Scale-Up and Optimization of a Continuous Flow Carboxylation of N-Boc-4,4-difluoropiperidine Using s-BuLi in THF

• Jean-Paul Kestemont^a
• James R. Frost^b
• Jérôme Jacq^a
• Patrick Pasau^a
• Frédéric Perl^a
• Julien Brown^b
• Matthieu Tissot*^a

• ^aUCB Biopharma SPRL, Avenue de l’industrie, 1420 Braine l’Alleud, Belgium
• ^bUCB, 216 Bath Road, Slough SL1 3WE, United Kingdom

We report a large-scale carboxylation of N-Boc-4,4-difluoropiperidine (1) enabled by a continuous flow process. The flow process involved N-Boc-directed α-deprotonation using s-BuLi in THF and subsequent trapping with CO2 gas. Flow chemistry enabled the safe and scalable preparation of 400 g of carboxylic acid 2 over the course of a day to support our medicinal chemistry research program.

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