Molecular structure of an organic catalyst containing a sulfur atom
Russian scientists have synthesized organic sulfur-containing compounds that can significantly speed up chemical reactions. The resulting substances are potentially less toxic and more stable than many other catalysts, such as those containing metals or metalloids. Due to this, new compounds can be used in pharmaceuticals for the synthesis of drugs. The results of the study, supported by a grant from the Russian Science Foundation (RSF), are published in The Journal of Organic Chemistry.
Catalysts based on organic compounds have a number of advantages over other types of catalysts, for example, those containing metal cations. They are resistant to oxidation in air and moisture, less toxic and environmentally much safer, due to which they are widely used in the pharmaceutical and chemical industries for the synthesis of drugs and polymers.
It is not easy to create a catalyst in which a non-metal atom would exhibit the properties of a metal necessary to bind to a molecule, activate it, and thereby accelerate the transformation. As a result, in most cases, the catalytic properties of organic compounds are provided by the activity of the atoms of metalloids - compounds capable of exhibiting the properties of both metal and non-metal. Metalloids are among the chalcogens - elements of group 16 of the periodic table of D. I. Mendeleev, and they include selenium, tellurium and polonium. Based on them, it is possible to create analogues of catalysts containing real metals, but these elements have a very high toxicity, which contradicts the very idea of "green" catalysts. Until recently, it was believed that it was impossible to obtain safe organic catalysts based on other chalcogens, oxygen and sulfur, since these chemical elements are typical nonmetals and do not exhibit metallic properties in compounds.
Scientists from St. Petersburg State University have synthesized stable and safe organic catalysts in which the sulfur atom behaves like a metal. The authors evaluated the ability of the proposed substances to accelerate chemical transformations by carrying out the reaction for the synthesis of nitrogen-containing compounds, which is used in the creation of many drugs. It turned out that the resulting catalysts accelerate the reaction under study by an order of magnitude.
Although experiments have shown that sulfur-based compounds are less active than similar selenium-based compounds, they can be considered more promising for use in organic synthesis because they are more environmentally friendly. So, in the case of further processing and disposal, the proposed catalysts can turn into hydrogen sulfide or sulfur oxide, which are many times less toxic than similar selenium compounds (as dangerous as arsenic compounds). In addition, the calculation of the parameters of the chemical reaction showed that the activity of new compounds is higher than that of catalysts containing tellurium, which is often used to accelerate transformations.
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