FR2768728A1 - A new process for the acylation of an aromatic compound - Google Patents

Abstract

The use of a uranium and/or uranyl halide as a catalyst for the preparation of acylated aromatic compounds, particularly alkoxyaromatic alkylketones.TF - TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The preferred aromatic compound is of general formula (I) : - -A = (i) mono or polyaromatic carbocyclic, (ii) mono or polyheterocyclic aromatic, or (iii) a compound comprising interconnected rings defined in (i) and (ii) and optionally connected by a group B; - R = H, OH, halogen, preferably F, Cl or Br, CF3, 1 - 6C (preferably 1-4C) alkyl, 2-6C (preferably 2-4C) alkenyl, (preferably 1-4C) 1 - 4C alkoxy, CHO, cyclohexyl, 2 - 6C acyl, -R1OH, -R1COOR2, -R1CHO, -R1NO2, -R1CN, -R1N(R2)2, -R1CON(R2)2, -R1X, -R1ZR2, -R1CF3 or -ZCF3; - R1 = a single bond or 1 - 6C divalent hydrocarbyl (optionally unsaturated); - R2 = H, 1 - 6C alkyl or phenyl; - X = Cl, Br or F; - Z = O, S, SO, SO2 or SO3; - n = 0, 1, 2 or 3; - B = a single bond, 1 - 4C alkylene or alkylidene, (preferably methylene or isopropylidene), -O-, -CO-, -COO-, -S-, -SO-, -SO2-, -SO3-, -N(R0)- or -CON(R0)-; - R0 = H, 1 - 4C alkyl, cyclohexyl or phenyl; - Preferably R is methyl, ethyl, (iso)propyl, (iso, sec. or tert.)butyl, vinyl, allyl, methoxy, ethoxy, (iso)propoxy or butoxy.- More preferably, the compound is of general formula (Ia) : - --or (Ib) : - -R, B and n = as above; - m = 0, 1 or 2; - p = 0, 1, 2 or 3; - The preferred acylating compound is of formula (II) : - -X1 = Halogen, preferably Cl or Br, or -OCOR4; - R3 = 1 - 24C (preferably 1-12C) alkyl, 2-4C cycloalkyl or aromatic, or an aliphatic group containing a cyclic substituent; - R4 = R3 or similar group - Preferred Process: The aromatic compound is reacted with an acylating agent in the presence of a suitable amount of a uranium and/or uranyl halide at 20 - 200degreesC , preferably 80 - 170degreesC. The ratio of moles of aromatic compound to moles of acylating agent is 0.1 - 10, preferably 1.0 - 5.0, and the ratio of moles of catalyst to moles of acylating agent is less than 1.0, preferably 0.001 - 0.8, more preferably 0.02 - 0.2.- INORGANIC CHEMISTRY - The catalyst is a uranium and/or uranyl halide in which the oxidation state of U is +4 or +6.A preferred system is a uranyl chloride or a uranium nitrate associated with a halogen source.The catalyst may be generated in situ by using a uranium compound associated with a halogen source. The uranium may be as the metal or oxide ; a mineral salt, e.g. nitrate, sulfate etc., or acetylacetonate ; or carboxylate, preferably acetate.The halogen source may be chlorine or bromine ; HCl or HBr ; SiCl4 or halogenosilanes ; PCl3 or SCl2

Description

PROCESS FOR ACYLATION OF AN AROMATIC COMPOUND
The present invention relates to a process for acylating an aromatic compound.

 The term "acylation" must be taken in a broad sense and includes, in particular, benzoylation reactions.

 The invention is particularly applicable to the preparation of alkoxyaromatic alkyl ketones.

 Conventional acylation processes for aromatic compounds, in particular phenol ethers, use, as an acylation reagent, a carboxylic acid, or a derivative thereof such as an acid halide, an ester or an anhydride.

 The reaction is generally carried out in the presence of a catalyst of the Lewis acid type (for example AlCl 3) or of the Brönsted acid type (H 2 SO 4, HF, etc.).

 An illustration of this Friedel-Crafts process is given by the work of C. KURODA et al [Sci. Papers Inst. Phys. Chem. Res. iia, pp. 51-60 (1932)] which described the preparation of methoxyacetophenones, by reaction of an aromatic compound carrying 1 to 3 methoxy groups with acetyl chloride, in the presence of aluminum chloride.

 However, the use of aluminum chloride has many disadvantages. Aluminum chloride is a corrosive and irritating product. In addition, it is necessary to use a large amount of aluminum chloride at least equal to the stoichiometry, as a result of the complexation of the ketone formed. As a result, aluminum chloride is therefore not a true catalyst.

 At the end of the reaction, it is necessary to remove the aluminum chloride from the reaction medium by acid or basic hydrolysis.

 This hydrolysis technique involves the addition of water to the reaction medium which considerably complicates the implementation of the process since the metal cation, and more particularly the aluminum cation then forms in the presence of water, polyoxo-etlou complexes. polyhydroxo-aluminum of milky consistency, difficult then to separate. This results in the need for a long and expensive treatment comprising, after the hydrolysis, an extraction of the organic phase, a separation of the aqueous and organic phases, or even a drying of the latter. The separation of aluminum chloride is therefore long and expensive.

 In addition, there is the problem of saline aqueous effluents which must then be neutralized which imposes an additional operation.

 In addition, aluminum chloride can not be recycled because of its hydrolysis.

 To overcome this drawback, Atsushi KAWADA et al [J. Chem. Soc. Chem.

Common. pp. 1158 (1993)] have proposed carrying out the acylation reaction of an aromatic compound with acetic anhydride in the presence of a catalytic amount of lanthanide trifluoromethanesulfonate, and in particular ytterbium.

 Acetylation of the anisole with acetic anhydride catalyzed by 20 mol% of ytterbium trifluoromethanesulphonate is carried out in several solvents: carbon disulfide, dichloroethane and nitromethane.

