Electrochemical Reduction of Pyrazines into Dihydropyrazines. Preparation of Dihydropyrazines

Abstract

The electrochemical reduction of several pyrazines in an alkaline hydroorganic medium leads to 1,4-dihydropyrazines too easily oxidizable to be isolated. These derivatives isomerize into 1,2- or 1,6-dihydropyrazines, the rate of this reaction depending among other things on the pH and on the cosolvent. The different chemical and electrochemical preparations of dihydropyrazines are discussed. It is shown that 3,6-dihydro-2,5-diphenylpyrazine and 1,6-dihydro-2,5-diphenylpyrazine are in thermodynamic equilibrium.