We describe regioselective synthesis of pyrazolo[3,4-b]quinoline
derivatives by multicomponent reaction of dimedone, 5-aminopyrazolone, and
aromatic aldehydes in presence of H3PW12O40 as catalyst. When this multicomponent reaction was investigated without catalyst under reflux conditions, a mixture
of products was obtained, while the reaction successfully proceeded to formation of
pyrazolo[3,4-b]quinoline in presence of H3PW12O40. Good product yield, short
experimental time, and low-cost catalyst provide convenient synthesis for formation
of pyrazolo[3,4-b]quinoline pharmacological compounds.