Continuous Flow Synthesis of Azoxybenzenes

  • Author: European Journal of Organic Chemistry
  • Published Date: 11 March 2021
  • Copyright: Wiley-VCH GmbH
thumbnail image: Continuous Flow Synthesis of Azoxybenzenes

Related Societies

Flow reactors are useful tools for continuous organic reactions with immobilized catalysts. Microfluidic reactors (MFRs) with small dimensions have advantages such as excellent heat exchange and a laminar flow. However, the fixation of catalysts within MFRs is quite challenging. To overcome this problem and to improve the catalytic activity inside the flow reactor, catalysts can be integrated within crosslinked polymer networks. Using relatively low crosslinker contents enables reactions inside of swollen, sponge-like, polymer networks. Compared with solid particles, this increases the amount of immobilized and accessible catalyst.

Dirk Kuckling, Paderborn University, Germany, and colleagues have developed an approach for the formation of a wide range of azoxybenzenes via the reductive dimerization of nitrosobenzenes using a microfluidic reactor with gel-bound proline organocatalysts (pictured). The team converted mono‐2‐(methacryloyloxy)ethyl succinate into the corresponding acid chloride using thionylchloride. This acid chloride was then treated with trans‐4‐hydroxy‐L‐proline in trifluoroacetic acid (TFA) to generate a proline ester derivative. Finally, the ester was immobilized via copolymerization with methyl methacrylate (MMA) and ethylene glycol dimethacrylate (EGDMA) to form a gel network.

The resulting gel was placed in an MFR, which was then used for the reductive dimerization of nitrosobenzenes. Azoxybenzenes were formed within minutes at mild conditions in good to almost quantitative yields. According to the researchers, this work could easily be extended to other reactions under continuous flow conditions, e.g., aldol reactions.



Article Views: 1522

Sign in Area

Please sign in below

Additional Sign In options

Please note that to comment on an article you must be registered and logged in.
Registration is for free, you may already be registered to receive, e.g., the newsletter. When you register on this website, please ensure you view our terms and conditions. All comments are subject to moderation.

Article Comments - To add a comment please sign in

If you would like to reuse any content, in print or online, from, please contact us first for permission and consult our permisson guidance prior to making your request

Follow on Facebook Follow on Twitter Follow on YouTube Follow on LinkedIn Follow on Instagram RSS Sign up for newsletters

Magazine of Chemistry Europe (16 European Chemical Societies) published by Wiley-VCH