FR2756279A1 - Acylating aromatic compounds in presence of triflate salt catalyst - Google Patents

Abstract

Acylation of an aromatic compound (I) involves reacting (I) with an acylating agent (II) in the presence of an effective amount of a salt (III) of triflic acid (trifluoromethanesulphonic acid CF3SO3H) in a mixture of at least one carboxylic acid (IV) and at least one carboxylic acid anhydride (V).

Description

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

 In its preferred variant, the invention resides in a process for condensing acetic anhydride or acetyl chloride with an aromatic compound.

 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 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-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 process for acylating an aromatic compound which comprises reacting said aromatic compound with an acylating agent characterized in that the the acylation reaction is carried out in the presence of an effective amount of a triflic acid salt in a mixture comprising at least one carboxylic acid and at least one carboxylic acid anhydride.

 It has been found quite unexpectedly that the use of a mixture comprising at least one carboxylic acid and at least one carboxylic acid anhydride makes it possible to improve the selectivity of the reaction.

 In the following description of the present invention, the term "triflic acid", trifluoromethanesulfonic acid CF3SO3H.

By "aromatic compound" is meant the classical notion of aromaticity as defined in the literature, in particular by Jerry MARCH, Advanced Organic
Chemistry, 4th edition, John Wiley and Sons, 1992, pp. 40 and following.

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 may carry a radical R representing
a hydrogen atom 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 1 preferably having at least 4 atoms in the ring, optionally substituted, and representing at least one 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 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 consisting of a series of rings, as defined in paragraphs 1 and / or 2 linked together: by a valency bond, by 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 rings under 1 to 3 include: 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'-oxbiphenyl, 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 residue A may optionally carry one or more substituents which are represented in formula (1) 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 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 radicals,
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 -R 1 -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 divalent hydrocarbon radical, linear or branched, saturated or unsaturated, having from 1 to 6 carbon atoms such as, for example, methylene, ethylene, propylene, isopropylene, isopropylidene ; the radicals R 2 which are identical or different represent a hydrogen atom or a linear or branched alkyl radical having from 1 to 6 carbon atoms or a phenyl radical; X represents 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 group -CHO,
. an acyl group having 2 to 6 carbon atoms,
a group -COOR2 where R2 has the meaning given above, a group -NO2,
a group CO-N (R2) 2 where R2 has the meaning given above
. a halogen atom, preferably fluorine, chlorine or bromine,
. a group-CF3.

 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 others, 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 (lb), 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:
-O-, -CO-, -COQ-, -OCOO
-S-, -SO-, -SO2-, -SO3-,

Among the compounds of formula (I), use is made more particularly of those corresponding to the following formulas:
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 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-, -COQ-, -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.

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

dans laquelle:
- n est un nombre inférieur ou égal à 4, de préférence égal à 1 ou 2,
- le radical R' représente un radical alkyle, linéaire ou ramifié, ayant de 1 à 6
atomes de carbone, de préférence de 1 à 4 atomes de carbone, tel que
méthyle, éthyle, propyle, isopropyle, butyle, isobutyle, sec-butyle, tert-butyle
ou un radical phényle,
- le ou les radicaux R représentent l'un des atomes ou groupes suivants
mentionnés comme substituants du reste A de la formule (I),
- les radicaux R' et R et les 2 atomes successifs du cycle benzénique peuvent
former entre eux, un cycle ayant de 5 à 7 atomes, comprenant éventuellement
un autre hétéroatome.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, optionally comprising
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 atoms
carbon or a phenyl radical,
R represents a linear or branched alkoxy radical having from 1 to 4 atoms
carbon, preferably a methoxy or ethoxy radical.

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

 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 benzene,
toluene1 chlorobenzene, dichlorobenzenes, trichlorobenzenes,
fluorobenzene, difluorobenzenes, chlorofluorobenzenes,
chlorotoluenes, fluorotoluenes, bromobenzene, dibromobenzenes,
bromofluorobenzenes, bromochlorobenzenes,
trifluoromethylbenzene, trifluoromethoxybenzene, trichloromethyl
benzene, trichloromethoxybenzene, trifluoromethylthiobenzene,
aromatic amine or nitro compounds such as aniline and
nitrobenzene
phenolic compounds such as phenol, o-cresol, guaiacol,
monoethers such as anisole, ethoxybenzene (phenetole),
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-trimethoxybenzene, 1,3,5
trimethoxybenzene, 1,3,5-triethoxybenzene.

The compounds to which the process according to the invention is more particularly applicable are benzene, toluene, phenol,
Anisole, veratrole, 1,2-methylenedioxybenzene, 2-methoxynaphthalene.

dans laquelle: - R3 représente:
un radical aliphatique saturé ou insaturé, linéaire ou ramifié ayant de 1 à
24 atomes de carbone ; un radical cycloaliphatique, saturé, insaturé ou
aromatique, monocyclique ou polycyclique, ayant de 3 à 8 atomes de
carbone ; un radical aliphatique saturé ou insaturé, linéaire ou ramifié,
porteur d'un substituant cyclique, - X' représente:
. un atome d'halogène, de préférence un atome de chlore ou de brome,
un groupe hydroxyle,
. un radical -O-CO-R4 avec R4, identique ou différent de R3, ayant la même
signification que R3: R3 et R4 pouvant former ensemble un radical divalent
aliphatique saturé ou insaturé, linéaire ou ramifié, ayant au moins 2 atomes
de carbone.With regard to the acylation reagent, it 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 3 to 8 carbon atoms
carbon; a saturated or unsaturated aliphatic radical, linear or branched,
bearing a cyclic substituent, X 'represents:
. a halogen atom, preferably a chlorine or bromine atom,
a hydroxyl group,
. a radical -O-CO-R4 with R4, identical to or different from R3, having the same
meaning that R3: R3 and R4 can together form a divalent radical
saturated or unsaturated, linear or branched aliphatic having at least 2 atoms
of carbon.

 By cyclic substituent, reference is made to what is described above.

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 -CO-) and / or a substituent (for example, a halogen or a group
CF3).

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

 R3 also represents an alkenyl radical having 2 to 10 carbon atoms, such as in particular vinyl, propenyl, butenyl, pentenyl, hexenyl, octenyl, decenyl.

 The radical R3 also preferably represents a phenyl radical which may be optionally substituted. Any substituent may be present on the cycle as long as it does not interfere with the desired product.

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 radicals,
ethoxypropoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, tert-butoxy,
a hydroxyl group,
a halogen atom, preferably a fluorine, chlorine or bromine atom.

 Preferred acylating agents are acid anhydrides. They more particularly correspond to formula (II) in which R3 and R4 are identical and represent an alkyl radical having from 1 to 4 carbon atoms.

 When the acylating agent is an acid halide, it preferably corresponds to formula (II) in which X 'represents a chlorine atom and R3 represents a methyl or ethyl radical.

By way of illustration of acylating agents corresponding to formula (II), mention may be made more particularly of:
- acetic anhydride,
propanoic anhydride,
isobutyric anhydride,
trichloroacetic anhydride,
trifluoroacetic anhydride,
benzoic anhydride.

monochloroacetyl anhydride,
dichloroacetyl anhydride,
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 acid.

 Acetic anhydride and acetyl chloride are the preferred acylating agents.

 The catalyst used in the process of the invention is a salt of triflic acid, preferably a metal or metalloidal salt.

 As more specific examples of catalysts suitable for the invention, mention may be made of the triflic acid salts of the metal or metalloid elements of groups (IIIa), (IVa), (VIII), (Ib), (IIIb), (IVb), (Vb) and (Vlb) of the periodic table of elements.

 In the present text, reference is made hereinafter to the Periodic Table of Elements published in the Bulletin of the Chemical Society of France, No. 1 (1966).

