Organic Solvent Nanofiltration as a Tool for Separation of Quinine-Based Organocatalysts

Organic solvent nanofiltration (OSN) promises to be a versatile tool for mild and energy-saving downstream processing. In this case study, the use of modern solvent-resistant membranes to separate organocatalysts from reaction media was investigated. Commercially available membranes with molecular weight cut-offs (MWCOs) between 150 and 500 g mol(-1) were used. They showed high rejections of up to 99% for native catalysts in THF. The enantioselective Henry reaction of ethyl pyruvate and nitromethane catalyzed by benzoyl cupreine was used to demonstrate the potential of this technique for preparative use.