Recyclable hydrotalcite catalysts for alcohol imination via acceptorless dehydrogenation

Abstract

Here we report that hydrotalcite-like materials (HTs) are active heterogeneous catalysts for alcohol imination, which proceeds through acceptorless alcohol dehydrogenation. The catalytic activity of a series of Mg–Al hydrotalcites doped with Fe³⁺, Zn²⁺, Ni²⁺, Cr³⁺ and Cu²⁺ is dependent on their composition, and Fe : Mg : Al HT yields up to 92% imine under mild conditions. Impregnation of Fe : Mg : Al HT with Pd⁰ resulted in an enhancement of activity for acceptorless dehydrogenation, but a decrease in the isolated yield of imine in a loading-dependent manner. This is attributed to the Pd loading-dependent retention of imine and aldehyde on the catalysts. The substrate scope for alcohol imination and recyclability of the catalysts is discussed.