 The disadvantage of this process is that it is not likely to be implemented on an industrial scale, because the best yields are obtained by conducting the reaction in nitromethane which is not a solvent. usable industrially.

 The present invention achieves this objective and provides a method of overcoming the aforementioned drawbacks.

 It has now been found and this is the object of the present invention, a method of acylating an aromatic compound which comprises reacting said aromatic compound with an acylating agent, in the presence of a characterized in that the acylation reaction is conducted in the presence of an effective amount of at least one uranium halide and / or uranyl.

 According to the process of the invention, an aromatic compound is acylated in the presence of at least one uranium halide and / or uranyl.

More specifically, the subject of the present invention is a process for the acylation of an aromatic compound corresponding to the general formula (I): in which:

- A symbolizes the remainder of a cycle forming all or part of a system
carbocyclic or heterocyclic, aromatic, monocyclic or polycyclic:
said cyclic residue being able to carry a radical R representing an atom
hydrogen or one or more substituents, identical or different,
n represents the number of substituents on the cycle.

The invention is particularly applicable to aromatic compounds corresponding to formula (I) in which A is the residue of a cyclic compound, preferably having at least 4 atoms in the ring, optionally substituted, and representing at least one one of the following cycles:
an aromatic carbocycle, monocyclic or polycyclic,
an aromatic, monocyclic or polycyclic heterocycle comprising at least
minus one of the heteroatoms O, N and S.

 It will be specified, without limiting the scope of the invention, that the optionally substituted residue A represents the remainder: 1 "- of an aromatic carbocyclic compound, monocyclic or polycyclic.

"Polycyclic carbocyclic compound" means:
. a compound consisting of at least 2 aromatic carbocycles and forming
between them ortho- or ortho- and peri-condensed systems,
a compound consisting of at least 2 carbocycles of which only one of
it is aromatic and forming between them ortho- or ortho- and
peri.

 2 "- an aromatic heterocyclic compound, monocyclic or polycyclic.

By "polycyclic heterocyclic compound" is defined:
a compound consisting of at least 2 heterocycles containing at least one
heteroatom in each cycle of which at least one of the two cycles is
aromatic and forming between them ortho- or ortho- and ortho-
peri,
. a compound consisting of at least one hydrocarbon ring and at least one
heterocycle of which at least one of the rings is aromatic and forming between
they are ortho- or ortho- and peri-condensed systems.

3c - a compound consisting of a series of cycles, as defined in paragraphs 1 and / or 2 linked together:
. by a valid link,
. with an alkylene or alkylidene radical having 1 to 4 carbon atoms,
preferably a methylene or isopropylidene radical,
. by one of the following groups:
-O-, -CO-, -COO-, -OCOO

in these formulas, Ro represents a hydrogen atom or a radical
alkyl having 1 to 4 carbon atoms, a cyclohexyl radical or
phenyl.

Examples of cycles under 1 "to 3 are:
1 "- benzene, toluene, xylene, naphthalene, anthracene,
2 "- furan, pyrrole, thiofen, isoxazole, furazan, isothiazole, imidazole,
pyrazole, pyridine, pyridazine, pyrimidine, quinoline, naphthyridine,
benzofuran, indole,
Biphenyl, 1,1'-methylenebiphenyl, 1,1'-isopropylidenebiphenyl, 1, 1
oxybiphenyl, 1,1'-iminobiphenyl.

 In the process of the invention, use is preferably made of an aromatic compound of formula (I) in which A represents a benzene ring.

 The aromatic compound of formula (I) may carry one or more substituents.

 The number of substituents present on the ring depends on the carbon condensation of the ring and the presence or absence of unsaturations on the ring.

 The maximum number of substituents likely to be borne by a ring is easily determined by those skilled in the art.

 In the present text, the term "several", generally, less than 4 substituents on an aromatic ring.

 Examples of substituents are given below but this list is not limiting in nature. The nature of the substituents is not critical insofar as they do not interfere with the desired product. In the case of the presence of a hydroxyl group on the starting substrate, it may be useful to protect it, in a conventional manner, in particular by reaction with a dihydropyran which will be removed after reaction.

The residue A may optionally carry one or more substituents which are represented in formula (I) by the symbol R and whose preferred meanings are defined below: the radical (s) R represent one of the groups following:
a hydrogen atom,
. a linear or branched alkyl radical having from 1 to 6 carbon atoms,
preferably from 1 to 4 carbon atoms, such as methyl, ethyl, propyl,
isopropyl, butyl, isobutyl, sec-butyl, tert-butyl,
a linear or branched alkenyl radical having from 2 to 6 carbon atoms,
preferably from 2 to 4 carbon atoms, such as vinyl, allyl,
. a linear or branched alkoxy radical having 1 to 6 carbon atoms,
preferably from 1 to 4 carbon atoms such as methoxy, ethoxy,
propoxy, isopropoxy, butoxy,
a cyclohexyl radical,
an acyl group having 2 to 6 carbon atoms,
a radical of formula:
-R1 -OH
-R 1 -COOR2
-Ri -CHO
-R 1 -NO2
-R1-CN
-R 1 -N (R 2) 2 -R 1 -CO-N (R 2) 2
-R1-X -R1 -Z-R2
-R1 -CF3
-Z-CF3
in said formulas, R1 represents a valency bond or a radical
divalent hydrocarbon, linear or branched, saturated or unsaturated, having from 1 to 6
carbon atoms such as, for example, methylene, ethylene, propylene,
isopropylene, isopropylidene; the identical or different radicals R2
represent a hydrogen atom or a linear or branched alkyl radical
having 1 to 6 carbon atoms or a phenyl radical; X symbolizes a
halogen atom, preferably a chlorine, bromine or fluorine atom; Z
represents one of the following groups: O, S, SO, SO2, SO3.

