Method for preparing anhydride by paraffin oil dehydration

Abstract

The invention provides a method for preparing anhydride by utilizing paraffin oil dehydration, which comprises the following step: carrying out dehydration reaction on a compound as shown in a formula I-1 in the presence of paraffin oil and an optional dehydrating aid to obtain the anhydride as shown in a formula I, according to the method, the cheap and easily available paraffin oil is adopted as a reaction medium, by-products are few, the acid anhydride yield of 98% or above and high purity can be achieved through simple post-treatment, the paraffin oil and the post-treatment solvent petroleum ether can be recycled through recycling, and the method is a method which is simple in reaction step and post-treatment process, mild in reaction condition and high in yield and purity. And the synthesis method is easy for industrial large-scale production. # imgabs0 #

Description

Technical Field

[0001] The invention belongs to the technical field of organic synthesis, and in particular relates to a method for preparing anhydride by dehydrating paraffin oil. Background Art

[0002] Phthalic anhydride is mainly used in the production of PVC plasticizers, unsaturated polyesters, alkyd resins, dyes, coatings, pesticides, pharmaceutical and instrument additives, edible saccharin, etc. It is an important organic chemical raw material with wide application value. In industry, o-xylene and air are often used for large-scale mass production under high temperature, high pressure and catalyst. As an important intermediate, phthalic anhydride and its derivatives are also widely used in the preparation of a variety of organic compounds. For example, in the design of organic optoelectronic materials, phthalic anhydride can be introduced into the molecular structure as a strong electron-pulling unit after reduction and functional group modification, thereby effectively adjusting the optoelectronic properties of the material. At present, its various derivatives have also been widely used in the design and synthesis of organic optoelectronic materials, and have broad application prospects.

[0003] Among the conventional methods for preparing phthalic anhydride and its derivatives, there are two relatively mature ones, but both have their own limitations. The first method is the gas phase oxidation method of o-xylene commonly used in industry, which can be prepared in tons. This method is that o-xylene reacts with air under the action of V2O5 catalyst. However, this method not only has high raw material costs, but also needs to be carried out under high temperature and high pressure conditions, and the catalyst is easily deactivated. This reaction is also prone to generate a variety of by-products, resulting in complex post-processing and affecting product purity. In addition, flammable and toxic gases are involved in the reaction process, which poses a safety hazard. The second method is the high-temperature dehydration method of phthalic acid, which is mostly used for small-batch gram-level preparation in the laboratory. However, this method has high preparation costs, uses flammable, explosive and corrosive acetic anhydride as a dehydrating agent, has a long reaction time and high temperature, and also produces a variety of by-products. The complex post-processing leads to a low yield. At the same time, due to the large number of impurities, it is difficult to obtain products with excellent properties.

[0004] Therefore, it is necessary to improve the existing preparation method. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] A method for preparing anhydride by dehydrating paraffin oil comprises the following steps:

[0007]

[0008] The compound represented by formula I-1 is subjected to a dehydration reaction in the presence of paraffin oil and optionally a dehydrating agent to obtain an acid anhydride represented by formula I;

[0009] in, C 3-20 Cycloalkyl, 3-20 membered heterocyclic group, C 6-20 Aryl or 5-20 membered heteroaryl;

[0010] X1 is selected from halogen, C 1-20 Alkyl, C 1-20 Alkoxy, halogenated C 1-20 Alkyl, halogenated C 1-20 Alkoxy, C 1-20 Alkylthio, C 2-20 Alkenyl, C 2-20 Alkynyl, -COOC 1-20 Alkyl, unsubstituted or optionally substituted by 1, 2 or more Rs: 3-20 Cycloalkyl, 3-20 membered heterocyclic group, C 6-20 Aryl and 5-20 membered heteroaryl;

[0011] Rs is selected from halogen, C 1-20 Alkyl, C 1-20 Alkoxy, halogenated C 1-20 Alkyl, halogenated C 1-20 Alkoxy, C 1-20 Alkylthio or -COOC 1-20 alkyl;

[0012] n is 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10;

[0013] In the compound represented by formula I-1 The two COOH groups above are ortho substituents.

[0014] According to an embodiment of the present invention, the dehydrating agent is selected from aromatic hydrocarbons or halogenated aromatic hydrocarbons, for example, at least one selected from o-dichlorobenzene, trimethylol, and bromobenzene.

