FR2768729A1 - A new process for the acylation of an aromatic compound - Google Patents

Abstract

The acylation of an aromatic compound in the presence of a catalyst comprising a rare earth halide or a borohydride type pseudo-halide optionally complexed with an ether. An Independent claim is also included for new catalytic complexes comprising a rare earth halide and an ether as ligand.

Description

PROCESS FOR ACYLATION OF AN AROMATIC COMPOUND
AND CATALYTIC COMPLEXES.

 The present invention relates to a process for acylating an aromatic compound.

 The expression "acylation" must be taken in the broad sense and includes in particular the benzoylation reaction.

The invention applies in particular to the preparation of alkoxyaromatic alkyl ketones
Another object of the invention resides in the catalytic complexes.

 Conventional methods of acylation of aromatic compounds, especially phenol ethers, use as an acylation reagent, a carboxylic acid. or one of its derivatives such as acid halide, ester or anhydride.

 The reaction is generally carried out in the presence of a Lewis acid type catalyst (for example AlCl 3) or of the Bronsted 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. 18, pp. 51-60 (1932) 1 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 complexes and and / or aluminum polyhydroxide of milky consistency, then difficult 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, and even 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 carried out in the presence of an effective amount of at least one rare earth halide or any compound capable of generating it in situ and / or a pseudo-halogenide of the borohydride type.

 According to the process of the invention, the acylation of an aromatic compound is carried out in the presence of at least one halide or a pseudo-rare earth halide.

 By "rare earth" is meant lanthanides having an atomic number of 57 to 71 and yttrium and scandium.

 In the aforementioned halogenated compounds, the rare earth is generally at the +3 oxidation state.

 A preferred variant of the process of the invention comprises introducing the complexed rare earth compound to an organic compound.

 Thus, another object of the invention are the catalytic complexes obtained.

dans laquelle:
- A symbolise le reste d'un cycle formant tout ou partie d'un système
carbocyclique ou hétérocyclique, aromatique, monocyclique ou polycyclique:
ledit reste cyclique pouvant porter un radical R représentant un atome
d'hydrogène ou un ou plusieurs substituants, identiques ou différents,
- n représente le nombre de substituants sur le cycle.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.

An aromatic, monocyclic or polycyclic heterocyclic compound.

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 rings 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.

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-, -50-, -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.

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,
30. 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 this text, "many" is understood to mean generally less than 4
Examples of substituents are given below but this list is not limiting in nature. The nature of the substituents is not critical insofar as it does 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 radicals R represent one of the following groups :
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
-R1 -COOR2
-R1 -CHO
-R1 -NO2
-R1-CN
-R1-N (R2) 2
-R1-CO-N (R2) 2
-R1-X
-R1 -Z-R2
-R 1 CF 3
-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 linked 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, bromine, a -C F3 group.

 n is a number equal to 0, 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 others1 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 (lb)

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 alkylidéne ayant de 1 à 4 atomes de carbone, de
préférence, un radical méthylène ou isopropylidène,
- I'un des groupes suivants:
-O-, -CO-, -COO-, -OCOO-
-S-, -SQ-, SO2- , -SO3-,

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 sequence of two or more monocyclic aromatic carbocycles corresponding to formula (lb)

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:
-O-, -CO-, -COO-, -OCOO-
-S-, -SQ-, 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.

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,
m is 0 or 1,
n is 0, 1 or 2,
- pestal toOr 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, ethyl, propyl, 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 bonded together by an alkylene, alkenylene or alkenylidene radical having from 2 to 4 carbon atoms to form a saturated heterocycle, unsaturated or aromatic having 5 to 7 carbon atoms. One or more carbon atoms may be replaced by another heteroatom, preferably oxygen. Thus, the radicals OR 'and R may represent a methylene dioxy or ethylene dioxy radical.

 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 0 or 1, the radicals R and
OR 'representing both alkoxy radicals, identical or different.

