Diester monomers from methyl oleate and proline via tandem hydroaminomethylation-esterification sequence with homogeneous catalyst recycling using TMS-technique



Diesters from renewables are attractive precursors in various polymer applications. In this regard, unsaturated fatty compounds such as methyl oleate are interesting starting materials as it is possible to introduce different functional groups by modifying the double bonds and due to the existing carboxylic moiety. Another interesting class of renewables are amino acids, such as L-proline, which provide naturally occurring amino and carboxylic moieties. Combining these two renewables in one reaction sequence consisting of hydroformylation, condensation, hydrogenation (i.e., hydroaminomethylation; HAM) and esterification results in interesting biopolymer-precursors. In this paper, we present a combination of these four reactions used to functionalize methyl oleate to produce diesters in one pot. These diesters were successfully separated from the catalyst using thermomorphic solvent systems (TMS)-technique, resulting in minimal leaching of the precious metal rhodium into the product phase. Catalyst recycling was shown for three recycling runs in which the catalyst activity was maintained.