A safe method for the nitration of alkanes was proposed at the ZIOC

The problem of direct C-H functionalization of non-activated alkanes has not lost its relevance for more than a century. The extremely low reactivity of most saturated hydrocarbons makes it difficult to use them as reagents in organic synthesis. Activation of alkanes usually requires harsh conditions: in industry, alkanes are nitrated with nitrogen oxides in the gas phase at temperatures up to 450 °C. Such processes are explosive, have low selectivity, and can only be used to obtain the simplest molecules.

Researchers of the I.N. Nazarov Laboratory of Fine Organic Synthesis of the Zelinsky Institute proposed a safe method for the functionalization of C5, C6, C8 cyclic alkanes with nitric (IV) oxide at a 35-50 ºС and UV irradiation in supercritical carbon dioxide, an accessible, non-flammable, and environmentally friendly solvent. Under the proposed conditions, nitroalkanes are formed in 19–25% yields, which significantly exceeds the performance of known liquid-phase processes (4–5%). When molecular oxygen is added to the reaction mixture, the process is accelerated, and the corresponding nitrates become the main products. The scientists demonstrated the applicability of the developed method for the functionalization of linear alkanes using propane as an example. A radical mechanism of reactions induced by UV light has been proposed.

Source:

Roman E. Ivanov, Mikhail N. Zharkov, Sergei G. Zlotin UV-induced C-H functionalization of alkanes with NO2 in supercritical carbon dioxide ChemPhotoChem 2022, e202200084. DOI: 10.1002/cptc.202200084.