[0015] According to an embodiment of the present invention, C 3-12 Cycloalkyl, 3-12 membered heterocyclic group, C 6-14 Aryl or 5-14 membered heteroaryl;

[0016] X1 is selected from halogen, C 1-12 Alkyl, halogenated C 1-12 Alkyl, halogenated C 1-12 Alkoxy, C 1-12 Alkoxy, C 1-12 Alkylthio, C 2-12 Alkenyl, C 2-12 Alkynyl, -COOC 1-12 Alkyl, unsubstituted or optionally substituted by 1, 2 or more Rs: 3-12 Cycloalkyl, 3-12 membered heterocyclic group, C6-14 Aryl and 5-14 membered heteroaryl;

[0017] Rs is selected from halogen, C 1-12 Alkyl, C 1-12 Alkoxy, halogenated C 1-12 Alkyl, halogenated C 1-12 Alkoxy, C 1-12 Alkylthio or -COOC 1-12 alkyl;

[0018] n is 0, 1, 2, 3, 4, 5 or 6;

[0019] In the compound represented by formula I-1 The two COOH groups above are ortho substituents.

[0020] According to an embodiment of the present invention, is phenyl or naphthyl;

[0021] X1 is selected from halogen, C 1-6 Alkyl, halogenated C 1-6 Alkyl, halogenated C 1-6 Alkoxy, C 1-6 Alkoxy, -COOC 1-6 Alkyl or C 1-6 Alkylthio;

[0022] n is 0, 1, 2, 3 or 4.

[0023] In some specific embodiments of the present invention, the compound represented by formula I-1 is selected from the following compounds:

[0024]

[0025] R1 and R2 are the same or different and are independently selected from C 1-6 alkyl.

[0026] According to an embodiment of the present invention, the method comprises the following steps:

[0027] The compound represented by formula I-1 is placed in a reactor, paraffin oil is added to cover the solid compound represented by formula I-1, and a dehydrating agent is optionally added to carry out heating reaction.

[0028] According to an embodiment of the present invention, the method further comprises the steps of cooling the system to room temperature after the reaction is completed, adding an appropriate amount of petroleum ether to dilute the reaction solution so that the system can be poured out, suction filtering, washing the filter cake with petroleum ether, and drying the filter cake.

[0029] According to an embodiment of the present invention, when a dehydrating agent is used, the mass ratio of the paraffin oil to the dehydrating agent is 10:1-100:1, such as 10:1-20:1.

[0030] According to an embodiment of the present invention, the amount of paraffin oil used is enough to cover the solid of the compound represented by formula I-1.

[0031] According to an embodiment of the present invention, the reaction temperature is 200-350°C, such as 250°C to 300°C.

[0032] According to an embodiment of the present invention, the reaction time is 0.5-12 h, such as 1-12 h.

[0033] The method of the invention can be used for preparing acid anhydride at kilogram level.

[0034] The beneficial effects of the method of the present invention are as follows:

[0035] The method of the invention adopts cheap and readily available paraffin oil as a reaction medium, has few by-products, can achieve an anhydride yield of more than 98% and high purity through simple post-treatment, and both the paraffin oil and the post-treatment solvent petroleum ether can be recycled and reused. The method of the invention has simple reaction steps and post-treatment processes, mild reaction conditions, and is easy to industrialize and scale up for production.

[0036] The method for preparing small batches of phthalic anhydride derivatives by the commonly used phthalic acid high temperature dehydration method reported at present is feasible, but has many shortcomings. For example, this method needs to use acetic anhydride, which is costly, flammable, explosive and corrosive, as a dehydrating agent, which not only has a long reaction time and high temperature, but also easily produces a variety of by-products, resulting in a low product yield. In addition, due to the high impurity content, it is difficult to obtain a product with excellent properties. Compared with the prior art, the reaction conditions adopted by the present invention are mild, reaction by-products are few, product purity and yield are high, and the reaction steps and post-processing process are simple.

[0037] The solvent paraffin oil used in the present invention and the solvent petroleum ether used in the post-treatment are both cheap and readily available, which can reduce the experimental cost and meet the high yield requirement. At the same time, the paraffin oil and the post-treatment solvent petroleum ether can be recycled and reused.

