Three-component synthesis of arylsulfonyl-substituted indolo[2,1-]isoquinolinones and benzimidazo-[2,1-]isoquinolin-6(5)-ones by SO insertion and radical cascade cyclization.

An efficient arylsulfonylation/cyclization of 2-aryl--methacryloyl indoles with potassium metabisulfite and aryldiazonium tetrafluoroborates was developed. A series of variously substituted arylsulfonyl indolo[2,1-]isoquinolin-6(5)-ones were formed in moderate to good yields utilization of the nature abundant inorganic salt potassium metabisulfite as a SO surrogate. Additionally, this three-component protocol can also be employed for the synthesis of arylsulfonyl-substituted benzimidazo-[2,1-]isoquinolin-6(5)-ones.