Enantioselective synthesis of a 2,3-benzodiazepine intermediate of BET inhibitor BAY 1238097 via catalytic asymmetric hydrogenation

Herein, we report the first example of the asymmetric hydrogenation of a prochiral benzodiazepine substrate as key transformation in a pilot-scale synthesis of BET inhibitor BAY 1238097. High-throughput screening in a parallel reactor enabled us to identify an efficient catalyst based on Ir and a chiral bisphosphine. An additive screening allowed significant reduction of catalyst loading. Ultimately, the hydrogenation was performed on a kilogram scale leading to the production of 27 kg of the desired product with an enantiomeric excess of 99% after crystallization.