[0038] In summary, the preparation method of the present invention has the advantages of high product yield, good properties, simple synthesis and post-treatment processes, recyclable solvents, effective shortening of reaction time, few by-products, and ability to achieve gram- and kilogram-level preparation, and has certain industrial application prospects.

[0039] Definitions and explanations of terms

[0040] The term "halogen" means fluorine, chlorine, bromine and / or iodine. Accordingly, the term "halo" refers to fluoro, chloro, bromo and / or iodo. Within the scope of this document, when an atom, residue, group or moiety is halogenated, the atom at the halogenated position may be monosubstituted, disubstituted or polysubstituted up to full substitution by halogen atoms, for example, "halo C1-20 Alkyl" and "halogenated C 1-20 Alkoxy" etc.

[0041] The term "C 1-20 "Alkyl" is understood to mean a straight or branched saturated monovalent hydrocarbon group having 1 to 20 carbon atoms, which may be C 1-12 Alkyl or C 1-6 Alkyl. "C 1-6 The term “alkyl” is understood to mean a linear or branched, saturated, monovalent hydrocarbon radical having 1, 2, 3, 4, 5 or 6 carbon atoms. The alkyl radical is, for example, methyl, ethyl, propyl, butyl, pentyl, hexyl, isopropyl, isobutyl, sec-butyl, tert-butyl, isopentyl, 2-methylbutyl, 1-methylbutyl, 1-ethylpropyl, 1,2-dimethylpropyl, neopentyl, 1,1-dimethylpropyl, 4-methylpentyl, 3-methylpentyl, 2-methylpentyl, 1-methylpentyl, 2-ethylbutyl, 1-ethylbutyl, 3,3-dimethylbutyl, 2,2-dimethylbutyl, 1,1-dimethylbutyl, 2,3-dimethylbutyl, 1,3-dimethylbutyl or 1,2-dimethylbutyl, or the like or isomers thereof. In particular, the radical has 1, 2 or 3 carbon atoms (“C 1-3 alkyl"), for example methyl, ethyl, n-propyl or isopropyl.

[0042] The term "-COOC 1-20 C 1-20 Alkyl has the same meaning as defined above.

[0043] The term "C 1-20 "Alkoxy" is understood to mean "-OC 1-20 Alkyl", where C 1-20 Alkyl has the same meaning as defined above.

[0044] The term "C 1-20 "Alkylthio" should be understood as "-SC 1-20 Alkyl", where C 1-20 Alkyl has the same meaning as defined above.

[0045] The term "halogenated C 1-20 "Alkyl" should be understood as "C 1-20 At least one H in the "alkyl" is substituted by "halogen" as described above, for example, a group formed by 1, 2, 3, 4, 5, or 6 H atoms being substituted by halogen.

[0046] The term "halogenated C 1-20 "Alkoxy" is to be understood as "C 1-20 Alkoxy or -OC 1-20At least one H in the "alkyl" is substituted by "halogen" as described above, for example, 1, 2, 3, 4, 5, or 6 H atoms are substituted by halogen to form the group.

[0047] The term "C 2-20 "Alkenyl" is understood to mean a linear or branched monovalent hydrocarbon radical containing one or more double bonds and having 2 to 20 carbon atoms, optionally 2-12 "Alkenyl" or "C 2-6 "C 2-6 "Alkenyl" is understood to mean optionally a linear or branched monovalent hydrocarbon radical containing one or more double bonds and having 2, 3, 4, 5, 6 carbon atoms, in particular 2 or 3 carbon atoms ("C 2-3 "alkenyl"), it being understood that, in the case where the alkenyl contains more than one double bond, the double bonds may be separated from one another or conjugated. The alkenyl is, for example, vinyl, allyl, (E)-2-methylvinyl, (Z)-2-methylvinyl, (E)-but-2-enyl, (Z)-but-2-enyl, (E)-but-1-enyl, (Z)-but-1-enyl, pent-4-enyl, (E)-pent-3-enyl, (Z)-pent-3-enyl, -enyl, (E)-pent-2-enyl, (Z)-pent-2-enyl, (E)-pent-1-enyl, (Z)-pent-1-enyl, hex-5-enyl, (E)-hex-4-enyl, (Z)-hex-4-enyl, (E)-hex-3-enyl, (Z)-hex-3-enyl, (E)-hex-2-enyl, (Z)-hex-2-enyl, (E)-hex-1-enyl, (Z)-hex-1-enyl, isopropenyl, 2-hexenyl, (E)-pent-2-enyl, (Z)-pent-2-enyl, (E)-pent-1-enyl, (Z)-pent ...1-enyl, (Z)-pent-1-enyl, isopropenyl, 2-hexenyl, (E)-pent-2- -methylprop-2-enyl, 1-methylprop-2-enyl, 2-methylprop-1-enyl, (E)-1-methylprop-1-enyl, (Z)-1-methylprop-1-enyl, 3-methylbut-3-enyl, 2-methylbut-3-enyl, 1-methylbut-3-enyl, 3-methylbut-2-enyl, (E)-2-methylbut-2-enyl, (Z)-2-methylbut-2-enyl, (E)-1-methylbut-2-enyl The invention can be substituted with vinyl or 1-isopropylvinyl, or a mixture of vinyl and 1-isopropylvinyl. The invention can be substituted with vinyl or 1-isopropylvinyl, or a mixture of vinyl and 1-isopropylvinyl.

