Development of a Green and Sustainable Manufacturing Process for a Key Intermediate to Nemtabrutinib (MK-1026): Sequential Deprotonation–Lithiation as a Batch–Flow Process

Nemtabrutinib (MK-1026) is a novel oral Bruton’s tyrosine kinase (BTK) inhibitor for treatment of B-cell cancers. An initial synthetic supply route to generate ketone 3 relied on the generation of a highly reactive transient intermediate and the use of n -butyllithium. Cryogenic temperatures (−60 °C) were also required to achieve a modest 61% yield, with one major impurity, resulting from dehalogenation, accounting for the majority of the mass balance. An alternative process was developed to increase the yield and decrease the dependence on cryogenic temperatures, and this advancement was critical to the long-term robustness of the commercial process. Key advancements included performing the requisite deprotonation and metalation steps sequentially and performing the metalation and quench steps in flow. The final flow process was rapidly scaled from grams to tens of kilograms and has been successfully executed in a production facility.