 The salts of triflic acid used in the process of the invention are more particularly those elements of group (IIIa) of the periodic table preferably, scandium, yttrium and lanthanides; the group (IVa) preferably titanium; preferably group (VIII), iron; group (lob) preferably, zinc; group (IIIb) preferably aluminum; group (IVb) preferably tin; group (Vb) preferably antimony and bismuth; of the group (Vlb) preferably tellurium.

 Among all its salts, the rare earth salts of triflic acid are preferably used.

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

 As regards the rare earth triflate used as a catalyst, it is more particularly a rare earth chosen from lanthanides, yttrium scandium and their mixtures, preferably lanthanides such as lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, hlormium, erbium, thulium, ytterbium and lutetium, and mixtures thereof.

 In the process of the invention, the following rare earths are more particularly contemplated: lanthanum, ytterbium, lutetium and / or scandium.

 The rare earth triflates are known products which are described in the literature, in particular in US Pat. No. 3,615,169. They are generally obtained by reaction of rare earth oxide and trifluoromethanesulphonic acid.

 According to a preferred variant of the process of the invention, the catalyst is advantageously prepared in situ by reacting trifluoromethanesulfonic acid and a rare earth source.

 The nature of the compounds providing the various elements used for the preparation of the catalyst of the invention is not critical.

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

 Preferably, the rare earth nitrates, chlorides and / or sulphates are used, such as cerium, lanthanum, praseodymium, neodymium, samarium, gadolinium, ytterbium and yttrium.

By way of examples of compounds which may be used for the preparation of the catalysts of the invention, mention may in particular be made of:
. yttrium (III) chloride,
lanthanum chloride (III),
. neodymium (III) chloride,
. samarium (III) chloride,
ytterbium chloride (III).

The bismuth salts of triflic acid disclosed in the patent application
PCT / FR96 / 01488 can also be used in the method of the invention.

 In a manner similar to the rare earth salts of triflic acid, the other metal triflates are prepared by reacting the trifluoromethanesulfonic acid and a source of the metal element.

 The zinc or iron salts of triflic acid are preferably chosen.

 According to the process of the invention, the acylation reaction is carried out in the presence of said catalyst, in a reaction mixture comprising at least one carboxylic acid and at least one carboxylic acid anhydride.

dans lesdites formules (III) et (IV):
- R5 représente un radical hydrocarboné monovalent, substitué ou non qui
peut être un radical aliphatique acyclique, saturé ou insaturé, linéaire ou
ramifié ; un radical carbocyclique ou hétérocyclique saturé, insaturé ou
aromatique, monocyclique ou polycyclique,
- R6, identique ou différent de R7, a la même signification que R5: R6 et R7
pouvant former These latter respond more particularly to the following formulas:

in said formulas (III) and (IV):
R5 represents a monovalent hydrocarbon radical, substituted or unsubstituted,
can be an acyclic aliphatic radical, saturated or unsaturated, linear or
branched; a saturated or unsaturated carbocyclic or heterocyclic radical
aromatic, monocyclic or polycyclic,
- R6, identical to or different from R7, has the same meaning as R5: R6 and R7
able to form

 The radicals R 51 R 6 and R 7 are preferably chosen so that the acid is liquid under the reaction conditions.

 As regards the carboxylic acid used, it is possible to use any carboxylic, mono- or polycarboxylic acid such as saturated or unsaturated, carbocyclic or heterocyclic aliphatic acids, saturated or unsaturated or aromatic, monocyclic or polycyclic; cyclo- or arylaliphatic, saturated or unsaturated.

 The carboxylic acids of general formula (III) in which R5 represents an acyclic aliphatic radical, saturated or unsaturated, linear or branched, are particularly well suited to carrying out the process of the invention.

 More specifically, R5 represents a linear or branched acyclic aliphatic radical preferably having from 1 to 12 carbon atoms, saturated or comprising one to more unsaturations on the chain, generally 1 to 3 unsaturations which may be single or conjugated double bonds or triple connections.

-S-;- S02-. dans ces formules R8 représente l'hydrogène ou un radical alkyle linéaire ou ramifié ayant de 1 à 4 atomes de carbone, de préférence, un radical méthyle ou éthyle,
(2) - et/ou porteuse de l'un des substituants suivants: -OH;-COOH;-CHO;- NOr, . CN ; -NHn.-SH;-X;-C
Conviennent également à la mise en oeuvre du procédé de l'invention, les acides carboxyliques de formule générale (III) dans laquelle R5 représente un radical hydrocarboné aromatique monocyclique ou polycyclique.The hydrocarbon chain can be optionally:
(1) - interrupted by one of the following groups called Y: -O-; -CO-;

-S -; - S02-. in these formulas R8 represents hydrogen or a linear or branched alkyl radical having from 1 to 4 carbon atoms, preferably a methyl or ethyl radical,
(2) - and / or carrier of one of the following substituents: -OH; -COOH; -CHO; - NOr,. CN; -NHn.-SH; -X, -C
The carboxylic acids of general formula (III) in which R5 represents a monocyclic or polycyclic aromatic hydrocarbon radical are also suitable for carrying out the process of the invention.

dans ladite formule (V):
- p est un nombre entier de O à 4, de préférence de O à 3,
- Rg représente l'un des groupes ou fonctions suivantes:
un atome d'hydrogène,
un radical alkyle linéaire ou ramifié, ayant de 1 à 4 atomes de carbone,
un radical alkoxy linéaire ou ramifié, ayant de 1 à 4 atomes de carbone,
un radical méthylène ou éthylène dioxy,
un groupe - CHO,
un radical phényle ou benzyle,
un atome d'halogène.R5 preferably represents an aromatic hydrocarbon radical, and in particular a benzene radical corresponding to the general formula (V):

in said formula (V):
p is an integer from 0 to 4, preferably from 0 to 3,
- Rg represents one of the following groups or functions:
a hydrogen atom,
a linear or branched alkyl radical having from 1 to 4 carbon atoms,
a linear or branched alkoxy radical having from 1 to 4 carbon atoms,
a methylene or ethylene dioxy radical,
a group - CHO,
a phenyl or benzyl radical,
a halogen atom.

 Even more preferentially, the acids of formula (III) in which the radical R 5 corresponds to formula (V) in which the radicals R 1, which are identical or different, represent a hydrogen atom, a methyl radical, a methoxy radical or a group, are chosen. - CHO.

 The carboxylic acids may correspond to the general formula (III) in which the radical R5 represents a polycyclic aromatic hydrocarbon radical; the cycles can form between them ortho-condensed, ortho- and peri-condensed systems. There may be mentioned more particularly, a naphthyl radical; said rings may be substituted with 1 to 4 radicals Rg preferably 1 to 3, Rg having the meanings stated above for the substituents of the aromatic hydrocarbon radical of general formula (V).

 R5 may also represent a carbocyclic radical saturated or comprising 1 or 2 unsaturations in the ring generally having from 3 to 7 carbon atoms, preferably 6 carbon atoms in the ring; said ring may be substituted with 1 to 5 radicals R9 preferably 1 to 3, Rg having the meanings stated above for the substituents of the aromatic hydrocarbon radical of general formula (V).

 As preferred examples of radicals Rs, there may be mentioned cyclohexyl radicals, optionally substituted by linear or branched alkyl radicals having from 1 to 4 carbon atoms.

 The carboxylic acids may also correspond to formula (III) in which R5 represents a divalent radical consisting of a sequence of two to four radicals as defined above, an aliphatic radical1 aromatic or cycloaliphatic radical. These can be interconnected by a link valentiel or by a functional group which can be in particular a group chosen from groups called Y.