 When n is greater than or equal to 2, two radicals R and the two successive atoms of the aromatic ring may be bonded together by an alkylene, alkenylene or alkenylidene radical having from 2 to 4 carbon atoms to form a saturated, unsaturated or aromatic heterocycle having from 5 to 7 carbon atoms. One or more carbon atoms may be replaced by another heteroatom, preferably oxygen. Thus, the radicals R may represent a methylene dioxy or ethylene dioxy radical.

The present invention is particularly applicable to aromatic compounds corresponding to formula (I) in which: the radical (s) R represent one of the following groups:
a hydrogen atom
an OH group,
a linear or branched alkyl radical having from 1 to 6 carbon atoms,
. a linear or branched alkenyl radical having from 2 to 6 carbon atoms
a linear or branched alkoxy radical having from 1 to 6 carbon atoms,
a -C HO group,
. an acyl group having 2 to 6 carbon atoms,
a group -COOR2 where R2 has the meaning given above,
. a group CO-N (R2) 2 where R2 has the meaning given above
. a halogen atom, preferably fluorine, chlorine or bromine,
a -CF3 group.

 n is a number equal to 1, 2 or 3.

 Preferred substituents are those that activate the aromatic ring, such as electron donor groups.

The concept of electro-donating groups is defined in the literature. One can refer among other things1 to the work of Jerry MARCH - Advanced Organic
Chemistry, 4th Edition, John Wiley and Sons, 1992, Chapter 9, pp. 273 - 292.

dans ladite formule (la), m représente un nombre égal à 0, 1 ou 2 et les symboles
R, identiques ou différents et n, ayant la signification donnée précédemment, - un composé constitué par un enchaînement de deux ou plusieurs carbocycles aromatiques monocycliques répondant à la formule (lob)

dans ladite formule (Ib), les symboles R, identiques ou différents et n, ont la signification donnée précédemment, p est un nombre égal à 0, 1, 2 ou 3 et B représente:
- un lien valentiel
- un radical alkylène ou alkylidène ayant de 1 à 4 atomes de carbone1 de
préférence, un radical méthylène ou isopropylidène,
- I'un des groupes suivants:

Among the compounds of formula (I), those of the following formulas are more particularly used: a monocyclic or polycyclic aromatic carbocyclic compound with rings which can form between them an orthocondensed system corresponding to formula (Ia):

in said formula (la), m represents a number equal to 0, 1 or 2 and the symbols
R, identical or different and n, having the meaning given above, a compound consisting of a chain of two or more monocyclic aromatic carbocycles corresponding to the formula (lob)

in said formula (Ib), the symbols R, identical or different and n, have the meaning given above, p is a number equal to 0, 1, 2 or 3 and B represents:
- a valid link
an alkylene or alkylidene radical having from 1 to 4 carbon atoms
preferably, a methylene or isopropylidene radical,
- one of the following groups:

in these formulas1 Ro represents a hydrogen atom or a radical
alkyl having 1 to 4 carbon atoms, a cyclohexyl radical or
phenyl.

The compounds of formula (I) used preferentially correspond to formulas (Ia) and (Ib) in which:
R represents a hydrogen atom, a hydroxyl group, an amine group,
an amide group, an ester group, a linear alkyl or alkoxy radical or
branched having from 1 to 6 carbon atoms, preferably from 1 to 4 carbon atoms
carbon or a halogen atom,
B symbolizes a valency bond, an alkylene or alkylidene radical having from 1 to 4
carbon atoms or an oxygen atom,
-equal toOou 1,
- equal to 0, 1 or 2,
- p is equal to 0 or 1.

 Even more preferentially, the compounds of formula (I) in which R represents a hydrogen atom, a hydroxyl group, a methyl radical, a methoxy radical or a halogen atom are chosen.

The process of the invention is more particularly applicable to aromatic ethers of formula (Ia) in which:

n is a number less than or equal to 4, preferably equal to 1 or 2,
the radical R 'represents a linear or branched alkyl radical having from 1 to 6
carbon atoms, preferably from 1 to 4 carbon atoms, such as
methyl, ethyl1 propyl1 isopropyl, butyl, isobutyl, sec-butyl, tert-butyl
or a phenyl radical,
the radical or radicals R represent one of the following atoms or groups
mentioned as substituents of the remainder A of the formula (I),
the radicals R 'and R and the two successive atoms of the benzene ring can
form between them, a ring having from 5 to 7 atoms, comprising
possibly another heteroatom.

When n is greater than or equal to 1, the radicals R 'and R and the two successive atoms of the benzene ring may be linked together by an alkylene-alkenylene or alkenylidene radical having from 2 to 4 carbon atoms to form a saturated, unsaturated heterocycle or aromatic having from 5 to 7 carbon atoms. One or more carbon atoms may be replaced by another heteroatom, preferably oxygen. Thus, the radicals OR 'and R can represent a methylene radical dioxy or ethylene dioxy
In formula (Ia), R 'preferably represents a linear or branched alkyl radical having from 1 to 4 carbon atoms, preferably a methyl or ethyl radical.

 The aromatic compound of formula (I) may carry one or more R.

R is more preferably one of the following atoms or groups:
a linear or branched alkyl radical having from 1 to 6 carbon atoms,
preferably from 1 to 4 carbon atoms, such as methyl, ethyl, propyl,
isopropyl, butyl, isobutyl, sec-butyl, tert-butyl,
a linear or branched alkoxy radical having 1 to 6 carbon atoms,
preferably from 1 to 4 carbon atoms such as methoxy radicals,
ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, tert-butoxy,
a halogen atom, preferably a fluorine, chlorine or bromine atom,
a trifluoromethyl radical.

Preferred in the process of the invention are aromatic ethers of formula (I) or (Ia) in which:
-equal toOou 1,
R 'represents a linear or branched alkyl radical having from 1 to 6 carbon atoms
carbon or a phenyl radical,
R represents a linear or branched alkoxy radical having from 1 to 4 carbon atoms;
carbon, preferably a methoxy or ethoxy radical.

 the radicals OR 'and R form a methylene dioxy or ethylene dioxy radical.