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,
trichloromethylbenzene, trichloromethoxybenzene,
trifluoromethylthiobenzene,
aromatic amine compounds such as aniline,
phenolic compounds such as o-cresol, galacol and ketol,
monoethers such as anisole, ethoxybenzene (pheneton),
butoxybenzene, isobutoxybenzene, 2-chloroanisole, 3-chloroanisole,
2-bromoanisole, 3-bromoanisole, 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-bromo-3-
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-trichlorohexylbenzene, 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 acylation reagent more particularly 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 -OCO-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-based chain may optionally be interrupted by a heteroatom (for example, oxygen), by a functional group (for example -CQ-) and / or carrier of substituents (for example, halogen atoms or a CF3 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 radicals,
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 rare earth halide catalyst or any compound capable of generating it.

 Although the salt of earth may be used in its hydrated form, an anhydrous form is preferred.

It is more particularly a rare earth chosen from lanthanides,
Yttrium scandium and mixtures thereof, preferably lanthanides such as lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, anthrium, and erbium , thulium, ytterbium and lutetium and their mixtures.

A mixture of ceric rare earth elements including La, Ce, Pr, Nd, and / or yttric rare earth elements comprising Y, Sm, Eu, may be used.
Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu.

 The preferred compounds are neodymium and samarium halides.

 It is also possible to use any rare earth 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. They can be supplied in the form of metal or oxide or in saline form, single or double salt, mineral or organic.

 Specifically, the rare earth elements can be provided in the form of a metal or in the form of an oxide or a hydroxide. It is possible to use a mineral salt preferably, nitrate, sulfate, oxysulfate, oxyhalide, silicate, carbonate, oxalate or an organic salt, preferably acetylacetonate; alkoxide and even more preferably methylate or ethylate; carboxylate and even more preferably acetate.

 Regarding the halogen source, it is possible to use any compound capable of providing halogen ions for generating in situ the rare earth halide.

 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 rare earth mineral or organic salt likely to generate a halogenated form.

 More specific examples include chlorine or bromine: hydrochloric acid, hydrobromic acid; acetyl chloride; SiC14 silicon chloride, halosilanes such as Me3SiCl, Me2SiCl2, MeSiCl3, PhMe2SiCl, PC13 phosphorus chloride, Su12 sulfur chloride.

 Another embodiment of the invention consists in implementing a pseudo-halide. Thus, use is made of rare earth borohydride having the formula TR (BH4) 3, TR symbolizing the rare earth element, and more particularly neodymium borohydride.

 Another variant of the process of the invention consists in introducing the halide or the pseudo-halide in complexed form. For this purpose, the rare earth salt is reacted with an organic, neutral, electro-donor ligand.

 The ligand is chosen such that the complex formed with the rare earth has good solubility in the reaction medium.

A dry and deperoxidized ligand should be used in a known manner, for example by passage over alumina. We can refer to the book
Fieser and Fieser, Reagents for Organic Synthesis - John Wiley p. 333 (1967).

As examples of organic ligands suitable for the invention, mention may be made of aliphatic, cycloaliphatic or aromatic ether-oxides and, more particularly, diethyloxide, dipropyloxide, diisopropyloxide and oxygen. dibutyl, methyltertiobutyl ether, dipentyl ether,
Diisopentyl ether, ethylene glycol dimethyl ether (or 1,2-dimethoxyethane), diethylene glycol dimethyl ether (or 1,5-diethoxy-3-oxapentane), dioxane, tetrahydrofuran.

 Tetrahydrofuran and dioxane are preferably chosen.

 The complex is prepared by reaction of the halide or pseudo-halide and the ligand.

The molar ratio in
TRX3, (dioxane) b (VI)
TR (BH4) 3, (dioxane) b (VII) in said formulas:
b is a number equal to 1 or 1.5,
- TR symbolizes the rare earth element,
X symbolizes a halogen atom, preferably a fluorine atom,
chlorine or bromine.

