Potassium carbonate-mediated tandem C-S and C-N coupling reaction for the synthesis of phenothiazines under transition-metal-free and ligand-free conditions

An efficient potassium carbonate-mediated tandem C-S and C-N coupling reaction between N-(2-iodophenyl) acetamides and 2-halo-benzenethiols has been developed. This protocol affords a simple and efficient approach for the construction of phenothiazine derivatives without the need for addition of transition-metal catalyst or ligand for the first time. Furthermore, the reaction can be easily performed on a large scale.