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.