Optimized Synthesis of an Abemaciclib Intermediate: Improved Conditions for a Miyaura Borylation/Suzuki Coupling Process

Improved reaction conditions have been developed for a telescoped Miyaura borylation/Suzuki coupling process, which is utilized in the synthesis of an abemaciclib intermediate. Key improvements include the in situ generation of a lipophilic base and tailored ligand selection for each palladium-catalyzed step. Optimizing ligand choice significantly reduced aryl scrambling, a major source of impurities in the borylation step. Additionally, the process improvements led to shortened reaction times and lower palladium loadings, resulting in a more efficient, higher-yielding process.