The discipline of chemistry deals with understanding (analysis) and making and transforming (synthesis) of matter. The size-range with which chemistry is most concerned with is that of molecules as building blocks of matter. Molecules are nothing but connected atoms, and when aiming at making, i.e. synthesizing, them, it is useful to chemists to subdivide them into subsets, which are so-called "functions" or "functional groups". Although every type of molecule is unique, it's subsets - the functional groups - will eventually be found in many other molecules. Therefore, approaches of generating a particular functional group may eventually benefit the synthesis of numerous molecules bearing ths functional group.

The research group of Miriam Unterlass, CeMM Adjunct Principal Investigator and Assistant Professor at the Technische Universität Wien, in collaboration with two other CeMM research groups, the Menche Lab and the Kubicek Lab, has now developed a novel synthesis for the so-called "quinoxaline" functional group, which is to date reported to be part of more than 100,000 molecules. Quinoxalines are highly important for especially pharmaceutical applications, where they are part of various drugs such as the antibiotic Echinomycin, or Brimonidine a drug to treat ocular hypertension. Furthermore, they display intriguing optoelectronic properties and therefore find application as e.g. dyes or electroluminescent materials. Classically, the quinoxaline function is made by rather harsh, harmful, and tedious routes (toxic organic solvents, expensive catalysts). In contrast, the new synthesis developed by Unterlass and colleagues employs 'hot water' as solvent and is therefore termed hydrothermal synthesis (HTS). Through the developed HTS, quinoxalines can be generated within only 10 minutes. In fact, the synthesis is the least harmful of all routes reported to date, as Amaya-García et al. show in their recently published manuscript, through a large-scale computational comparison with all existing alternatives. Moreover, the researchers show that the generated quinoxalines exhibit fluorescence and can be used to stain different cell lines.

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The study "Green hydrothermal synthesis of fluorescent 2,3-diarylquinoxalines and large-scale computational comparison to existing alternatives" was published online ahead of print on ChemSusChem on 4 March 2021. DOI: https://doi.org/10.1002/cssc.202100433

Authors: Fabián Amaya-García, Michael Caldera, Anna Koren, Stefan Kubicek, Jörg Menche, Miriam M. Unterlass

Funding: This project was funded by the Austrian Science Fund (FWF) under grant no. START Y1037‐N28 and the Vienna Science and Technology Fund (WWTF) under grant number LS17‐051.