[0048] The term "C 2-20 "Alkynyl" is understood to mean a linear or branched monovalent hydrocarbon radical containing one or more triple bonds and having 2 to 20 carbon atoms, optionally 2-12The term "C2-C6-alkynyl" is understood to mean optionally a linear or branched, monovalent hydrocarbon radical which contains one or more triple bonds and has 2, 3, 4, 5, 6 carbon atoms, in particular 2 or 3 carbon atoms ("C2-C3-alkynyl"). The alkynyl radical is, for example, ethynyl, prop-1-ynyl, prop-2-ynyl, but-1-ynyl, but-2-ynyl, but-3-ynyl, pent-1-ynyl, pent-2-ynyl, pent-3-ynyl, pent-4-ynyl, hex-1-ynyl, hex-2-ynyl, hex-3-ynyl, hex-4-ynyl, hex-5-ynyl, 1-methylprop-2-ynyl, 2-methylbut-3-ynyl, 1-methylbut-3-ynyl, 1-methylbut-2-ynyl, 3-methylbut- In some embodiments, the alkynyl group is ethynyl, prop-1-ynyl or prop-2-ynyl.

[0049] The term "C 3-20 "Cycloalkyl" is understood to mean a saturated or partially unsaturated monovalent monocyclic, bicyclic or polycyclic hydrocarbon ring, preferably "C 3-12 The term "Cycloalkyl" 3-12 "Cycloalkyl" should be understood to mean a saturated or partially unsaturated monovalent monocyclic, bicyclic or polycyclic hydrocarbon ring having 3-12 carbon atoms. Bicyclic or polycyclic cycloalkyls include paracyclic cycloalkyls, bridged cycloalkyls and spirocyclic cycloalkyls; the paracyclic refers to a condensed ring structure formed by two or more cyclic structures sharing two adjacent ring atoms (i.e., sharing a bond). The bridged ring refers to a condensed ring structure formed by two or more cyclic structures sharing two non-adjacent ring atoms. The spirocyclic refers to a condensed ring structure formed by two or more cyclic structures sharing one ring atom. For example, the C 3-12 The cycloalkyl group may be a fully saturated C 3-8 or C 3-6 Monocyclic cycloalkyl, such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, or C 7-12 Cycloalkyl, such as decahydronaphthalene; it can also be C 7-12A bridged cycloalkyl group, such as norbornane, adamantane, and bicyclo[2,2,2]octane; or a partially unsaturated cyclic structure, such as a C 3-8 A monocyclic cycloalkenyl or a C 3-6 Monocyclic cycloalkenyl, such as cyclopropenyl, cyclobutenyl, cyclopentenyl, cyclohexenyl, cyclobutadienyl, cyclopentadienyl or cyclohexadienyl, etc. Two hydrogen atoms on the carbon atoms of the cycloalkyl group may be replaced by an exocyclic double bond.

