A one step synthesis of 1-alkylpyrazolo[5,4-d]pyrimidines

A new synthesis of 1-alkylpyrazolo[5,4-d]pyrimidines is described. The reaction of 4,6-dichloropyrimidine-5-carbaldehyde with various substituted hydrazines provides such compounds in a single step from commercially available starting materials. This method has advantages over methods currently described in the literature for the construction of such ring systems.