CC BY 4.0 · Synthesis 2022; 54(15): 3367-3382
DOI: 10.1055/s-0040-1719922
special topic
Bürgenstock Special Section 2021 – Future Stars in Organic Chemistry

Synthesis of 2,3-Diarylquinoxaline Carboxylic Acids in High-Temperature Water

Fabián Amaya-García
a   Universität Konstanz, Department of Chemistry, Solid State Chemistry, Universitätstrasse 10, 78464, Konstanz, Germany
b   CeMM - Research Centre of Molecular Medicine of the Austrian Academy of Sciences, Lazarettgasse 14, AKH BT 25.3, 1090, Vienna, Austria
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a   Universität Konstanz, Department of Chemistry, Solid State Chemistry, Universitätstrasse 10, 78464, Konstanz, Germany
b   CeMM - Research Centre of Molecular Medicine of the Austrian Academy of Sciences, Lazarettgasse 14, AKH BT 25.3, 1090, Vienna, Austria
› Author Affiliations
This work was funded by the Vienna Science and Technology Fund (WWTF) (Grant No. LS17-051) and the Austrian Science Fund (FWF) (Grant No. START Y1037-N28).


Abstract

Aromatic carboxylic acids are prone to decarboxylate in high-temperature water (HTW). While the decarboxylation kinetics of several aromatic carboxylic acids have been explored, studies on their compatibility with organic syntheses in HTW are scarce. Herein, we report the hydrothermal synthesis (HTS) of 2,3-diarylquinoxaline carboxylic acids from 1,2-diarylketones and 3,4-diaminobenzoic acid. A detailed study of the reaction parameters was performed to identify reaction conditions towards minimal decarboxylation. Thirteen 2,3-diarylquinoxaline-6-carboxylic acids are obtained at temperatures between 150–230 °C within 5–30 minutes. The reported conditions feature comparable performance to those of classic syntheses, avoiding volatile organic solvents, strong acids and toxic catalysts. Decarboxylated quinoxalines arise as side products in variable amounts via direct decarboxylation of the 3,4-diaminobenzoic acid. To completely inhibit the decarboxylation, we show that suitable structural analogues of 3,4-diaminobenzoic acid can act as starting compounds. Thus, ester hydrolysis of methyl 3,4-diaminobenzoate and deprotection of di-Boc-protected 3,4-diminobenzoic can be coupled with the HTS of quinoxaline towards quinoxaline carboxylic acids, while fully avoiding decarboxylated side products.

Supporting Information



Publication History

Received: 09 March 2022

Accepted after revision: 07 April 2022

Article published online:
07 June 2022

© 2022. 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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