Electrochemical reduction of 4-aminopyrimidine and cytosine in dimethyl sulfoxide

Abstract

The electrochemical reduction in dimethyl sulfoxide of cytosine (4-amino-2-hydroxypyrimidine) and one of its model compounds (4-aminopyrimidine) has been examined. Initially, each pyrimidine (RH) undergoes a reversible, diffusion-controlled one-electron reduction of the 3, 4 N=C double bond to the radical anion (RH-), which can dimerize or can react with the parent compound (father-son reaction) to form the neutral free radical (RH2) and the pyrimidine anion (R-); the radical can dimerize or be further reduced, perhaps after effective protonation: the anion forms a redox couple with Hg(I)-Hg(0). Other coupled reactions, which may occur under suitable conditions, include reaction between anionic dimer (-RH-RH-) and RH proton-assisted decomposition of dimer to form reducible RH+3 and deamination of the two-electron reduction product (RH3) which is a gem diamine, to generate 2-hydroxypyrimidine or pyrimidine itself. The effects on the electrochemical redox pattern of added water, strong acid (HClO4) weak acid (chloroacetic and benzoic acids), and strong base (Et4NOH) are described.