Process for preparing asymmetrical imidazolium salts

Patent metadata

Field	Value
Publication number	US-9688641-B2
Application number	US-201314651239-A
Country	US
Kind code	B2
Filing date	Dec 11, 2013
Priority date	Dec 12, 2012
Publication date	Jun 27, 2017
Grant date	Jun 27, 2017

Abstract

The invention relates to a process for preparing an asymmetrical imidazolium salt of formula (1A), in which R1 is an aromatic group, R2 is chosen from a cyclic secondary aliphatic alkyl group and a heteroalkyl group, R3 and R4 are chosen, independently of one another, from the group consisting of hydrogen, a halide and an alkyl group, and A″ is an anion. The process comprises a first substep of forming a reaction mixture by bringing one equivalent of an aniline into contact with one equivalent of a compound bearing an amine group, in the presence of at least four point five equivalents of a Brønsted acid. The process also comprises a second substep of forming a solution comprising one equivalent of a dicarbonyl, one equivalent of formaldehyde, and at least four point five equivalents of the Brønsted acid, and adding thereto the reaction mixture formed in the first substep. The mixture is left to stir for a predetermined time at a predetermined temperature. The intermediate asymmetrical imidazolium salt 1A is then isolated.

First claim

The invention claimed is:

1. Method of preparing an intermediate asymmetric imidazolium salt of formula 1A:

in which
R1 is an aromatic group,
R2 is selected from a secondary cyclic aliphatic alkyl group and a heteroalkyl group,
R3 and R4 are selected independently of one another from the group consisting of hydrogen, a halide and an alkyl group, and
A− is an anion,
comprising the following steps:
a. forming a reaction mixture by contacting one equivalent (1 eq) of an aniline of formula 2:

with one equivalent (1 eq) of a compound of formula 3:

in the presence of at least four point five equivalents (4.5 eq) of a Brønsted acid of formula 4:
AH  (4);

b. forming a solution comprising one equivalent (1 eq) of a dicarbonyl of formula 5

one equivalent (1 eq) of formaldehyde, and at least four point five equivalents (4.5 eq) of the Brønsted acid of formula 4, heating said solution to about 80° C. and then adding the reaction mixture formed in step a.;
c. stirring for at least 2 hours at about 80° C.; and
d. isolating the intermediate asymmetric imidazolium salt of formula 1A.

2. Method of preparing an asymmetric imidazolium salt of formula 1B:

in which
R1 is an aromatic group,
R2 is selected from a secondary cyclic aliphatic alkyl group and a heteroalkyl group,
R3 and R4 are selected independently of one another from the group consisting of hydrogen, a halide and an alkyl group, and
A− is selected from the group consisting of a tetrafluoroborate anion, a hexafluorophosphate anion, a hexafluoroantimony anion, a tetrakis[(3,5-trifluoromethyl)phenyl]borate anion and a halide anion,
said method comprising steps a. to d. according to claim 1 , and further comprising the steps of:
e. adding one equivalent (1 eq) of an inorganic salt and solvent, preferably dichloromethane, to the intermediate asymmetric imidazolium salt isolated in step d.;
f. stirring at room temperature for at least one hour and carrying out water/organic solvent extraction followed by evaporation of said organic solvent;
g. precipitating by a polar organic solvent, then isolating the asymmetric imidazolium salt of formula 1B.

3. Method of preparing an asymmetric imidazolium salt according to claim 2 , in which the inorganic salt in step e. is selected from the group consisting of potassium tetrafluoroborate, sodium tetrafluoroborate, lithium tetrafluoroborate, hydrogen tetrafluoroborate, ammonium tetrafluoroborate, potassium hexafluorophosphate, sodium hexafluorophosphate, lithium hexafluorophosphate, hydrogen hexafluorophosphate, ammonium hexafluorophosphate, silver hexafluoroantimony, potassium hexafluoroantimony, sodium hexafluoroantimony, lithium hexafluoroantimony, potassium tetrakis[(3,5-trifluoromethyl)phenyl]borate, sodium tetrakis[(3,5-trifluoromethyl)phenyl]borate and lithium tetrakis[(3,5-trifluoromethyl)phenyl]borate and halogen acid.

4. Method of preparing an asymmetric imidazolium salt of formula 1C:

in which
R1 is an aromatic group,
R2 is a heteroalkyl group,
R3 and R4 are selected independently of one another from the group consisting of hydrogen, a halide and an alkyl group, and
A− is a negative charge on group R2,
said method comprising steps a. to d. according to claim 1 , and further comprising the steps of:
h. adding at least ten equivalents (10 eq) of a carbonate base to the intermediate asymmetric imidazolium salt isolated in step d.;
i. isolating the asymmetric imidazolium salt of formula 1C.

5. Method of preparing an asymmetric imidazolium salt according to claim 4 , in which said carbonate base in step h. is selected from the group consisting of sodium bicarbonate, potassium bicarbonate, sodium hydrogen carbonate and potassium hydrogen carbonate.

6. Method according to claim, in which the Brønsted acid of formula 4 in said steps a. and b. is acetic acid.

7. Method according to claim 1 , in which R1 is selected from the group consisting of 2,4,6-trimethylphenyl, 3,5-dinitrophenyl, 2,4,6-tris(trifluoromethyl)phenyl, 2,4,6-trichlorophenyl, and hexafluorophenyl.

8. Method according to one of claim 1 , in which R2 is selected from the group consisting of cyclopentyl, cyclohexyl, cyclooctyl, cyclodecyl, cyclododecyl, and cyclopentadecyl.

9. Method according to claim 4 , in which R2 is selected from the group consisting of 3-methyl butanoate and 3,3-dimethyl butanoate.

10. Method according to claim 1 , in which R3 and R4 are each hydrogen.

11. Asymmetric imidazolium salt of formula 1D comprising:

in which
R1 is selected from the group consisting of 2,4,6-trimethlphenyl, 3,5-dinitrophenyl, 2,4,6-tris(trifluoromethyl)phenyl, 2,4,6-trichlorophenyl, and hexafluorophenyl,
R2 is a secondary cyclic aliphatic alkyl group,
R3 and R4 are selected independently of one another from the group consisting of hydrogen, a halide and an alkyl group, and
A− is an anion selected from the group consisting of a tetrafluoroborate anion, a hexafluorophosphate anion, an acetate anion, a hexafluoroantimony anion, a tetrakis[(3,5-trifluoromethyl)phenyl]borate anion and a halide anion.

12. Asymmetric imidazolium salt according to claim 11 , in which R2 is selected from the group consisting of cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclodecyl, cyclododecyl, and cyclopentadecyl.

13. Asymmetric imidazolium salt according to claim 11 , in which R3 and R4 are each hydrogen.

Assignees

• Ecole Nat Superieure De Chimie De Rennes
• Centre Nat Rech Scient

Inventors

• Mauduit Marc
• Basle Olivier
• Rouen Mathieu

Classifications

• C07D233/56 Primary

  with only hydrogen atoms or radicals containing only hydrogen and carbon atoms, attached to ring carbon atoms · CPC title

• C07D233/58

  with only hydrogen atoms or radicals containing only hydrogen and carbon atoms, attached to ring nitrogen atoms · CPC title

• C07D233/60

  with hydrocarbon radicals, substituted by oxygen or sulfur atoms, attached to ring nitrogen atoms · CPC title