Synthesis of [1,4]Thiazino[4,3‑a]indol-10-one Derivatives through Radical Anti Aza-Michael Addition of 2′-Aminochalcones

An efficient method for the synthesis of [1,4]­thiazino­[4,3-a]­indole derivatives using sodium chlorodifluoroacetate (ClCF₂CO₂Na) and elemental sulfur as the difluoromethylthiolating reagent system has been developed. Three-component reactions of 2′-aminochalcones, sulfur, and ClCF₂CO₂Na under basic conditions using TEMPO as the oxidant afforded [1,4]­thiazino­[4,3-a]­indol-10-ones containing a difluoromethyl thioether moiety in good yields. Four bonds including one C–N, two C–S, and one C–C bonds are selectively formed in the sequential transformation process.