As carboxylic acids corresponding to the formula (lit), the following carboxylic acids are more particularly used:
saturated aliphatic monocarboxylic acids such as acid
formic, acetic, propionic, butyric, isobutyric, valeric,
isovaleric, pivalic, auric, myristic, palmitic, stearic,
saturated aliphatic dicarboxylic acids such as oxalic acid,
malonic, succinic, glutaric, adipic, pimelic, suberic,
azelaic, sebacic,
unsaturated aliphatic monocarboxylic or dicarboxylic acids
such as crotonic, isocrotonic, oleic, maleic, fumaric acid,
citraconic, mesaconic,
saturated or unsaturated carbocyclic carboxylic acids such as
camphoric acid, chrysanthemic acid,
heterocyclic carboxylic acids such as fu acids
Rannecarboxylic, thiophenecarboxylic, pyrrolecarboxylic,
pyrazinecarboxylic acid, nicotinic acid, icotinic acid, acid
picolinic,
aromatic carbocyclic carboxylic acids such as
benzoic, phthalic, isophthalic, terephthalic, acids
naphthalenecarboxylic acids, toluic acids,
saturated arylaliphatic carboxylic acids such as, in particular,
arylpropionics such as 2-phenylpropionic acid, [(butyl-2) -4
2-phenylpropionic acid, 2- (3-benzoylphenyl) propionic acid, the acid
2- (2-methoxy-2-naphthyl) propionic acid or the unsaturated acids as
2-phenylpropenoic acid, cinnamic acid, halogenated carboxylic acids such as monochloroacetic acid,
dichloroacetic, trichloroacetic, monohydroperopropionic, a-
bromopropionic, a-bromobutyric, trifluoroacetic,
aliphatic, cycloaliphatic and arylaliphatic hydroxy acids, such as
that glycolic acid, lactic acid, glyceric acid, hydroxy acid
2 butanoic acid, 3-hydroxy-butanoic acid, 2-methyl-lactic acid,
2-hydroxy-4-methylthiobutanoic acid, tartronic acid, acid
malic acid, tartaric acid, 1-hydroxy-cyclopropane carboxylic acid,
2-hydroxyphenylpropanoic acid, 2-hydroxycinnamic acid,
3-hydroxy cinnamic acid, 4-hydroxy cinnamic acid,
the following hydroxybenzoic acids: 2-hydroxybenzoic acid
(salicylic acid), 3-hydroxy-benzoic acid, 4-hydroxy-acid
benzoic acid, 3-methyl-salicylic acid, 4-methyl-salicylic acid,
5-methyl-salicylic acid, 3-hydroxy-4-methylbenzoic acid, the acid
3-methoxy salicylic acid, 4-methoxy salicylic acid, 5-methoxy acid
salicylic acid, 3-hydroxy-4-methoxybenzoic acid (isovanillic acid),
4-hydroxy-3-methoxybenzoic acid (vanillic acid), hydroxy acid
3-dimethoxy-4,5-benzoic acid, 4-hydroxy-3,5-dimethoxy benzoic acid
(syringic acid), 5-hydroxyisophthalic acid, 3-amino acid
salicylic acid, 4-amino salicylic acid, 5-amino-salicylic acid, the acid
3-hydroxy-2-amino-benzoic acid, 3-nitro-salicylic acid, 3-hydroxy-acid
4-nitro-benzoic acid, 4-hydroxy-3-nitro-benzoic acid, 3-hydroxy-acid
4-methyl-2-nitro benzoic acid, 3,5-diiodo-salicylic acid, acid
2,3-dihydroxybenzoic acid, 2,4-dihydroxybenzoic acid,
2,5-dihydroxybenzoic acid, 2,6-dihydroxybenzoic acid,
3,4-dihydroxybenzoic acid (protocatechic acid), 3,5-dihydroxy acid
benzoic acid, 3,5-dihydroxy-4-methyl-benzoic acid1 trihydroxy acid
2,3,4 benzoic acid, 2,4,6-trihydroxybenzoic acid1 trihydroxy acid
3,4,5 benzoic1
alkoxy and phenoxyacids, such as methoxyacetic acid,
phenoxyacetic, 2,4-dichlorophenoxyacetic, phenoxypropionic,
2,4-dichlorophenoxypropionic, p-hydroxyphenoxypropionic, m
chlorophenoxypropionic acid, 4-phenoxybenzoic acid, the acid
(4-carboxy-4-phenoxy) benzoic acid, piperonylic acid,
oxo-acids such as 2-acetylbenzoic acid, 4-acid
acetylbenzoic acid, 2-benzoylbenzoic acid, acid 4
benzoylbenzoic,
acyloxy acids such as 3-benzoyloxypropionic acid, acid 2
acetoxybenzoic acid, 4-acetoxybenzoic acid,
amido-acids such as 2-acetamidoacrylic acid, acid 2
acetamidobenzoic acid, 3-acetamidobenzoic acid, N-acid
4-acetamido benzoic acid.

The carboxylic acids used are preferably acetic acid, propionic acid, pivalic acid, trifluoroacetic acid or benzoic acid.
As regards the use of an anhydride, it can be cyclic or not.

 More precisely, use is made of a cyclic anhydride having from 5 to 10 atoms in the ring not comprising or comprising a double bond, one of the atoms being able to be replaced by an oxygen atom.

 The cyclic anhydrides used preferentially are saturated or comprise a double bond and have 5 or 6 atoms in the ring.

 The cycle may include one or more substituents. More particular examples of substituents that may be mentioned include, in particular, a linear or branched acyclic aliphatic radical preferably having from 1 to 24, preferably from 1 to 12, saturated or comprising one to more unsaturations on the chain, generally , 1 to 3 unsaturations which may be single or conjugated double bonds or triple bonds: the hydrocarbon chain may be interrupted by one of the following groups -O-; -CO-; and / or carrier of one or more substituents, in particular: -OH; CHO; -COX; -X; -CX3.

The preferred substituents are chosen from:
a linear or branched alkyl radical having from 1 to 24 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 2 to 12 carbon atoms,
preferably from 2 to 4 carbon atoms, such as vinyl, allyl,
a linear or branched alkynyl radical having from 2 to 12 carbon atoms,
preferably, -CH2-CECH,
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,
a halogen atom or a trihalomethyl group.

With regard to the use of a non-cyclic anhydride corresponding to formula (IV), the radicals R6 and R7, which may be identical or different, more particularly represent:
a linear or branched acyclic aliphatic radical preferably having
1 to 24, preferably from 1 to 12 carbon atoms, saturated or comprising
one to several unsaturations on the chain, generally, 1 to 3
unsaturations which may be single or conjugated double bonds
or triple bonds: the hydrocarbon chain can be interrupted
by one of the following groups: -0-; -CO-; and / or carrier of one or
several substituents including -OH; -CHO; -COX; -x; -CX3.

a carbocyclic radical, saturated, unsaturated or aromatic, having from 3 to 8
carbon atoms, preferably 6 carbon atoms, optionally
carrier of one or more halogen atoms, preferably chlorine or
bromine or of which one of the carbon atoms is a carbonyl group,
a saturated or unsaturated heterocyclic radical, in particular comprising 5 or 6
atoms in the ring of which 1 or 2 preferably heteroatoms, an atom
oxygen.

Among the radicals specified, R6 and R7 preferably represent:
a linear or branched alkyl or alkenyl radical comprising from 1 to 12
carbon atoms, possibly carrying one or more atoms
halogen,
a cyclohexyl or phenyl radical, optionally carrying one or
several halogen atoms, a trihalomethyl radical,
a furyl radical, a tetrahydrofuryl radical.

As examples of anhydrides, mention may be made of:
acetic anhydride, propanoic anhydride,
isobutyric anhydride,
trichloroacetic anhydride,
trifluoroacetic anhydride,
benzoic anhydride.

monochloroacetyl anhydride,
dichloroacetyl anhydride,
pivalic anhydride

 The reaction between the aromatic compound and the acylating agent is therefore carried out in the presence of a catalyst which is a salt of triflic acid in a mixture comprising at least one carboxylic acid and at least one carboxylic acid anhydride. .