 This complexed form of the rare earth makes it possible to improve its solubility in the reaction medium. Thus, the catalyst sees its activity increase.

 Another method for preparing complexes comprising a ligand other than THF, in particular those of formula (VI) and (VIl), consists of moving the THF ligand by another ligand: the operation is carried out at a temperature situated between the temperature room temperature (145 ° C to 25 ° C) and the reflux temperature of the ligand.

 According to the process of the invention, the reaction between the aromatic compound and the acylating agent can be carried out 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 Solvesso-type cups
As regards halogenated or nonhalogenated aliphatic, cycloaliphatic or aromatic hydrocarbons, mention may in particular be made of dichloromethane, dichloroethane, monochlorobenzene, dichlorobenzene and their mixtures.

 The solvents are the 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 so 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 200 ° C, preferably between 80 ° C and 170 ° 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, it should preferably be done under a controlled atmosphere of inert gases. It is possible to establish an atmosphere of rare gases, preferably argon, but it is more economical to use nitrogen.

 After contacting the reagents, the reaction mixture is brought to the desired temperature.

 Another variant of the invention consists in heating one of the reagents (acylating agent or aromatic compound) with the catalyst and then introducing the other reagent.

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

 Then, the product formed is recovered according to several variants.

 It is possible to perform a hydrolysis treatment of the reaction mass obtained.

 The amount of water used can vary widely. The ratio between the number of moles of water and the number of moles of aromatic compound can vary between 10 and 100, and preferably between 20 and 30.

 For this purpose, a preferred embodiment of this operation is to add the reaction mass on a foot of water heated to a temperature between 00C and 100 "C, preferably between 15" C and 30 "C.

 A variant of the invention consists in replacing the water with a basic solution, generally sodium hydroxide, carbonate or sodium hydrogencarbonate having a concentration of 5 to 20% by weight.

 The catalyst is separated from the organic phase by aqueous treatment.

 At the end of the reaction, the desired product, the aromatic ketone in the organic phase, is recovered.

 The aqueous and organic phases are separated.

 The organic phase is washed one or more times, preferably twice, with water.

 The aqueous and organic phases are separated.

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

 Another variant of the invention consists in recovering the aromatic ketone, directly, by distillation of the organic phase comprising this and the catalyst.

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 and 2
In this example, the benzoylation of the 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 5 mol% expressed relative to the number of
moles of acylating agent involved.

 The catalyst employed is anhydrous neodymium chloride in Example 1 and anhydrous yttrium chloride in Example 2.

 The catalyst is stored in a dry place (in a glove box).

 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 with stirring.

 The reaction time is 5 hours.

 At the end of the reaction, the product formed is analyzed by gas chromatography.

The results obtained are recorded in the following table:
Board

<tb> N "<SEP> ex <SEP> Catalyst <SEP> Yield <SEP> RR
<tb><SEP> (%)
<tb><SEP> 1 <SEP> NdCl3hydrous <SEP> 5
<tb><SEP> 2 <SEP> YC13 <SEP> anhydrous <SEP> 60.2
<Tb>
Examples 3 to 5
In this series of tests, yttrium chloride is used as a catalyst in a variable amount of 2 mol% (Example 3), 5 mol% (Example 4) and 10 mol% (Example 5), expressed amount. compared to benzoyl chloride.

 The procedure of Examples 1 and 2 is reproduced.

 The results obtained are recorded in Table II.

Table II

<tb> N <SEP> ex <SEP> | <SEP> Catalyst <SEP> | <SEP> Quantity <SEP> of <SEP> Catalyst <SEP> | <SEP> Yield <SEP> RR
<tb><SEP> l <SEP>% <SEP> mol <SEP> (%)
<tb><SEP> 3 <SEP> | <SEP> YC13 <SEP> 2 <SEP> 17
<tb><SEP> 4 <SEP> YC13 <SEP> 5 <SEP> | <SEP> 50
<tb><SEP> 5 <SEP> YC13 <SEP> 10 <SEP> | <SEP> 78
<Tb>
Example 6
Example 2 was reproduced but not controlling the atmosphere which is air.

