Synthesis of diethyl-2-iminocoumarin-3-phosphonates

The organophosphorus compounds (OPCs) are important synthetic targets in modern organic synthesis. They have wide range of applications in different areas such as agriculture, medicine and industry.1 In our knowledge the synthesis of the diethyl-2-iminocoumarin-3-Phosphonates haven’t been reported previously. A survey of the literature show a lot of work have been done on the synthesis of Diethyl coumarine-3-phosphonate such as reaction of salicylaldehyde and triethyl phosphonoacetate in presence of TiCl42 or Piperidene.3 Nowadays phosphorylation of coumarine skeleton in the presence of Mn(OAc)3,4 Ag2CO3 5 and NHC-Pd 6 as catalyst is used.Herein, we report for the first time the synthesis of diethyl-2-iminocoumarin-3-Phosphonates from the reaction between salicyladehyde 1 and cyanomethylphosphonate 2 in presence of NEt3 and MgSO4 in toluene as solvent at 65 °C. We have been able to obtain the desired product 4 by using derivative of salicyladehyde with electonwithdrawing group. When we use salicyladehyde, the major product was the iminocoumaine 3 (Fig 1).

Keywords:

Knoevenagel Reaction , Horner-Wadsworth-Emmons Reaction (HWE) , Diethyl cyanomethylphosphonate , Diethyl-2-iminocoumarin-3-phosphonate