Selective synthesis of propenyl‐branched diunsaturated fatty esters via catalytic codimerization of ethyl linoleate and propylene

Abstract

A bimetallic catalyst system consisting of RhCl3 and Pd(MeCN)2Cl2 efficiently promotes the conversion of ethyl linoleate selectively to mono‐propenylated diunsaturated products. The reaction proceeds in high yields under mild conditions. The key advantage of the new process is that it is based on the readily available linoleate rather than a preformed conjuenic acid ester. Practical applications: The new protocol opens up a high yielding and environmentally friendly method for the introduction of side chains with a defined length into fatty acid derivatives. The products are of profound potential interest for industrial applications, e.g., in lubricants, cosmetics, plastics, and coatings, as branched fatty acids are known to have a lower solidifying point and viscosity and an increased solubility than their linear counterparts. Rh/Pd‐catalyzed selective conversion of ethyl linoleate to mono‐propenylated diunsaturated products under mild conditions.

Fatty Acids and their Derivatives as Renewable Platform Molecules for the Chemical Industry

“…used a Rh/Pd catalyst to propenylate 4 c giving product 31 as a mixture of isomers (Scheme 10). Pd catalyzes the conjugation of the two double bonds, which are propenylated with Rh catalysis [59] . The protocol for the synthesis of well‐defined alkyl‐branched oleochemicals was considerably improved by using haloalkanes instead of chlorocarbonates [4] to give the hydroalkylation products in excellent to good yields (Scheme 11).…”

“…Pd catalyzes the conjugation of the two double bonds, which are propenylated with Rh catalysis. [59] The protocol for the synthesis of well‐defined alkyl‐branched oleochemicals was considerably improved by using haloalkanes instead of chlorocarbonates [4] to give the hydroalkylation products in excellent to good yields (Scheme 11 ). [60] Importantly, the reaction protocol was scalable (>500 g 2 b ) and was also applied to substrates with two or more double bonds as well as to triglycerides.…”

Fettsäuren und Fettsäurederivate als nachwachsende Plattformmoleküle für die chemische Industrie

“…Pd katalysiert die Konjugation der beiden Doppelbindungen, die Rh-katalysiert propenyliert werden. [59] Die Vorschrift für die Synthese von klar definierten alkylverzweigten Oleochemikalien wurde durch die Verwendung von Halogenalkanen statt von Chlorformiaten wesentlich verbessert [4] und erlaubt die Isolierung der Hydroalkylierungs-Produkte in ausgezeichneten bis guten Ausbeuten (Schema 11). [60] Es ist von Bedeutung, dass sich die Vorschrift als skalierbar erwies (> 500 g 2 b) und auch auf Substrate mit zwei oder mehr Doppelbindungen wie auch auf Triglyceride angewendet werden konnte.…”

Synthetic Transformations for the Valorization of Fatty Acid Derivatives

“…Branched fatty acids can alternatively obtained by reaction of methyl linoleate with propene using a double catalytic system, RhCl 3 •3H 2 O and Pd(MeCN) 2 Cl 2 . 148 The reaction takes place in an aromatic solvent at 100 °C using 10 bar of propene and gives up to 81% yield (by GC). The palladium catalysts are responsible for the isomerization of linoleate to the conjugate diene, this then reacts with propene in a rhodium-catalyzed reaction (Scheme 20).…”