The catalyst-free syntheses of pyrazolo[3,4-b]quinolin-5-one and pyrazolo[4′,3′:5,6]pyrido[2,3-d]pyrimidin-5,7-dione derivatives by one-pot, three-component reactions

Herein we report the syntheses of pyrazolo[3,4-b]quinolin-5-one and pyrazolo[4′,3′:5,6]pyrido[2,3-d]pyrimidin-5,7-dione derivatives by cyclocondensation of 1,3-diketones, 3-methyl-1-phenyl-1H-pyrazole-5-amine and arylglyoxals, under catalyst-free conditions in H₂O/EtOH at reflux in 65–98% and 73–96% yields respectively. This protocol provides mild reaction conditions, good to high yields, non-catalytic, simple procedures and easy isolation of products to structurally diverse tricyclic pyrazolo[3,4-b]quinolin-5-one and pyrazolo[4′,3′:5,6]pyrido[2,3-d]pyrimidin-5,7-dione derivatives, which may have biological and pharmacological activities.