Gram-scale synthesis of the N-phenyl phenothiazine photocatalyst by benzyne addition

Abstract

N-phenyl phenothiazine is one of the most reducing photoredox catalysts. Its synthesis commonly requires transition metal-catalyzed cross-coupling reactions. Here, we show the syntheses of four aryl phenothiazines via a benzyne route, including a multigram-scale synthesis of N-phenyl phenothiazine. While yields are modest, the simplicity, low cost, and lack of requirement for cross-coupling catalysts in this synthesis will be attractive to users of this photocatalyst.