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A green one----pot three----component synthesis of tetrahydrobenzo [b]pyran and 3,4----dihydropyrano[c]chromene derivatives using Fe 3 O 4 @SiO 2 -imid-PMA n magnetic nanocatalystunder ultrasonic irradiationor reflux conditions Abstract An efficient and environmentally benign procedure for the synthesis of tetrahydrobenzo [b]pyran and 3,4-dihydropyrano[c]chromene derivatives has been developed by one-pot three-component reaction of various aldehydes, malononitrile, and dimedoneor hydroxycoumarinin the presence of Fe 3 O 4 @SiO 2 -imid-PMA n nanoparticles as magnetic catalysts under ultrasonic irradiation or reflux conditions in water.This new procedure has the notable advantages such as operational simplicity, excellent yields, short reaction time, and absence of any tedious workup or purification. In addition, the excellent catalytic performance in water medium and the easy preparation, thermal stability and separation of the catalyst make it a good heterogeneous system and a useful alternative to other heterogeneous catalysts. Also, the catalyst can be easily recovered by a magnetic field and reused for eight consecutive reaction cycles without significant loss of activity.

Fe3O4@SiO2-imid-PMAn: a novel and reusable nanocatalysts.

Synthesis of 14-aryl- or alkyl-14H-dibenzo[a,j]xanthenes and 1,8-dioxooctahydroxanthene derivatives by Fe3O4@SiO2–imid–PMA nanocatalysts.