Visible-Light-Induced Synthesis of Alkylsulfonated Isoquinolinones from 2-Aryl Indoles/Benzimidazoles through Insertion of Sulfur Dioxide

Abstract

A visible-light-induced three-component reaction of 2-aryl indoles/benzimidazoles, Hantzsch esters, and sodium pyrosulfite through a radical cascade cyclization process with the insertion of sulfur dioxide is described. It provides a novel and powerful way for the synthesis of alkylsulfonated isoquinolinones. Hantzsch esters and Na2S2O5 are employed as alkyl radical precursors and SO2 surrogate, respectively. This transformation exhibits good functional group tolerance and substrate applicability under mild conditions.

Oxidant-Assisted Sulfonylation/Cyclization Cascade Synthesis of Alkylsulfonylated Oxindoles via the Insertion of SO2

“…In recent years, the 4-alkyl-substituted Hantzsch ester derivatives were found to be excellent alkylation reagents via the single-electron transfer process . Encouraged by the significant progress in the radical alkylation of the various alkenes by employing 4-substituted Hantzsch esters as radical precursors and our group’s continuous research interests of the in situ insertion of sulfur dioxide reactions, we envisioned that the alkylsulfonated oxindole derivatives might be produced from the reaction of 4-substituted Hantzsch esters, sulfur dioxide, and N -arylacrylamides under oxidation conditions. Following our continuous interest in the generation of the alkylsulfonyl radical intermediates via alkyl radical intermediates in situ trapping sulfur dioxide by using DABSO or inorganic sulfites as the source of sulfur dioxide, we intend to employ 4-substituted Hantzsch esters to produce the alkyl radical intermediates, which can further react with inorganic sulfites to give the alkylsulfonyl radicals.…”