Selective Synthesis of Imines Via Oxidative Coupling of Primary Amines and Oxidation of Secondary Amines by Peroxides and Other Competent Oxidants: A Short Review

Imines are certainly important constituents of many biomolecules, pharmaceuticals, agrochemicals, and fine chemicals. This review article highlights the standard protocols reported so far for the selective synthesis of imines via catalyzed and non-catalyzed (i) oxidative coupling of primary amines and (ii) oxidation of secondary amines in the presence of some competent/resourceful oxidants other than molecular O2 such as tert-butyl hydroperoxide (TBHP), H2O2, hypervalent iodines, persulfate, hypochlorite, electroactive species and graphene oxide. Indeed, the use of such oxidants offers a cost-effective experimental set-up, operational simplicity and also minimization of by-products. The cooperativity between catalyst, amine substrate, and oxidant is discussed in this review to understand the proposed mechanisms. Three consolidated data tables (Table 1, 2 & 3) are prepared to provide the summary of optimized reaction conditions (type of catalyst, type of oxidant, choice of solvent, amine-to-oxidant ratio, reaction time/temperature, conversion of amine, yield/selectivity of imine) of each article published to have a comparison.