Vilsmeier Formylation

Abstract

This reaction is a formylation of an electron‐enriched aromatic or heterocyclic compound using N , N‐ disubstituted formamide (e.g., DMF) as the acylating agent in the presence of an activating reagent, such as POCl 3 and is generally known as the Vilsmeier formylation. The study finds that this reaction is applicable only for aromatics that are more reactive than benzene. In addition, the Vilsmeier formylation has a similar trend of regioselectivity as observed in the Friedel‐Crafts acylation, which primarily depends on the electron density of the attacked site on the substrate. Furthermore, the benzene ring can be easily formylated when the ring is activated by complexing with Mn(CO) 3 and many acyl chlorides have been suggested as effective activating reagents. Overall, this reaction is a very useful formylation method and has wide applications in the organic synthesis.