A new high efficient and green protocol for the preparation of dihydropyrimido [4,5-b]quinolinetrione derivatives using magnetically solid acid catalyst was presented. High performance solid acid catalyst was prepared through a three-step reaction. Firstly, CoFe 2 O 4 nano particles were synthesized using co-precipitation method. In second step, CoFe 2 O 4 nano particles were coated with SiO 2 shell through treatment with tetraethyl orthosilicate (CoFe 2 O 4 @SiO 2 ). Finaly, CoFe 2 O 4 @SiO 2 was modified with polyphosphoric acid (CoFe 2 O 4 @SiO 2 /PPA) in a simple manner. Green reusable catalyst was characterized in details using FTIR, VSM, TEM, FESEM, EDX and used as catalyst for the synthesis of dihydropyrimido[4,5-b]quinolinetrione derivatives.Reaction was performed under ultrasonic irradiation as green, effective and mild conditions and products were achieved in high to excellent yields.Green and eco-friendly conditions, short reaction times with high yield of products in addition to easy workup are some merits of presented method.
KEYWORDSCoFe 2 O 4 @SiO 2 /PPA, dihydropyrimido[4,5-b]quinolinetrione, green chemistry, solid acidic catalyst, ultrasonic irradiation