Accelerating Medicinal Chemistry: A C(sp 3 )‐Rich Fragment Toolbox for Redox‐Neutral Cross‐Coupling

Abstract The hit‐to‐lead phase of drug discovery is frequently bottlenecked by the time‐consuming, iterative synthesis of analogs, especially when incorporating small C(sp 3 )‐rich fragments such as methyl, cyclopropyl, or oxetanyl groups—moieties known to improve drug solubility, bioactivity, and metabolic stability. Conventional approaches like Suzuki or Negishi couplings make use of unstable reagents, high costs, and harsh reaction conditions, while many modern radical‐based methods rely on exogenous redox agents or costly metal catalysts. To overcome these limitations, a toolbox of 15 sulfonyl hydrazide reagents is disclosed to facilitate redox‐neutral, nickel‐catalyzed radical cross‐coupling of 14 distinct small fragments onto (hetero)arenes under mild conditions. These crystalline, bench‐stable reagents are straightforward to synthesize from accessible precursors and require no additional oxidants, reductants, or precious metals, offering a modular and operationally simple platform. Demonstrated across a diverse set of over 60 (hetero)aryl halides, the method exhibits exceptional substrate scope and functional group tolerance, accommodating complex, medicinally relevant scaffolds. Comparative studies with existing techniques underscore its advantages, including a 51% yield for trideuteromethylation of a MET kinase inhibitor precursor (versus a precedented 14% via Kumada coupling) and a streamlined one‐step cyclobutylation of an NLRP3 inhibitor intermediate at 41% yield (versus a known < 5% over a four‐step sequence).