A Scalable FlowElectrolysis of Heterogeneous MixturesUsing a Rotating Cylinder Electrode Reactor: Access to a Chiral Iminophosphorane

We report the application of rotating cylinder electrode (RCE) reactors for the electrolysis of heterogeneous reactions in batch and in recirculating flow. A scalable method for the synthesis of an <i>N</i>-cyano iminophosphorane ligand in an RCE reactor is also reported. In the development of this process, a graphite felt attached to the inner impervious graphite was used as a rotating anode, and the outer stainless steel wall of the reactor was used as the cathode. The reaction was first evaluated in batch using a small RCE reactor to optimize the spinning rate, supporting electrolyte, and current density. The optimal batch condition was then scaled up in a medium-sized RCE reactor with modifications to adapt it to a flow process. The electrosynthesis was demonstrated up to a 100 g scale, and the impact of the reaction temperature was investigated. Finally, an operationally simple direct crystallization using water as the antisolvent provided a chiral <i>N</i>-cyano iminophosphorane ligand in 74% isolated yield on a 100 g scale from commercially available (<i>S</i>)-BINAP and bis(trimethylsilyl)carbodiimide.