 The process of the invention is more particularly applicable to aromatic ethers of formula (Ia) in which n is equal to 1, the radicals R and OR 'both representing identical or different alkoxy radicals.

By way of illustration of compounds corresponding to formula (I), mention may be made more particularly of:
halogenated or non-halogenated aromatic compounds such as toluene,
chlorobenzene, chlorotoluenes, fluorotoluenes, bromobenzene,
trifluoromethylbenzene, trifluoromethoxybenzene, trichloromethyl
benzene, trichloromethoxybenzene, trifluoromethylthiobenzene,
aromatic amine compounds such as aniline,
phenolic compounds such as o-cresol, galacol and ketol,
monoethers such as anisole, ethoxybenzene (phenetole),
butoxybenzene, isobutoxybenzene, 2-chloroanisole, 3-chloroanisole,
2-bromoanisole, Sbromoanisole, 2-methylanisole, 3-methylanisole,
2-ethylanisole, 3-ethylanisole, 2-isopropylanisole, 3-isopropylanisole,
2-propylanisole, 3-propylanisole, 2-allylanisole, 2-butylanisole, 3
butylanisole, 2-tert-butylanisole, 3-tert-butylanisole, 2-benzylanisole,
2-cyclohexylanisole, 1-bromo-2-ethoxybenzene, 1-bromo3-
ethoxybenzene, 1-chloro-2-ethoxybenzene, 1-chloro-3-ethoxybenzene,
1-ethoxy-2-ethylbenzene, 1-ethoxy-3-ethylbenzene, 2,3
dimethylanisole, 2,5-dimethylanisole,
diethers such as veratrole, 1,3-dimethoxybenzene, 1,2
diethoxybenzene, 1,3-diethoxybenzene, 1,2-dipropoxybenzene, 1,3
dipropoxybenzene, 1,2-methylenedioxybenzene, 1,2-ethylene
dioxybenzene,
triethers such as 1, 2,3-trimethoxybenzene, 1,3,5-trimethoxybenzene,
1,3,5-triethoxybenzene.

 The compounds to which the process according to the invention is more particularly applicable are anisole, veratrole, 1,2-methylenedioxybenzene and 2-methoxynaphthalene.

 With regard to the acylation reagent, the carboxylic acids and their derivatives, halides or anhydrides are preferably used with anhydrides.

The acvlation reagent more particularly corresponds to formula (II): embedded image in which: R 3 represents:

a saturated or unsaturated, linear or branched aliphatic radical having from 1 to
24 carbon atoms; a cycloaliphatic radical, saturated, unsaturated or
aromatic, monocyclic or polycyclic, having from 4 to 12 carbon atoms
carbon; a saturated or unsaturated aliphatic radical, linear or branched,
carrier of a cyclic substituent,
X 'represents:
. a halogen atom, preferably a chlorine or bromine atom,
. a radical -O-CO-R4 with R4, identical to or different from R3, having the same
meaning that R3.

 The term "cyclic substituent" preferably means a saturated, unsaturated or aromatic carbocyclic ring, preferably cycloaliphatic or aromatic cycloaliphatic ring in particular comprising 6 carbon atoms in the ring or benzene.

 More preferentially, R3 represents a linear or branched alkyl radical having from 1 to 12 carbon atoms, preferably from 1 to 6 carbon atoms: the hydrocarbon chain possibly being interrupted by a heteroatom (for example, oxygen), by a functional group (for example -CO-) and / or carrying substituents (for example, halogen atoms or a CF 3 group).

 R3 preferably represents an alkyl radical having 1 to 4 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, secbutyl, tert-butyl.

 The radical R3 also preferably represents a phenyl radical which may be optionally substituted. It is necessary that this radical is more deactivated than the aromatic compound, otherwise the acylation agent itself would be acylated.

As more specific examples of substituents, there may be mentioned, in particular:
a linear or branched alkyl radical having from 1 to 6 carbon atoms,
preferably from 1 to 4 carbon atoms, such as methyl, ethyl, propyl,
isopropyl, butyl, isobutyl, sec-butyl, tert-butyl,
a linear or branched alkoxy radical having 1 to 6 carbon atoms,
preferably from 1 to 4 carbon atoms such as methoxy, ethoxy,
propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, tert-butoxy,
a hydroxyl group,
. a halogen atom, preferably a fluorine, chlorine or bromine atom.

 The preferred acylating agents correspond to the formula (II) in which X 'represents a chlorine atom and R3 represents an alkyl radical having from 1 to 4 carbon atoms, preferably methyl or ethyl, optionally carrying carbon atoms. halogen, preferably chlorine.

 When the acylating agent is an acid anhydride, the preferred compounds correspond to formula (II) in which R 3 and R 4 are identical and represent an alkyl radical having from 1 to 4 carbon atoms, optionally carrying atoms. halogen, preferably chlorine.

By way of illustration of acylating agents corresponding to formula (II), mention may be made more particularly of:
acetyl chloride,
- monochloroacetyl chloride,
dichloroacetyl chloride,
propanoyl chloride,
isobutanoyl chloride,
pivaloyl chloride,
stearoyl chloride,
- crotonyl chloride,
- benzoyl chloride,
chlorobenzoyl chlorides,
p-nitrobenzoyl chloride
methoxybenzoyl chlorides,
naphthoyl chlorides,
- acetic anhydride,
Isobutyric anhydride,
Trifluoroacetic anhydride,
Benzoic anhydride.

 Benzoyl chloride and acetyl chloride are the preferred acylating agents.

 According to the process of the invention, the acylation reaction of an aromatic compound is carried out in the presence of a catalyst consisting of a uranium halide and / or uranyl or any compound capable of generating it.

 In the aforementioned halogenated compounds, uranium is generally at the +4 or +6 oxidation state.

