Fused double oxazolidine vs Imine ligands and Zn-complexes formation: Experimental and theoretical calculations

Abstract

The condensation reaction between minodiols and carboxaldehydes offers the possibility to obtain either 1-aza-3,7-dioxabicycle[3.3.0]octane (namely here as fused double oxazolidine) or imine compounds. Till now, only limited information is available regarding the factors influencing this behavior. Thus, the present work explored the substituent effect on the reactivity of aminodiols with pyridine carboxaldehydes both in the presence and absence of Zn (II). Without the presence of the metal, the condensation reactions favor the production of fused double oxazolidine derivatives, with identification of both cis and trans isomers in relation to the pyridyl moieties. Notably, the presence of a methyl substituent favors the trans isomers owing to the steric hindrance effect, while a hydrogen substituent favors the cis isomers. Conversely, in the presence of ZnCl2, the main product is the imine-metal complex when the substituent is a methyl group. However, in the presence of a hydrogen substituent, both the imine-metal and the fused double oxazolidine-metal complexes were produced as a mixture in similar proportions. These experimental results are supported by theoretical calculations.