Increased functionality of methyl oleate using alkene metathesis

Figures & data

Table 1 Homogeneous catalysts used in this study.

Catalyst
G-1	Grubbs catalyst, first generation, bis(tricyclohexylphosphine)benzylidene ruthenium dichloride
G-2	Grubbs catalyst, second generation, [1,3-bis-(2,4,6-trimethylphenyl)-2-imidazolidinylidene]dichloro(phenylmethylene)(tricyclohexylphosphine)ruthenium
HG-1	Hoveyda–Grubbs catalyst, first generation, dichloro(o-isopropoxyphenylmethylene)(tricyclohexylphosphine)ruthenium
HG-2	Hoveyda–Grubbs catalyst, second generation, (1,3-bis-(2,4,6-trimethylphenyl)-2-imidazolidinylidene)dichloro(o-isopropoxyphenylmethylene)ruthenium
C-1	Dichloro(3-methyl-2-butenylidene)bis(tricyclohexylphosphine)ruthenium
C-2	Dichloro[1,3-bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene](3-methyl-2-butenylidene)(tricyclohexylphosphine)ruthenium
C-3	Dichloro[1,3-bis(2-methylphenyl)-2-imidazolidinylidene](2-isopropoxyphenylmethylene)ruthenium
C-4	Dichloro[1,3-dimesityl-2-imida-zolidinylidene][3-(2-pyridinyl)-propylidene]ruthenium
C-5	Dichloro[1,3-bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene](benzylidene)bis(3-bromopyridine)ruthenium
C-6	Dichloro[1,3-bis(2-methylphenyl)-2-imidazolidinylidene]-(benzylidene)(tricyclohexylphosphine)ruthenium

Table 2 Self-metathesis of methyl oleate under various conditions.

Conditions		Conversion (GC area %)
0.1 wt% G-1, 40°C	Time (h)
	0	0.4
	1	24
	3	34
	4	24
0.1 wt% G-1, 2 h	Temperature (°C)
	40	23
	60	14
	80	20
G-1 catalyst, 40°C, 2 h	Concentration (wt%)
	0.05	18
	0.1	23
	0.2	36

Figure 1 Conversion observed in the alkene metathesis reaction of methyl oleate using various homogeneous catalysts (Table 1) at 0.2 wt%, at 40°C over 2 h.

Table 3 Conversion and product distributions of cross-metatheses of methyl oleate with various alkenes.

Alkene		Conversion of starting material (GC area %)		Functional incorporation:self-metathesis (GC area %)
		(A)	(D)	(E+F):(B+C)
Stilbene	G-2	56	67	1:4.1
	HG-2	61	90	1:1.6
		(A)	(G)	(E+F):(B+C)
Styrene	G-1	36	63	1:1.0
	G-2	60	96	1:2.4
	HG-2	59	97	1:2.1
		(A)	(K)	(E+F):(B+C) aromatic	(M+N):(B+C) α,β-ester
Methyl cinnamate	G-2	62	22	1:1.8	1:2.9
	HG-2	70	45	1:0.9	1:1.4
		(A)	(O)	(P+Q):(B+C)
1-Hexene-3-ol	G-2^#	58	97	1:5.0
	HG-2	58	100	1:5.7

Notes: The data for conversion of each of the starting material are displayed separately in the first two columns, showing the different activity towards metathesis for each of the substrates. The distributions are taken by the addition of relative areas. For example, in the HG-2 metathesis with stilbene, the products B, C, E and F have relative area percentages of 25.8, 13.9, 7.0 and 18.3, respectively. This gives a ratio of 39.7–25.3, or 1:1.3 of the cross-products (E+F) versus the self-metathesis products (B+C). The data for each of the cross-metatheses were analysed in a similar fashion. The G-2 with the 1-hexene-3-ol experiment was run for 1 h instead of 2.

^#This experiment utilized a 1 h reaction time instead of 2 h.

Scheme 1 Self-metathesis of methyl oleate yields three product groups. Starting material and its trans isomer (A), the cis and trans isomers of dimethyl octadec-9-endioate (B) and cis- and trans-9-octadecene (C).

Scheme 4 Self-metathesis reaction of methyl linoleate.

Scheme 2 Cross-metathesis of methyl oleate and another alkene. In the final product, all of the self-metathesis products of each material as well as all the possible combinations of cross-products are produced. If R = R′, then the system will give six product sets instead of 10.

Scheme 3 Observed products of the cross-metathesis reaction of methyl oleate with various alkenes.