 It is also possible to use any uranium compound insofar as it is associated with a source of halogen.

 Indeed, it is possible to generate a halide in situ and therefore, implement any compound of the aforementioned elements insofar as it is associated with a halogen source.

Thus, one can appeal to metal or in any form. We can
bring them in the form of metal or oxides or salt form, simple salt or
double, mineral or organic.

More precisely, the uranium element can be provided in the form of a
metal or in the form of an oxide. It is possible to use a mineral salt of
preferably, nitrate, sulfate, oxysulfate, carbonate, oxalate or an organic salt
preferably, acetylacetonate; carboxylate and even more preferentially
acetate.

 Regarding the halogen source, it is possible to use any compound capable of providing halogen ions for generating in situ the uranium halide and / or uranyl.

 As examples of halogen sources, halogen can be used in molecular form; any inorganic or organic acid halide, and more particularly aliphatic carboxylic acids; any uranium, mineral or organic salt likely to generate a halogenated form.

 More specific examples include chlorine or bromine: hydrochloric acid, hydrobromic acid; acetyl chloride; SiCI4 silicon chloride, halosilanes such as Me3SiCl, Me2SiCl2, MeSiCl3, PhMe2SiCl, phosphorus chloride Pu13, sulfur chloride Su12.

The uranium compounds used preferentially are uranium tetrachloride and uranyl chloride; Uranium oxide (in particular
U308) and uranium nitrate associated with a source of halogen.

 According to the process of the invention, the reaction between the aromatic compound and the acylating agent can be conducted in the presence or absence of an organic solvent: one of the reagents can be used as a reaction solvent.

 A variant of the process of the invention consists in conducting the reaction in an organic solvent.

 The choice of the solvent is made taking into account the reactivity of the starting substrate. It must be inert with respect to the acylating agent.

 As examples of suitable solvents for the present invention, mention may in particular be made of aliphatic, cycloaliphatic or aromatic hydrocarbons, halogenated or not.

 By way of examples of aliphatic or cycloaliphatic hydrocarbons, mention may be made more particularly of paraffins, such as in particular nonane, decane, undecane, dodecane, tetradecane or cyclohexane, and aromatic hydrocarbons such as in particular benzene, toluene, xylenes, cumene, petroleum fractions consisting of a mixture of alkylbenzenes, especially the Solvesso type cuts.

 As regards halogenated or nonhalogenated aliphatic, cycloaliphatic or aromatic hydrocarbons, mention may in particular be made of dichloromethane, dichloroethane, monochlorobenzene, dichlorobenzene and their mixtures.

 Preferred solvents are deactivated solvents such as, for example, toluene, chlorobenzene and dichlorobenzene.

 According to the process of the invention, the acylation of the aromatic compound is carried out.

 The ratio between the number of moles of aromatic compound and the number of moles of acylating agent can vary because the substrate can serve as a reaction solvent. Thus, the ratio can range from 0.1 to 10, preferably from 1.0 to 5.0.

 The amount of catalyst used is determined such that the ratio between the number of moles of catalyst and the number of moles of acylating agent is less than 1.0 and preferably varies between 0.001 and 0, 8, and even more preferably between 0.02 and 0.2.

 As regards the amount of organic solvent used, it is generally chosen such that the ratio between the number of moles of organic solvent and the number of moles of aromatic compound preferably varies between 0 and 100 and more more preferably between 0 and 50.

 The temperature at which the acylation reaction is carried out depends on the reactivity of the starting substrate and that of the acylating agent.

 It is between 20 ° C and 2000 ° C, preferably between 80 ° C and 1700 ° C.

 Generally, the reaction is conducted at atmospheric pressure but lower or higher pressures may also be suitable.

 From a practical point of view, there are no constraints on the implementation of the reagents. They are introduced preferentially in the following order: the catalyst, the acylating agent and the substrate.

 In the case where the catalyst is first loaded

 The duration of the reaction depends on many parameters. Most often, it is 30 minutes to 8 hours.

 The aromatic ketone is then recovered from the organic phase according to known techniques, by distillation or by crystallization.

 Another variant of the invention consists in recovering the aromatic ketone, by extraction with the aid of a suitable solvent, for example with the aid of an ether (preferably methyl tert-butyl ether), a ketone (especially methyl isobutyl ketone) or an aromatic hydrocarbon (such as toluene).

 Subsequent purifications may be carried out, for example, by washing with water.

dans ladite formule (III), A, R, R3 et n ont la signification donnée précédemment.According to the process of the invention, an aromatic ketone is obtained, which can generally be represented by formula (III):

in said formula (III), A, R, R3 and n have the meaning given above.

 The following examples illustrate the invention without limiting it.

In the examples, the yields mentioned correspond to the following definition:
number of moles of aromatic ketone formed Yield =
number of moles of minority reactant introduced
By "minority reactant" is meant either the aromatic substrate or the acylating agent, depending on the relative amounts of each introduced.

 The following examples illustrate the invention without limiting it.

Examples 1 to 3
In this example, the benzoylation of anisole is carried out with benzoyl chloride.

 The following is the operating protocol that will be repeated in the other examples.

In a 50 ml two-neck flask fitted with a condenser, a device for taking samples, with stirring by a magnetic stirrer and a magnet bar, are charged:
62.5 mmol of anisole,
- 12.5 mmol of benzoyl chloride,
the catalyst at a rate of 1 mol% expressed relative to the number of
moles of acylating agent involved.

The catalyst used is:
uranyl nitrate UO 2 (N0 3) 2, 6H 2 O, commercial product,
U3O8 uranium oxide,
uranyl chloride prepared from U308 and hydrochloric acid.

 The catalyst is first charged and then an atmosphere of inert gases (nitrogen) is established. The acylating agent and the substrate are then loaded by means of a syringe.

 The reaction mixture is brought to reflux (15 ° C.) with stirring.

