Efficient access to 1,4-benzothiazine: palladium-catalyzed double C-S bond formation using Na2S2O3 as sulfurating reagent.

A novel Pd-catalyzed double C-S bond formation coupling reaction has been developed. This protocol, in which Na2S2O3 was used as sulfurating reagent in metal-catalyzed reactions, provides an efficient method for the synthesis of substituted 1,4-benzothiazine derivates, which are structural elements of numerous bioactivity molecules rendering this protocol attractive to both synthetic and medicinal chemistry.