One pot synthesis of 1,4-dihydropyridine derivatives was achieved via condensation of various 𝛽-ketoesters with aromatic/aliphatic aldehydes and ammonium acetate. The reaction was catalysed by a stable and reusable Brønsted acidic ionic liquid (IL), 1-methyl-imidazolium trifluoroacetate ([Hmim]Tfa), under microwave (MW) irradiation. The synergistic combination ofMWwith IL can potentially go a long way tomeet the increasing demand for chemical processes. This homogeneous catalytic procedure is simple and efficient. The catalyst can be reused at least four times with almost complete retention in its activity.

Polystyrene divinylbenzene supported sulphanilic acid was prepared, characterized and tested as an acidic catalyst in multicomponent organic synthesis. This is the first report focusing on the development of one-pot solvent-free synthesis of 4,5- dihydropyrano [3,2-c]chromenes under acidic conditions. It proved to be a versatile catalyst for microwave-assisted synthesis of 4,5-dihydropyrano[3,2-c]chromenes. This methodology is mild, high yielding, green and the catalyst could be easily recycled for several times.