Green one-pot synthesis of 2H-indazolo[2,1-b]phthalazine-triones: a comparative study of heterogeneous solid acid catalysts with magnetic core

The catalytic activity of four heterogeneous solid acid catalysts with magnetic core and sulfonic acid groups is evaluated and compared using one-pot three component synthesis of phthalazine-trione derivatives under solvent-free condition. The NiFe2O4 particles were selected as magnetic core, due to their enhanced chemical and magnetic stability. Furthermore, the desired products were obtained in excellent yields at short reaction times and environmentally friendly condition using the novel and reusable sulfonic acid grafted onto TiO2-coated nickel ferrite nanoparticles. This protocol avoids the use of expensive catalysts, toxic solvents and harsh reaction conditions.