Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2003-09-26
2004-11-16
Killos, Paul J. (Department: 1625)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C568S346000, C568S397000, C568S398000
Reexamination Certificate
active
06818796
ABSTRACT:
A subject of the present invention is a process for preparation of fluorinated ketones. The invention is used more particularly for ketones having at least one fluorine atom, preferably three fluorine atoms at position &agr; with respect to the carbonyl group.
It is known to prepare an &agr;-trifluorinated ketone which consists of reacting an organometallic compound with trifluoroacetic acid or its esters [Chem. L. S. et al, J. Fluorine Chem. VIII, p. 117 (1981)].
This process has several disadvantages. It includes several stages, preparation of the organometallic compound from bromobenzene, then reaction with trifluoracetic acid at a low temperature (−78° C.) and hydrolysis, which complicates its implementation, and it is difficult to transfer to an industrial scale. Moreover, the reaction yield is not satisfactory due to the formation of by-products.
It is also known, in a general fashion, to prepare a ketone from one or more carboxylic acids according to the Piria reaction which consists of reacting the carboxylic acid or acids in the gaseous phase, in the presence of a metal oxide which can be chosen from the alkaline, alkaline-earth metal oxides, oxides of the metals of the groups IIIb, IVb and Vb.
It turns out that the preparation of a fluorinated ketone and more particularly an &agr;-trifluorinated ketone according to the Piria reaction has not been described in the literature, as defluorination of the starting reagent is carried out at high temperature, thus leading to fluorination of the catalyst.
A process has now been found, which constitutes the subject of the present invention, for preparation of a fluorinated ketone corresponding to the general formula:
in which:
R
1
and R
2
, which are identical or different, represent a hydrocarbon group containing 1 to 40 carbon atoms, which can be a linear or branched, saturated or unsaturated acyclic aliphatic group; a monocyclic or polycyclic, saturated, unsaturated or aromatic carbocyclic or heterocyclic group; a sequence of the above-mentioned groups.
at least one of the R
1
and R
2
groups does not comprise hydrogen atoms on the carbon atom at position &agr; with respect to the carbonyl group,
at least one of the R
1
and R
2
groups comprises one or more fluorine atoms,
said process being characterized in that, in the gaseous phase,
a carboxylic acid of Formula (II):
in which R
1
is as defined above,
and a carboxylic acid of formula (III):
in which R
2
is as defined above,
is reacted in the presence of a catalyst comprising at least one oxide of an element chosen from the rare earths, thorium, titanium and aluminum.
By “rare earth” is meant the lanthanides having an atomic number from 57 to 71, and yttrium as well as scandium.
According to the invention, carboxylic acids of Formulae (II) and (III) are divided, but the invention includes the use of carboxylic acid derivatives such as carboxylic acid anhydrides or corresponding ketenes.
The invention makes it possible to obtain symmetrical ketones if, in Formula (I), R
1
is identical to R
2
, and asymmetrical ketones if R
1
is different from R
2
.
More precisely, in Formulae (I) to (III), R
1
and R
2
represent a hydrocarbon group having 1 to 20 carbon atoms, which can be a linear or branched, saturated or unsaturated acyclic aliphatic group; a monocyclic or polycyclic, saturated, unsaturated or aromatic, carbocyclic or heterocyclic group; a linear or branched, saturated or unsaturated aliphatic group, carrying a cyclic substituent.
R
1
and R
2
preferably represent a linear or branched, saturated acyclic aliphatic group, preferably having 1 to 12 carbon atoms, and yet more preferably 1 to 4 carbon atoms.
The invention does not exclude the presence of an insaturation on the hydrocarbon chain, such as one or more double bonds which can be conjugated or non-conjugated, or a triple bond.
The hydrocarbon chain can optionally be interrupted by a heteroatom (for example oxygen or sulphur) or by a functional group to the extent that the latter does not react and a group such as in particular —CO— can in particular be mentioned.
