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Cross‐metathesis versus palladium‐catalyzed CH activation: Acetoxy ester functionalization of unsaturated fatty acid methyl esters
Author(s) -
von Czapiewski Marc,
Kreye Oliver,
Mutlu Hatice,
Meier Michael A. R.
Publication year - 2013
Publication title -
european journal of lipid science and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.614
H-Index - 94
eISSN - 1438-9312
pISSN - 1438-7697
DOI - 10.1002/ejlt.201200196
Subject(s) - metathesis , catalysis , chemistry , palladium , organic chemistry , selectivity , ketone , olefin fiber , surface modification , salt metathesis reaction , polymerization , polymer
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 CH 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 CH activation is an attractive alternative to the well‐established olefin cross‐metathesis procedure.