Palladium(II)-Catalyzed Intramolecular Oxidative C-H/C-H Cross-Coupling Reaction of C3,N-Linked Biheterocycles: Rapid Access to Polycyclic Nitrogen Heterocycles.

A Pd(II)-catalyzed intramolecular oxidative C-H/C-H cross-coupling has been developed for the direct construction of valuable polycyclic heteroarene scaffolds. From a retrosynthetic point of view, the strategic formation of a C-C bond via C(sp)-H/C(sp)-H dehydrogenative coupling across C3,N-linked biheterocyclic precursors may be useful in de novo syntheses of indole-derived natural products and pharmaceuticals. The reaction exhibited good functional group/heterocycle tolerance, and a proposed mechanism involving an azoylpalladium complex is also supported.