Synthesis of Redox-Active Phenanthrene-Fused Heteroarenes by Palladium-Catalyzed C–H Annulation

Abstract

Pd-catalyzed C-H annulation reactions of halo- and aryl-heteroarenes were developed using readily available <i>o</i>-bromobiaryls and <i>o</i>-dibromoaryls, respectively. A variety of five-membered heteroarenes rapidly provided the corresponding phenanthrene-fused heteroarenes, which led to the identification of phenanthro-pyrazole and thiazole as new, stable -2 V redox couples. The flexible syntheses and tunability of the redox potentials of these azole-fused phenanthrenes over a wide range are expected to facilitate their application as redox-active organic functional materials.