Kozo Shirai

Electrolytic Reduction of 2‐Amino‐4‐chloropyrimidine, 2‐Amino‐4‐choro‐6‐methylpyrimidine, and 2‐Aminopyrimidine

2‐Amino‐4‐chloropyrimidine and its 6‐methyl derivative give two polarographic waves in the pH region of 7.4–8.9; 2‐aminopyrimidine and 2‐amino‐6‐methylpyrimidine yield but a single wave in this region. Macroscale electrolysis at lead or mercury cathodes in ammoniacal medium shows that the first wave of the chlorocompounds arises from reductive dehalogenation. The second wave of the chlorocompounds coincides with the single wave of their parent compounds, the 2‐aminopyrimidines, and is ascribed to reduction of the pyrimidine nucleus in both cases. The macroreduction of 2‐aminopyrimidine takes place easily at lead or mercury cathodes in ammoniacal medium to yield 2 ‐aminodihydropyrimidine. The mechanism of reduction is tentatively identified as pure electrolytic reduction.The reduction of 2‐amino‐4‐chloropyrimidine to 2‐aminopyrimidine at cathodes of lead and mercury in aqueous methanolic ammonium sulfate was found to be impractical on a preparative scale. On the other hand at spongy cadmium the reduction takes place in 90% yield. At spongy zinc the yield is poorer due to further reduction of the pyrimidine nucleus. However, for the reduction of 2‐amino‐4‐chloro‐6‐methylpyrimidine zinc is superior to cadmium as a cathode.