 The yield obtained, as mentioned in Table III is slightly lower.

Table III

<tb> N ex <SEP> | <SEP> Catalyst <SEP> | <SEP> Yield <SEP> RR
<tb><SEP> (%)
<tb><SEP> 6 <SEP> YCl3 <SEP> 53
<Tb>
Example 7
Example 2 is repeated but replacing the benzoyl chloride with acetyl chloride.

The results obtained are as follows:
Table IV

<tb><SEP> N ex <SEP> Catalyst <SEP> Yield <SEP> RR
<tb><SEP> Agent <SEP> acylation
<tb> (%)
<tb><SEP> 7 <SEP> YCl3 <SEP> Acetyl Chloride <SEP> 14.6
<tb> Examples 8 and 9
In the examples which follow, the acetylation is carried out using acetyl chloride, from two different substrates namely veratrole (Example 8) and 2-methoxynaphthalene (Example 9).

 The reaction time is 5 hours.

 The results obtained are shown in Table V.

Table V

<tb><SEP> N <SEP> ex <SEP> Substrate <SEP> Catalyst <SEP> Yield
<tb><SEP> Product <SEP> obtained
<tb><SEP> RR
<tb><SEP> (%)
<tb> 8 <SEP> veratrole <SEP> YCl3 <SEP> 4-acetoveratrole <SEP> 4
<tb><SEP> 9 <SEP> 2-methoxynaphthalene <SEP> YCl3 <SEP> 1-acetyl- <SEP> 21
<tb><SEP> 2-methoxynaphthalene
<tb> Example 10 to 25
In order to compare the reactivity of the various rare earth chlorides, the benzoylation of an isole with benzoyl chloride is studied.

 A series of tests is carried out with hydrated catalysts, followed by the same reaction with the dehydrated catalysts.

The dehydration of the rare earth chlorides is carried out by heating at 105 ° C. for 6 hours and then at 1900 ° C. for one day, followed by drying under vacuum (10 mm Hg) in a desiccator in the presence of
P2O5.

The operating protocol is as follows:
In a 30 ml flask equipped with a magnetic stirrer, 9.0 g (1.2 eq) of an isole, 9.7 g (1 eq) of benzoyl chloride, 5 mol% of catalyst, and the reaction mixture is heated at 120 ° C. for 5 hours. At the end of the reaction, the amount of 4-methoxybenzophenone formed as well as the remaining anisole is determined by gas chromatography.

 The results obtained are collated in Table VI.

