Improved method for preparing benzonitrile compound from trichlorotoluene compound

Abstract

The present invention discloses an improved process for preparing a benzonitrile compound of formula (I) from the corresponding trichlorotoluene compound of formula (II).

Description

Technical Field

[0001] This invention relates to an improved method for preparing benzonitrile compounds. More specifically, this invention relates to an improved method for preparing benzonitrile compounds of formula (I) by nitrilation of trichlorotoluene compounds of formula (II). Background Technology

[0002] Benzonitrile is a known product in the art and is used particularly as an intermediate in the preparation of dyes, pharmaceuticals, and agrochemicals. J. Am. Chem. Soc. 1930, 52, 7, 2951–2954 discloses a method for preparing o-chlorobenzonitrile from o-chlorotrichlorotoluene using ammonium chloride. The disadvantages of this method are that it requires a closed tube and a high temperature of 210 to 220 °C. Furthermore, at least a 60% excess of o-chlorotrichlorotoluene is required to completely consume the ammonium chloride. In addition, this method leads to the polymerization of benzonitrile, yielding tetraphenylmethane as a byproduct.

[0003] EP441004 discloses a method for preparing o-chlorobenzonitrile from o-chlorotrichlorotoluene using copper(II) chloride or zinc chloride as a catalyst and ammonium chloride. A disadvantage associated with this method is that the reaction is carried out at a high temperature above 210 °C and requires an expensive jacketed reactor.

[0004] WO2022091014 discloses a method for preparing o-chlorobenzonitrile, wherein the method comprises reacting 2-chlorotrichlorotoluene with ammonium chloride in the presence of water, sulfuric acid, and zinc acetate at room temperature. The reaction mixture is heated to 180 to 200 °C for 16 hours. Disadvantages associated with this method include low yields (85%-90%) and low purity (96%) of o-chlorobenzonitrile.

[0005] JP2652563 discloses a method for preparing o-chlorobenzonitrile and o-chlorobenzoyl chloride from o-chlorotrichlorotoluene and o-chlorobenzoamide using concentrated sulfuric acid as a catalyst in the presence of o-chlorotoluene solvent. The reaction mixture is heated to 140 °C. Further, the reaction solution is treated with ammonia to convert the acyl chloride product to its corresponding amide. Typical reactions involve the conversion of o-chlorotrichlorotoluene to o-chlorobenzoyl chloride and the conversion of o-chlorobenzoamide to o-chlorobenzonitrile.

[0006] WO2024171098 discloses the synthesis of benzonitrile compounds from the corresponding trichlorotoluene compounds. However, this method results in a low yield of ~90%.

[0007] Therefore, there is a need to develop a method for preparing improved benzonitrile compounds that avoids at least one of the problems of existing methods, such as impure benzonitrile, specific reaction settings, polymerization, low yield, and low cost-effectiveness.

[0008] The inventors of this invention have discovered a simple, industrially feasible, and advantageous method that avoids the use of expensive jacketed reactors, the application of high-temperature conditions, the generation of residues, the formation of byproducts such as benzonitrile polymers and tetraphenylmethane, and results in improved yields.

[0009] Purpose of the invention

[0010] Some of the objectives of this invention are described below:

[0011] The purpose of this invention is to improve one or more problems of the prior art or at least provide a useful alternative.

[0012] The object of the present invention is to provide an improved method for preparing benzonitrile compounds of formula (I) from trichlorotoluene compounds of formula (II).

[0013] Another object of the present invention is to provide an improved method for preparing benzonitrile compounds of formula (I) from trichlorotoluene compounds of formula (II), which avoids the use of expensive jacketed reactors or closed tubes.

[0014] Another object of the present invention is to provide an improved method for preparing high-purity benzonitrile compounds of formula (I) from trichlorotoluene compounds of the corresponding formula (II), which avoids or reduces polymerization and the formation of undesirable byproducts and results in improved yields.

[0015] Another object of the present invention is to provide an improved method for preparing benzonitrile compounds of formula (I) from trichlorotoluene compounds of formula (II), which avoids the generation of solid waste and is therefore environmentally friendly.

[0016] Another object of the present invention is to provide an improved method for preparing benzonitrile compounds of formula (I) from trichlorotoluene compounds of formula (II), which provides improved yields with fewer byproducts and is therefore industrially feasible.

