CC BY 4.0 · SynOpen 2023; 07(04): 674-679
DOI: 10.1055/a-2189-3334
paper

Truly Catalytic Gewald Synthesis of 2-Aminothiophenes Using Piperidinium Borate (Pip Borate), a Conjugate Acid–Base Pair

Kanchan D. Gavali
,
This work was supported by the Council of Scientific and Industrial Research New Delhi, India, under grant (09/991(00062)/2020-EMR-I).


Abstract

The Gewald reaction has been well-known for more than half a century as an excellent method to provide bioactive 2-aminothiophene heterocycles from the reaction of carbonyl compounds, α-cyanoacetates, and elemental sulfur, in the presence of amines, in stoichiometric amounts. This work describes the use of salts of boric acid as conjugate acid-base pairs in a truly catalytic amount for the cyclocondensation of ketones with active methylenes such as malononitrile, ethyl cyanoacetate, and benzoyl acetonitrile with sulfur to give 2-aminothiophenes via the Gewald reaction. The present protocol is also applied for synthesizing Tinoridine, an anti-peroxidative NSAID, with excellent yield. Additionally, the catalyst has great recyclability and reusability.

Supporting Information



Publikationsverlauf

Eingereicht: 05. September 2023

Angenommen nach Revision: 09. Oktober 2023

Accepted Manuscript online:
10. Oktober 2023

Artikel online veröffentlicht:
23. November 2023

© 2023. The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes or adapted, remixed, transformed or built upon. (https://creativecommons.org/licenses/by/4.0/)

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