The condensation of 1-ethyl-5-aminopyrazole (I) with diethyl ethoxymethylenemalonate (II) by heating at 120 C gives diethyl [((1-ethyl-5-pyrazolyl)amino)methylene]malonate (III), which by heating at 235-5 C in diphenyl ether is converted into ethyl 1-ethyl-4-hydroxy-1H-pyrazolo[3,4-b]pyridine-5-carboxylate (IV). The reaction of (IV) with ethyl iodide (A) and K2CO3 in DMF affords ethyl 1-ethyl-4-ethoxy-1H-pyrazolo[3,4-b]pyridine-5-carboxylate (V), which is condensed with hydrazine in refluxing ethanol with ZnCl2 yielding ethyl 1-ethyl-4-hydrazino-1H-pyrazolo[3,4-b]pyridine-5-carboxylate (VI). Finally, (VI) is condensed with refluxing acetone (B).