Targeting a Mirabegron precursor by BH3-mediated continuous flow reduction process

Abstract A continuous-flow reduction of ( R )-2-hydroxy- N -[2-(4-nitrophenyl)ethyl]-2-phenylacetamide, involved in the synthetic pathway of Mirabegron, has been developed. This study demonstrated the possibility to safely handling BH 3 complexes within microfluidic reactors using 2-MeTHF as greener alternative to traditional solvents, and without requiring any additive such as DMI. In addition, NMR and HPLC purity analysis revealed that the sole by-product of this process is the diamine 3, which wouldn’t affect the following synthetic steps towards Mirabegron.