No abstract

Selective product crystallization proved to be a very attractive recycling strategy for homogeneous catalysts. This approach was demonstrated for the Pd-catalyzed isomerizing methoxycarbonylation of the renewable oleochemical methyl oleate using technical-grade starting material. The corresponding product, dimethyl-1,19-nonadecanedioate, is a valuable linear platform chemical for biobased polycondensates. A pure product phase (>96%) was produced by selectively controlled cooling crystallization following the reaction, whereas at the same time, the superior chemo-and regioselectivity of the known catalyst system was not compromised. The use of auxiliaries was avoided entirely; only the deliberate exploitation of the solubility behavior of the desired product led to success. The homogeneous Pd catalyst remained in the used methanol and was successfully recycled in up to eight repetitive batch runs. More than 39 g of linear C19 diester were isolated with an average selectivity in the methoxycarbonylation of 88%. The literature-known productivity of the Pd catalyst, expressed as its turnover number, was thus more than 6-fold increased from typically 400 to >2800. For compounds having suitable solubility behavior, selective product crystallization, therefore, complements the toolbox of available recycling techniques for homogeneous catalysts. The complete elimination of auxiliaries, the production of a pure product phase, and the possible use of commercial catalyst systems are some of the particularly sustainable features of this approach.

Observing and understanding the phenomena associated with the reaction mechanisms and catalyst deactivation in molecular catalysis is a very challenging task in green chemisty. This knowledge is crucial for applying...

In this work, a green‐catalytic procedure is used to demonstrate the synthesis of long‐chain anhydrides. This is accomplished by the carbonylation of alkenes with carboxylic acids. Anhydrides are important intermediates, finding specific applications as acetylation agents. The process is catalyzed by a Pd phosphine catalyst system in the presence of an acid promotor. Through optimization experiments, the importance of the phosphine ligand and acid promotor is demonstrated, without which the catalyst shows no activity. Although the yield was limited because of catalyst deactivation (42 %), to the best of our knowledge, the synthesis of long‐chain anhydrides through this route have not been reported previously. It therefore represents a significant result. Isolation of the anhydrides were also successfully demonstrated, however, as a result of the sensitivity of the anhydrides to water, the isolated yields were much lower than the HPLC yield. Furthermore, a mechanistic study by means of HP‐NMR (High Pressure Nuclear Magnetic Resonance) spectroscopy provided significant insights into the mechanism of the reaction.