The hydrocarbon chain can optionally carry one or more substituents (for example halogen, ester) to the extent that they do not interfere with the ketonization reaction.
The linear or branched, saturated or unsaturated acyclic aliphatic group can optionally carry a cyclic substituent. By ring is meant a saturated, unsaturated or aromatic, carbocyclic or heterocyclic ring.
The acyclic aliphatic group can be bonded to the ring by a valency bond, a heteroatom or a functional group such an oxy, carbonyl, carboxy, sulfonyl group, etc.
As examples of cyclic substituents, aromatic or heterocyclic, cycloaliphatic substituents can be envisaged, in particular cycloaliphatics comprising 6 carbon atoms in the ring, or benzenic, these cyclic substituents themselves optionally carrying any substituent to the extent that they do not impede the reactions intervening in the process of the invention. The alkyl, alkoxy groups having 1 to 4 carbon atoms can be mentioned in particular.
Among the aliphatic groups carrying a cyclic substituent, reference is made more particularly to the cycloalkylalkyl groups, for example cyclohexylalkyl, or the aralkyl groups having 7 to 12 carbon atoms, in particular benzyl or phenylethyl.
In Formulae (I) to (III), R
1
and R
2
can also represent a saturated or unsaturated carbocyclic group preferably having 5 or 6 carbon atoms in the ring; a saturated or unsaturated heterocyclic group, containing in particular 5 or 6 carbon atoms in the ring, including 1 or 2 heteroatoms such as nitrogen, sulphur and oxygen atoms; a monocyclic, aromatic carbocyclic or heterocyclic group, preferably phenyl, pyridyl, pyrazolyl, imidazolyl or polycyclic, condensed or non-condensed, preferably naphthyl.
As soon as one of the R
1
and R
2
groups comprises a ring, this can also be substituted. The substituent can be of any kind, to the extent that it does not interfere with the principal reaction. The number of substituents is generally 4 per ring at the most, but most often equal to 1 or 2.
Among all the meanings previously given for R
1
and R
2
, they preferably represent a linear or branched alkyl group having 1 to 12 carbon atoms, preferably 1 to 6 carbon atoms or a phenyl group.
As previously mentioned, at least one of the R
1
and R
2
groups does not comprise hydrogen atoms on the carbon atom at position a with respect to the carbonyl group.
Therefore, one of the carbon atoms at position a with respect to the carbonyl group is a tertiary carbon atom. It can be represented by the formula (R
3
) (R
4
) (R
5
) C—in which R
3
, R
4
, R
5
in particular represent a halogen atom, preferably a fluorine atom; a linear or branched alkyl group having 1 to 6 carbon atoms, the R
3
, R
4
, R
5
groups can also form a ring, for example a phenyl group.
As examples of carboxylic acids comprising a tertiary carbon atom, perfluorinated carboxylic acids can be mentioned.
In effect, the invention is used quite particularly for the preparation of fluorinated ketones from carboxylic acids, one of which is at least a fluorinated aliphatic carboxylic acid corresponding more particularly to Formula (IIa):
in which:
R
f
represents a perfluorinated chain of formula:
—[CF
2
]
p
—CF
3
in said formula, p represents a number from 0 to 10.
The preferred aliphatic carboxylic acids correspond to Formula (IIa) in which R
f
preferably represents the groups:
—CF
3
—CF
2
—CF
3
The invention is also used for the preparation of fluorinated ketones from fluorinated aromatic carboxylic acids, corresponding more particularly to Formula (IIb):
in which R
f
has the meaning given previously but preferably represents a trifluoromethyl group.
As examples of carboxylic acids of Formula (IIa) or Formula (IIb):
trifluoroacetic acid,
pentafluoroacetic acid,
the o-, m-and p-trifluoromethylbenzoic acids
can be mentioned.
As regards the carboxylic acid of Formula (III), those used preferably correspond to Formula (III) in which R
2
represents:
a linear or branched
Killos Paul J.
Rhodia Chimie
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