Evidences for the Key Role of Hydrogen Bonds in Nucleophilic Aromatic Substitution Reactions

The effect of hydrogen bonds on the fate of nucleophilic aromatic substitutions (S(N)Ar) has been studied in silico using a density functional theory approach in the condensed phase. The importance of these hydrogen bonds can explain the "built-in solvation" model of Bunnett concerning intermolecular processes between halogenonitrobenzenes and amines. It is also demonstrated that it can explain experimental results for a multicomponent reaction (the Ugi-Smiles coupling), involving an intramolecular S(N)Ar (the Smiles rearrangement) as the key step of the process. Modeling reveals that when an intramolecular hydrogen bond is present, it lowers the activation barrier of this step and enables the multicomponent reaction to proceed.