Carbene-Catalyzed Alkylation of Aldehydes

  • Author:
  • Published: 05 March 2019
  • Copyright: Wiley-VCH Verlag GmbH & Co. KGaA
  • Source / Publisher: Journal of the American Chemical Society/ACS Publications
  • Associated Societies: American Chemical Society (ACS), USA
thumbnail image: Carbene-Catalyzed Alkylation of Aldehydes

N-heterocyclic carbenes (NHCs) can be used as organocatalysts. They can, e.g., promote radical reactions. Thiazolium salts, for example, are NHC precursors that can react with aldehydes in the presence of a base to form enamines. These enamines, so-called "Breslow intermediates", can then perform a single-electron transfer (SET) to various electron acceptors and induce radical reactions.

Kazunori Nagao, Hirohisa Ohmiya, and colleagues, Kanazawa University, Japan, have used an N-2,6-diisopropylphenyl-substituted seven-membered ring-fused thiazolium salt as a precursor for an NHC catalyst (pictured right). This catalyst was used to promote the decarboxylative coupling between aryl aldehydes and redox-active esters derived from tertiary or secondary alkyl carboxylic acids (pictured below).

The reaction was performed using 10 mol % of the catalyst precursor and Cs2CO3 as a base in dimethylsulfoxide (DMSO) at 60 °C. The desired products were obtained in good to excellent yields. The reaction proceeds under mild conditions and is transition-metal-free. The researchers propose a mechanism that involves an SET from an enolate form of the Breslow intermediate.




Article Views: 2299

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