Nonclogging Liquid-WalledContinuous Flow Reactors

Flow chemistry is rapidly growing as it can outperform batch processes in terms of production costs, product quality, and overall environmental footprint. However, the reaction scope in flow is currently restricted due to solid handling limitations. Solids such as heterogeneous catalysts (powders) or precipitates are known to clog flow reactors, leading to periods of downtime to clean (or sometimes even replace) the reactor. Here, we report on liquid-walled continuous flow reactors that are virtually insensitive to clogging (or abrasion) and mix an order of magnitude faster than do solid-wall analogs. Our walls consist of chemically inert ferrofluids that are held in place with permanent magnets, leading to a stable liquid–liquid interface. We show efficient formylation of aryl bromides that is normally plagued by in-line precipitation.