Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
1999-06-01
2001-06-12
Higel, Floyd D. (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
C546S348000, C546S349000
Reexamination Certificate
active
06245918
ABSTRACT:
The present invention relates to a process for preparing an ionic compound Q
+
A
−
, which is a liquid at low temperature, by reacting a trialkyloxonium of the anion and an amine, in a hydrocarbon solvent, and to its use.
Said compound forms part of non aqueous ionic media, also known as molten salts, which are organic/inorganic slats with general formula Q
+
A
−
, wherein Q
+
represents a quaternary ammonium ion and A
−
represents an anion which is known to be non coordinating and capable of forming a liquid salt at low temperatures, such as, as is preferable, tetrafluoroborate, hexafluoroborate, hexafluoroantimonate, hexafluoroarsenate and tetrachloroaluminate anions. The quaternary ammonium cations are preferably imidazolium and pyridinium, such as 1-methyl-3-butylimidazolium, 1-ethyl-1-butylimidazolium or N-butylpyridinium. These media can be used as solvents in catalytic reactions.
Different methods for preparing these salts are known. As an example, in J. Chem. Comm. 965 (1992). Wilkes describes a synthesis method starting from silver salts such as acetates, tetrafluoroborates, nitrates, sulphates and 1-ethyl-3-methylimidazolium chloride in a water-methanol mixture as the solvent. The silver chloride is filtered at the end of the reaction and the solvent is evaporated off under vacuum.
Further, in International patent WO 96/18459, a more economical process has been described wherein lead salts are reacted with acetate, fluoroborate, nitrate and sulphate anions with pyridinium, imidazolium and phosphonium chlorides in the same water-methanol solvent.
However, for use as solvents for Diels-Alder reactions and reactions catalyzed by transition metals such as hydrogenation, hydroformylation, isomerization of the double bond in the olefin, the presence of residual chloride ions or traces of water in the molten salts can have a deleterious effect on the catalytic activity of the system. One means which is usually used to eliminate practically all of the chloride ions is to wash the salt with water when the salt is not miscible with water.
The preparation methods described above have the disadvantage of resulting in ionic media from which it is difficult to eliminate traces of unreacted chloride ions and traces of water. This is particularly the case for salts which are miscible with water, for example tetrafluoroborate salts such as those of 1-methyl-3-butylimidazolium tetrafluoroborate for which the unreacted dialkylimidazolium chloride cannot be eliminated by washing with water.
It has now been discovered that it is possible to use in these processes these salts which are liquid at low temperature, i.e., below 150° C., or even below 120° C., advantageously below 90° C., and preferably at most 85° C., and at most 50° C. synthesized in the absence of free chloride ion by reacting the trialkyloxonium of the anion with an amine in a hydrocarbon solvent. The reaction is advantageously carried out in the absence of water or in the presence of small quantities of water supplied, for example, by the solvent.
A further advantage of the present invention is that the only by-product formed during the preparation is a volatile ether which is readily separable from the salt by vacuum evaporation.
The amines of the invention preferably have general formulae NR
1
R
2
R
3
(I) or general formulae R
1
N═CR
2
R
3
(II), where R
1
, R
2
and R
3
, which may be identical or different, represent hydrogen with the exception of ammonia, and preferably a single substituent represents hydrogen, or hydrocarbyl residues containing 1 to 12 carbon atoms, for example saturated or unsaturated, cycloalkyl or aromatic, aryl or aralkyl alkyl groups containing 1 to 12 carbon atoms. The amines can also be derivatives of nitrogen-containing heterocycles containing 1, 2 or 3 nitrogen atoms with general formulae (III) and (IV):
where the cycles are constituted by 4 to 10 atoms, preferably 5 to 6 atoms, R
1
being as defined above.
The amines can have the following formula:
R
1
N═CR
2
—R
4
—R
2
C═NR
1
(V)
where R
1
and R
2
, which may be identical or different, are as defined above and R
4
represents as alkylene or phenylene residue. Examples of groups R
1
and R
2
are methyl, ethyl, propyl, isopropyl, butyl, secondary butyl, tertiary butyl, amyl, methylene, ethylidene, phenyl or benzyl radicals; R
4
can be a methylene, ethylene, propylene or phenylene group.
The amine is preferably selected from the group formed by pyridine, 1-methylimidazole, 1-ethylpyrazole, 1-ethylimidazole, 1-butylimidazole and 1,2-dimethylimidazole.
The trialkyloxonium of the anion is selected from the group formed by the trimethyloxonium and the triethyloxonium of the anion.
The hydrocarbon solvent used in the invention is preferably non miscible with the ionic medium formed. Advantageously, a polar solvent is used. It contains no or only a little water. Examples are 1,2-dichloroethane, dichloromethane, and 1,1,1-trichloroethane.
The temperature at which the reaction is carried out is in the range 50° C. to 200° C.; advantageously the temperature is less than 150° C. and advantageously less than 90° C. and will remain below the decomposition temperature of the reactants.
The molar ratio between the trialkoxonium of the anion and the amine is in the range 0.5 to 3, preferably in the range 0.9 to 2.
REFERENCES:
patent: 0 404 179 (1990-12-01), None
patent: 0 748 653 (1996-12-01), None
patent: 0 748 785 (1996-12-01), None
patent: 2 684 375 (1993-06-01), None
patent: 98/06106 (1998-02-01), None
Favre Frédéric
Olivier Helene
Higel Floyd D.
Institut Francais du Pe'trole
Millen White Zelano & Branigan P.C.
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