Pd-catalyzed C-H annulation reactions of halo- and aryl-heteroarenes were developed using readily available o-bromobiaryls and o-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