 The duration of the reaction is mentioned in the table below.

 The formed product, p-methoxybenzophenone, is determined by gas chromatography.

The results obtained are recorded in the following table:
Board

<tb> Ref. <SEP> Catalyst <SEP> Yield <SEP> Yield <SEP> Yield
<tb> ex. <SEP> 1h <SEP> 4h <SEP> 24h
<tb><SEP> 1 <SEP> OU <SEP> (NO <SEP>, <SEP> 6H? 0. <SEP> 77 <SEP> 88
<tb><SEP> 2 <SEP> UO2Cl2, <SEP> HCl, <SEP> 2H2O <SEP> 93
<tb><SEP> 3 <SEP> U <SEP> O <SEP> 29 <SEP> 55 <SEP> 1 <SEP> 95
<tb> Examples 4 to 7
In this series of tests, the benzoylation of an aromatic hydrocarbon is carried out using, as a catalyst,
uranyl chloride, in Examples 4 to 6,
uranyl nitrate, in Example 7.

 The procedure of Examples 1 to 3 is repeated: the molar ratio of benzoyl chloride to aromatic hydrocarbon is 5/1 in Examples 4 and 5 and 1/5 in Examples 6 and 7.

 The results obtained are recorded in Table II.

Table II

<tb> Ref <SEP> Hydrocarbon <SEP> Report <SEP> Product <SEP> Yield <SEP> Yield <SEP> Yield
<tb><SEP> ex. <SEP> molar <SEP> formed <SEP> i <SEP> h <SEP> 4 <SEP> h <SEP> 8 <SEP> h
<tb><SEP> Chloride <SEP> from
<tb><SEP> Benzoyl /
<tb> ~ <SEP> drocarbon <SEP>
<tb><SEP> 4 <SEP> toluene <SEP> 5/1 <SEP> p-methyl- <SEP> 44 <SEP> 70 <SEP> 83
<tb><SEP> Benzophenone
<tb><SEP> 5 <SEP> p-xylene <SEP> 5/1 <SEP> 2,5-dimethyl- <SEP> 76 <SEP> 86 <SEP> 93
<tb><SEP> Benzophenone
<tb><SEP> 6 <SEP> mesitylene <SEP> 5/1 <SEP> 2,4,6-trimethyl- <SEP> 92 <SEP> 100
<tb><SEP> Benzophenone
<tb><SEP> 7 <SEP> durene <SEP> 1/5 <SEP> 1,2,4,5-tetra- <SEP> 33 <SEP> 47
<tb><SEP> methyl- <SEP>
<tb><SEP> Benzophenone
<tb> Exernples 8 to 10
In the following tests, the reaction of mesitylene and benzoyl chloride is carried out in the presence of uranyl choride (1 mol%).

 The results are shown in Table III.

Table lii

<tb> Ref. <SEP> ex. <SEP> Ratio <SEP> molar <SEP> Yield
<tb><SEP> mesitylene / chloride <SEP> of <SEP> benzoyl <SEP> bis / mono
<tb><SEP> 1h <SEP> 4h <SEP> 1 <SEP><SEP> 8h <SEP> 24h
<tb><SEP> 8 <SEP> 1/2 <SEP> 17/83 <SEP> 46/54 <SEP> 53/47 <SEP> 74/26
<tb><SEP> 9 <SEP> 1/3 <SEP> 1 <SEP> 77/23 <SEP> 93/7 <SEP> 1 <SEP><SEP> 95/5
<tb><SEP> 10 <SEP> they <SEP> L <SEP><SEP> 92/8 <SEP> 100/0 <SEP> mono = 2,4,6-trimethylbenzophenone bis = 3-benzoyl-2, 4,6-trimethylbenzophenone
Examples he and 12
In the following two examples, mesitylene is reacted with terephthaloyl chloride in the presence of uranyl chloride (1%) molar.

The results are shown in Table IV.
Table IV

<tb> Ref. <SEP> Ratio <SEP> molar <SEP> Yield
<tb> Ex. <SEP> mesitylene / chloride <SEP> from <SEP> bis / mono
<tb><SEP> terephthaloyl
<tb><SEP> 1h <SEP> 4h
<tb><SEP> 11 <SEP> 1/1 <SEP> 86/14 <SEP> 90/10
<tb><SEP> 12 <SEP> 2/1 <SEP> 96/4 <SEP> 100/0
<Tb>

Exemole 13
The terephthaloyl chloride and durene are reacted in the presence of 1 mol% uranyl chloride.

We obtain the following product:

The results are summarized in Table V.
Table V

<tb> Ref. <SEP> Ratio <SEP> molar <SEP> Yield
<tb> Ex. <SEP> durene / chloride <SEP> from
<tb><SEP> terephthaloyl
<tb><SEP> 1 <SEP> 1 <SEP> h <SEP> 4 <SEP> h <SEP><SEP> 24 <SEP> h
<tb><SEP> 13 <SEP> 2/1 <SEP> 24 <SEP> 32 <SEP> 73
<Tb>
Examples 14 and 15
In the following examples, diphenyl ether and benzoyl chloride are reacted in the presence of 1 mol% uranyl chloride.

We obtain the following product:

The results are recorded in Table VI.

Table VI

<tb> Ref. <SEP> ex. <SEP> Ratio <SEP> molar <SEP> Yield
<tb><SEP> oxide <SEP> of <SEP> diphenyl / <SEP>
<tb><SEP> chloride <SEP> of <SEP> benzoyl
<tb><SEP> 1h <SEP> 4 <SEP> h <SEP> 8 <SEP> h <SEP> 24 <SEP> h <SEP>
<tb><SEP> 14 <SEP> 1/2 <SEP> t <SEP> 45 <SEP> 1 <SEP> 55 <SEP> 72
<tb><SEP> 15 <SEP> ~ <SEP><SEP> 1/5 <SEP> 45 <SEP> 55 <SEP> 92
<tb> Example 1 6
In a 50 ml two-neck flask fitted with a condenser, a device for taking samples, with stirring by a magnetic stirrer and a magnet bar, are charged:
12.5 mmol of mesitylene,
25 mmol of terephthaloyl chloride,
the catalyst, namely uranyl chloride used at a rate of 1 mol%
expressed in relation to the number of moles of acylating agent involved.

