Improved Synthesis of Bridged Azobenzenes

  • Author:
  • Published: 05 February 2020
  • Copyright: Wiley-VCH Verlag GmbH & Co. KGaA
  • Source / Publisher: Organic Letters/ACS Publications
  • Associated Societies: American Chemical Society (ACS), USA
thumbnail image: Improved Synthesis of Bridged Azobenzenes

Diazocines are the ethylene-bridged derivatives of azobenzene (pictured). These molecules could be useful as molecular switches that can be isomerized using light. Their stability behaves opposite to the "normal", linear azobenzene: Their (Z)-isomers are thermodynamically more stable than the (E)-isomers. Diazocines, however, are challenging to synthesize. Existing methods give low yields and/or have limited substrate scopes.

Anne Staubitz, University of Kiel and University of Bremen, both Germany, and colleagues have developed a new synthetic approach to diazocines. The method is based on inserting the diazo group between the two tethered benzene rings by consecutive C–N cross-coupling reactions. The team first prepared an ethylene-bridged precursor with two arene rings from two equivalents of a 2-bromobenzyl bromide derivative. Quenching the reaction with I2 gave an iodide-functionalized product. This product was reacted with di-tert-butyl hydrazodicarboxylate (DBADH2) in a copper-catalyzed cascade C–N coupling to give the desired closed ring system, which was then oxidized to the final product.

This three-step process is simple to execute and the desired products are obtained in moderate to excellent yields. The reaction tolerates a variety of substituents on the aryl rings, both electron-withdrawing and electron-donating. Heterocycles (thiophene or pyridine) can also be used in place of benzene derivatives.



Article Views: 1016

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

Bookmark and Share

If you would like to reuse any content, in print or online, from, please contact us first for permission. more

CONNECT: on Facebook on Twitter on YouTube on LinkedIn Sign up for our free newsletter

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