Smiles Rearrangement
Smiles rearrangement is an intramolecular nucleophilic substitution which involves the attacking on an aromatic system possessing an activating electron-withdrawing group at ortho- or para-position to the reaction centre connected to a heteroatom. Smiles rearrangement is further involves the migration of an aromatic ring from the heteroatom binding to the reaction center to a more nucleophilic heteroatom.
X may be S, SO, SO2, O or COO and YH may be OH, NH2, NHR or SH. The reaction has also been carried out with YH = CH3 (PhLi was used as base) in this particular case the rearrangement is known as Truce-Smiles rearrangement.
Mechanism of Smiles Rearrangement
The presence of EWG para to the YH group in the substrate retards the rate of the smiles rearrangement because such groups reduce the nucleophilicity of Y−.
Z and Z' are activating groups for nucleophilic aromatic substitution reaction. Z and/or Z' should be an EWG such as -NO2, -CN or CF3 to stabilize the cyclohexadienylide anion formed.
Examples of Smiles Rearrangement
