Synthesis of 2-Substituted Pyrazolo[3,4-d]pyrimidines

The reaction of 1-acetyl-2-phenylhydrazine with ethoxymethylenemalononitrile yielded [(4-cyano-1-phenylpyrazol-3-yl)aminomethylene]propanedinitrile. Hydrolysis followed by annulation with methyl isocyanate provided a synthetic route to 2-phenylpyrazolo[3,4-d]pyrimidines.