Nitroalkenes are useful intermediates in organic synthesis. They can be prepared, e.g., via the nitration of alkenes using reagents such as gaseous NO and NO₂ or metal nitrates/nitrites as nitro sources along with oxidants. However, these existing methods can have some drawbacks, e.g., low selectivity or limited functional group tolerance.

Zhong-Quan Liu, Nanjing University of Chinese Medicine, China, and colleagues have developed a method for the radical nitration of alkenes using NaNO₂, mediated by I₂O₅, to obtain nitroalkenes (general reaction pictured). The team proposed that I₂O₅ can serve as a green and safe single-electron oxidant to generate NO₂ radicals from NaNO₂. They reacted a variety of alkenes with NaNO₂ in the presence of I₂O₅, using a CH₂Cl₂/H2O mixture as the solvent. The reactions were performed at room temperature.

Using this approach, the desired nitroalkenes were obtained in good to high yields. The team proposes a mechanism that involves a single-electron oxidation of NO₂^– to give an NO₂ radical, which reacts with the alkene to give a carbon-centered radical intermediate. A deprotonation step and another single-electron oxidation then give the nitroalkene. According to the researchers, the method provides a mild, safe, and environmentally friendly path to a broad range of nitroalkenes.

• A Free Radical Nitration of Olefins with NaNO₂/I₂O₅,
  Xuan Huang, Huichao You, Fang Fang, Fan Wang, Zhongquan Liu,
  Chem. Commun. 2023.
  https://doi.org/10.1039/D3CC04275H