Theoretical study of the Aza˗Wittig reaction, Me3P=NR (R = Methyl or Phenyl) with aldehyde by the DFT and DFT-D methods (dispersion correction)

The Aza-Wittig reaction played an important role in organic transformations and has known considerable development in the construction of cyclic and acyclic compounds in neutral solvents in the absence of catalysts with a high yield of product.

Today, the use of iminophosphoranes (Phosphazenes) has become a powerful tool in organic synthesis strategies directed towards the construction of nitrogenous heterocycles. These can react with carbonyl compounds, an excellent method for the construction of C=N double bonds via intermolecular and intramolecular aza-Wittig reactions.

In this study, we were interested in the theoretical study of the reaction path of the aza˗Wittig reaction between trimethyl-iminophosphoranes (CH3) 3P=NR, R=CH3 or Ph) for the two substituents methyl and phenyl with ethanal, including continuum solvation. Our calculations were carried out by means of ab-initio calculations using the theory of DFT and DFT-D, dispersion correction term using the Grimme method [8] in the program Gaussian09, using the functional B3LYP and B3LYP-GD3BJ with a 6-31G ** base.

The results obtained allowed us to highlight the mechanisms of the Aza-Wittig reaction in particular after the addition of the term of dispersion correction or Van der Walls correction which provided a new description of this reaction and its chemical path.