Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2001-09-27
2002-08-06
Padmanabhan, Sreeni (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C568S437000
Reexamination Certificate
active
06429340
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a production method of 2,4,5-trialkylbenzaldehydes. More particularly, the invention relates to the production method of a 2,4,5-trialkylbenzaldehyde of value as an intermediate of various chemical products, particularly as a starting material for pyromellitic anhydride.
BACKGROUND ART
Aromatic aldehydes are compounds of great use as intermediates of various chemical products, and trialkylbenzaldehydes, in particular, are intermediates of great industrial importance as precursors of aromatic polycarboxylic acids. Especially 2,4,5-trialkylbenzaldehydes are very important compounds as starting materials of pyromellitic anhydride, the importance of which is steadily increasing in recent years as heat-resistant resins, plasticizers, and epoxy resin curing agents.
The known production method for a trialkylbenzaldehyde includes the method which comprises the liquid-phase oxidation of a tetraalkylbenzene and the carbonylation reaction of a trialkylbenzene with carbon monoxide.
Among these, the carbonylation reaction of a trialkylbenzene with carbon monoxide insures a good yield and may be regarded as an industrially preferred method. However, the known processes involve high reaction pressures and, hence, high equipment costs. Moreover, a catalyst must be used in a large excess over the reactant starting material, thus leaving room for improvement from industrial points of view. It is also known that trimethylbenzaldehyde can be produced from a trialkylbenzene by using an HF-BF
3
system as the catalyst in a small amount and conducting the reaction at low temperature and low pressure. In this connection, Komatsu in Chemical Engineering, 50[9] (1986) at pages 614-618 discloses the use of HF-BF
3
as the catalyst in the reaction between pseudocumene(1,2,4-trimethylbenzene) and carbon monoxide relating to the synthesis process for a production of an aromatic aldehyde. However, the catalyst components HF and BF
3
are not only highly toxic and corrosive but also gaseous at atmospheric temperature, thus calling for meticulous care in handling.
Meanwhile, in the production of a 2,4,5-trialkylbenzaldehyde for use as a starting material for pyromellitic anhydride, the substituting positions of the three alkyl groups of a starting material trialkylbenzene is necessary be 1-, 2- and 4-positions and additionally selective carbonylation reaction is necessarily effected on the 5-position. Thus, the 5-position of the 1,2,4-trialkylbenzene is necessarily selectively carbonylated and if other positions are carbonylated to give 2,3,5-trimethylbenzaldehyde and 2,3,6-trimethylbenzaldehyde in large amounts, the yield of the object compound is lowered. Furthermore, when a disproportionation reaction of the 1,2,4-trialkylbenzene takes place as described in Examples 17 to 19 of the pamphlet (2000) of WO 00/15594, still more kinds of byproducts are formed to depress the yield. Therefore, a need exists for a technology by which the 5-position of a 1,2,4-trialkylbenzene can be carbonylated with high selectivity and without causing disproportionation reaction.
J. Org. Chem. 50[9] (1985) at page 1483 discloses a carbonylation technology using a 1,3,5-trialkylbenzene as the substrate and CF
3
SO
3
H as the peracid catalyst. However, there is no description concerning 1,2,4-trialkylbenzenes and the technology has room for further improvement for producing a 2,4,5-trialkylbenzaldehyde with efficiency.
The pamphlet (2000) of WO 00/15593 relating to the method for reacting an alkyl aromatic compound with carbon monoxide in the presence of a carbonylation catalyst with high-boiling point to obtain an alkyl aromatic aldehyde discloses a perfluoroalkylsulfonic acid of 2 to 18 carbon atoms as the carbonylation catalyst with high-boiling point and the pamphlet (2000) of WO 00/15594 discloses a method comprising reacting an alkyl aromatic compound with carbon monoxide in the presence of an acid ionic liquid to obtain an alkyl aromatic aldehyde. Moreover, Japanese Kokai Publication Sho-64-75442 discloses a production method of an aromatic aldehyde which comprises reacting an aromatic compound with carbon monoxide in a super-strong acid in the presence of a copper (I) or silver carbonyl catalyst and Japanese Kokoku Publication Hei-6-21093 discloses a production method of an aromatic aldehyde which comprises reacting an aromatic compound with carbon monoxide in a defined super-strong acid, such as fluorosulfuric acid-antimony pentafluoride, in the presence of a copper (I) or silver carbonyl catalyst.