[0050] The term "3-20 membered heterocyclyl" means a saturated or partially unsaturated monovalent monocyclic, bicyclic or polycyclic non-aromatic hydrocarbon ring comprising carbon atoms and 1-5 heteroatoms independently selected from N, O and S, and wherein there are no shared non-localized n electrons (aromaticity) between ring carbons or heteroatoms, preferably a "3-12 membered heterocyclyl". The term "3-12 membered heterocyclyl" means a saturated or partially unsaturated monovalent monocyclic or bicyclic non-aromatic hydrocarbon ring containing 1-5 heteroatoms independently selected from N, O and S and having a total of 3-12 ring atoms; in particular, the heterocyclyl may include, but is not limited to: a 4-membered ring, such as azetidinyl, azetidinyl, oxetanyl or oxetanyl; a 5-membered ring, such as tetrahydrofuranyl, dihydrofuranyl, dioxolyl, pyrrolidinyl, dihydroimidazolyl, imidazolidinyl, dihydropyrazolyl, pyrazolidinyl, pyrrolinyl, oxazolinyl, oxazolidinyl, thiazolinyl or thiazolidinyl; or a 6-membered ring, such as pyranyl, tetrahydropyranyl, thiopyranyl, dihydropyrimidinyl, piperidinyl, morpholinyl, dithianyl, thiomorpholinyl, piperazinyl or trithianyl; or a 7-membered ring, such as diazepanyl or diazepanyl. Optionally, the heterocyclic group can be a fused ring, a bridged ring or a spiro ring. The heterocyclic group can be bicyclic, such as but not limited to hexahydropyrrolo[1,2-a]pyrazine-2(1H)-yl. The heterocyclic group can be partially unsaturated, that is, it can contain one, two or more double bonds, such as but not limited to 2,5-dihydro-1H-pyrrolyl, 3,6-dihydro-2H-pyranyl, 1,2,3,6-tetrahydropyridyl, 4H-[1,3,4]thiadiazinyl, 4,5-dihydrooxazolyl or 4H-[1,4]thiazinyl, 5H,6H,8H-[1,2,4]triazolo[4,3-a]pyrazinyl. Two hydrogens on the carbon atoms of the heterocyclic group can be replaced by exocyclic double bonds. The heterocyclic group may be fused with the above 4-membered, 5-membered, 6-membered, or 7-membered ring, such as 2,3-dihydrobenzofuran, benzopyran, 1,2-dihydroquinazoline, 3,4-dihydroquinazoline, and the like.

[0051] The term "C 6-20 "Aryl" is understood to mean an aromatic monocyclic, bicyclic or polycyclic hydrocarbon ring having 6 to 20 carbon atoms, preferably "C 6-14 The term "C 6-14The term "aryl" is understood to mean preferably a monovalent aromatic or partially aromatic monocyclic, bicyclic or tricyclic hydrocarbon ring ("C 6-14 or a ring having 9 carbon atoms ("C9 aryl"), for example indanyl or indenyl, or a ring having 10 carbon atoms ("C 10 aryl), such as tetrahydronaphthyl, dihydronaphthyl or naphthyl, or a ring having 13 carbon atoms ("C 13 aryl), such as fluorenyl, or a ring having 14 carbon atoms ("C 14 aryl”), such as anthracenyl. When the C 6-20 When the aryl group is substituted, it may be monosubstituted or polysubstituted. Also, there is no limitation on the substitution position, for example, it may be substituted at the ortho position, para position or meta position.

[0052] The term "5-20 membered heteroaryl" is understood to include monovalent monocyclic, bicyclic or tricyclic aromatic ring systems having 5 to 20 ring atoms and containing 1 to 5 heteroatoms independently selected from N, O and S, for example "5-14 membered heteroaryl". The term "5-14 membered heteroaryl" is understood to include monovalent monocyclic, bicyclic or tricyclic aromatic ring systems having 5, 6, 7, 8, 9, 10, 11, 12, 13 or 14 ring atoms, in particular 5 or 6 or 9 or 10 carbon atoms, and containing 1 to 5, preferably 1 to 3 heteroatoms independently selected from N, O and S and, in addition, in each case may be benzo-fused. In particular, the heteroaryl group is selected from thienyl, furanyl, pyrrolyl, oxazolyl, thiazolyl, imidazolyl, pyrazolyl, isoxazolyl, isothiazolyl, oxadiazolyl, triazolyl, thiadiazolyl, thia-4H-pyrazolyl, and the like, and benzo derivatives thereof, such as benzofuranyl, benzothienyl, dibenzothienyl, and oxazolyl, benzisoxazolyl, benzimidazolyl, benzotriazolyl, indazolyl, indole, and the like. or cinnolinyl, phthalazinyl, quinazolinyl, quinoxalinyl, naphthyridinyl, pteridinyl, carbazolyl, acridinyl, phenazinyl, phenothiazinyl, phenoxazinyl, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0054] Figure 1 This is the NMR characterization diagram of the product provided in Example 1 of the present invention.

