The use of added base to drive the equilibrium in the formation of amides from amines and acid chlorides.
The acylation of amines with carboxylic acid chlorides leads to the production of one equivalent acid, which will form a salt with unreacted amine and diminish the yield. The addition of an additional equivalent of base to neutralise this acid is a way to optimise the conditions. Normally, aqueous base is slowly added to the reaction mixture.
In general, the use of biphasic aqueous basic conditions is often named "Schotten-Baumann conditions".
Mechanism of the Schotten-Baumann Reaction