Chemoselective three-phase hydrogenation of an Ombrabulin nitro-stilbene intermediate in a continuous-flow mobile platform

The chemoselective three-phase hydrogenation of an Ombrabulin intermediate based on a nitro-stilbene framework was used as a case study for the formation of the primary amine without affecting the Cdouble bond; length as m-dashC double bond. Two catalysts were tested: Pt nanoparticles supported on ZnO (Pt/ZnO) and agglomerated nitrogen-doped carbon nanotubes (NCNTs). Both materials show a high selectivity at close to full conversion in terms of amine formation (>99%) without changing the configuration of the central stilbene Cdouble bond; length as m-dashC double bond. The continuous hydrogenation process was first tested in lab scale reactors (2 mL and 6 mL) combined with a high pressure interdigital micromixer to ensure efficient three-phase contact. While the specific reactor performance (defined as productivity per unit of reactor volume) was 1.5-fold higher for the Pt/ZnO, the NCNT catalyst was found to be more suitable for flow operation due to a lower pressure drop over the catalytic packed bed. The catalytic reactor was then scaled up to 50 mL and operated in the EcoTrainer mobile modular platform for the hydrogenation of the Ombrabulin intermediate demonstrating a safe, flexible and sustainable fine chemical synthesis.