A new preprint from Maud T. H. Tregear, Shisato Yamamura and Darren J. Dixon introduces an iminophosphorane-based Mitsunobu reagent system that addresses several of the transformation’s biggest industrial drawbacks. https://chemrxiv.org/doi/pdf/10.26434/chemrxiv.15006188/v1
Key points for process chemists:
✅ Improved safety – avoids explosive DEAD and thermally unstable DIAD. The active reagent is generated rapidly from commercially available components, and the authors also demonstrate a pre-formed reagent solution that removes the need for end-user azide handling.
✅ Simpler purification – by-products are readily removed by aqueous work-up, avoiding the persistent triphenylphosphine oxide issues that often make Mitsunobu reactions unattractive on scale. Products were isolated on 10–20 mmol scale with aqueous work-up and a short silica plug.
✅ Broader utility – the method enables not only traditional C–O, C–N and C–S bond formation but also C–C bond formation from alcohols, expanding the synthetic toolbox available from a single platform.
✅ Scale-up friendly – operationally simple, one-pot conditions using commercially available reagents, with successful scale-up and late-stage functionalization examples.
While still awaiting peer review, this looks like a thoughtful piece of reagent design that tackles the long-standing safety, purification and scalability challenges associated with classical Mitsunobu chemistry. It will be interesting to see whether it gains traction in route development and process applications.
