The Vilsmeier Reaction allows the formylation of electron-rich arenes.
Mechanism of the Vilsmeier-Haak Reaction
The formylating agent, also known as the Vilsmeyer-Haack Reagent, is formed
in situ from DMF and phosphorus oxychlorid:
An electrophilic aromatic substitution leads to α-chloro amines, which are
rapidly hydrolyzed during work up to give the aldehyde:
An Efficient Route to 1-Vinylpyrrole-2-carbaldehydes
A. I. Mikhaleva, A. V. Ivanoc, E. V. Skital'tseva, I. A. Ushakov, A. M.
Vasil'tsov, B. A. Trofimov, Synthesis, 2009,
Metal-Free One-Pot Conversion of Electron-Rich Aromatics into Aromatic Nitriles
S. Ushijima, H. Togo, Synlett, 2010, 1067-1070.
Synthesis of 4-Ynamides and Cyclization by the Vilsmeier Reagent to
J. Zheng, J.-H. Lin, L.-Y. Yu, Y. Wei, X. Zheng, J.-C. Xiao, Org. Lett.,