Chemicals from Biomass: Chemoselective reductive amination of ethyl levulinate with amines

Abstract

N-substituted-5-methyl-2-piyrrolidones have been obtained by reductive amination of ethyl levulinate with amines in the presence of H-2 as reducing agent under solvent-free conditions. The process involves as a first step the formation of an imine intermediate followed by hydrogenation of the imine group and subsequent cyclization into pyrrolidone. Pt/TiO2 with Pt crystal faces decorated with TiOx is a very active and chemoselective catalyst, being possible to achieve high conversion and selectivity to the corresponding N-substituted-5-methyl-2-pyrrolidones even when other groups susceptible of hydrogenation such as vinyl, carbonyl, or cyano groups are present in the amine moiety. A kinetic study showed that the reaction-controlling step is the formation of the imine intermediate. The rate of formation is enhanced by the presence of protonic acid sites generated on the support by hydrogen dissociation on the metal, resulting in a true bifunctional catalyst for the reaction.