Enhancement of SNAr reactions by CH3SO3- ionic liquid and organic solvent dimethylformamide as bifunctional organocatalysts: A mechanistic study

Quantum chemical analysis is presented for the mechanism of SNAr reaction of p-fluoronitrobenzene and p-anisidine promoted by [C(4)C(1)im][CH3SO3] and by dimethylformamide (DMF), experimentally observed by Welton and co-workers (Org. Lett. 2007, 9, 5247-5250). We find that [C(4)C(1)im](+) assists the detachment of the fluoride leaving group, while [CH3SO3](-) supplies partial negative charge to the nucleophile -NH2 to enhance the reactivity. We also show the moderate yield (22.1%) in DMF can also be understood by considering the solvent molecule as a bifunctional organocatalyst. The calculated Gibbs free energies of activation are in excellent agreement with the experimental observations.