Cross‐metathesis versus palladium‐catalyzed CH activation: Acetoxy ester functionalization of unsaturated fatty acid methyl esters

Abstract

Two synthetic approaches to functionalize plant oil derived platform chemicals were investigated. For this purpose, methyl 10‐undecenoate, which can be obtained by pyrolysis of castor oil, was used in olefin cross‐metathesis under neat conditions forming an unsaturated α,ω‐acetoxy ester. A catalyst screening with 11 different ruthenium‐based metathesis catalysts was performed, revealing that well‐suited catalysts allow for full conversion and very good cross‐metathesis selectivity at a loading of only 0.5 mol%. An alternative possibility to the aforementioned synthetic method is a palladium‐catalyzed reaction of methyl 10‐undecenoate with acetic acid in the presence of dimethyl sulfoxide. Here, the formation of linear and branched unsaturated acetoxy esters as well as a ketone was observed. The conversion as well as the selectivity of this procedure was studied under different reaction conditions and compared to the cross‐metathesis results. Based on the successful functionalization of methyl 10‐undecenoate, methyl oleate was investigated in this palladium‐catalyzed CH activation reaction. Due to the lower reactivity of the internal double bond the desired acetoxy ester was only obtained in moderate conversion in this case. In summary, this study clearly shows that palladium‐catalyzed functionalization of unsaturated fatty compounds via CH activation is an attractive alternative to the well‐established olefin cross‐metathesis procedure.

Olefin cross metathesis and ring-closing metathesis in polymer chemistry

“…There are many reports that use olefin CM to generate potential precursors for step-growth polymerisation, in particular the functionalisation of renewable fatty acids, including the work of Dixneuf, Bruneau and Meier. [18][19][20][21][22] Yet, reports that demonstrate successful CM for the formation of novel monomers and prove their corresponding polymerisation is more rare. [23][24][25] In 2010, Cádiz et al targeted modified vegetable-oils as alternative feedstocks to fossil fuel derived monomers, a topical challenge in polymer science.…”

Fettsäuren und Fettsäurederivate als nachwachsende Plattformmoleküle für die chemische Industrie

“…[106] 3.2.6.2. Kreuz-Metathese mit funktionalisierten Alkenen Die Kreuz-Metathese von ungesättigten Fettstoffen mit funktionalisierten Alkenen, wie Methylacrylat, [107] Dimethylmaleat" [108] Maleinsäure, [109] Allylacetat und cis-1,4-Diacetoxy-2-buten, [110][111][112] Acrylnitril [113,114] oder Acrolein, [115] ermçglicht den einfachen und oft mit hoher (E)-Stereoselektivitätv erbundenem Zugang zu interessanten bifunktionellen ungesättigten Verbindungen.…”

Light‐Driven Single‐Electron Transfer Processes as an Enabling Principle in Sulfur and Selenium Multicatalysis

“…It is particularly noteworthy that esters 76 were generally formed with very high regioselectivity,e xclusively furnishing products with transposed double bonds.C ognate reactions catalyzed by Pd II complexes generally led to regioisomeric mixtures of allylic acetates,i nw hich the double bond partly remained in its original position. [51] Subsequently,Breder and co-workers extended their dual photoredox selenium-p-acid catalysis concept to other coupling processes,s uch as lactonizations,a llylic etherifications, and phosphatations of simple olefins (Scheme 14 B-D). [49b-e] Thel ast transformation is particularly noteworthy,a si t represents the first catalytic example of an allylic oxidative coupling of non-activated hydrogen phosphates with simple alkenes 71 under aerobic conditions.The authors furthermore showed that the resulting allylic phosphates 79 could be directly converted with organocuprates to give the corresponding allylic alkylation products.…”