Reductive transamination of methoxyacetone with benzylamine over Pd/SiO₂ catalyst modified with anchored chiral compounds

Abstract

Methoxyacetone was transaminated with benzylamine to methoxyisopropylamine over a Pd/SiO₂ catalyst modified with L‐alaninol or L‐phenylalaninol covalently anchored to the surface of the support via an organo‐silicon spacer group. In the first step of transamination a Schiff base was formed from the ketone and benzylamine, and then it was hydrogenated in the second step on the chirally modified Pd/SiO₂ catalysts to an asymmetric secondary amine (N‐benzyl‐methoxyisopropylamine). In the third step the hydrogenolysis of the asymmetric secondary amine resulting in methoxyisopropylamine and toluene was carried out over a 10 wt% Pd/C catalyst. The highest enantiomeric excess of (S)‐methoxyisopropylamine was observed in cyclohexane (ee = −20–21%) using anchored L‐alaninol as a chiral modifier.