Palladium-Catalyzed Three-Component Synthesis of Phenothiazines

Significance

A Pd-catalyzed three-component synthesis of phenothiazines in which one C-S and two C-N bonds are formed is reported. Of the various ligands screened, dppf showed best performance. Aliphatic primary amines, benzylamines, and anilines were effective amines in this reaction. However, the reaction is limited to the use of 1,2-iodobromobenzenes, as it was shown that 1,2-dibromobenzenes gave much lower yields. ­Although microwave irradiation was used as an effective method of heating, control experiments in an oil bath indicated that similar yields of products are obtained under the latter conditions. Yields were generally good and the substrate scope was well studied with respect to the amine and the ­iodobromobenzene but not the o-halothiophenol component, perhaps due to availability.