The reactions of N-substituted saccharins and phthalimides with amines were promoted by water. Various o-sulfamoyl benzamides and N,N′-disubstituted phthalamides were prepared in moderate to good yields. These reactions have prominent advantages, such as short reaction time, less by-products and simple isolation of the products. Water can probably stabilize the reaction intermediates and facilitate precipitation of the ring-opening products. When steric hindrance arose, hydrolytic compounds, either free acid or salts of the acids, were obtained. Possible reason for the formation of amine salts of o-sulfamoyl benzoic acids was proposed.