 It should be noted that the carboxylic anhydride can also act as an acylating agent.

 It is also possible that the carboxylic anhydride is generated in the medium from the carboxylic acid.

 The products obtained therefore depend on the reactivity of the acylating agent with respect to the mixture of the carboxylic acid and the carboxylic acid anhydride.

 In a first step of the process of the invention, the acylation of the aromatic compound is carried out. In a next step, the hydrolysis of the reaction mass obtained is carried out.

 The quantity of reagents used is generally such that the ratio between the number of moles of metal or metalloidic element, preferably rare earth element, and the number of moles of triflic acid is preferably chosen between 0.9 and 1.0. .

 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 4.0.

 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.

 The molar ratio between the carboxylic acid and the carboxylic anhydride is chosen between 0.05 and 0.95, preferably between 0.3 and 0.7.

 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 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 40 ° C and 1500 ° 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 can be introduced in any order.

 After contacting the reactants, 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.

 In a next step of the process of the invention, a hydrolysis treatment of the reaction mass obtained is carried out.

 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 brought to a temperature between 0 C and 1000C, 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, preferably by filtration. The catalyst can be recycled after drying.

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

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

 Depending on the reactivity of the carboxylic anhydride and the carboxylic acid used, it is possible that in some cases R3 is replaced by a radical derived therefrom.

 The following examples illustrate the invention without limiting it.

In the examples, the yields mentioned correspond to the following definition:
number of moles of substrate introduced
Yield (RR) =
number of moles of aromatic ketone formed
Example 1

 Acylation of anisole in the presence of scandium triflate.

 The following is the operating protocol which is repeated in the examples which follow.

 In a 50 ml flask, purged with argon, equipped with a condenser equipped with a calcium chloride-giving tube, the scandium triflate (III), Sc (OTf) 3, the substrate and the acylating agent.

 5 mmol of substrate and 60 mmol of acetic anhydride and 50 mmol of acetic acid are used.

 The catalyst is introduced at a rate of 20 mol% relative to the substrate, ie 0.492 g.

 The mixture is brought to the reaction temperature of 50 ° C.

After one hour of reaction, the analysis by gas chromatography gives the following results:
-TTanisole = 80.5%
- Rmethoxyacetophenone = 63> 4%
-RT4-methoxyacetophenone = 79%
After 2 hours of reaction, the analysis by gas chromatography gives the following results:
~ TTanisole = 92%
-RR4-methoxyacetophenone = 71%
- RT4methoxyacetophnone = 77%
Example 2
Example 2bis
Comparative test
In an apparatus as described in Example 1, the scandium triflate Sc (OTf) 3, the substrate and the acylating agent are introduced.

5 mmol of substrate are used and respectively:
. in example 2: 60 mmol of acetic anhydride and 50 mmol of acid
acetic,
. in Example 2bis: 100 mmol of acetic acid and 10 mmol of anhydride
acetic,
. in the test: 110 mmol of acetic anhydride.

 The catalyst is introduced at a rate of 20 mol% relative to the substrate, ie 0.492 g.

 The mixture is brought to the reaction temperature of 50.degree.

After 2 hours of reaction, the analysis by gas chromatography gives the following results:
Table (I)

Ref <SEP> ex. <SEP> Agent <SEP> TTanisole <SEP> RR4-methoxyacetophenone <SEP> RT <SEP> (%)
<tb><SEP> acylation <SEP> (%) <SEP> (%)
<tb><SEP> 2 <SEP> anhydride <SEP> 92 <SEP> 71 <SEP> 77
<tb><SEP> acetic acid
<tb> +
<tb><SEP> acid <SEP> acetic acid
<tb><SEP> 2bis <SEP> anhydride <SEP> 16 <SEP> 14 <SEP> 88
<tb><SEP> acetic acid
<tb><SEP> +
<tb><SEP> acid
<tb><SEP> acetic acid
<tb><SEP> a <SEP> anhydride <SEP> 100 <SEP> 31 <SEP> 31
<tb><SEP> acetic acid
<Tb>
The acetic acid acetic acetic acid system makes it possible to improve the selectivity of the reaction and the choice of an acetic anhydride / acetic acid ratio as defined in Example 2 makes it possible to improve, in an unexpected manner, both the yield and the selectivity of this reaction.

Examples 3 and 4
In the following examples, the example 1 is reproduced but with variation
temperature.

 The results obtained are recorded in Table (II).

Table (II)

<tb> Ref <SEP> ex. <SEP> Tempe <SEP> Time <SEP> of <SEP> TTanisole <SEP> RR4-methoxyacetophenone <SEP> RT <SEP> (%)
<tb><SEP> rature <SEP> reaction <SEP> (%) <SEP> (%)
<tb><SEP> 3 <SEP> 50 <SEP>;<SEP> 1 <SEP> h <SEP> 80.5 <SE> 63.4 <SEP> 79
<tb><SEP> 2h <SEP> 92 <SEP> 71 <SEP> 77
<tb><SEP> 4 <SEP> 90 <SEP>. <SEP> 15 <SEP> min <SEP> 100 <SEP> 62 <SEP> - <SEP> 62
<tb> 30 <SEP> min <SEP> 100 <SEQ> 54 <SEP> 54
<tb> Examples 5 to 10
Example 1 is repeated using the same catalyst, scandium triflate but in a smaller amount is 1 mol%: the temperature is either 75 ° C or 900C.

The results obtained are collated in Table (III): Table (III)

Ref. <SEP> Quantity <SEP> Qunatity <SEP> Quantity <SEP> Temperature <SEP> Time <SEP> of <SEP> TTanisole <SEP> RR4-methoxy * <SEP> RT4-methoxy *
<tb> ex. <SEP> catalyst <SEP> acid <SEP> anhydride <SEP> reaction
<tb> acetic acid <SEP> acetic acid
<tb> (%)
<tb> (%) <SEP> (mmol) <SEP> (mmol) <SEP> (C) <SEP> min <SEP> or <SEP> h <SEP> (%) <SEP> (%)
<tb> 5 <SEP> 1 <SEP> 50 <SEP> 60 <SEP> 75 <SEP> 30 <SEP> min <SEP> 65.5 <SEP> 59.8 <SEP> 91.3
<tb> 6 <SEP> 1 <SEP> 50 <SEP> 60 <SEP> 75 <SEP> 1 <SEP> h <SEP> 78.1 <SE> 69.2 <SE> 88.6
<tb> 7 <SEP> 1 <SEP> 50 <SEP> 60 <SEP> 75 <SEP> 1 <SEP> h <SEP> 30 <SEP> 82.6 <SEP> 72 <SEP> 87.2
<tb> 8 <SEP> 1 <SEP> 50 <SEP> 60 <SEP> 90 <SEP> 30 <SEP> min <SEP> 81.6 <SEP> 69.7 <SEP> 85.4
<tb> 9 <SEP> 1 <SEP> 50 <SEP> 60 <SEP> 90 <SEP> 1 <SEP> h <SEP> 87.2 <SE> 76.6 <SE> 87.8
<tb> 10 <SEP> 1 <SEP> 50 <SEP> 60 <SEP> 90 <SEP> 1h <SEP> 30 <SEP> 89.6 <SEP> 77.2 <SEP> 86.2
<tb> * 4-methoxy means 4-methoxyacetophenone
Examples 11 to 16
In the examples which follow, the reaction is carried out as in Example 1, at a temperature of 90 ° C., and in the presence of different amounts of catalyst.

