The Vilsmeier–Haack reaction is the chemical reaction of a substituted formamide with phosphorus oxychloride and an electron-rich arene to produce an aryl aldehyde or ketone: RCNR′R″ + HArZ + POCl₃ + H₂O → RCArZ + NR′R″H + HCl + H₃PO₄ The reaction... Wikipedia