Process for preparing an unsaturated carboxylic acid salt
Catalytic process for preparing an α,β-ethylenically unsaturated carboxylic acid salt, comprising reacting an alkene and carbon dioxide in the presence of a carboxylation catalyst and releasing the α,β-ethylenically unsaturated carboxylic acid salt with a base, the carboxylation catalyst being a transition metal complex, which comprises a structurally constrained bidentate P,X ligand, wherein X is selected from the group consisting of P, N, O, and carbene, the P and X atom are separated by 2 to 4 bridging atoms, and wherein the bridging atoms are part of at least one 5- to 7-membered cyclic substructure. A further catalytic processes for preparing α,βethylenically unsaturated carboxylic acid derivatives from CO 2 and an alkene is provided.
1. A catalytic process for preparing an α,β-ethylenically unsaturated carboxylic acid salt, the process comprising reacting an alkene and carbon dioxide in the presence of a carboxylation catalyst and releasing the α,β-ethylenically unsaturated carboxylic acid salt with a base,
wherein:
the carboxylation catalyst is a transition metal complex comprising a structurally constrained bidentate P,P ligand;
the P atoms of the P,P ligand are separated by 2 to 4 bridging atoms;
the bridging atoms are contained in at least one 5- to 7-membered cyclic substructures;
the base is at least one selected from the group consisting of a hydride, an amide, an alkoxide and an aryloxide;
the alkene has the following formula:
and
R a , R b and R c are each independently hydrogen, C 1-12 -alkyl, C 2-12 -alkenyl, or R a and R b together with the carbon atoms to which they are bonded are a mono- or diethylenically unsaturated, 5- to 8-membered carbocycle.
2. The catalytic process according to claim 1 , wherein:
each bridging atom of the P,P ligand that is directly linked to a P atom, together with the P atom to which it is linked is contained in a 5- to 7-membered cyclic substructure; or
two neighboring bridging atoms of the P,P ligand are contained in a 5- to 7-membered cyclic substructure.
3. The catalytic process according to claim 1 , wherein the structurally constrained bidentate P,P ligand is selected from the group consisting of:
a ligand of formula (IIa):
wherein
R 6 is independently selected from the group consisting of CHR 7 2 , CR 7 3 , and a C 3 -C 8 -cycloalkyl,
R 7 is independently a linear C 1 -C 4 -alkyl,
A 1 together with carbon atoms to which it is bound and an interjacent phosphorous atom forms a 5- to 7-membered cyclic substructure, and
R 8 is independently selected from the group consisting of hydrogen, a C 1 -C 12 -alkyl, a C 3 -C 12 -cycloalkyl, a C 3 -C 12 -heterocycloalkyl, a C 6 -C 14 -aryl, a C 6 -C 14 -heteroaryl, a C 1 -C 12 -alkoxy, a C 3 -C 12 -cycloalkoxy, a C 3 -C 12 -heterocycloalkoxy, a C 6 -C 14 -aryloxy, and a C 6 -C 14 -heteroaryloxy;
a ligand of formula (IIb):
wherein
R 10 is independently selected from the group consisting of a C 1 -C 8 -alkyl and a C 3 -C 8 -cycloalkyl,
R 11 is independently selected from the group consisting of CHR 10 2 , CR 10 3 , and a C 3 -C 8 -cycloalkyl,
X is independently selected from the group consisting of C—H, C—CH 3 , and N, and
A 2 together with moieties X to which it is bound and interjacent carbon atoms forms a 5- to 7-membered cyclic substructure; and
a ligand of formula (IIc):
wherein
R 13 and R 14 are independently a C 3 -C 8 -cycloalkyl, and
R 15 is H, O—C 1 -C 6 -alkyl, or both R 15 together constitute a —CH═CH— bridge.
4. The catalytic process according to claim 3 , wherein:
the structurally constrained bidentate P,P ligand is a ligand of formula (IIa); and
R 6 is CR 7 3 .
5. The catalytic process according to claim 3 , wherein:
the structurally constrained bidentate P,P ligand is a ligand of formula (IIa); and
A 1 is selected from the group consisting of ethylene, ethenylene, 1,2-phenylene, 1,2-naphthylene, 2,3-naphthylene, and formula:
6. The catalytic process according to claim 3 , wherein:
the structurally constrained bidentate P,P ligand is a ligand of formula (IIb); and
each R 10 is independently selected from the group consisting of a C 1 -C 6 -alkyl and a C 3 -C 7 -cycloalkyl; and
R 11 is CR 10 3 .