However, these technologies have room for improvement for the low-cost and safe production of a 2,4,5-trialkylbenzaldehyde through highly selective carbonylation reaction on the 5-position of the 1,2,4-trialkylbenzene.
SUMMARY OF THE INVENTION
Having been developed in the light of the above state of the art, the present invention has for its object to provide a production method of a 2,4,5-trialkylbenzaldehyde from a 1,2,4-trialkylbenzene at low cost and safely.
In the course of their investigation into the various production methods of trialkylbenzaldehydes, the inventors of the present invention paid attention, in the first place, to the carbonylation reaction of a trialkylbenzene with carbon monoxide. In this type of technology, for example, for the purpose of obtaining a starting material for pyromellitic anhydride, the position selectivity of carbonylation is important, that is to say it is necessary that the 5-position of the 1,2,4-trialkylbenzene be selectively carbonylated. If other positions are carbonylated to give 2,3,5-trimethylbenzaldehyde and 2,3,6-trimethylbenzaldehyde in substantial amounts, the yield of the objective compound will be lowered to frustrate the endeavor. However, the inventor found that when a catalyst which comprises trifluoromethanesulfonic acid is used, the 5-position of a 1,2,4-trialkylbenzene is carbonylated with extremely high selectivity to give a 2,4,5-trialkylbenzaldehyde, thus neatly solving the above problems. The finding has resulted in the present invention.
The present invention, therefore, provides a production method of a 2,4,5-trialkylbenzaldehyde which comprises carbonylating a 1,2,4-trialkylbenzene with carbon monoxide in the presence of a catalyst, said catalyst comprising trifluoromethanesulfonic acid.
In the following, the present invention is described in detail.
DETAILED DESCRIPTION OF THE INVENTION
The production method of a 2,4,5-trialkylbenzaldehyde according to the invention includes a step of carbonylating a 1,2,4-trialkylbenzene with carbon monoxide in the presence of a catalyst. In this step, the 2,4,5-trialkylbenzaldehyde is produced by using the 1,2,4-trialkylbenzene as a starting material. The above starting material may or may not contain compounds other than the 1,2,4-trialkylbenzene but preferably the 1,2,4-trialkylbenzene alone is subjected to the production of the 2,4,5-trialkylbenzaldehyde. In this connection, the 1,2,4-trialkylbenzene may be used one species or two or more species.
The alkyl groups of said 1,2,4-trialkylbenzene are not particularly restricted but when the obtained 2,4,5-trialkylbenzaldehyde is to be used as a starting material for pyromellic anhydride, the number of carbon atoms constituting each alkyl group is desirably small, preferably within the range of 1 to 3 carbon atoms. Thus, for example, a methyl, ethyl, propyl and isopropyl group may be mentioned. Three alkyl groups of the 1,2,4-trialkylbenzene may be the same or different.
In the production method according to the invention, the above-mentioned catalyst comprises trifluoromethanesulfonic acid. The catalyst used in the present invention may or may not contain one or more species of compounds other than trifluoromethanesulfonic acid.
The mode of use of trifluoromethanesulfonic acid to be used as said catalyst is not particularly restricted but may be used as it is or as immobilized, for example, by supporting it on a carrier. Immobilization of a catalyst provides for industrial advantages, for example by facilita
Ohnoki Yasuo
Takahashi Tsukasa
Xu Bo-Qing
Nippon Shokubai Co. , Ltd.
Padmanabhan Sreeni
Sughrue & Mion, PLLC
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