[0055] Figure 2 This is the mass spectrum of the product provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0056] In order to better understand the technical solution of the present invention, the technical solution of the present invention is described in detail below in conjunction with embodiments.

[0057] It should be clear that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0058] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms "a", "said" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0059] The purity in the following examples was obtained by HPLC testing.

[0060] Example 1: Preparation of 4,5-dichlorophthalic anhydride (about 50g level)

[0061]

[0062] The specific reaction process is as follows:

[0063] Place 47g of 4,5-dichlorophthalic acid in a two-necked bottle, add 60ml of paraffin oil and 6ml of o-dichlorobenzene, and connect a thermometer and a distillation device to the two-necked bottle. Heat the system to 250°C under stirring and keep the reaction for about 2h. Then cool to room temperature, add an appropriate amount of petroleum ether to dilute the reaction solution so that the system can be poured out. Filter by suction, rinse the filter cake with petroleum ether, and dry to obtain an off-white solid product 4,5-dichlorophthalic anhydride with a yield of 98% (purity of 99.3%).

[0064] H NMR spectrum Figure 1 As shown, the results of NMR analysis: 1H NMR (300 MHz, CHLOROFORM-d) δ 8.11 (s, 2H).

[0065] Mass spectrometry Figure 2 As shown, the molecular weight was 215.94 as determined by mass spectrometry.

[0066] Example 2: Preparation of 4,5-dichlorophthalic anhydride (about 800g level)

[0067]

[0068] The specific reaction process is as follows:

[0069] Place 800g of 4,5-dichlorophthalic acid in a 1L two-necked bottle, add 300ml of paraffin oil and 30ml of o-dichlorobenzene, and connect a thermometer and a distillation device to the two-necked bottle. Heat the system to 250°C under stirring and keep the reaction for about 2h. Then cool to room temperature, add an appropriate amount of petroleum ether to dilute the reaction solution so that the system can be poured out. Filter with suction, rinse the filter cake twice with petroleum ether, and dry to obtain an off-white solid product 4,5-dichlorophthalic anhydride with a yield of 98% (purity of 99.1%).

[0070] Example 3: Preparation of 4,5-dibromophthalic anhydride (about 10g level)

[0071]

[0072] The specific reaction process is as follows:

[0073] Place 16.2g of 4,5-dibromophthalic acid in a two-necked bottle, add 20ml paraffin oil and 2ml o-dichlorobenzene, and connect a thermometer and a distillation device to the two-necked bottle. Heat the system to 250°C under stirring and keep the temperature for about 2h. Then cool to room temperature, add an appropriate amount of petroleum ether to dilute the reaction solution so that the system can be poured out. Filter by suction, rinse the filter cake with petroleum ether, and dry to obtain an off-white solid product 4,5-dibromophthalic anhydride with a yield of 95% (purity of 99.3%).

[0074] Example 4

[0075] Refer to the operation of Example 1, except that o-dichlorobenzene is not added. Since the water generated during the reaction will flow back into the reaction solution (high-temperature paraffin oil), resulting in the "boiling" sound phenomenon, the product yield and purity are equivalent to those of Example 1.

[0076] The above is a detailed introduction to the method for preparing anhydride by dehydrating paraffin oil provided by the present application. The description of the above embodiments is only used to help understand the method and its core idea of ​​the present application; at the same time, for those skilled in the art, according to the idea of ​​the present application, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as limiting the present application.

[0077] For example, certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that hardware manufacturers may use different nouns to refer to the same component. This specification and claims do not use differences in names as a way to distinguish components, but use differences in the functions of components as the criteria for distinction. As mentioned throughout the specification and claims, "including" and "comprising" are open-ended terms, so they should be interpreted as "including / including but not limited to". "Approximately" means that within an acceptable error range, those skilled in the art can solve the technical problem within a certain error range and basically achieve the technical effect. The subsequent description of the specification is a preferred embodiment of the present application, but the description is for the purpose of illustrating the general principles of the present application, and is not used to limit the scope of the present application. The scope of protection of the present application shall be determined by the definition of the attached claims.

