Palladium-Catalyzed, Three-Bond Forming Cascade

  • Author: ChemistryViews.org
  • Published: 15 December 2020
  • Copyright: Wiley-VCH GmbH
  • Associated Societies: Royal Society of Chemistry (RSC), UK
thumbnail image: Palladium-Catalyzed, Three-Bond Forming Cascade

Cascade reactions are efficient processes for forming several new chemical bonds in a single step. They can, e.g., be based on radical or cationic intermediates. Radical cascade reactions often have drawbacks such as a need for toxic or hazardous reagents. Visible-light photocatalysis can promote single-electron transfers, and thus, act as an alternative method to initiate radical cascades. Palladium-phosphine complexes, which combine the properties of photocatalysts and cross-coupling-catalysts, are particularly useful for this type of reaction.


Frank Glorius and colleagues, University of Münster, Germany, have developed a three-component radical cascade reaction that involves a radical cyclization/allylic substitution sequence between alkyl/aryl bromides, 1,3-dienes, and nucleophiles. This type of reaction forms three new bonds in one step (example product pictured, newly formed bonds pictured in black). The team used Pd(PPh3)4 as a catalyst together with bis[(2-diphenylphosphino)phenyl] ether (DPEPhos) as a ligand, K2CO3 as a base, and 1,4-dioxane as the solvent. The reactions were performed under blue LED light at 25–30 °C.


The team performed over 80 different examples of this cascade reaction, using both (hetero-)aryl and alkyl bromides, different substituted dienes, and a variety of nitrogen, sulfur, carbon, and oxygen nucleophiles, e.g., amines, sulfinates, 1,3-dicarbonyls, and phenols. The desired products were obtained in moderate to excellent yields. The team also used the reaction in a flow process, which represents the first time a palladium-catalyzed photoredox reaction involving radical species was performed using flow chemistry.


 

 

Article Views: 2377

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 ChemistryViews.org, 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