Solvent-free oxidative coupling of benzylamine to imine using reusable MnO4−1 incorporated Mg–Al hydrotalcite catalyst.

Highly stable, basic and ordered structural MnO₄⁻¹ incorporated Mg–Al hydrotalcite (Mn-HT) catalysts were prepared and then tested first time for oxidative coupling reaction of different benzylamine derivatives to biologically active imine intermediate compounds with high yield under the solvent-free reaction condition. Among the prepared hydrotalcite catalysts like Mn-HT (0.2), Mn-HT (0.3) and Mn-HT (0.5) by co-precipitation method, Mn-HT (0.3) catalyst showed high catalytic activity with yield 95%. This is due to the ligand to metal charge transfer transition of O₂⁻ → Mn²⁺ in the Mn-HT catalyst. Recovery of catalyst in 3rd cycle produced 90% imine product without significant loss in yield from fresh cycle (95%). Recycle study validated the stability, retention of the hydrotalcite structure and morphology as confirmed by XRD and SEM–EDX analysis. The substrate study showed that high imine yield could be obtained for electron-donating as compared to electron-withdrawing group in the benzylamine. Thus, the reported Mn-HT hydrotalcite heterogeneous catalyst could be a choice for conversion of benzylamine derivatives to imine product without use of any toxic solvents in organic synthesis for commercial process. [ABSTRACT FROM AUTHOR]