The Knoevenagel reaction in electrochemically activated solvents

The electrochemical activation of organic solvents HS (CH3CN, CH3CH2CN, DMF, DMSO) containing Et4NPF6 as supporting electrolyte (i.e. their electrolysis under galvanostatic control) allows to induce in these solutions, in the absence of any catalyst, the Knoevenagel condensation between CH-acid CH2(CN)2 (1) and carbonylic substrates 2a–e. Reaction products 3a–e were isolated in good yields 97–48%. The progress of the Knoevenagel condensation is affected by Q (number of Faradays per mol of 1 supplied to the electrodes) and, moderately, by the nature of the solvents. The rates of the single steps were compared by elementary voltammetric analysis.