Synthesis of 4-aryl-1-ethyl-7-methyl-1,9-dihydropyrano[4,3-b]pyrazolo[4,3-e] pyridin-5(4H)-one via a three-component condensation

An efficient synthesis of a series of 4-aryl-1-ethyl-7-methyl-1,9-dihydropyrano[4,3-b]pyrazolo[4,3-e]pyridin-5(4H)-one is reported by condensation of aryl aldehydes, 4-hydroxy-6-methyl-2H-pyran-2-one and 1-ethylpyrazol-5-amine in the presence of 10 mol% molecular I2 in ethanol under reflux conditions through a one-pot reaction. The present method offers several advantages such as use of a metal-free catalyst, being inexpensive, high yielding and environmental acceptability.