Synthesis of Imines from Aromatic Aldehydes and Aliphatic Amines in Aqueous Solution

Abstract

Imines (also called Schiff bases and azomethines) have been of chemical and biological interest for some time.^1-4 The formation reaction has been studied extensively and the proposed mechanism includes the presence of a carbinolamine intermediate.

Under most conditions in aqueous solution, equilibrium considerations usually favor the carbonyl and amine as the predominant species. Therefore, imines are usually prepared by direct reaction of liquid amines and aldehydes^5,6 or in some appropriate nonaqueous solvent.^7,8 Water is then removed during the course of the reaction by means of a drying agent^5,6 or a Dean-Stark trap.^7,8 Cordes and Jencks⁹ have shown that imines prepared from certain substituted benzaldehydes and t-butylamine can be isolated from aqueous solution if it is saturated with KOH. In all of the above methods the crude product is purified by distillation.