Background:
Quinoxaline 1,4-dioxides have a broad range of biological activity that causes a
growing interest in their derivatives for drug discovery. Recent studies demonstrated that quinoxaline 1,4-
dioxides have a promising anticancer activity and good hypoxia-selectivity.
Objective:
The preparation, isolation, structure characterization, and screening for anticancer activity of the
first representatives of 6-substituted quinoxaline-2-carbonitrile 1,4-dioxides have been described.
Material and Method:
A series of 7- and 6-halogeno-3-phenylquinoxaline-2-carbonitrile 1,4-dioxides was
synthesized by the Beirut reaction. The cytotoxicity was assessed by MTT test (72 h incubation) in normoxia
(21% O2) and hypoxia (1% O2) conditions.
Results:
We found that during the Beirut reaction between a benzofuroxan bearing an electron withdrawing
group and benzoylacetonitrile in the presence of triethylamine, in addition to well-known 7-substituted
quinoxaline-2-carbonitrile 1,4-dioxides 7-11a, the 6-isomers 7-11b are formed. Moreover, the yield of the 6-
isomers increased with the increase in the electron-withdrawing character of the substituent. For benzofuroxans
with CO2Me and CF3 groups, 6-substituted quinoxaline-2-carbonitrile 1,4-dioxides 10-11b were the major
products. Despite similarities in physicochemical and spectroscopic properties, the obtained isomers exhibit
considerable differences in their anticancer activity and hypoxia selectivity.
Conclusion:
Substituents and their electronic effects play a key role in the formation of 7- and 6-substituted
quinoxaline-2-carbonitrile 1,4-dioxides in the Beirut reaction and in the cytotoxicity properties of the obtained
isomers.
New magnetic nanomaterials with magnetization up to 32 Gs·cm3/g were synthesized from highly branched ferrocene-containing polymers by thermal structural transformations in a field of 2.5 kOe. The structure and properties of the prepared polymers were studied by IR spectroscopy, transmission electron microscopy (TEM) and thermogravimetric analyses. According to IR spectroscopy the content of 1,3,5-substituted benzene rings in the ferrocene-containing polymer increases at 500°C. X-ray diffraction study showed that iron in such a sample is present exclusively in the form of Fe3O4 magnetite. As the heating temperature increased to 600°C, the composition of the samples became more complex: along with magnetite they contain cementite Fe3C and wustite FeO.97O. The magnetization of the ferrocene-containing polymer depends on the synthesis and heat treatment temperature. For a sample synthesized at 140°C the formation of a magnetically ordered phase begins at 500°C, and at 800°C the magnetization reaches a maximum value of 32 Gs·cm3/g. The average size of magnetic particles according to TEM analysis was 8-26 nm. The principal possibility of controlling the size and composition of the nanoparticles, as well as their magnetization depending on the conditions of production and the temperature of polymer structuring is shown. The obtained results provide a good basis for the directed synthesis of magnetic ferrocene-containing polymers with preset characteristics.
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