The operating conditions and results are given in Table (IV): Table (IV)

Ref. <SEP> Quantity <SEP> Quantity <SEP> Quantity <SEP> Temperature <SEP> Time <SEP> of <SEP> TTanisole <SEP> RR4-methoxy * <SEP> RT4-methoxy *
<tb> ex. <SEP> catalyst <SEP> acid <SEP> anhydride <SEP> reaction
<tb> acetic acid <SEP> acetic acid
<tb> (%) <SEP> (mmol) <SEP> (mmol) <SEP> (C) <SEP> min <SEP> or <SEP> h <SEP> (%) <SEP> (%) <SEP > (%)
<tb> 11 <SEP> 20 <SEP> 50 <SEP> 60 <SEP> 90 <SEP> 15 <SEP> min <SEP> 100 <SEP> 62 <SEP> 62
<tb> 12 <SEP> 20 <SEP> 50 <SEP> 60 <SEP> 90 <SEP> 30 <SEP> min <SEP> 100 <SEP> 54 <SEP> 54
<tb> 13 <SEP> 10 <SEP> 50 <SEP> 60 <SEP> 90 <SEP> 15 <SEP> min <SEP> 100 <SEP> 68 <SEP> 68
<tb> 14 <SEP> 1 <SEP> 50 <SEP> 60 <SEP> 90 <SEP> 30 <SEP> min <SEP> 81.6 <SEP> 69.7 <SEP> 85.4
<tb> 15 <SEP> 1 <SEP> 50 <SEP> 60 <SEP> 90 <SEP> 1 <SEP> h <SEP> 87.2 <SE> 76.6 <SE> 87.8
<tb> 16 <SEP> 1 <SEP> 50 <SEP> 60 <SEP> 90 <SEP> 1 <SEP> h <SEP> 30 <SEP> 89.6 <SEP> 77.2 <SE> 86.2
<tb> * 4-methoxy means 4-methoxyacetophenone
Examples 17 to 24
In the following series of examples, the influence of the ratio of acetic anhydride to acetic acid is highlighted.

 The catalyst used is still the scandium triflate at 20 mol%.

All amounts of reagents, catalyst, operating conditions and results are shown in Table (V): Table (V)

Ref. <SEP> Quantity <SEP> Quantity <SEP> Quantity <SEP> Ratio <SEP> Time <SEP> Time <SEP> of <SEP> TTanisole <SEP> RR4-methoxy * <SEP> RT4-methoxv *
<tb> ex. <SEP> catalyst <SEP> acid <SEP> anhydride <SEP> anhydride <SEP> structure <SEP> reaction
<tb> acetic acid <SEP> acetic acid <SEP> /
<tb> (%) <SEP> (mmol) <SEP> (mmol) <SEP> acid <SEP> (C) <SEP> min <SEP> or <SEP> h <SEP> (%) <SEP> ( %) <SEP> (%)
<tb> 17 <SEP> 20 <SEP> 50 <SEP> 60 <SEP> 1.2 <SEP> 50 <SEP> 1 <SEP> h <SEP> 80.5 <SE> 63.4 <SEP> 79
<tb> 18 <SEP> 20 <SEP> 50 <SEP> 60 <SEP> 1,2 <SEP> 50 <SEP> 2 <SEP> h <SEP> 92 <SEP> 71 <SEP> 77
<tb> 19 <SEP> 20 <SEP> 50 <SEP> 60 <SEP> 1.2 <SEP> 90 <SEP> 15 <SEP> min <SEP> 100 <SEP> 62 <SEP> 62
<tb> 20 <SEP> 20 <SEP> 50 <SEP> 60 <SEP> 1,2 <SEP> 90 <SEP> 30 <SEP> min <SEP> 100 <SE> 54 <SEP> 54
<tb> 21 <SEP> 20 <SEP> 50 <SEP> 30 <SEP> 0.6 <SEP> 90 <SEP> 40 <SEP> min <SEP> 100 <SEP> 57 <SEP> 57
<tb> 22 <SEP> 20 <SEP> 50 <SEP> 30 <SEP> 0.6 <SEP> 90 <SEP> 60 <SEP> min <SEP> 100 <SEP> 56.5 <SEP> 56.5
<tb> 23 <SEP> 20 <SEP> 25 <SEP> 15 <SEP> 0.6 <SEP> 90 <SEP> 30 <SEP> min <SEP> 98.6 <SEP> 57.2 <SEP> 58
<tb> 24 <SEP> 20 <SEP> 25 <SEP> 15 <SEP> 0.6 <SEP> 90 <SEP> 60 <SEP> min <SEP> 100 <SEP> 48.5 <SEP> 48.5
<tb> * 4-methoxy means 4-methoxyacetophenone
Examples 25 to 33
Another series of tests is carried out in which the ratio between acetic anhydride and acetic acid is varied.

 The catalyst used is scandium triflate but it is used in smaller amounts, ie 1 mol%.

All amounts of reagents, catalyst, operating conditions and results are shown in Table ('II): Table (VI)

Ref. <SEP> Quantity <SEP> Quantity <SEP> Quantity <SEP> Ratio <SEP> Time <SEP> Time <SEP> of <SEP> TTanisole <SEP> RR4-methoxy * <SEP> RT4-methoxy *
<tb> ex. <SEP> catalyst <SEP> acid <SEP> anhydride <SEP> anhydride / <SEP> reaction <SEP> reaction
<tb> acetic acid <SEP> acetic acid <SEP>
<tb> (%) <SEP> (mmol) <SEP> (mmol) <SEP> (C) <SEP> min <SEP> or <SEP> h <SEP> (%) <SEP> (%) <SEP > (%)
<tb> 25 <SEP> 1 <SEP> 50 <SEP> 60 <SEP> 1.2 <SEP> 90 <SEP> 30 <SEP> min <SEP> 81.6 <SEP> 69.7 <SEP> 85 4
<tb> 26 <SEP> 1 <SEP> 50 <SEP> 60 <SEP> 1.2 <SEP> 90 <SEP> 1 <SEP> h <SEP> 87.2 <SE> 76.6 <SEP> 87 8
<tb> 27 <SEP> 1 <SEP> 50 <SEP> 60 <SEP> 1.2 <SEP> 90 <SEP> 1 <SEP> h <SEP> 30 <SEP> 89.6 <SE> 77.2 <SEP> 86.2
<tb> 28 <SEP> 1 <SEP> 25 <SEP> 15 <SEP> 0.6 <SEP> 90 <SEP> 30 <SEP> min <SEP>
Examples 34 to 36
In these examples, other triflates of rare earths are used.

 50 mmol of acetic acid, 30 mmol of acetic anhydride and 1 mol% of catalyst are used, the reaction being carried out at 9000.

 After one hour of reaction, the results obtained are recorded in Table (VII).

TABLE (VII)

<tb> Ref. <SEP> Nature <SEP> of <SEP> TTanisoïe <SEP> RR4 <SEP> RTs <SEP>
<tb><SEP> ex. <SEP> | <SEP> catalyst <SEP> | <SEP> (%) <SEP> | <SEP> methoxyacetophenone <SEP> | <SEP> methoxyacetophenone
<tb><SEP> (%) <SEP> (%)
<tb><SEP> 34 <SEP> Sc (OTf) 3 <SEP> 77 <SEP> 70 <SEP> 91
<tb><SEP> 35 <SEP> Yb (OTf) 3 <SEP> 60 <SEQ> 54 <SEP> 91
<tb><SEP> 36 <SE> Sm (OTf) 3 <SEP> 36 <SEP> 32 <SEP> 89
<Tb>
Examples 37 to 52
In these examples, other triflates of rare earths are used.

 50 mmol of acetic acid, 30 mmol of acetic anhydride and 1 mol% of catalyst are used, the reaction being carried out at 90 ° C.