Table VI

<tb> N <SEP> Cata- <SEP> SEP Rate <SEP> Yield <SEP> Selectivity
<tb> ex <SEP> real <SEP><SEP> lyser
<tb><SEP> TT <SEP> (%) <SEP> RR <SEP> (%) <SEP> RT <SEP> (%)
<tb><SEP> catalyst <SEP> catalyst <SEP> catalyst <SEP> catalyst <SEP> catalyst <SEP> catalyst
<tb><SEP> hydrated <SEP> dehydrated <SEP> hydrated <SEP> dehydrated <SEP> hydrated <SEP> dehydrated
<tb> 10 <SEP> ScCl3 <SEP> 12 <SEP> - <SEP> 5 <SEP> - <SEP> - <SEP> 42 <SEP>
<tb> 11 <SEP> YCl <SEP> 41 <SEP> 52 <SEP> 18 <SEP> 32 <SEP> 44 <SEP> 61
<tb> 12 <SEP> LaCl3 <SEP> 12 <SEP> 0.84 <SEP> 4 <SEP> 2 <SEP> 34 <SEP> 23.8
<tb> 13 <SEP> CeCI <SEP> 41 <SEP> 19 <SEP> 23 <SEP> 3 <SEP> 56 <SEP> 16
<tb> 14 <SEP> PrCl3 <SEP> 37 <SEP> 8 <SEP> 12 <SEP> 3 <SEP> 32 <SEP> 37
<tb> 15 <SEP> NdCl <SEP> 37 <SEP> - <SEP> 12 <SEP> - <SEP> 32 <SEP>
<tb> 16 <SEP> SmCl3 <SEP> 40 <SEP> - <SEP> 16 <SEP> - <SEP> 40 <SEP>
<tb> 17 <SEP> EuCl3 <SEP> 49 <SEP> 44 <SEP> 15 <SEP> 27 <SEP> 31 <SEP> 61
<tb> 18 <SEP> GdCl3 <SEP> 35 <SEP> - <SEP> 15 <SEP> - <SEP> 43 <SEP>
<tb> 19 <SEP> TbCl <SEP><SEP> 26 <SEP> 64 <SEP> 19 <SEP> 33 <SEP> 73 <SEP> 51
<tb> 20 <SEP> DyCl3 <SEP> 40 <SEP> 62 <SEP> 21 <SEP> 34 <SEP> 53 <SEP> 55
<tb> 21 <SEP> HoCl3 <SEP> 46 <SEP> 70 <SEP> 23 <SEP> 33 <SEP> 50 <SEP> 47
<tb> 22 <SEP> ErCl3 <SEP> 35 <SEP> 67 <SEP> 27 <SEP> 38 <SEP> 77 <SEP> 57
<tb> 23 <SEP> TmCl3 <SEP> 50 <SEP> 64 <SEP> 27 <SEP> 35 <SEP> 54 <SEP> 55
<tb> 24 <SEP> YbCl <SEP> 53 <SEP> 62 <SEP> 30 <SEP> 34 <SEP> 51 <SEP> 55
<tb> 25 <SEP> LuCl3 <SEP> 56 <SEP> 64 <SEP> 27 <SEP> 32 <SEP> 48 <SEP> 50
<Tb>
Note: The transformation rate is calculated from the amount of transformed anisole.

 Apart from dehydrated LaC13, CeC13, PrC13 and EuCl3 which give heterogeneous media, all the other catalysts are completely dissolved at the end of the reaction.

Examples 26 and 27
To study the influence of temperature on the benzoylation of the anisole, two tests are carried out; the first at 120 C and the second at 155 C (reflux of anisole).

 Dehydrated erbium chloride is used as a catalyst because it gives good results (Example 16 of Table VI) and is inexpensive.

 Each experiment is conducted in a 100 ml reactor equipped with a refrigerant, a mechanical stirrer, a bubbler and a nitrogen inlet.

The reaction parameters are as follows
- 37.5 g (5 eq.) Of an isole
- 9.7 g (1 eq) of benzoyl chloride
0.9 g (5 mol%) of dehydrated ErCl3 - temperature: 1 155 C
- duration: 5 hours
The results obtained are shown in Table VII.

Table VII

<tb> N <SEP> @ <SEP> ex <SEP> Temperature <SEP> TT <SEP> RR <SEP> RT
<tb><SEP> (C) <SEP> (%) <SEP> (%) <SEP> (%)
<tb><SEP> 26 <SEP> 155 C <SEP> 95 <SEP> 61 <SEP> 65
<tb><SEP> 27 <SEP> 120 <SEP> 90 <SEP> 48 <SEP> 54
<Tb>
Examples 28 to 30
The molar ratio anisole / mole benzoyl chloride is varied in the case of benzoylation of anisole catalyzed by ErCl3 hydrate.

 The operating protocol is identical to that described in Example 26.

 The results obtained are recorded in Table VI II.

