Dual Reactivity of the Formyl Cation as an Electrophile and a Broensted Acid in Superacids

Article abstract of DOI:10.1021/jo00117a041

The nature of the formyl cation in the Gattermann-Koch formylation was studied by comparing the formylation with the acetylation and sulfonation in CF3SO3H-SbF5 and FSO3H-SbF5, respectively.The results of the kinetic studies in CF3SO3H-SbF5 showed that the formyl cation has dual reactivity as an electrophile and as a Broensted acid.Upon comparing the formylation with the sulfonation in FSO3H-SbF5, it was found that the protonated aromatic compounds also act as Broensted acids to produce formyl cations.Therefore, the formylation has a priority over other typical electrophilic substitutions under conditions where most of aromatic compounds are protonated because the formyl cation is reproduced close to the aromatic compounds by the protonation of CO with not only superacids but also protonated aromatic compounds.