Reaction in water/aqueous surfactants/PTC
Mechanism + Description
As per N-based dipolar aprotic solvents
Some SNAr reactions will take place in water / aqueous mixtures provided that the nucleophile is significantly more reactive than water which could compete to produce phenol by-products. Often, phase transfer catalysts or surfactants are added to aid mixing and provide micelles where the organic reagents can dissolve and react. In the presence of chiral PTC, asymmetric SNAr products can be obtained with certain reactants.
PTC's can be added to less polar solvents to provide a more polar environment for reaction and to aid dissolution.
The use of PTC/surfactant systems in water can reduce the amount of organic solvent employed, but care needs to be taken with disposal of any aqueous waste since some quaternary nitrogen / phosphorus based PTC's can be quite ecotoxic.
Relevant scale up examples solvents under pressure