Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
2001-12-05
2003-06-10
Solola, Taofiq (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
C549S248000
Reexamination Certificate
active
06576770
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
Not applicable.
FEDERAL RESEARCH STATEMENT
Not applicable.
BACKGROUND OF INVENTION
The disclosure relates to a process for the formation of substituted phthalic anhydrides and substituted-N-alkyl-phthalimides from the corresponding substituted-N-alkyl-tetrahydrophthalimides. This disclosure particularly relates to a process for the formation of halophthalic anhydrides and halogen substituted-N-alkyl-phthalimides from the corresponding halogen substituted-N-alkyl-tetrahydrophthalimides.
The increasing importance of high performance polyimides has led to an interest in substituted phthalic anhydrides, especially halophthalic anhydrides. Halophthalic anhydrides are particularly useful as intermediates for the preparation of dianhydride monomers, such as oxydiphthalic anhydride which may be co-polymerized with a suitable diamine to form a condensation polyimide. The preparation of dianhydride monomers for the high performance polymer industry requires halophthalic anhydrides of very high purity, since the presence of even what normally would be considered as minor amounts of impurities would degrade the polymer product and perhaps render the product unsuitable for certain uses.
It is known that 3-chlorophthalic anhydride can be obtained by oxidation of 3-chloro-o-xylene with, for example, nitric acid at elevated temperature and elevated pressure and subsequent conversion to the anhydride of the 3-chlorophthalic acid formed in the oxidation. The isomerically pure 3-chloro-o-xylene is obtained by distillative separation of the products of the nuclear chlorination of o-xylene, but this distillative separation is extremely complicated because of the low boiling point differences (relative volatilities) of 3- and 4-chloro-o-xylene. An industrial column for the simultaneous preparation of 3-chloro-o-xylene and 4-chloro-o-xylene in purities of, in each case, above 99% needs, in the case of continuous operation, approximately 250 theoretical separation stages. Other separation processes for separating the isomers, such as fractional crystallization, are no less complicated.
Nanophthlaic anhydrides may also be prepared by the aromatization of halo-substituted saturated or partially saturated phthalic anhydrides. Substituted tetrahydrophthalic anhydrides may be aromatized using a halogen such as bromine or chlorine, a brominating agent, phosphorous pentoxide, excess sulfur in combination with a catalytic amount of zinc oxide and 2-mercaptobenxothiazole, palladium, or activated carbon in the absence of air. Each of these approaches to aromatization suffers from drawbacks such as the production of highly corrosive by-products, low yields, decarboxylation, and difficulty in the isolation of the desired product.
3-Chlorophthalic anhydride can also be prepared from 3-nitrophthalic anhydride by replacement of the nitro group by chlorine. The 3-nitrophthalic anhydride needed for this is prepared in three process steps by nitration of phthalic anhydride in moderate yield, isomer separation of the nitrophthalic acids formed by fractional crystallization, and conversion to the anhydride. This multistage and complicated route, which additionally gives poor yields, is not very suitable for industrial use.
The chlorination of phthalic anhydride using Lewis acid catalysts leads to mixtures that contain not only the two isomeric 3- and 4-chlorophthalic anhydrides, which are separable by distillation, but also more highly chlorinated phthalic anhydrides. Specialized distillation equipment is required to separate the desired isomer from the close boiling points mixture.
Although the chemical literature discloses a variety of methods for the preparation of substituted phthalic anhydrides, it will be appreciated that a need continues to for a more economical and efficient process, suitable for the preparation of high purity halophthalic anhydrides.
SUMMARY OF INVENTION
The needs discussed above have been generally satisfied by the discovery of a process for the formation of halophthalic anhydrides comprising heating a halogen substituted-N-alkyl tetrahydrophthalimide in the presence of a metal catalyst and an oxygen containing gas.
In another aspect, a process for the formation of halogen substituted-N-alkyl-phthalimide comprises heating a halogen substituted-N-alkyl tetrahydrophthalimide in the presence of a metal catalyst and an oxygen containing gas.
BRIEF DESCRIPTION OF DRAWINGS
Not applicable.
DETAILED DESCRIPTION
As indicated above, this invention relates to a novel process for the formation of halophthalic anhydrides and halogen substituted-N-alkyl-phthalimides from the corresponding halogen substituted-N-alkyl-tetrahydrophthalimide by passing the halogen substituted-N-alkyl-tetrahydrophthalimide over a metal catalyst, preferably vanadium oxide, in the gaseous phase in the presence of an oxygen containing gas. By selection of the reaction temperature, reaction time, and catalyst, high conversions and purity of the substituted anhydride or imide can be selectively obtained.
In a first embodiment, a halogen substituted-N-alkyl-tetrahydrophthalimide of the formula
where Y is a halogen and X is a straight chain or branched alkyl moiety having 1 to about 18 carbons is heated in the gaseous phase in the presence of a metal catalyst and an oxygen containing gas to result in a halophthalic anhydride of the formula
In a second embodiment, a halogen substituted-N-alkyl-tetrahydrophthalimide of the formula
where Y is a halogen and X is straight chain or branched alkyl moiety having 1 to about 18 carbons is heated in the gaseous phase in the presence of a metal catalyst and oxygen to result in a halogen substituted-N-alkyl-phthalimide of the formula
In a third embodiment, a halogen substituted-N-alkyl-tetrahydrophthalimide of the formula
where Y is a halogen and X is a straight chain or branched alkyl moiety having 1 to about 18 carbons is passed, in the gaseous phase, over vanadium oxide in the presence of oxygen at a temperature and rate sufficient to result in at least a 90% conversion of the halogen substituted-N-alkyl-tetrahydrophthalimide to a halophthalic anhydride of the formula
In a fourth embodiment, a halogen substituted-N-alkyl-tetrahydrophthalimide of the formula
where Y is a halogen and X is a straight chain or branched alkyl moiety of having 1 to about 18 carbons is passed over, in the gaseous phase, a metal catalyst in the presence of oxygen at a temperature and rate sufficient to result in at least a 90% conversion of the halogen substituted-N-alkyl-tetrahydrophthalimide to a halogen substituted-N-alkyl-phthalimide of the formula
These and other embodiments will become apparent in the detailed description of the invention that follows.
The starting material for the formation of halophthalic anhydrides and halogen substituted N-alkyl-phthalimides is 4-halo-N-alkyl-tetrahydrophthalimide of the formula
wherein Y is a halogen and X is a straight chain or branched alkyl moiety having 1 to about 18 carbons in length. These compounds are conveniently prepared by the known Diels-Alder reaction of the 2-halo-1,3-butadiene with maleic anhydride to result in the 4-halo-tetrahydrophthalic anhydride of the formula
wherein Y is a halogen, preferably chlorine. A detailed description of the methods of synthesizing these starting materials is disclosed in U.S. Pat. No. 5,003,088 to Spohn.
It was discovered that side reactions, such as decarboxylation and carbon formation, could be avoided by converting the anhydride to the imide for the aromatization reaction. The anhydride is imidized with a primary amine, preferably straight chain or branched alkyl amine having 1 to about 18 carbons, using standard techniques of the art to afford the 4-halo-N-alkyl-tetrahydrophthalimide.
In some embodiments, chloroprene, maleic anhydride, and methyl amine are utilized as the precursors to result in a 4-halo-N-alkyl-tetrahydrophthalimide of the formula
wherein Y is chlorine and X is methyl.
Suitable catalysts for the conversion of 4-halo-N-alkyl-tetrahydrophthalimide include the
Angermeier Philip L.
Guggenheim Thomas Link
Odle Roy Ray
General Electric Company
Solola Taofiq
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