Table VIII

<tb> N <SEP> ex <SEP> Ratio <SEP> TT <SEP> RR <SEP> RT
<tb><SEP> (eq.) <SEP> (%) <SEP> (%) <SEP> (%)
<tb><SEP> 28 <SEP> 1,2 <SEP> 90 <SE> 48 <SEP> 55
<tb><SEP> 29 <SEP> 2.5 <SEP> 95 <SEP> 62 <SEP> 65
<tb><SEP> 30 <SEP> 5 <SEP> 95 <SEP> 61 <SEP> 65
<Tb>
Examples 31 and 32
The influence of the percentage of catalyst on the yield of the reaction is studied.

 The same experimental protocol as that described in Example 26 is used.

 The results obtained are reported in Table IX.

Table IX

<tb> N <SEP> ex <SEP> Catalyst <SEP> TT <SEP> RR <SEP> RT
<tb><SEP> (%) <SEP> (%) <SEP> (%) <SEP> (%)
<tb><SEP> 31 <SEP> 5 <SEP> 95 <SEP> 61 <SEP> 65
<tb><SEP> 32 <SEP> 10 <SEP> 90 <SEP> 70 <SEP> 75
<tb> Example 33
The preparation of a catalyst NdCl3 (THF) 3 is carried out.

 The preparation is carried out in a Soxlhet type apparatus.

 1 g of neodymium chloride are charged into the cartridge under an argon atmosphere and the mixture is continuously extracted with 50 ml of boiling tetrahydrofuran (at around 65 ° C.).

 When the extraction is complete, the excess solvent is distilled off (possibly under reduced pressure of 1 mm Hg).

 A microcrystalline powder of NdCl3 (THF) 3 is recovered which is preserved in the absence of moisture.

 The reaction is almost quantitative 90%.

 For the preparation of other compounds in which the ligand is with dioxane or diglyme instead of THF, 500 mg of NdCl 3 (THF) 3 in the Soxhlet cartridge are introduced into the glove box and uses 20 ml of deoxygenated dioxane with sodium + benzophenone.

 Stirred for about 12 hours and evaporated to dryness, the dioxane.

 An NdCl 3, dioxane powder is recovered.

Example 34
The preparation of another type of catalyst Nd (BH4) 3, (THF) 3 is carried out.

 It is prepared according to Mirsaidov (U. Mirsaidov, I. B. Shainuradov, M.

Khikmatov - Russ. J. Inorg. Chem. 31, 5, p. 753 (1986) with the difference that LiBH4 is used instead of NaBH4. The yield is 27%.

Examples 35 and 36
The benzoylation of the anisole is carried out according to the procedure of Examples 1 and 2 but not involving, respectively in Example 35, the catalyst of Example 33 and in Example 36, the catalyst of the example 34.

 The results obtained are collated in Table X.

Paintings

<tb> N <SEP> ex <SEP> Catalyst <SEP> Yield <SEP> RR
<tb><SEP> (%)
<tb><SEP> 35 <SEP> NdCl3, <SEP> (THF) 3 <SEP> 83.3
<tb><SEP> 36 <SEP> Nd (BH4) 3, <SEP> (THF) 3 <SEP> 80
<Tb>
Examples 37 to 44
Various catalysts are prepared comprising a rare earth halide complexed with THF.

 The preparation is carried out according to Example 33.

 The benzoylation of the anisole is carried out according to the procedure of Examples 1 and 2.

 The results obtained are collated in Table XI.

