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A simple, catalyst-free, green synthetic protocol is described for the one-pot synthesis of pyrazoles via multicomponent reaction of aromatic aldehydes, hydrazine monohydrate and ethyl acetoacetate and malononitrile/ammonium acetate in water under ultrasound irradiation. This protocol avoids traditional chromatography and purification steps and it affords highly selective conversion with no byproducts.

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Catalyst-free multicomponent protocol for the condensation of malononitrile, 2-naphthol/resorcinol, aldehydes, and ammonium acetate in aqueous medium under ultrasound irradiation at 60 o C afforded a wide range of valuable dihydroquinolines in high yields (90-97%) with short reaction times (60-90 min). This approach offers vital improvements for the synthesis of target compounds with regard to yield of products, simplicity in operation, utilization of water as solvent, and green aspects by avoiding the catalysts or solvents.

Using ultrasound irradiation, two simple one-pot multicomponent methods are described for syntheses of highly functionalized pyrimidine/pyridine derivatives in excellent yields in the presence of NaOH at room temperature. While one route involved aromatic aldehyde, thiourea and acetoacetanilide, the other employed aromatic aldehyde, malononitrile and benzyl mercaptane or EtOH. These approaches afford several advantages over former and contemporary reaction methodologies in terms of operational simplicity, simple work-up procedure, higher yield, short reaction time and environment friendly protocols.