 After two hours of reaction, the results obtained are recorded in Table (VIII).

Table (VIII)

<tb> Ref. <SEP> Nature <SEP> of <SEP> TTanisole <SEP> RR4-methoxyacetophenone <SEP> RT4-methoxyacetophenone
<tb> ex. <SEP> Catalyst <SEP> (%) <SEP> (%) <SEP> (%)
<tb><SEP> 37 <SEP> Sc (OTf) 3 <SEP> 82.6 <SEP> 73.2 <SEP> 88.6
<tb><SEP> 38 <SEP> Y (OTf) 3 <SEP> 58.3 <SEP> 49.4 <SEP> 84.7
<tb><SEP> 39 <SEP> The (OTf) 3 <SEP> 38.9 <SEP> 35.9 <SEP> 92.3
<tb><SEP> 40 <SEP> This (OTf) 4 <SEP> 30.0 <SEP> 18.6 <SEP> 62.0
<tb><SEP> 41 <SEP> Pr (OTf) 3 <SEP> 45.9 <SEP> 40.5 <SEP> 88.2
<tb><SEP> 42 <SEP> Nd (OTf) 3 <SEP> 37.0 <SEP> 33.2 <SEP> 89.7
<tb><SEP> 43 <SEP> Sm (OTf) 3 <SEP> 48.3 <SEP> 44.6 <SEP> 92.0
<tb><SEP> 44 <SEP> Eu (OTf) 3 <SEP> 56.7 <SEP> 51.9 <SEP> 91.5
<tb><SEP> 45 <SEP> Gd (OTf) 3 <SEP> 47.0 <SEP> 41.2 <SEP> 87.7
<tb><SEP> 46 <SEP> Tb (OTf) 3 <SEP> 56.7 <SEP> 50.0 <SEP> 88.2
<tb><SEP> 47 <SEP> Dy (OTf) 3 <SEP> 36.1 <SEP> 32.2 <SEP> 89.2
<tb><SEP> 48 <SEP> Ho (OTf) 3 <SEP> 64.9 <SEP> 56.1 <SEP> 86.4
<tb><SEP> 49 <SEP> Er (OTf) 3 <SEP> 67.1 <SEP> 59.4 <SEP> 88.5
<tb><SEP> 50 <SEP> Tm (OTf) 3 <SEP> 64.0 <SEP> 57.9 <SEP> 90.5
<tb><SEP> 51 <SEP> Yb (OTf) 3 <SEP> 69.5 <SEP> 64.0 <SEP> 92.0
<tb><SEP> 52 <SEP> Lu (OTf) 3 <SEP> 68.3 <SEP> 62.5 <SEP> 91.5
<Tb>
Example 53
In this example, the acetylation of veratrole is carried out.

 The catalyst used is scandium triflate.

After 30 minutes of reaction, the results obtained are as follows:
- TTsubstrate = 93%
- RRproduced aC4l = 92%
- RTpruit acetyl = 99% Example S4
Acetylation of 1,2-methylene dioxybenzene is carried out.

 The catalyst used is scandium triflate.

After 30 minutes of reaction, the results obtained are as follows:
Usubseat = 51%
- RR acetylated product = 48
- Reproduced acetylated = 94%
Examples 55 and 56
Comparative tests c and d
Acetylation of 2-methoxynaphthalene is conducted.

 Two types of catalysts are used, scandium triflate and cerium triflate.

 The acetylation of 2-methoxynaphthalene is carried out with acetic anhydride (50 mmol) in the presence of scandium triflate or cerium triflate.

 In Examples 55 and 56, the reaction is carried out in the acetic anhydride system (60 mmol) and acetic acid as solvent (50 mmol).

 In the comparative tests c and d, acetic anhydride is used as the reaction solvent in a proportion of 100 ml.

 The results obtained are recorded in Table (IX).

Table (IX)

Ref. <SEP> Nature <SEP> of <SEP> Agent <SEP> Time <SEP> of <SEP><SEP> TT2-methoxy <SEP> RR1-acetyl <SEP> RR6-acetyl <SEP> RT
<tb> ex. <SEP> catalyst <SEP> acylation <SEP> reaction
<tb> (h)
<tb> 55 <SEP> Sc (OTf) 3 <SEP> anhydride <SEP> acetic acid <SEP> 1 <SEP> h <SEP> 92 <SEP> 66 <SEP> 3 <SEP> 75
<tb> acid <SEP> acetic acid
<tb> c <SEP> Sc (OTf) 3 <SEP> anhydride <SEP> acetic acid <SEP> 1 <SEP> h <SEP> 100 <SEP> 50 <SEP> - <SEP> 50
<tb> 56 <SEP> Ce (OTf) 4 <SEP> anhydride <SEP> acetic acid <SEP> 2 <SEP> h <SEP> 68 <SEP> 60 <SEP> - <SEP> 88
<tb> acid <SEP> acetic acid
<tb> d <SEP> Ce (OTf) 4 <SEP> anhydride <SEP> acetic acid <SEP> 2 <SEP> h <SEP> 96 <SEP> 71 <SEP> - <SEP> 74
<tb> 1-acetyl means 1-acetyl-2-methoxynaphthalene 6-acetyl means 6-acetyl-2-methoxynaphthalene Examples 57 to 59
In the following examples, the acetylation of the anisole is carried out in the presence of scandium triflate prepared in situ in the reaction medium from 1 mol% of Sc (OAc) 3 (Example 58) or Sc (Cl) 3 (Example 59).

 After 1 hour of reaction, the results obtained are as follows.

Paintings)

<tb> Ref. <SEP> Nature <SEP> of <SEP> TTanisole <SEP> RR4methoxvacetonhénone <SEP> RT4methoxvacétonhénone <SEP>
<tb> ex. <SEP> Catalyst
<tb><SEP> (%) <SEP> (%) <SEP> (%)
<tb><SEP> 57 <SEP> Sc (OTf) 3 <SEP> 77 <SEP> 70 <SEP> 91
<tb><SEP> 58 <SEP> Sc (OAC) 3 <SEP> 85 <SEP> 76 <SEP> 89
<tb><SEP> acid
<tb><SEP> trifli <SEP> ue <SEP>
<tb><SEP> 59 <SEP> Sc (CI) 3 <SEP> 88 <SEP> 76 <SEP> 86
<tb><SEP> acid
<tb><SEP> triflic
<tb> Examples 60 to 64
In the following examples, the influence of the nature of the carboxylic acid is demonstrated.

 The acetylation of the anisole (5 mmol) is carried out at 90 ° C., with 1 mol% of scandium triflate in a mixture of acetic anhydride (30 mmol) and of different carboxylic acids (50 mmol).

After 1 hour of reaction, the results obtained are as follows: Table (XI)

Ref. <SEP> Anhydride <SEP> acetic acid / <SEP> TTanisole <SEP> RR4-metho-aceto <SEP> RR <SEP> other <SEP> products <SEP> acylated <SEP> RT <SEP> total
<tb> ex. <SEP> carboxyl <SEP> acid <SEP>% <SEP>% <SEP>% <SEP>%
<tb> 60 <SEP> AcOH <SEP> 83 <SEP> 73 <SEP> - <SEP> 88
<tb> 61 <SEP> C2H5COOH <SEP> 83 <SEP> 31 <SEP> 4-methoxypropiophenone <SEP> 82
<tb> 37
<tb> 62 <SEP> Ph-COOH <SEP> 74 <SEP> 64 <SEP> qq <SEP> 86
<tb> 63 <SEP> (CH3) 3CCOOH <SEP> 37 <SEP> 33 <SEP> qq <SEP> 89
<tb> 64 <SEP> CF3COOH <SEP> 100 <SEP> 40 <SEP> - <SEP> 40
<Tb>
Examples 65 to 70
In the following examples, the influence of the nature of the carboxylic anhydride is demonstrated.

