Tandem Continuous Flow Curtius Rearrangement and Subsequent Enzyme-Mediated Impurity Tagging

The use of continuous flow as an enabling technology within the fine chemical and pharmaceutical industries continues to gain momentum. The associated safety benefits with flow for handling of hazardous or highly reactive intermediates are often exploited to offer industrially relevant and scalable Curtius rearrangements. However, in many cases the Curtius rearrangement requires excess nucleophile for the reaction to proceed to high conversions. This can complicate work procedures to deliver high-purity products. However, tandem processing and coupling of the Curtius rearrangement with an immobilized enzyme can elegantly facilitate chemoselective tagging of the residual reagent, resulting in a facile purification process under continuous flow.