Table XI

<tb> N <SEP> ex <SEP> Catalyst <SEP> Yield <SEP> RR
<tb><SEP> (%)
<tb><SEP> 37 <SEP> LaCl3, <SEP> (THF) 3 <SEP> 19
<tb><SEP> 38 <SEP> LaBr3, <SEP> (THF) 3 <SEP> 67.8
<tb><SEP> 39 <SEP> CeCl3, <SEP> (THF) 3 <SEP> 10.9
<tb><SEP> 40 <SEP> NdCl3, <SEP> (THF) 3 <SEP> 83.3
<tb><SEP> 41 <SEP> SmCl3, <SEP> (THF) 3 <SEP> 83.4
<tb><SEP> 42 <SEP> SmBr3, <SEP> (THF) 3 <SEP> 68.9
<tb><SEP> 43 <SEP> GdCl3, <SEP> (THF) 3 <SEP> 70
<tb><SEP> 44 <SEP> YCl3, <SEP> (THF) 3 <SEP> 56.6
<Tb>
Examples 45 to 49
Various catalysts are prepared comprising a rare earth halide complexed with a compound other than THF.

 The preparation is carried out according to Example 33.

 The benzoylation of the anisole is carried out according to the procedure of Examples 1 and 2.

 The results obtained are collated in Table XII.

Table XII

<tb> N <SEP> ex <SEP> Catalyst <SEP> Yield <SEP> RR
<tb><SEP> (%)
<tb><SEP> 1 <SEP> NdCl3 <SEP> 5
<tb><SEP> 45 <SEP> NdCl3, <SEP><THF) 3 <SEP> 83.3
<tb><SEP> 46 <SEP> NdCI3, <SEP> diglyme <SEP> 11.9
<tb><SEP> 47 <SEP> NdCl3, <SEP> dioxane <SEP> 90.3
<tb><SEP> 4 <SEP> YC13 <SEP> 50.0
<tb><SEP> 48 <SEP> YCl3, <SEP> (THF) 3 <SEP> 56.6
<tb><SEP> 49 <SEP> YCl3, <SEP> dioxane <SEP> 51.0
<Tb>
Example 50
In these examples, the reaction is carried out in an organic solvent.

 The catalyst used is that of Example 2.

The following compounds are charged:
0.126 g of anhydrous yttrium chloride,
17.77 g of decane,
- 1.35 g of anisole,
1.75 g of benzoyl chloride.

 It is heated to the reflux temperature of the mixture.

 The reaction time is 5 hours.

 At the end of the reaction, the assay is carried out by gas chromatography.

Paintings

<tb> N <SEP> ex <SEP> Solvent <SEP> Yield <SEP> RR
<tb><SEP> (%)
<tb><SEP> 50 <SEP> Decane <SEP> 15.2
<tb> Example 51
In this example, the reaction is conducted in an organic solvent.

 The catalyst used is that of Example 2.

The following compounds are charged:
- 0.123 anhydrous yttrium chloride
4.47 g of 1,2,4-trichlorobenzene,
- 1.35 g of anisole,
1.76 g of benzoyl chloride.

 It is heated to the reflux temperature of the mixture.

 The reaction time is 5 hours.

 At the end of the reaction, the assay is carried out by gas chromatography.

Table Xl

<tb> N <SEP> ex <SEP> Solvent <SEP> Yield <SEP> RR
<tb><SEP> (%)
<tb><SEP> 51 <SEP> 1,2,4-trichlorobenzene. <SEP> 47.5
<Tb>

Claims (29)

The process for the acylation of 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 rare earth halide or any compound capable of generating it in situ and / or a pseudo-halide of the borohydride type. 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-, -OCQO  -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  -R 1 -N (R 2) 2 -R 1 -CO-N (R 2) 2  -R1-X-R1-Z-R2  -R 1 CF 3  -Z-CF3  in said formulas, R1 represents a valency bond or a radical  divalent hydrocarbon, linear or branched, saturated or n saturated, having from 1 to 6  carbon atoms such as, for example, methylene, ethylenepropylene,  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  a halogen atom, preferably a bromine or fluorine chlorine 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 group -CHO,  . 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 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- Method 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 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:  -O-, -CO-, -COO-, -OCOO  -S-, -SO-, -SO2-, -SO3-,