 The acylation of the anisole (5 mmol) is carried out at 90 ° C., with 1 mol% of scandium triflate in a mixture of acetic acid (50 mmol) and of various carboxylic anhydrides (30 mmol).

After 1 hour of reaction, the results obtained are as follows: Table (XII)

Ref. <SEP> Acid <SEP> acetic acid / <SEP> TTanisole <SEP> RR4-metho-aceto <SEP> RR <SEP> other <SEP> acylated <SEP> RT <SEP> total
<tb> ex. <SEP> carboxylic anhydride <SEP><SEP>%<SEP>%<SEP>%<SEP>%
<tb> 65 <SEP> anhydride <SEP> acetic acid <SEP> 83 <SEP> 73 <SEP> - <SEP> 88
<tb> 66 <SEP><SEP> propionic anhydride <SEP> 86 <SEP> 24 <SEP> 4-methoxypropiophenone <SEP> 73
<tb> 39
<tb> 67 <SEP> Benzoic anhydride <SEP><SEP> 68 <SEP> 58 <SEP> - <SEP> 85
<tb> 68 <SEP> Pigmental anhydride <SEP><SEP> 18 <SEP> 16 <SEP> - <SEP> 89
<tb> 69 <SEP> Trifluoroacetic anhydride <SEP><SEP> 85 <SEP> 50 <SEP> - <SEP> 59
<tb> 70 <SEP> succinic anhydride <SEP><SEP> 12 <SEP> 9 <SEP> - <SEP> 72
<Tb>
Examples 71 to 73
In the following examples, the acylation of the anisole is carried out by other anhydride / carboxylic acid couples.

 In the following examples, the acylation of anisole (5 mmol) is carried out at 90 ° C., with 1% of scandium triflate in an acid mixture (50 mmol) and the corresponding anhydride (30 mmol).

After 2 hours of reaction, the results obtained are as follows: Table (Xlil)

<tb> Ref. <SEP> TTanisole <SEP> RRproduct <SEP> acvl <SEP> RT
<tb><SEP> ex.
<Tb>

<SEP> 71 <SEP> Acetylation <SEP> 83 <SEP> 4-methoxyacetophenone <SEP> 88
<tb><SEP> 73
<tb><SEP> 72 <SEP> Propionylation <SEP> 84 <SEP> 4-methoxypropiophenone <SEP> 69
<tb><SEP> 58 <SEP>
<tb><SEP> 73 <SEP> Benzoylation <SEP> 67 <SEP> 4-methoxybenzophenone <SEP> 92
<tb><SEP> 62
<Tb>
Examples 74 to 76
In the following examples, the acetylation of an aromatic compound (5 mmol) at different temperatures with 1 mol% of scandium triflate in a mixture of acetic anhydride (30 mmol) and acetic acid (50 mmol) is carried out. .

After 1 hour of reaction, the results obtained are as follows: Table (XIV)

Ref. <SEP> Substrate <SEP> Time <SEP> of <SEP> Temperature <SEP> TT <SEP> RR <SEP> RT
<tb> ex. <SEP> reaction <SEP> (h) <SEP> (C) <SEP> substrate <SEP>% <SEP>%
<tb> 74 <SEP> 1-acetoxy-2- <SEP> 2 <SEP> 90 <SEP> 24 <SEP> 3-acetoxy-4-methoxyacetophenone <SEP> 48
<tb> methoxybenzene <SEP> 20
<tb> 75 <SEP> acetoxybenzene <SEP> 4 <SEP> 175 <SEP> 10 <SEP> 4-acetoxyacetophenone <SEP> 99
<tb> 9
<tb> 76 <SEP> acetanilide <SEP> 4 <SEP> 175 <SEP> 67 <SEP> 4-acetamidoacetophenone <SEP> 21
<tb> 31
<Tb>
Examples 77 to 79
In the following examples, other metal triflates are used to carry out the acetylation of anisole: zinc triflate in Example 77, iron triflate in Example 78 and bismuth triflate in Example 1. Example 79

After 2 hours of reaction, the results obtained are as follows: Table (XV)

Ref. <SEP> Nature <SEP> of <SEP> Agent <SEP> Time <SEP> of <SEP><SEP> TTanisole <SEP> RR4-acethoxyacetophenone <SEP> RT
<tb> ex. <SEP> catalyst <SEP> acylation <SEP> reaction
<tb> (h)
<tb> 77 <SEP> Zn (Otf) 2 <SEP> anhydride <SEP> acetic acid <SEP> 2 <SEP> h <SEP> 59 <SEP> 48 <SEP> 81
<tb> acid <SEP> acetic acid
<tb> 78 <SEP> Fe (Otf) 2 <SEP> anhydride <SEP> acetic acid <SEP> 2 <SEP> h <SEP> 69 <SEP> 63 <SEP> 91
<tb> acid <SEP> acetic acid
<tb> 79 <SEP> Bi (Otf) 3 <SEP> anhydride <SEP> acetic acid <SEP> 2 <SEP> h <SEP> 89 <SEP> 77 <SEP> 87
<tb> acid <SEP> acetic acid
<Tb>

Claims (29)

 1 - A process for acylating an aromatic compound which comprises reacting said aromatic compound with an acylating agent characterized in that the acylation reaction is carried out in the presence of an effective amount of a triflic acid salt, in a mixture comprising at least one carboxylic acid and at least one carboxylic acid anhydride. 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 may carry a radical R representing  a hydrogen atom 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.

 -S-, -SO-, -SO2-, -SO3-,  -O-, -CO-, -COO-, -OCOO  . by one of the following groups:  preferably a methylene or isopropylidene radical,  . with an alkylene or alkylidene radical having from 1 to 4 carbon atoms,  . by a valid link,  3 - a compound constituted by a series of cycles, as defined in paragraphs 1 and / or 2 linked together:  phenyl.  alkyl having 1 to 4 carbon atoms, a cyclohexyl radical or  in these formulas, Ro represents a hydrogen atom or a radical 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 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 from 1 to 6 carbon atoms  preferably from 1 to 4 carbon atoms such as methoxy radicals,  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  -R 1 -N (R2) 2  -R 1 -CO-N (R2) 2  -R1-X  -R 1 -Z-R2  -R 1 CF 3  -Z-CF3 in said formulas, R1 represents a valency bond or a divalent hydrocarbon radical, linear or branched, saturated or unsaturated, having from 1 to 6 carbon atoms such as, for example, methylene, ethylene, propylene, isopropylene, isopropylidene ; the radicals R 2 which are identical or different represent a hydrogen atom or a linear or branched alkyl radical having from 1 to 6 carbon atoms or a phenyl radical; X represents a halogen atom, preferably a chlorine, bromine or fluorine atom; Z represents one of the following groups: O, S, SO, SO2, SO3. 5- Method 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 -NO2,  . a group -NH2,  . 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.

