Bidentate Directing-Enabled, Traceless Heterocycle Synthesis: Cobalt-Catalyzed Access to Isoquinolines

Traceless
heterocycle synthesis based on transition-metal-catalyzed
C–H functionalization is synthetically appealing but has been
realized only in monodentate directing systems. Bidentate directing
systems allow for the achievement of high catalytic reactivity without
the need for a high-cost privileged ligand. The first bidentate directing-enabled,
traceless heterocycle synthesis is demonstrated in the cobalt-catalyzed
synthesis of isoquinolines via 2-hydrazinylpyridine-directed C–H
coupling/cyclization with alkynes. Convenient directing group installation
through a ubiquitously present ketone group allows synthetic elaboration
for complex molecules.