Radical reactions: A novel and effective catalyst-free method of C−H functionalization of alkanes in mild conditions using UV-activated nitrogen oxide (IV) in liquefied carbon dioxide medium allows to produce nitrates and nitro alkanes in high yields.
A novel catalyst-free method for functionalization of unbranched alkanes via radical nitration with UV-activated nitrogen oxide (IV) in supercritical carbon dioxide medium has been developed. The method allows to transform these inactive substrates into corresponding nitrates and nitro compounds with outstanding yields (up to 65 %), using available reagents (NO2, O2) under mild reaction conditions (35–50 °C), and exhibits lower hazards compared to conventional analogues. An improved selectivity towards the nitrates has been achieved by adding pure oxygen to the reaction. Based on changes in reaction rate and product composition, the plausible reaction mechanism for the UV-induced C−H functionalization of alkanes with nitrogen oxide (IV) and pure oxygen has been proposed.Zum Volltext