 -S-, -SO-, -SO2-, -SO3-,  -O-, -CO-, -COO-, -OCOO  - one of the following groups:  preferably, a methylene or isopropylidene radical,  an alkylene or alkylidene radical having from 1 to 4 carbon atoms,  - a valid link  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:

 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):  phenyl.  alkyl having 1 to 4 carbon atoms, a cyclohexyl radical or  in these formulas1 Ro represents a hydrogen atom or a radical 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, a group  amine, an amide group, an ester group, an alkyl or alkoxy radical  linear or branched having 1 to 6 carbon atoms, preferably 1  at 4 carbon atoms or a halogen atom,  B symbolizes a valency bond, an alkylene or alkylidene radical having 1  at 4 carbon atoms or an oxygen atom,  -equal toO or 1, - n is 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 or a methoxy radical or a halogen atom. 11 - Process according to claim 1 and 2 characterized in that the aromatic compound is benzene, toluene, phenol, anisole, veratrole, 1,2-methylenedioxybenzene, 2-methoxynaphthalene. 12- Method according to one of claims 1 to 11 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 3 to 8 carbon atoms  carbon; a saturated or unsaturated aliphatic radical, linear or branched,  bearing a cyclic substituent, X 'represents:  a halogen atom, preferably a chlorine or bromine atom,  a hydroxyl group,  a radical -O-CO-R4 with R4, identical to or different from R3, having the same  meaning that R3: R3 and R4 can together form a divalent radical  saturated or unsaturated, linear or branched aliphatic having at least 2 atoms  of carbon. 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 a substituent; R3 represents an optionally substituted phenyl radical; or X 'represents a radical -O-CO-R3. in which R3 and R4 are identical and represent an alkyl radical having 1 to 4 carbon atoms. 14- Method according to claim 12 and 13 characterized in that the acylating agent is chosen from:  acetic anhydride, propanoic anhydride,  isobutyric anhydride,  trichloroacetic anhydride,  trifluoroacetic anhydride,  benzoic anhydride.  - acetic acid.  naphthoyl chlorides,  methoxybenzoyl chlorides,  p-nitrobenzoyl chloride  chlorobenzoyl chlorides,  - benzoyl chloride,  - crotonyl chloride,  stearoyl chloride,  pivaloyl chloride,  isobutanoyl chloride,  propanoyl chloride,  dichloroacetyl chloride,  - monochloroacetyl chloride,  acetyl chloride,  dichloroacetyl anhydride,  monochloroacetyl anhydride, 15 - Process according to one of claims 1 to 14 characterized in that the catalyst used is a metal or metalloidal salt of trifluoromethanesulfonic acid. 16- The method of claim 15 characterized in that the catalyst is a trifluoromethanesulfonic acid salt of the elements of group (IIIa) of the periodic table preferably, scandium, yttrium and lanthanides; the group (IVa) preferably titanium; preferably group (VIII), iron; group (lob) preferably, zinc; group (IIIb) preferably aluminum; group (IVb) preferably tin; group (Vb) preferably antimony and bismuth; of the group (Vlb) preferably tellurium. 17- The method of claim 15 characterized in that the catalyst is a rare earth salt of trifluoromethanesulfonic acid or mixtures thereof. 18 - Process according to one of claims 1 to 17, characterized in that the reaction mixture comprises at least one carboxylic acid and at least one carboxylic acid anhydride corresponding to the formulas:

 in said formulas (III) and (1V)  R5 represents a monovalent hydrocarbon radical, substituted or unsubstituted,  can be a saturated or unsaturated, linear acyclic aliphatic radical1 or  branched; a saturated or unsaturated carbocyclic or heterocyclic radical  aromatic, monocyclic or polycyclic,  - R6, identical to or different from R7, has the same meaning as R5: R6 and R7  which may together form a saturated or unsaturated divalent aliphatic radical,  linear or branched, having at least 2 carbon atoms. 19- Process according to claim 18 characterized in that the carboxylic acid used is any carboxylic acid, mono- or polycarboxylic such as saturated or unsaturated, carbocyclic or heterocyclic aliphatic acids, saturated or unsaturated or aromatic, monocyclic or polycyclic ; cyclo- or arylaliphatic, saturated or unsaturated. 20 - Process according to one of claims 18 and 19 characterized in that the carboxylic acid corresponds to formula (III) wherein R5 represents a linear or branched acyclic aliphatic radical preferably having from 1 to 12 carbon atoms, saturated or comprising one to more unsaturations on the chain, generally 1 to 3 unsaturations which may be single or conjugated double bonds or triple bonds: the hydrocarbon chain may be optionally: (1) - interrupted by one of the following groups called Y: -O -; - CO -; - COO-;

 In these formulas, R.sup.8 represents hydrogen or a linear or branched alkyl radical having from 1 to 4 carbon atoms, preferably a methyl or ethyl radical.  (2) - and / or carrier of one of the following substituents: - OH; - COOH; - CHO; - NO2; - CN; - NH2 - SH; - X; - CF3. 21 - Process according to claims 18 and 19 characterized in that the carboxylic acid corresponds to formula (III) wherein R5 represents: - a carbocyclic radical saturated or comprising 1 or 2 unsaturations in the ring, generally having from 3 to 7 carbon atoms, preferably 6 carbon atoms in the ring; said cycle being substitutable; - a preferably monocyclic aromatic hydrocarbon radical, benzene corresponding to the general formula (V):

 a halogen atom.  a phenyl or benzyl radical,  a group - CHO,  a methylene or ethylene dioxy radical,  a linear or branched alkoxy radical having from 1 to 4 carbon atoms,  a linear or branched alkyl radical having from 1 to 4 carbon atoms  a hydrogen atom,  - Rg represents one of the following groups or functions:  p is an integer from 0 to 4, preferably from 0 to 3,  in said formula (V): or a polycyclic aromatic hydrocarbon radical; the rings being able to form between them ortho-condensed, ortho- and peri-condensed systems, preferably a naphthyl radical, said cycles being able to be substituted; - or a sequence of two to four radicals as defined. 22 - Process according to claim 18 characterized in that one uses a cyclic anhydride having 5 to 10 atoms; preferably, 5 or 6 atoms in the ring not comprising or comprising a double bond, one of the atoms may be replaced by an oxygen atom. 23- The method of claim 22 characterized in that the ring comprises one or more substituents which may be a linear or branched acyclic aliphatic radical preferably having from 1 to 24, preferably from 1 to 12 carbon atoms, saturated or comprising one to more unsaturations on the chain, generally 1 to 3 unsaturations which may be single or conjugated double bonds or triple bonds: the hydrocarbon chain may be interrupted by one of the following groups -O-; -CO-; and / or carrier of one or more substituents, in particular: -OH; -CHO; -COX; -X; -CX3. 24 - Process according to claim 18 characterized in that one uses a non-cyclic anhydride corresponding to the formula (IV) in which the radicals R6 and R7, which are identical or different, represent:  a linear or branched acyclic aliphatic radical preferably having  1 to 24, preferably from 1 to 12 carbon atoms, saturated or comprising  one to several unsaturations on the chain, generally, 1 to 3  unsaturations which may be single or conjugated double bonds  or triple bonds: the hydrocarbon chain can be interrupted  by one of the following groups: -O-; -CO-; and / or carrier of one or  several substituents including -OH; -CHO; -COX; -X; -CX3.  oxygen.  atoms in the ring of which 1 or 2 preferably heteroatoms, an atom  a saturated or unsaturated heterocyclic radical, in particular comprising 5 or 6  bromine or of which one of the carbon atoms is a carbonyl group,  carrier of one or more halogen atoms, preferably chlorine or  carbon atoms, preferably 6 carbon atoms, optionally  a carbocyclic radical, saturated, unsaturated or aromatic, having from 3 to 8 25 - Method according to one of claims 18 to 24, characterized in that the carboxylic acid and the carboxylic anhydride are chosen from: for the carboxylic acid:  - acetic acid,  - propionic acid,  - pivalic acid,  trifluoroacetic acid,  benzoic acid, for the carboxylic anhydride: propanoic anhydride,  isobutyric anhydride,  trichloroacetic anhydride,  trifluoroacetic anhydride,  benzoic anhydride.  pivalic anhydride  dichloroacetyl anhydride,  monochloroacetyl anhydride, 26 - Method according to one of claims 1 to 25, characterized in that the molar ratio between the carboxylic acid and the carboxylic anhydride is chosen between 0.05 and 0.95, preferably between 0.3 and 0.7. 27 - Process according to one of claims 1 to 26, characterized in that the molar 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 4.0. 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 40 C and 1500C.