Development of a Continuous Flow Grignard Reaction to Manufacture a Key Intermediate of Ipatasertib

This article outlines the development of a continuous flow process for the manufacture of a key intermediate of the active pharmaceutical ingredient ipatasertib for the treatment of metastatic castration-resistant prostate cancer and triple-negative metastatic breast cancer. The reaction sequence incorporates multiple telescoped unit continuous operations, including a Br/Mg exchange reaction leading to intramolecular cyclization of the magnesium species onto a neighboring nitrile group to form a five-membered ring in 5-exo-dig fashion. The product from the reaction mixture is obtained after continuous aqueous acidic hydrolysis, neutralization/extraction, water wash, and phase separation. Each of these unit operations took place in a cascade of continuous stirred tank reactors. The control strategy was refined via a series of continuous lab studies at 20 g/h using a Design of Experiments approach to define process parameter ranges and to help identify any criticality therein. The learnings from this laboratory study served as a basis for the construction of a suitable pilot-plant facility, where the control strategy was verified at a representative manufacturing scale of about 1.0 kg/h.