Jan 29, 2018
A freshly prepared Vilsmier-Haack Reagent.
This stuff was originally described by Anton Vilsmeier and Albrecht Haack in 1927. It is made up by mixing phosphorous oxychloride and a formamide at low temperature. It is a quite practical thing that is widely used for the formylation of various compounds including sensitive compounds e.g.: pyrroles, furanes and various heterocyclic systems.Â
The reagent is formed and reacts as the following mechanism illustrates:
The reaction of the amide with phosphorus oxychloride produces an electrophilic iminium cation. The subsequent electrophilic aromatic substitution produces an iminium ion intermediate, which is hydrolyzed to give the desired aryl ketone or aryl aldehyde.Â
