The continuous flow Barbier reaction: an improved environmental alternative to the Grignard reaction?

A key pharmaceutical intermediate (1) for production of edivoxetine·HCl was prepared in >99% ee via a continuous Barbier reaction, which improves the greenness of the process relative to a traditional Grignard batch process. The Barbier flow process was run optimally by Eli Lilly and Company in a series of continuous stirred tank reactors (CSTR) where residence times, solventcomposition, stoichiometry, and operations temperature were optimized to produce 12 g h⁻¹crude ketone 6 with 98% ee and 88% in situ yield for 47 hours total flow time. Continuous salt formation and isolation of intermediate 1 from the ketone solution was demonstrated at 89% yield, >99% purity, and 22 g h⁻¹ production rates using MSMPRs in series for 18 hours total flow time. Key benefits to this continuous approach include greater than 30% reduced process mass intensity and magnesium usage relative to a traditional batch process. In addition…