Multigram-scale flow synthesis of the chiral key intermediate of (–)-paroxetine enabled by solvent-free heterogeneous organocatalysis† †Electronic supplementary information (ESI) available: Synthetic procedures, additional batch and flow reaction data, characterization data, copies of NMR spectra and HPLC chromatograms. See DOI: 10.1039/c9sc04752b

The continuous flow synthesis of the chiral key intermediate of (–)-paroxetine is demonstrated via a solvent-free organocatalytic conjugate addition followed by a telescoped reductive amination–lactamization–amide/ester reduction sequence.
The catalytic enantioselective synthesis of the chiral key intermediate of the antidepressant (–)-paroxetine is demonstrated as a continuous flow process on multi-gram scale. The critical step is a solvent-free organocatalytic conjugate addition followed by a telescoped reductive amination–lactamization–amide/ester reduction sequence. Due to the efficient heterogeneous catalysts and the solvent-free or highly concentrated conditions applied, the flow method offers key advances in terms of productivity and sustainability compared to earlier batch approaches.