FeCl₃-Catalyzed Cross-Coupling for Improving the Synthesis of Upadacitinib

As an oral Janus kinase 1 inhibitor, upadacitinib shows good activity in the treatment of rheumatoid arthritis, especially for other drug-resistant and refractory rheumatoid arthritis patients. A key step in the synthesis of upadacitinib is the introduction of ethyl on the pyrroline ring. Here, a FeCl₃/p-aminophenol catalyst system was used to increase the ethyl introduction for synthesis of pyrroline building blocks of upadaticinib. This catalytic system allows milder reaction conditions and increases the yield of this step by 25% compared to the existing reports, and the scale-up experiment is still effective. In addition, a possible Fe^II/Fe^IV catalytic mechanism for this reaction was also proposed.

Keywords:
iron catalysis; p-aminophenol; cross-coupling; upadaticinib; synthesis