7. The catalytic process according to claim 3 , wherein:
the structurally constrained bidentate P,P ligand is a ligand of formula (IIb); and
A 2 is a —CH═CH— bridge.
8. The catalytic process according to claim 3 , wherein:
the structurally constrained bidentate P,P ligand is a ligand of formula (IIc); and
R 15 is H or OCH 3 .
9. The catalytic process according to claim 3 , wherein:
the structurally constrained bidentate P,P ligand is a ligand of formula (IIb); and
X is CH.
10. The catalytic process according to claim 1 , wherein the structurally constrained bidentate P,P ligand is selected from the group consisting of
wherein Cy represents cyclohexyl.
11. The catalytic process according to claim 1 , wherein the transition metal complex is a nickel complex.
12. The catalytic process according to claim 1 , wherein:
the alkene is ethene; and
the α,β-ethylenically unsaturated carboxylic acid is acrylic acid.
13. The catalytic process according to claim 1 , wherein the alkene and the carbon dioxide are reacted in the presence of a reducing agent.
14. The catalytic process according to claim 1 , wherein the reacting occurs in the presence of a reaction medium comprising an aprotic organic solvent.
15. The catalytic process according to claim 14 , wherein the aprotic organic solvent is selected from the group consisting of
a cyclic alkyl ether having 4 to 8 carbon atoms,
a dialkyl ether having 2 to 12 carbon atoms,
a cycloalkyl alkyl ether having 4 to 12 carbon atoms,
an aryl alkyl ether having 7 to 16 carbon atoms,
a biaryl having 12 to 16 carbon atoms,
a diaryl oxide having 12 to 16 carbon atoms,
a C 1 -C 8 -alkyl ester of a C 6 -C 10 -aryl monocarboxylic acid,
a di-C 1 -C 8 -alkyl ester of a C 6 -C 10 -aryl dicarboxylic acid,
a dialkyl carbonate having 3 to 13 carbon atoms,
a diether s consisting of a dioxyalkylene residue having 2 to 8 carbon atoms and two C 1 -C 8 -alkyl residues,
a benzenes wherein 1 to 4 hydrogen atoms are substituted by 1 to 4 C 1 -C 4 -alkyl residues,
a halogenated benzene,
an alkane having 5 to 18 carbon atoms, and
mixtures thereof.
16. The catalytic process according to claim 1 , wherein the base is an aryloxide.
17. The catalytic process according to claim 16 , wherein the aryloxide is selected from the group consisting of sodium 2-fluorophenolate, sodium 3-fluorophenolate, sodium 2-chlorophenolate, and sodium 3-chlorophenolate.
18. The catalytic process according to claim 16 , wherein the aryloxide is selected from the group consisting of sodium 2,6-dimethyl phenolate, sodium 2,6-diisopropyl phenolate, sodium 2-methyl-6-tert-butyl phenolate, sodium 2,6-di-tert-butyl phenoxide, sodium 2,6-dimethyl phenolate, sodium 2,6-dimethyl-4-tert-butyl phenolate, sodium 2,4,6-trimethyl phenolate, sodium 2,6-di-tert-butyl-4-methyl phenolate, sodium 2,6-di-tert-butyl-4-sec-butyl phenolate, and 2,4,6-tri-tert-butyl phenolate.
19. The catalytic process according to claim 1 , wherein:
the reacting occurs in the presence of a reaction medium;
the α,β-ethylenically unsaturated carboxylic acid salt is removed from the reaction medium;
the removal of the α,β-ethylenically unsaturated carboxylic acid salt from the reaction medium comprises a liquid-liquid phase separation into
a first liquid phase in which the α,β-ethylenically unsaturated carboxylic acid salt is enriched, and
a second liquid phase in which the carboxylation catalyst, the base and a conjugate acid of the base are enriched; and,
the first and second liquid phases are obtained by contacting the reaction medium with a polar solvent.
20. The catalytic process according to claim 16 , further, comprising regenerating the aryloxide by adding an alkaline material.