Tris(dichloromethyl)amine (4), triformamide (1) and tris(diformylamino)methane (“formylaalen”) (2) can be activated by addition of trifluoromethanesulfonic acid. The formylating systems thus formed transform activated aromatic compounds, such as toluene, anisole or 2,4- dimethoxybenzene to the corresponding aldehydes. The formylating ability of systems from 4 and superacids, such as FSO3H, FSO3H/SbF5, C4F9SO3H, and mixtures of aluminum chloride with C4F9SO3H and chlorosulfonic acid, respectively, is compared. In general, low reaction temperatures (−20 to −10 °C) are necessary to obtain aldehydes with acceptable to good yields. Remarkably, at higher temperatures (~ 100 °C) compound 4 can also act as a formylating agent in the presence of suitable zeolites, as e. g. zeolite HBEA. Reaction mechanisms of the new formylation reactions are proposed.
Arene Chemistry: Reaction Mechanisms and Methods for Aromatic Compounds
