With a robust set of optimized conditions in hand, the substrate scope was explored as depicted in Table with a focus only on 23 known structures from the medicinal chemistry literature (9 patents, 5, 12 2 publications ). Strikingly, all of these disclosures use only two general strategies for synthesis, both of which rely on classic 2-electron disconnections: (1) Pd-cross-coupling of protected pyridine (itself requiting a 3-step synthesis), and ( ) stepwise glutarimide ring synthesis through condensation, hereby referred to as [Lit. A] and [Lit. B], respectively. For instance, seemingly simple structures 10 and 14 were previously prepared by either [Lit. A] for 10 or [Lit. B] for 14 in 2-4 steps and 4-75% overall yield respectively. In contrast the same structures were accessed via GCC in a single step when coupled with the corresponding aryl iodide in 42-84% yield. For completeness sake, several known radical cross-couplings (chemical, electrochemical, photochemical) were benchmarked on seven different substrates and the highest yield observed for any substrate or condition was less than 5% (compound with most entries giving no observable product. In all cases debrominated glutarimide was observed as the major product. GCC tolerates numerous functional groups and displays a high degree of chemoselectivity that appears to be not only superior to other radical methods tested but also the more laborious literature conditions. Thus, unactivated aryl fluorides , electron-rich arenes , free alcohols (20, 33), pyridines , pyrimidines (20), indoles (19), labile acetate (28), indazoles (29), isoquinolines (32), quinolones (30), oxazolidinones (31), and even aryl bromides (34) were successfully employed. Remarkably, even a nitro-containing arene was tolerated under these mildly reductive conditions (18) with no reduction to the amine. The choice of aryl halide coupling partner with 1 in the GCC deserves further comment. In general, for electronrich (hetero)arenes, an aryl iodide is preferrable whereas aryl bromides are acceptable when using electron-poor (hetero)arenes. For medicinal chemistry explorations this is advantageous for orthogonal synthesis as the iodide can react preferentially in GCC followed by conventional metal(Pd/Ni/Cu/Fe)-couplings of the remaining aryl bromide (34). In terms of limitations, electron-rich (hetero)aryl bromides, imidazoles, pyridinones, and isoindolinones are so far not amenable to GCC (see SI for listing of the currently known problematic coupling partners).