Methyl erucate

The production of a,m-diesters from fatty esters can be realized via their SM as already explained, but it can also be performed by CM with methyl acrylate. The bulk CM of several unsaturated fatty acid methyl esters containing double bonds in different positions with methyl acrylate was studied by Rybak and Meier (Scheme 6) [43], C4 and C5 displayed very good activities with high conversions and CM selectivities. Among them, C5 showed the best performance for both methyl oleate (97% conversion, 92% selectivity, with 0.2 mol%) and methyl 10-undecenoate (99% conversion, 99% selectivity, with 0.1 mol%). The same conditions were successfully applied to methyl erucate and methyl petroselinate. The reaction conditions were further optimized, also considering the effect of 1,4-benzoquinone as additive for the reduction of double-bond isomerization [39], The CM of methyl 10-undecenoate and methyl acrylate worked with full conversions and high selectivity if five- to tenfold excess of methyl acrylate is used. Furthermore, using a 1 1 ratio between both reactants led, after optimization of the reaction... 

Interestingly, the reaction procedure also worked well with methyl oleate [lb], methyl petroselinate [3b], and methyl erucate [4b]. Addition of ethyl 2-iodopropi-onate [5b] gave the regioisomeric y-lactones [7] and [8] in good yields and a ratio of... 

Results of the Copper-Initialed Additions of Ethyl 2-Haloallcanoates [5] to Methyl Oleate (Ibh Methyl 10-Undecenoate [2b], Methyl Petroselinate [3b], and Methyl Erucate [4b] (Schemes 1 and 2)... 

SCHEME 8. Additions of 2-haloalkanenitriles to methyl 10-unde-cenoate [2b] and methyl erucate [4b]. Source. Ref. 7. 

Renewable polyamides (PA) can also be prepared taking advantage of the synthesis of thiol-ene monomers. Meier and co-workers [30] studied the thiol-ene addition of cysteamine hydrochloride to the double bonds of methyl 10-undecenoate, methyl oleate, and methyl erucate (Scheme 6.8), which yielded heterodifunctional monomers at good yields. Ensuing monomers were homopolymerised, copolymerised with each other, as well as copolymerised with adipic acid and 1,6-hexamethylene diamine to yield copolyamides with TBD as the catalyst. The produced PA were obtained with Mn values of 4-19 kDa. 

The same research team used a,fl>dienes derived from oleic acid and erucic acid to be copolymerised further with a derivative of ferulic acid obtained from rapeseed cake (Scheme 6.12). Methyl erucate and methyl oleate were epoxidised and subsequently reacted with allyl alcohol in acidic conditions to yield the corresponding ct,(0-dienes [21, 34]. These monomers were polymerised by ADMET or thiol-ene reactions for the sake of comparison. For thiol-ene reactions, 1,4-butanedithiol was used to give polyhydroxyesters with Mn values of 4-14 kDa and Tg values ranging from -63 to -33 °C. 

Many other unsaturated fatty acid methyl esters of the general formula Me(CH2) CH=CH(CH2) COOMe have been shown to undergo metathesis with high selectivity, such as methyl palmitoleate (n = 5, m = 7), methyl erucate (n = 1, m = l) and methyl petroselenate ( = 10, m = 4) [8]. Another example is methyl 10-undecenoate, which can be obtained from castor oil via pyrolysis cleavage of the ricinoleic acid. The metathesis of methyl 10-undecenoate proceeds to completion when the by-product ethene is continuously removed during the reaction equation (3). 

From a synthetic point of view, cross-metathesis reactions are very useful for the production of fine chemicals, which often can hardly be obtained by other means. An example is the synthesis of 1-triacontanol, CH3(CH2)28CH20H, a plant growth stimulant. This synthesis was performed in a relatively simple two-step process by cross-metathesis of methyl erucate with 1-octadecene in the presence of a WCl6/Me4Sn catalyst, equation (7), followed by hydrogenation over a Cu/Zn catalyst of the ester thus obtained [14]. 

This successful separation of erucic acid was reported to the EEC Committee of Experts in September 1976 as an outline procedure possibly suitable as the basis of an official method. The report proposed that the procedure could be made quantitative by scraping-off the methyl erucate spot, extracting the ester from the powdered silica gel with ether and, after adding methyl tetracosanoate (C24 0) as an internal standard, determining the erucic acid by conventional GLC as in the analysis of rapeseed oil. 

Fig. 2. Typical thin-layer chromatogram showing the separation of fatty acid methyl esters 1—Margarine methyl esters 2—Methyl erucate 3—Methyl brassidate 4— Fish oil methyl esters 5—Partially hydrogenated fish oil methyl esters A—Saturated esters B—Trans-isomers C—Methyl erucate D—Methyl cetoleate E—Other monoene esters F—Diene and polyene esters.

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