A series of 8-alkyl- and 8-aryl-8,9-dihydro-7 H-isoindolo[5,6- g]quinoxaline-7,9-diones were synthesized using sultine chemistry as a key step in good yield. These compounds were evaluated for their in vitro cytotoxicity against six human cancer cell lines (HCT15, SK-OV-3, A549, SNB19, MCF7 and MCF7/ADR).