Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
1999-04-06
2001-02-27
Padmanabhan, Sreeni (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C568S319000, C568S332000, C568S335000
Reexamination Certificate
active
06194616
ABSTRACT:
The present invention concerns a process for the acylation of an aromatic compound, in particular an aromatic ether or thioether.
In its preferred variation, the invention concerns a process for the acylation of an aromatic ether or thioether by carboxylic acid anhydrides, preferably acetic anhydride.
More particularly, the invention is applicable to the preparation of alkoxy- or alkylthio-aromatic alkylketones.
Conventional processes for the acylation of aromatic compounds, in particular the ethers of phenols, use a carboxylic acid or one of its derivatives such as the acid halide, ester or anhydride as the acylation reactant.
The reaction is generally carried out in the presence of a Lewis acid type catalyst (for example AlCl
3
) or a Brönsted acid type catalyst (H
2
SO
4
, HF, etc . . . ).
For about ten years, zeolites have been used as acylation catalysts.
Thus European patent EP-A-0 279 322 describes the vapour phase reaction of an aromatic compound (veratrole) with a carboxylic acid derivative in the presence of a zeolite in its H form such as mordenite, faujasite and ZSM-5.
U.S. Pat. No. 4,960,943 describes an acylation process, particularly for anisole, in the presence of zeolites which have a pore size of at least 5 Angströms and which have the following formula: M
m/z
[mMe
1
O
2
.nMe
2
O
2
],qH
2
O] where M is an exchangeable cation, z is the valency of the cation and Me
1
and Me
2
represent the elements of the anionic skeleton, n/m is a number from 1-3000, preferably 1-2000, and q represents the adsorbed water.
Prins et al. have described the acetylation of anisole using acetic anhydride [9
th
International Zeolite Congress- Montreal Congress (1992)], in the presence of zeolites such as &bgr; zeolite or US-Y zeolite. It should be noted that &bgr; zeolites can produce more interesting results as regards both the degree of conversion and the reaction yield.
However, the catalyst performances described are not satisfactory. The use of such a catalyst on an industrial scale is problematic since the productivity of the catalyst is unsatisfactory and would thus necessitate the use of a very large reactor.
The aim of the present invention is to provide a process which can overcome the above disadvantages.
It has now been discovered, and this constitutes the aim of the present invention, a process for the acylation of an aromatic compound, by reacting said compound with an acylation agent in the presence of a zeolitic catalyst, characterized in that it consists of:
mixing the aromatic compound and the acylation compound in any manner;
passing said mixture over a catalytic bed comprising at least one zeolite;
recirculating the reaction mixture from the catalytic bed over the catalytic bed for a number of times which is sufficient to obtain the desired degree of conversion of the substrate.
The process of the invention thus uses an aromatic compound and an acylation agent.
In the following disclosure of the present invention, the term “aromatic compound” encompasses the conventional concept of aromaticity as defined in the literature, in particular by Jerry MARCH, “Advanced Organic Chemistry”, 4
th
edition, John Wiley and Sons, 1992, p40 ff.
The term “by an aromatic ether or thioether” means an aromatic compound in which one hydrogen atom which is directly bonded to the aromatic ring has been replaced by an ether or thioether group respectively.
More precisely, the present invention provides a process for acylation of an aromatic compound with general formula (I):
where:
A represents the residue of a cycle forming all or part of a carbocyclic or heterocyclic, aromatic, monocyclic or polycyclic system; said cyclic residue may carry a radical R which represents a hydrogen atom or one or more substituents, which may be identical or different;
n represents the number of substituents in the cycle.
The invention is particularly applicable to aromatic compounds with formula (I) in which A is the residue of a cyclic compound which preferably contains at least 4 atoms in the cycle, preferably 5 or 6, which may be substituted, and which represents at least one of the following cycles:
an aromatic, monocyclic or polycyclic carbocycle;
an aromatic, monocyclic or polycyclic heterocycle comprising at least one of heteroatoms O, N or S.
In more detail, without in any way limiting the scope of the invention, residue A which may optionally be substituted represents the residue:
1° of an aromatic, monocyclic or polycyclic carbocyclic compound.
The term “polycyclic carbocyclic compound” means:
a compound constituted by at least 2 aromatic carbocycles and forming ortho- or ortho- and peri-condensed systems between them;
a compound constituted by at least 2 carbocycles, only one of them being aromatic and forming ortho- or ortho- and peri-condensed systems between them;
2° of an aromatic, monocyclic or polycyclic heterocyclic compound.
The term “polycyclic heterocyclic compound” defines:
a compound constituted by at least 2 heterocycles containing at least one heteroatom in each cycle, at least one of the two cycles being aromatic and forming ortho- or ortho- and peri-condensed systems between them;
a compound constituted by at least one hydrocarbon cycle and at least one heterocycle, at least one of the cycles being aromatic and forming ortho- or ortho-and peri-condensed systems between them;
3° of a compound constituted by linked cycles as defined in paragraphs 1 and/or 2 linked together by:
a valence bond;
an alkylene or alkylidene radical containing 1 to 4 carbon atoms, preferably a methylene radical or an isopropylidene radical;
one of the following groups:
in these formulae, R
0
represents a hydrogen atom or an alkyl radical containing 1 to 4 carbon atoms, or a cyclohexyl or phenyl radical.
More particularly, residue A which may optionally be substituted represents the residue:
of an aromatic carbocyclic monocyclic compound such as benzene, toluene, isobutylbenzene, anisole, thioanisole, phenetole or veratrole, guaiacol or guetol;
of an aromatic condensed polycyclic compound, such as naphthalene or 2-methoxynaphthalene;
of an aromatic carbocyclic, non condensed polycyclic compound such as phenoxybenzene;
of a partially aromatic carbocyclic condensed polycyclic compound such as tetrahydronaphthalene or 1,2-methylenedioxybenzene;
of a partially aromatic carbocyclic non condensed polycyclic compound such as cyclohexylbenzene;
of an aromatic heterocyclic monocyclic compound such as pyridine, furan or thiophene;
of a partially heterocyclic aromatic condensed polycyclic compound such as quinoline, indole or benzofuran;
of a partially heterocyclic aromatic, non condensed polycyclic compound such as phenylpyridines, or naphthylpyridines;
of a partially heterocyclic, partially aromatic condensed polycyclic compound such as tetrahydroquinoline;
of a partially heterocyclic, partially aromatic, non condensed polycyclic compound such as cyclohexylpyridine.
In the process of the invention, an aromatic compound with formula (I) is preferably used in which A represents an aromatic nucleus, preferably a benzenic or naphthalene nucleus.
The aromatic compound with formula (I) can carry one or more substituents.
The number of substituents present in the cycle depend on the carbon condensation of the cycle and the presence or otherwise of unsaturations in the cycle.
The maximum number of substituents which can be carried by a cycle can readily be determined by the skilled person.
In the present description, the term “several” generally means less than 4 substituents on one aromatic nucleus.
Examples of substituents are given below but these are not limiting.
Radicals R, which may be identical or different, preferably represent one of the following groups:
a hydrogen atom;
a linear or branched alkyl radical containing 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 containing 2 to 6 carbon atoms, preferably 2 to 4 carbon atoms, such as vinyl, allyl;
a linear
Gilbert Laurent
Guillot Henri
Spagnol Michel
Tirel Philippe-Jean
Burns Doane Swecker & Mathis L.L.P.
Padmanabhan Sreeni
Rhodia Chimie
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