Predictable C-H Functionalization of Complex -Fused Azines: A Mechanistically Bound Site-Specific Oxidation.

Direct manipulation of C-H bonds enclosed in complex scaffolds persists today as an elusive disconnection when aiming for high and predictable site-selectivity. Its development toward the late-stage diversification of heterocycles remains of the upmost interest due to their ubiquitous presence in synthetic drugs and new methods consistently emerge to facilitate more versatile routes. The underlying challenge of activating a single C-H bond often leads to isomeric mixtures and a limited scope, which gets magnified in polycyclic frameworks, and the biased selectivity depending on the ring decoration recurrently hampers reliable retrosynthetic analyses. Here we report the straightforward C-H functionalization of multiple -fused azines toward a C-O bond formation with exclusive as well as predictable regiocontrol. Mild conditions enable the presence of a vast variety of motifs with orthogonal reactivity to transition-metals and highly sensitive moieties while also adding a divergent synthetic handle for further derivatizations in >10 distinct heterocyclic scaffolds.