Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Patent
1997-01-09
2000-01-11
Killos, Paul J.
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
568337, C07C 4500
Patent
active
060138408
DESCRIPTION:
BRIEF SUMMARY
The present invention concerns is a process for the acylation of an aromatic ether.
Preferably, the invention relates to a process for the acylation of a substituted aromatic ether, more particularly veratrol.
The invention is applicable to the preparation of alkoxyaromatic alkylketones.
Conventional processes for the acylation of aromatic compounds, in particular the ethers of phenols, consist of carrying out a Friedel-Crafts acylation reaction.
The aromatic compound is reacted with an acylation agent in the presence of a catalyst which is generally aluminium chloride.
This type of process is illustrated by the work of C KURODA et al., [Sci. Papers Inst. Phys. Chem. Res. 18, pp 51-60 (1932)] which describes the preparation of methoxyacetophenones by the reaction of an aromatic compound carrying 1 to 3 methoxy groups with acetyl chloride in the presence of aluminium chloride.
The use of aluminium chloride, however, has a number of disadvantages. Aluminium chloride is corrosive and an irritant. Further, a large quantity of aluminium chloride must be used, at least equal to the stoichiometric quantity, because of complexation with the ketone formed. As a result, the aluminium chloride is not a true catalyst.
At the end of the reaction, the aluminium chloride must be eliminated from the reaction medium by carrying out acidic or basic hydrolysis.
Hydrolysis implies the addition of water to the reaction medium, considerably complicating the process since the metal cation, and more particularly the aluminium cation, forms aluminium polyoxo- and/or polyhydroxo complexes of milky consistency, which are difficult to separate. This necessitates a long, expensive treatment following hydrolysis comprising extraction of the organic phase, separation of the aqueous and organic phases, and even drying of the latter. Separation of aluminium chloride is thus lengthy and expensive.
Further, there are problems with aqueous saline effluents which must then be neutralised and which necessitate an additional operation.
Still further, the aluminium chloride cannot be recycled as it has been hydrolysed.
In order to overcome this disadvantage, it has been suggested that the reaction be carried out in the presence of heterogeneous catalysts.
Thus for about a decade, the use of zeolites as acylation catalysts has been recommended.
Prins et al. described the acetylation of anisole by acetic anhydride [9th International Zeolite Congress--Montreal Congres (1992)] in the presence of zeolites such as .beta. zeolite or USY zeolite. It should be noted that .beta. zeolites produced more interesting results as regards both the degree of conversion and the reaction yield.
European patent EP-A-0 279 322 disclosed a vapour phase reaction of an aromatic compound (veratrol) with a carboxylic acid derivative in the presence of a zeolite in its H form such as mordenite, faujasite and ZSM-5. However, the yield for the reaction of veratrol and p-chlorobenzoyl chloride mentioned in Example 1 was only 22%.
It appears that the use of zeolites as catalysts for a reaction using bulky molecules causes problems to the skilled person in that the sensitivity and yield of the reaction are not satisfactory.
An object of the present invention is to provide a process which can overcome the above disadvantages.
We have now discovered, and this constitutes an object of the present invention, a process for the acylation of an aromatic ether which consists of reacting the ether with an acylation agent in the presence of a zeolitic catalyst, the process being characterized in that the acylation reaction is carried out in the presence of an effective quantity of a catalyst comprising a faujasite type zeolite or a Y zeolite with the following physico-chemical characteristics: of the element silicon and the number of atoms of every trivalent element Me.sup.1 contained in the zeolite in the range 2.4 to 90, preferably in the range 2.4 to 75, and more preferably in the range 2.4 to 60; /Me.sup.1(IV) between the number of atoms of alkali metal Me.sup.2 and the number of ato
REFERENCES:
patent: 3130007 (1964-04-01), Breck
patent: 4960943 (1990-10-01), Botta et al.
patent: 5227529 (1993-07-01), Neuber et al.
Benazzi Eric
Gilbert Laurent
Marcilly Christian
Spagnol Michel
Killos Paul J.
Rhodia Chimie
Wood John Daniel
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