A Practical and Robust Multistep Continuous Process for Manufacturing 5‑Bromo‑N‑(tert-butyl)pyridine-3-sulfonamide

A multistep continuous flow process involving (1) magnesium–halogen exchange, (2) sulfonylation with sulfuryl chloride, and (3) reaction with tert-butylamine was developed for the synthesis of an arylsulfonamide pharmaceutical intermediate in the synthesis of BMS-919373. The process was successfully implemented, including a robust control strategy to manage the levels of several process impurities, to produce 76 kg of 5-bromo-N-(tert-butyl)­pyridine-3-sulfonamide (2). As the instability of the reactive intermediates and existence of strong exotherms made a batch process unsuitable for production beyond a 1 kg scale, the alternative continuous process led to a practical and robust manufacturing route to the active pharmaceutical ingredient.