Synthesis of benzoxanthene derivatives using Brønsted acidic ionic liquids (BAILs), 2-pyrrolidonium hydrogen sulfate and (4-sulfobutyl)tris(4-sulfophenyl)phosphonium hydrogen sulfate

► Two Brønsted acidic ionic liquids were used as catalysts. ► 14-Aryl-14H-dibenzo[a,i]xanthene-8,13-dione derivatives were prepared. ► 3,4-Dihydro-1H-benzo[b]xanthene-1,6,11(2H,12H)-trione derivatives were synthesized. ► Aryl-5H-dibenzo[b,i]xanthene-5,7,12,14(13H)-tetraone derivatives were prepared. ► The ionic liquids are recyclable catalysts and reuse several times.