A new and facile synthesis of 3-(2-aryl-6-nitro-1H-indol-3-yl)quinoline-2,4(1H,3H)-diones by sodium alginate as biopolymeric catalyst

New 3-(2-aryl-6-nitro-1H-indol-3-yl)quinoline-2,4(1H,3H)-diones were synthesized, and good-to-excellent yields were achieved through one-pot, three-component condensation of aryl glyoxal monohydrates, 4-hydroxyquinolin-2(1H)-one and 3-nitroaniline using sodium alginate and water/ethanol (1:1) as a green solvent at mild reaction conditions. The noticeable features of the present procedure are mild reaction conditions, economic procedure, availability of starting materials, very simple operation, easy isolation, no need for column chromatography separation and using sodium alginate as a natural polysaccharide that is a transition-metal-free, biodegradable, reusable and commercially affordable catalyst. In addition, sodium alginate was recycled up to five times with no remarkable loss of its catalytic properties. [GRAPHICS] .