Nitronium tetrafluoroborate reactions with alkenes

The reaction of alkenes with nitronium tetrafluoroborate in anhydrous acetonitrile/dichloro-methane solution at low temperature afforded, after aqueous workup, / -acetamido nitro compounds (Table 6, Method A). These result from preliminary attack of the nitronium ion on the alkene followed by addition of acetonitrile as the nucleophile to the intermediate carbonium ion thus formed, and hydrolytic workup140. Acceptable yields of the adducts were obtained only from phenyl-substituted alkenes141. 

Nitroacetamidation of conjugated dienes is efficient when a solution of nitronium tetrafluoroborate in acetonitrile obtained by anodic oxidation of dinitrogen tetroxide is used substantial amounts of both 1,2- and 1,4-adducts are usually obtained.34 Some conjugated nitroalkenes can be readily prepared by reaction of alkenes with sodium nitrite and iodine under mild conditions (Scheme 158).347... 

---