[0078] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a product or system that includes a series of elements includes not only those elements, but also includes other elements that are not explicitly listed, or also includes elements that are inherent to such product or system.

[0079] "Optionally" means optional or not.

[0080] The above description shows and describes several preferred embodiments of the present application, but as mentioned above, it should be understood that the present application is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the application concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art do not deviate from the spirit and scope of the present application, and should be within the scope of protection of the claims attached to the present application.

Claims

1. A method for preparing anhydride by dehydrating paraffin oil, characterized in that: The steps include: The compound represented by formula I-1 is subjected to a dehydration reaction in the presence of paraffin oil and optionally a dehydrating agent to obtain an acid anhydride represented by formula I; in, C 3-20 Cycloalkyl, 3-20 membered heterocyclic group, C 6-20 Aryl or 5-20 membered heteroaryl; X1 is selected from halogen, C 1-20 Alkyl, C 1-20 Alkoxy, halogenated C 1-20 Alkyl, halogenated C 1-20 Alkoxy, C 1-20 Alkylthio, C 2-20 Alkenyl, C 2-20 Alkynyl, -COOC 1-20 Alkyl, unsubstituted or optionally substituted by 1, 2 or more Rs: 3-20 Cycloalkyl, 3-20 membered heterocyclic group, C 6-20 Aryl and 5-20 membered heteroaryl; Rs is selected from halogen, C 1-20 Alkyl, C 1-20 Alkoxy, halogenated C 1-20 Alkyl, halogenated C 1-20 Alkoxy, C 1-20 Alkylthio or -COOC 1-20 alkyl; n is 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10; In the compound represented by formula I-1 The two COOH groups above are ortho substituents.

2. The method according to claim 1, characterized in that The dehydrating agent is selected from aromatic hydrocarbons or halogenated aromatic hydrocarbons, for example, at least one selected from o-dichlorobenzene, trimethylbenzene, and bromobenzene.

3. The method according to claim 1 or 2, characterized in that: C 3-12 Cycloalkyl, 3-12 membered heterocyclic group, C 6-14 Aryl or 5-14 membered heteroaryl; X1 is selected from halogen, C 1-12 Alkyl, halogenated C 1-12 Alkyl, halogenated C 1-12 Alkoxy, C 1-12 Alkoxy, C 1-12 Alkylthio, C 2-12 Alkenyl, C 2-12 Alkynyl, -COOC 1-12 Alkyl, unsubstituted or optionally substituted by 1, 2 or more Rs: 3-12 Cycloalkyl, 3-12 membered heterocyclic group, C 6-14 Aryl and 5-14 membered heteroaryl; Rs is selected from halogen, C 1-12 Alkyl, C 1-12 Alkoxy, halogenated C 1-12 Alkyl, halogenated C 1-12 Alkoxy, C 1-12 Alkylthio or -COOC 1-12 alkyl; n is 0, 1, 2, 3, 4, 5 or 6; In the compound represented by formula I-1 The two COOH groups above are ortho substituents.

4. The method according to any one of claims 1 to 3, characterized in that: is phenyl or naphthyl; X1 is selected from halogen, C 1-6 Alkyl, halogenated C 1-6 Alkyl, halogenated C 1-6 Alkoxy, C 1-6 Alkoxy, -COOC 1-6 Alkyl or C 1-6 Alkylthio; n is 0, 1, 2, 3 or 4.

5. The method according to any one of claims 1 to 4, characterized in that: The compound represented by formula I-1 is selected from the following compounds: R1 and R2 are the same or different and are independently selected from C 1-6 alkyl.

6. The method according to any one of claims 1 to 5, characterized in that: The method comprises the following steps: The compound represented by formula I-1 is placed in a reactor, paraffin oil in an amount exceeding the solid content of the compound represented by formula I-1 is added, and a dehydrating agent is optionally added to carry out heating reaction.

7. The method according to any one of claims 1 to 6, characterized in that: When a dehydrating agent is used, the mass ratio of the paraffin oil to the dehydrating agent is 10:1-100:

1.

8. The method according to any one of claims 1 to 7, characterized in that: The amount of paraffin oil used is enough to cover the solid compound represented by formula I-1.

9. The method according to any one of claims 1 to 8, characterized in that: The reaction temperature is 200-350°C.

10. The method according to any one of claims 1 to 9, characterized in that: The reaction time is 0.5-12h.

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