 The pure catalyst is initially charged and an atmosphere of inert gases (nitrogen) is established. The acylating agent and the substrate are then loaded by means of a syringe.

 The reaction mixture is refluxed (163 ° C.) with stirring.

 The crude product, identical to that of Example 13, is extracted with toluene, the toluene phase is cooled.

 49.4% of white crystals are recovered.

 After concentration of the toluene phase, a further 17.1% of crystals are collected, which makes 66.5% in total.

Example 17
In a 50 ml two-neck flask fitted with a condenser, a device for taking samples, with stirring by a magnetic stirrer and a magnet bar, are charged:
118.2 mmol of benzoyl chloride,
124.1 mmol of anisole,
the catalyst namely uranyl chloride used at a rate of 1 mol%
expressed in relation to the number of moles of acylating agent involved.

 The catalyst is first charged and then an atmosphere of inert gases (nitrogen) is established. The acylating agent and the substrate are then loaded by means of a syringe.

 The reaction mixture is refluxed (154 ° C.) with stirring.

 The crude product is extracted with toluene, the toluene phase is evaporated to dryness.

 87.4% of methoxybenzophenone is recovered comprising 96% of para isomer and 4% of ortho isomer.

 After recrystallization twice in hexane, 74% para isomer is recovered.

Claims (21)

1. A process for acylating an aromatic compound which comprises reacting said aromatic compound with an acylating agent, in the presence of a catalyst characterized in that the acylation reaction is carried out in the presence of an effective amount of at least one uranium halide and / or uranyl. 2- Process according to Claim 1, characterized in that the aromatic compound corresponds to the general formula (I): in which:

 - A symbolizes the remainder of a cycle forming all or part of a system  carbocyclic or heterocyclic, aromatic, monocyclic or polycyclic:  said cyclic residue being able to carry a radical R representing an atom  hydrogen or one or more substituents, identical or different.  n represents the number of substituents on the cycle. 3 - Process according to one of claims 1 and 2 characterized in that the aromatic compound corresponds to the general formula (I) wherein the optionally substituted residue A represents the remainder: 1 "- of an aromatic carbocyclic compound, monocyclic or polycyclic.  2 "- an aromatic heterocyclic compound, monocyclic or polycyclic.  3 - a compound constituted by a series of cycles, as defined in paragraphs 1 and / or 2 linked together:  . by a valid link,  with an alkylene or alkylidene radical having from 1 to 4 carbon atoms,  preferably a methylene or isopropylidene radical,  . by one of the following groups:  -O-, -CO-, -COO-, -OCOO  -S-, -SO-, -SO2-, -SO3-,

 in these formulas, Ro represents a hydrogen atom or a radical  alkyl having 1 to 4 carbon atoms, a cyclohexyl radical or  phenyl. 4- Process according to one of claims 1 to 3 characterized in that the aromatic compound corresponds to the general formula (I) wherein the R radicals represent one of the following groups:  . a hydrogen atom,  . a linear or branched alkyl radical having from 1 to 6 carbon atoms,  preferably 1 to 4 carbon atoms, such as methyl, ethyl, propyl  isopropyl, butyl, isobutyl, sec-butyl, tert-butyl,  . a linear or branched alkenyl radical having from 2 to 6 carbon atoms,  preferably from 2 to 4 carbon atoms, such as vinyl, allyl,  . a linear or branched alkoxy radical having 1 to 6 carbon atoms,  preferably from 1 to 4 carbon atoms such as methoxy, ethoxy,  propoxy, isopropoxy, butoxy,  a cyclohexyl radical,  . an acyl group having 2 to 6 carbon atoms,  . a radical of formula:  -R1-OH -R 1 -COOR2  -R1 -CHO  -R1 -NO2  -R1-CN  -R1 -N (R2) 2  -R1 -CO-N (R2) 2  -R1-X  -R1 -Z-R2  -R1 -CF3  -Z-CF3  in said formulas, R1 represents a valency bond or a radical  divalent hydrocarbon, linear or branched, saturated or unsaturated, having from 1 to 6  carbon atoms such as, for example, methylene, ethylene, propylene,  isopropylene, isopropylidene; the identical or different radicals R2  represent a hydrogen atom or a linear or branched alkyl radical  having 1 to 6 carbon atoms or a phenyl radical; X symbolizes a  halogen atom, preferably a chlorine, bromine or fluorine atom; Z  represents one of the following groups: O, S, SO, SO2, SO3. 5 - Process according to one of claims 1 to 4 characterized in that the aromatic compound corresponds to the general formula (I) wherein when n is greater than or equal to 2, two radicals R and the two successive atoms of the aromatic ring may be bonded to each other by an alkylene, alkenylene or alkenylidene radical having 2 to 4 carbon atoms to form a saturated, unsaturated or aromatic heterocycle having from 5 to 7 carbon atoms: one or more carbon atoms may be replaced by a another heteroatom, preferably oxygen. 6 - Process according to one of claims 1 to 5 characterized in that the aromatic compound corresponds to the general formula (I) wherein: - the R radicals represent one of the following groups:  a hydrogen atom  an OH group,  a linear or branched alkyl radical having from 1 to 6 carbon atoms,  a linear or branched alkenyl radical having from 2 to 6 carbon atoms,  a linear or branched alkoxy radical having from 1 to 6 carbon atoms,  a -C HO group,  an acyl group having 2 to 6 carbon atoms,  a group -COOR2 where R2 has the meaning given above,  a group CO-N (R2) 2 where R2 has the meaning given above  . a halogen atom, preferably fluorine, chlorine or bromine,  a group -C F3.  n is a number equal to 0.1, 2 or 3. 7 - Process according to one of claims 1 to 6 characterized in that the aromatic compound corresponding to the general formula (I) is a monocyclic or polycyclic aromatic carbocyclic compound with rings which can form between them an orthocondensed system corresponding to the formula (the)

