Development of a horizontal dynamically mixed flow reactor for laboratory scale-up of photochemical Wohl–Ziegler bromination

Flow reactors with enhanced mixing are of interest to the pharmaceutical industry for a range of photochemical applications. Taylor–Couette (vortex, dynamically mixed) reactors have been reported to have intensified mixing and have been used with heterogeneous systems. Our photochemical workflow has previously been demonstrated for the development of a photochemical Wohl–Ziegler process and scale-up in flow using a plug flow reactor (PFR). In this work, a 20 mL dynamically mixed Autichem, Ltd. prototype photochemical DART reactor (Taylor–Couette reactor) was paired with four custom Kessil PR160L 400 nm lamps. The reactor was evaluated as a 500 g scale-up option for the bromination of ethyl 4-methylbenzoate. Herein we describe our workflow moving from a Pacer International Photochemistry LED Illuminator (HTS system) to the photochemical DART reactor in the scale-up of the synthesis of ethyl 4-(bromomethyl)benzoate via a radical bromination process.