A green, efficient protocol for the catalyst-free synthesis of tetrahydro-1H-pyrazolo-[3,4-b]-quinolin-5(4H)-ones supported by ultrasonicirradiation

Abstract

• A facile, an efficient protocol using ultrasound irradiation. • Synthesis of tetrahydro-1H-pyrazolo-[3,4-b]-quinolin-5(4H)-ones. • One-pot/multi-component green solvent (ethanol) protocol. • Excellent yields (94 to 98%) in short reaction times (< 10 min). A green and efficient protocol for the one-pot, multicomponent, catalyst-free synthesis of tetrahydro-1H-pyrazolo-[3,4-b]-quinolin-5(4H)-ones (4a-j) from the reaction of 5-amino-3-methyl-1-phenylpyrazole, aromatic aldehydes, and dimedone in ethanol as green solvent under ultrasound irradiation is described. This protocol offers several benefits such as simple handling, easy workup process, waste-free, milder reaction conditions, cleaner reaction, environment-friendly, short reaction times, absence of any tedious purification and excellent yields.