrate. The gas phase and solvent dependent PM3 semiempirical modelling allowed further rationalization of experimental data pertinent to the suggested electrochemical redox mechanism and the reactivity of the intermediate species involved.

► Cyclovoltammetric and in situ spectroelectrochemical study in aprotic and basic media.
► Proposed mechanism: an ECCEE reaction sequence.
► Keto–monoenol tautomerization as the chemical step following the first electron transfer.
► PM3 MO modelling accounts for the experimental results.