Continuous-flow synthesis of highly functionalized imidazo-oxadiazoles facilitated by microfluidic extraction

A versatile continuous-flow synthesis of highly functionalized 1,2,4-oxadiazoles starting from carboxylic acids is reported. This process was applied to the multistep synthesis of imidazo[1,2-a]pyridin-2-yl-1,2,4-oxadiazoles, using a three reactor, multistep continuous-flow system without isolation of intermediates. This continuous-flow method was successfully combined with a single-step liquid-liquid microextraction unit to remove high boiling point polar solvents and impurities and provides the target compounds in high purity with excellent overall yields.