Synthesis of terminal alkenes from internal alkenes and ethylene via olefin metathesis
This invention relates generally to olefin metathesis, and more particularly relates to the synthesis of terminal alkenes from internal alkenes using a cross-metathesis reaction catalyzed by a selected olefin metathesis catalyst. In one embodiment of the invention, for example, a method is provided for synthesizing a terminal olefin, the method comprising contacting an olefinic substrate comprised of at least one internal olefin with ethylene, in the presence of a metathesis catalyst, wherein the catalyst is present in an amount that is less than about 1000 ppm relative to the olefinic substrate, and wherein the metathesis catalyst has the structure of formula (II) wherein the various substituents are as defined herein. The invention has utility, for example, in the fields of catalysis, organic synthesis, and industrial chemistry.
1. A method for synthesizing a metathesis reaction product having a terminal olefin, the method comprising contacting, in the presence of a metathesis catalyst, an olefinic substrate comprised of at least one internal olefin with ethylene, wherein the catalyst is present in an amount that is less than about 1000 ppm relative to the amount of the olefinic substrate, and wherein the metathesis catalyst has the structure of formula (XII):
wherein:
M is Ru or Os;
t is zero;
X 1 and X 2 are anionic ligands;
R 1 and R 2 are independently selected from the group consisting of hydrogen, hydrocarbyl, substituted hydrocarbyl, heteroatom-containing hydrocarbyl, and substituted heteroatom-containing hydrocarbyl;
Z 3 is a cationic moiety selected from the group consisting of P(R 2 ) 3 and N(R 2 ) 3 ;
Y is a non-coordinating anion; and
L 1 is a carbene ligand with the structure of formula (IIIc):
wherein Ar 1 and Ar 2 are independently aryl substituted with at least one group selected from the group consisting of C 1 -C 12 alkyl, C 2 -C 12 alkenyl, C 2 -C 12 alkynyl, C 5 -C 12 aryl, C 6 -C 12 aralkyl, and C 6 -C 12 alkaryl; a is an optional double bond; R 13 , R 14 , R 15 , and R 16 are independently selected from the group consisting of hydrogen, hydrocarbyl, substituted hydrocarbyl, heteroatom-containing hydrocarbyl, and substituted heteroatom-containing hydrocarbyl, wherein any two or more of A 1 , Ar 2 , R 13 , R 14 , R 15 , and R 16 may be taken together to form a cyclic group, and provided that R 14 and R 16 are not present if a is present.
2. The method of claim 1 , wherein L 1 has the structure of formula (IIId):
wherein R 22 , R 23 , R 27 , and R 28 are independently selected from the group consisting of C 1 -C 12 alkyl, C 2 -C 12 alkenyl, C 2 -C 12 alkynyl, C 5 -C 12 aryl, C 6 -C 12 aralkyl, and C 6 -C 12 alkaryl, and R 24 , R 25 , R 26 , R 29 , R 30 , and R 31 are independently selected from hydrogen, C 1 -C 12 alkyl, C 2 -C 12 alkenyl, C 2 -C 12 alkynyl, C 5 -C 12 aryl, C 6 -C 12 aralkyl, and C 6 -C 12 alkaryl.
3. The method of claim 2 , wherein a is not present, such that L 1 has the structure of formula (IIId-1):
4. The method of claim 3 , wherein R 24 , R 25 , R 26 , R 29 , R 30 , and R 31 are hydrogen, such that L 1 has the structure of formula (IIIe):
5. The method of claim 1 , wherein the catalyst is:
6. The method of claim 1 , wherein the catalyst is present in an amount that is 100 ppm or less relative to the amount of the olefinic substrate.
7. The method of claim 1 , wherein the olefinic substrate is selected from the group consisting of seed oils, alkyl esters of unsaturated fatty acids, and aryl esters of unsaturated fatty acids.
8. The method of claim 1 , wherein the olefinic substrate comprises a mixture of internal olefins selected from the group consisting of monoacylglycerols, diacylglycerols, triacylglycerols, and combinations thereof.
9. The method of claim 1 , wherein the olefinic substrate is of the formula (R I )(R II )C≡C(R III )(R IV ), wherein R I , R II , R III , and R IV are independently selected from the group consisting of hydrogen, hydrocarbyl, substituted hydrocarbyl, heteroatom-containing hydrocarbyl, substituted heteroatom-containing hydrocarbyl, and functional groups, provided that at least one of R I or R II and at least one of R III or R IV is other than hydrogen.