A facile synthesis of regioisomeric 4-amino- and 6-amino-3-arylpyrazolo[3,4-b]pyridine-5-carbonitriles

Boiling of 3-aryl-1-R-1H-pyrazol-5-amines with ethoxymethylidenemalononitrile in butanol affords 6-amino-3-aryl-1-R-1H-pyrazolo-[3,4-b]pyridine-5-carbonitriles, whereas low temperature condensation of the same reactants followed by heating to 230°C in diphenyl ether gives the isomeric 4-amino derivatives.