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 [C4C1im][CH3SO3] and by dimethylformamide (DMF), experimentally observed by Welton and co‐workers (Org. Lett. 2007, 9, 5247–5250). We find that [C4C1im]+ 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. Ionic liquid or DMF acts as bifunctional organocatalyst for SNAr reactions.