 in these formulas, R0 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,  -equal toOou 1,  n is equal to 0.1 or 2,  -PestaltoOou 1. 10- Method 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, 2methoxynaphthalene. 12- Method according to one of claims 1 to 1 1, characterized in that the acylating agent 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 -O-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- A method according to claim 1 characterized in that the catalyst used is a halide or pseudo-halide of a rare earth selected from lanthanides, yttrium scandium and mixtures thereof, preferably lanthanides such as lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, Hydrolium, erbium, thulium, ytterbium and lutetium and their mixtures. 16 - Process according to claim 15, characterized in that the catalyst used is a mixed ceric rare earth halide including the elements La, Ce, Pr, Nd and / or yttric rare earths in a mixture comprising Y, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu. 17- The method of claim 15 characterized in that the catalyst used is a halogenide neodymium or samarium. 18 - Process according to claim 15 characterized in that the catalyst is generated in situ by using any rare earth compound associated with a halogen source. 19- The method of claim 18 characterized in that the rare earth elements are provided in the form of a metal or in the form of an oxide or a hydroxide; a mineral salt preferably, nitrate, sulfate, oxysulphate, oxyhalogenide, silicate, carbonate, oxalate or an organic salt, preferably acetylacetonate; alkoxide and even more preferably methylate or ethylate; carboxylate and even more preferably acetate. 20- Method according to 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 rare earth mineral or organic salt likely to generate a halogenated form. 21- The method of claim 20 characterized in that the source of halogen is chlorine or bromine hydrochloric acid, hydrobromic acid; acetyl chloride; SiC 14 silicon chloride, halosilanes such as Me3SiCl, Me2SiCl2, MeSiCl3, PhMe2SiCl, PC13 phosphorus chloride, SCI2 sulfur chloride. 22 - Process according to claim 1 characterized in that the catalyst is a rare earth borohydride, preferably a neodymium borohydride. 23 - Method according to one of claims 15 to 22 characterized in that the halide or the pseudo-rare earth halide is in the form of a complex comprising the rare earth halide or pseudo-halide and a ligand organic, neutral, electro-donor. 24. Process according to claim 23, characterized in that the ligand is chosen from aliphatic, cycloaliphatic or aromatic ether-oxides and, more particularly, diethyloxide, dipropyloxide and diisopropyl ether. dibutyl ether, methyltertiobutyl ether, dipentyl ether, Dilsopentyl oxide, ethylene glycol dimethyl ether (or 1,2-dimethoxyethane), diethylene glycol dimethyl ether (or 1,5-diethoxy-3-oxapentane), dioxane, tetrahydrofuran. 25 - Method according to one of claims 23 and 24 characterized in that the catalyst is in the form of a complex corresponding to one of the following formulas  TRX3, (THF) a (IV)  TR (BH4) 3, (THF) a (V)  TRX3, (dioxane) b (VI)  TR (BH4) 3, (dioxane) b (VII) in said formulas:  - a is a number equal to 2 or 3,  b is a number equal to 1 or 1.5,  - TR symbolizes the rare earth element,  X symbolizes a halogen atom, preferably a fluorine atom,  chlorine or bromine,  THF represents tetrahydrofuran. 26- Method according to one of claims 1 to 25, characterized in that the reaction solvent is one of the reagents or an organic solvent, preferably an aliphatic hydrocarbon, cycloaliphatic, aromatic, halogenated or not. 27- Method according to one of claims 1 to 26 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. 28 - Method according to one of claims 1 to 27 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 1.0 and preferably varies between 0.001 and 0.8, and even more preferably between 0.02 and 0.2. 29 - Process according to one of claims 1 to 28, 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 170" C. Catalyst complex comprising a rare earth halide complexed with an ether. 31 - Complex according to claim 30 of formula:  TRX3, (dioxane) b (VI)  TR (BH4) 3, (dioxane) b (VII) in said formulas:  b is a number equal to 1 or 1.5,  - TR symbolizes the rare earth element,  X symbolizes a halogen atom, preferably a fluorine atom,  chlorine or bromine.