New applications of phosphoric acid supported on alumina (H3PO4-Al2O3) as a reusable heterogeneous catalyst for preparation of 2,3-dihydroquinazoline-4(1H)-ones, 2H-indazolo[2,1-b]phthalazinetriones, and benzo[4,5]imidazo[1,2-a]pyrimidines

An eco-friendly procedure for synthesis of 2,3-dihydroquinazoline-4(1H)-one, 2H-indazolo[2,1-b]phthalazinetrione, and benzo[4,5]imidazo[1,2-a]pyrimidine derivatives by three-component reaction, with phosphoric acid supported on alumina as catalyst, is described. Noticeable features of the method are that it is solvent-free, work-up is easy, yields are excellent, and the catalyst is reusable.