On the formation of imines in water—a comparison

The reaction of aniline with aryl aldehydes in water has been investigated in the past, but contradictory results have been published. While only small amounts of imines 3 were detected by NMR analysis, isolation afforded high imine yields. A reinvestigation of the reaction of benzaldehyde (1a) and salicylaldehyde (1b) with aniline (2) revealed two important factors which explain the putative contradiction: (i) NMR only reveals the fraction of products which is soluble in water, and (ii) imines 3 form during or after workup.