Biopolymeric alginic acid: An efficient recyclable green catalyst for the Friedel-Crafts reaction of indoles with isoquinoline-1,3,4-triones in water

Abstract

A very cheap, naturally available, nontoxic and biopolymeric alginic acid has been found to be an efficient, recyclable and heterogeneous green catalyst for the Friedel-Crafts reactions of indoles at C-3 and C-2 positions with isoquinoline-1,3,4-triones and hydroxyindolyl derivatives in water under mild conditions. These operational simple procedures furnish good to high yields of corresponding synthetically as well as biologically interesting functionalized 4-hydroxy-4-indolylisoquinoline-1,3(2H,4H)-diones and 4,4-diindolylisoquinoline-1,3(2H,4H)-diones, respectively. Moreover, alginic acid could be recovered and reused several times (up to 5 times) without significant loss in activity. © 2015 Elsevier Ltd.