Methyl oleate hydroformylation

In the case of rhodium as a catalyst metal for the hydroformylation of methyl oleate, lower pressure and lower temperature have to be compared to cobalt catalysis [20, 21], The use of rhodium is also advantageous because of the lower isomerization. Frankel showed that with a rhodium triphenylphosphine catalyst, hydroformylation occurs only on the ninth and tenth carbon atoms of the methyl oleate [22]. 

Triglycerides and technical-grade fatty acid esters can be used as the starting material in hydroformylation (Scheme 7). Soybean oil and technical-grade methyl oleate were hydroformylated by [RhH(CO)2PPh3)] with triphenylphosphine as the ligand. 

Lai R, Naudet M, Ucciani E (1966) Oxo synthesis in lipochemistry. Preliminary study of the hydroformylation of methyl oleate. Rev Fr Corps Gras 13 737-745... 

Friedrich J, List G, Sohns V (1973) Hydroformylation of methyl oleate with a recycled rhodium catalyst and estimated costs for a batch process. J Am Oil Chem Soc 50 (11) 455—458. doi 10.1007/bfi)2639853... 

The first investigations concerning the hydroformylation of fatty compounds were accomplished by Ucciani and co-workers with cobalt catalysts such as cobalt bislaurate and dicobalt octacarbonyl [29]. Later, Frankel and co-workers found that the cobalt-catalyzed hydroformylation of methyl oleate also leads to the corresponding fatty alcohols [30]. In recent investigations on the hydroformylation of fatty compounds, the preferred catalyst is based on rhodium. For instance, the hydroformylation of methyl oleate catalyzed by [Rh(acac)(CO)2]/biphephos yields an isomeric mixture of formylstearic add methyl esters [31]. 

A particularly ambitious synthesis is isomerizing hydroformylation (Equation 3.1). In this reaction, first the internal double bond of the methyl oleate isomerizes to the terminal position, which is then hydroformylated to the co-aldehyde [32],... 

The hydroformylation reaction converts the unsaturation into a carbonyl moiety, as illustrated in the example of Scheme 2.6, in which methyl oleate is converted into methyl-9-stearate with methyl stearate as a byproduct, under the action of a rhodium-based catalyst. 

One of the commercial apphcations of bulky phosphites is the production of 3-methylpentane-11,5-diol by hydroformylation of 3-methylbut-3-en-l-01 by Kuraray [17]. Furthermore, they reported the use of bulky phosphite in the hydroformylation of vinyl acetate and 7-octenal, the latter providing an intermediate for the preparation of nonanediol. The high reactivity induced by bulky phosphite hgands has also led to the application of hydroformylation in the functionalization of natural product derivatives that are otherwise hardly reactive. Syntheses of important intermediates to fine-chemicals have been reported by hydroformylation of dihydroluran [18], glucal derivatives [19] and methyl oleate [20] (see also chapter 6 for further details). 

Figure 14. Hydroformylation of pure methyl oleate (3.64 mmol), Pinitiaiiy = 20 bar, CO/H2 = 1 1, T=100 °C, Rh=4.10" mmol, Llgand Rh =25 1, A methyl oleate, methyl elaidate, methyl fomylstearate, 0 methyl formylstearate (Isomers)...

In 2014, Liihr and Borner [52] investigated the hydrolysis stability of four phos-phoramidites based on lactam rings (Figure 2.42). The phosphoramidite with the smallest ring was by far the most stable. Remarkably, it also exhibited the highest activity in the rhodium-catalyzed hydroformylation of methyl oleate. 

A set of different reaction protocols allows a meaningful comparison of different phosphite ligands on the rhodium-catalyzed hydroformylation of methyl oleate (Scheme 5.21). 

Scheme 5.21 Isomerization-hydroformylation of methyl oleate with different rhodium phosphite catalysts.

With methyl oleate, 53% yield of the terminal alcohol was observed. With unmodified internal olefins (2-decene, 2-tridecene, 4-octene), even higher regioselectivities in favor of the terminal alcohol could be achieved l/b up to 12 1). Proof was given that both rhodium and ruthenium complexes catalyze the isomerization-hydroformylation-hydrogenation reaction in a cooperative manner. 

Scheme 5.41 Hydroformylation-hydrogenation of methyl oleate with two different catalysts using the same reaction conditions.

Up until now, mostly pure substrates such as methyl oleate and its -isomer, methyl elaidate, have been tested as model substrates for hydroformylation, but in a few cases, linoleates, linolenates, and esters of ricinoleic acid have also been investigated (Figure 6.10). Oleic acid can be derived from new sunflower, linoleic acid from soybean, linolenic acid from linseed, and ricinoleic acid from castor oil. The long-chain mono-unsaturated fatty acid erucic acid (C22) can be extracted from old rapeseed oil. 

Scheme 6.80 Hydroformylation of methyl oleate with a Rh phosphite catalyst.

The double bond in methyl oleate can migrate to the terminus under the effect of Rh catalysts containing a sterically demanding diphosphite ligand, as shown by Behr et al. [26] with BIPHEPHOS (Scheme 6.81, lower part). The subsequent hydroformylation achieved 65% conversion of the substrate and produced methyl 19-oxononadecanoate in 26% yield within 17 h. Approximately 12% of the olefin hydrogenation product was simultaneously observed. 

Scheme 6.81 Non-isomerizing and isomerizing hydroformylation of methyl oleate.

In comparison to methyl oleate, somewhat higher yields of monoformyl product were observed in the hydroformylation of ethyl linoleate (Scheme 6.83) [26]. Under the same conditions, besides isomeric aldehydes, ethyl oleate and ethyl stearate were formed. Higher syngas pressure reduced the degree of hydrogenation. 

Scheme 6.90 Hydroformylation of methyl oleate under different conditions.

Scheme 6.91 Hydroformylation of methyl oleate with a Co catalyst, and subsequent hydrogenation or trapping of the aldehyde as acetal.

Aqueous two-phase hydroformylation of methyl oleate and a technical linseed oil was conducted by anchoring the Rh(TPPTS) catalyst either on silica [2] or on activated carbon (Nuchar WV-B) [47]. Especially, the latter proved highly efficient as a mass transfer promoter. 

Hydroformylation of pure or technical grade methyl oleate was conducted by Monflier and colleagues [40] under the assistance of activated carbon (Nuchar WV-B mesoporous activated carbon with an average pore size of 3.1 nm) as mass transfer promotor (Scheme 7.9). Noteworthy, in comparison to the hydroformylation with a rhodium-phosphite catalyst in toluene [41], impurities of the technical grade feed did not significantly perturb the reaction. Under similar conditions, also other biomass-based substrates such as methyl hnoleate... 

Scheme 7.9 Hydroformylation of technical-grade methyl oleate in water in the presence of activated carbon.

Phosphoramidites 59a-d were prepared by treatment of a biatyl chlorophosphite with the desired lactam in the presence of triethylamine as HCl-scavenger (Scheme 14). The ligands were shown to be useful for rhodium-catalyzed hydroformylation of methyl oleate under mild conditions. The best results were achieved with the most stable 59b (99% chemoselectivity for methyl 9- and 10-formylstearate). 

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