Safe and Fast Flow Synthesis of Functionalized Oxazoles with Molecular Oxygen in a Microstructured Reactor

The synthesis of hydroperoxymethyl oxazoles by oxidation of alkylideneoxazoles with molecular oxygen was implemented in a microstructured reactor for increased safety and larger-scale applications. Elaborate studies on the influence of pressure and temperature were performed, and the apparent activation energy for the oxidation reaction was determined. Elevated temperatures up to 100 degrees C and pressures up to 18 bar(a) led to a conversion rate of approximately 90% within 4 h of the reaction time, thus displaying the high potential and beneficial effect of using a microreactor setup with liquid recycle loop for this oxidation. The in situ reduction of the generated hydroperoxide functionality shows the capability of this setup for follow-up transformations.