 in said formula (la), m represents a number equal to 0, 1 or 2 and the symbols R, identical or different and n, having the meaning given above. 8 - Process according to one of claims 1 to 6, characterized in that the aromatic compound corresponding to the general formula (I) is a compound consisting of a chain of two or more monocyclic aromatic carbocycles corresponding to the formula (Ib)

 in said formula (Ib), the symbols R, identical or different and n, have the meaning given above, p is a number equal to 0, 1, 2 or 3 and B represents:  - a valid link  an alkylene or alkylidene radical having from 1 to 4 carbon atoms,  preferably, a methylene or isopropylidene radical,  - one of the following groups:

 in these formulas, Ro represents a hydrogen atom or a radical  alkyl having 1 to 4 carbon atoms, a cyclohexyl radical or  phenyl. 9 - Process according to one of claims 7 and 8 characterized in that the aromatic compound corresponds to the formula (la) or (lb) wherein:  R represents a hydrogen atom, a hydroxyl group, an amine group,  an amide group, an ester group, a linear alkyl or alkoxy radical or  branched having from 1 to 6 carbon atoms, preferably from 1 to 4 carbon atoms  carbon or a halogen atom,  B symbolizes a valency bond, an alkylene or alkylidene radical having from 1 to 4  carbon atoms or an oxygen atom,  - m is equal toOou 1,  n is 0, 1 or 2,  -PestaltoOou 1. 10 - Process according to one of claims 1 to 9 characterized in that the aromatic compound corresponds to the general formula (I) wherein R represents a hydrogen atom, a hydroxyl group, a methyl radical, a methoxy radical or a halogen atom.  1 1 - Process according to claim 1 and 2 characterized in that the aromatic compound is an isole, veratrole, 1,2-methylenedioxybenzene, 2 methoxynaphthalene. 12- Method according to one of claims 1 to 11 characterized in that  the acvlation axis corresponds to formula (II):

 in which:  R3 represents:  a saturated or unsaturated, linear or branched aliphatic radical having from 1 to  24 carbon atoms; a cycloaliphatic radical, saturated, unsaturated or  aromatic, monocyclic or polycyclic, having from 4 to 12 carbon atoms  carbon; a saturated or unsaturated aliphatic radical, linear or branched,  carrier of a cyclic substituent,  X 'represents:  . a halogen atom, preferably a chlorine or bromine atom,  . a radical -C-CO-R4 with R4, identical to or different from R3, having the same  meaning that R3. 13- Process according to claim 12, characterized in that the acylating agent corresponds to formula (II) in which X 'represents a chlorine atom and R3 represents a linear or branched alkyl radical having from 1 to 12 carbon atoms. carbon: the hydrocarbon chain may optionally be interrupted by a heteroatom or by a functional group or bearing substituents, preferably halogen atoms; R3 represents an optionally substituted phenyl group; X 'represents a radical -O-CO-R4. in which R3 and R4 are identical and represent an alkyl radical having from 1 to 4 carbon atoms optionally carrying halogen atoms. 14- Method according to claim 12 and 13 characterized in that the acylating agent is chosen from  acetyl chloride,  - monochloroacetyl chloride,  dichloroacetyl chloride,  propanoyl chloride,  isobutanoyl chloride,  pivaloyl chloride,  stearoyl chloride,  - crotonyl chloride,  - benzoyl chloride,  chlorobenzoyl chlorides,  p-nitrobenzoyl chloride  methoxybenzoyl chlorides,  naphthoyl chlorides,  - acetic anhydride,  Isobutyric anhydride,  Trifluoroacetic anhydride,  Benzoic anhydride. 15- The method of claim 1 characterized in that the catalyst used is a uranium halide and / or uranyl in which the uranium is at oxidation state +4 or +6. 16- The method of claim 15 characterized in that the catalyst used is uranium tetrachloride or uranyl chloride; Uranium oxide (in particular U308) and uranium nitrate associated with a source of halogen. 17 - Process according to claim 15 characterized in that the catalyst is generated in situ by using any uranium compound associated with a source of halogen. 18- The method of claim 17 characterized in that the uranium element is provided in the form of a metal or in the form of an oxide; a mineral salt, preferably nitrate, sulfate, oxysulphate, carbonate, oxalate or an organic salt, preferably acetylacetonate; carboxylate and even more preferably acetate. 19- The method of claim 18 characterized in that the source of halogen is halogen in molecular form; any inorganic or organic acid halide, and more particularly aliphatic carboxylic acids; any uranium, mineral or organic salt capable of generating a halogenated form. 20- A method according to claim 19 characterized in that the source of halogen is chlorine or bromine hydrochloric acid, hydrobromic acid; acetyl chloride; silicon chloride SiCl 4, halosilanes and Me 3 SiCl, Me 2 SiCl 2 MeSiCl 3, PhMe 2 SiCl, phosphorus chloride PCl 3, sulfur chloride Spi 2. 21 - Method according rune of claims 1 to 20, characterized in that the ratio between the number of moles of aromatic compound and the number of moles of acylating agent varies between 0.1 and 10, preferably between 1.0 and 5.0. 22 - Process according rune of claims 1 to 21, characterized in that the amount of catalyst used is such that the ratio between the number of moles of catalyst and the number of moles of acylating agent is less than 1, And preferably varies between 0.001 and 0.8, and even more preferably between 0.02 and 0.2. 23 - A method according rune claims 1 to 22 characterized in that the temperature at which the acylation reaction is carried out is between 20 "C and 200" C, preferably between 80 "C and 1700C.