Simplified the Production of Important Medicinal Molecules

Researchers at TSU's S.P. Korshunov Research Laboratory No. 13 “Organic Synthesis and Analysis” worked with complex organic molecules with multiple active sites for chemical transformations. The second key component was hydrazine, a highly reactive nitrogen-containing reagent. The scientists discovered that by simply adjusting the proportions of starting materials, they could precisely direct the reaction toward the formation of specific target compounds.

“If the components are mixed in a 1:1 ratio, the reaction follows the first pathway, yielding pyrazolines – cyclic molecules in high demand in pharmacology. The yield of the target product reaches 92%,” explains TSU Professor Alexander Golovanov. “When a significant excess of hydrazine is added, the reaction switches to a second pathway, producing pyrazoles – another class of valuable compounds – with yields of 79–84%.” 

“The research was primarily conducted by my graduate student, Evgeny Zatynatsky, in collaboration with the Ufa Institute of Chemistry and Professor Stanislav Grabovsky,” Professor Golovanov added.

Previously, pyrazoles were synthesized via the classical method involving the reaction of organic compounds with hydrazine. However, this approach had significant drawbacks: it often produced mixtures of structurally similar byproducts that were difficult to separate. Many reactions required elevated temperatures, extended reaction times, or harsh reagents. Most critically, the method lacked flexibility, making it poorly suited for constructing complex molecules with tailored properties, as it did not allow for the straightforward incorporation of specific functional groups essential for biological activity at precise molecular positions.

The new TSU-developed approach effectively overcomes these limitations. The chemists not only documented the outcomes but also thoroughly studied the reaction mechanism using modern analytical techniques, including nuclear magnetic resonance (NMR) spectroscopy and X-ray crystallography. They experimentally demonstrated that pyrazoles and pyrazolines form via parallel pathways rather than through mutual conversion, rendering the method highly selective and efficient.

“The most significant aspect is that we succeeded in isolating pure pyrazolines in their original form,” says Evgeny Zatynatsky. “Previously, their direct synthesis was practically impossible. These molecules are highly reactive: they contain a particularly labile site – the nitrogen atom – which readily reacts even with atmospheric oxygen, leading to compound degradation. Consequently, chemists previously had to employ temporary 'protecting groups' to study them. Under optimized conditions, this reactive site in pyrazolines remains accessible for functionalization with other molecular moieties – a crucial advantage for designing novel compounds and, ultimately, developing more effective pharmaceuticals.”

The research findings were published in Tetrahedron, a prestigious international journal dedicated to organic chemistry and its applications across related scientific disciplines.