[0017] Other objects and advantages of the invention will become more apparent from the following description, but the description is not intended to limit the scope of the invention. Summary of the Invention

[0018] In one aspect, the present invention provides an improved method for preparing benzonitrile compounds of formula (I), comprising the steps of using a suitable ammonium salt in the presence of a suitable catalyst and optionally in the presence of a suitable inert solvent at a temperature in the range of 150 to 210°C, and then treating the reaction mixture with a suitable reagent to nitrify a trichlorotoluene compound of formula (II) to provide a benzonitrile compound of formula (I).

[0019] Compound of formula (I):

[0020]

[0021] Wherein, R1 and R2 are independently selected from hydrogen and cyano; when R1 and / or R2 are hydrogen, the hydrogen may be substituted by X; n is an integer from 0 to 3;

[0022] Compound of formula (II):

[0023]

[0024] R3 and R4 are independently selected from hydrogen and trichloromethyl; X is selected from fluorine and chlorine; when R3 and / or R4 is hydrogen, the hydrogen may be substituted by X; n is an integer from 0 to 3.

[0025] According to the present invention, compound (I) is obtained in a yield of 98 to 99.5%.

[0026] According to the present invention, the purity of the compound of formula (I) is greater than 99.5%.

[0027] In a second aspect, the present invention provides an improved method for preparing benzonitrile compounds of formula (I), comprising the steps of using a suitable ammonium salt in the presence of a suitable initiator, a suitable catalyst, and optionally in the presence of a suitable inert solvent, at a temperature in the range of 150 to 210°C, and then treating the reaction mixture with a suitable reagent to nitrify a trichlorotoluene compound of formula (II) to provide a benzonitrile compound of formula (I).

[0028] Compound of formula (I):

[0029]

[0030] R1 and R2 are independently selected from hydrogen and cyano; when R1 and / or R2 is hydrogen, the hydrogen may be substituted by X; n is an integer from 0 to 3;

[0031] Compound of formula (II):

[0032]

[0033] R3 and R4 are independently selected from hydrogen and trichloromethyl; X is a halogen selected from fluorine and chlorine; when R3 and / or R4 is hydrogen, the hydrogen may be substituted by X; n is an integer from 0 to 3.

[0034] According to the present invention, compound (I) is obtained in a yield of 98 to 99.5%.

[0035] According to the present invention, the purity of the compound of formula (I) is greater than 99.5%.

[0036] To the inventors’ surprise, the amounts of initiator, catalyst and reagent play a significant role in avoiding the use of expensive jacketed reactors, applying high-temperature conditions and substantially reducing or avoiding the formation of byproducts (e.g. benzonitrile polymers), while simultaneously leading to improved product yields. Invention Details

[0038] The reference to "one embodiment" or "implementation" in the specification means that a particular feature, structure, characteristic, or function described in connection with that embodiment is included in at least one embodiment of the invention. The phrase "in one embodiment" appearing in different places in the specification does not necessarily refer to the same embodiment.

[0039] In the specification, references to "preferred embodiments" mean a detailed description of a specific feature, structure, characteristic, or function, thereby omitting known constructions and functions in order to clearly describe the invention.

[0040] For purposes of illustration and description, the foregoing description of specific embodiments of the invention has been given. These descriptions are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and it will be apparent that many modifications and variations are possible in accordance with the foregoing teachings.

[0041] The terminology used in this disclosure is for the purpose of explaining a particular embodiment only, and such terminology should not be construed as limiting the scope of this disclosure.

[0042] The use of the terms "at least" or "at least one" indicates the use of one or more elements or components or quantities, as the use may achieve one or more desired purposes or results in the embodiments of this disclosure.

[0043] The values ​​mentioned for various physical parameters, dimensions, or quantities are approximate only, and values ​​higher or lower than those assigned to parameters, dimensions, or quantities are contemplated to fall within the scope of this disclosure unless expressly stated otherwise in the specification.

[0044] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. In case of conflict, the terms in this document, including definitions, shall prevail. Preferred methods and materials are described below, although similar or equivalent methods and materials may be used in the practice or testing of the invention. All publications, patent applications, patents, and other references mentioned herein are incorporated herein by reference in their entirety. The materials, methods, and embodiments disclosed herein are illustrative only and are not intended to be limiting.

[0045] As used herein, the terms “comprise(s)”, “include(s)”, “having(s)”, “has(s)”, “can(s)”, “contain(s)”, and their variations are intended to be open-ended transitional phrases, terms, or words that do not preclude the possibility of additional actions or structures.

[0046] The term "halogen" includes either fluorine or chlorine.

[0047] The singular forms “a,” “an,” and “the” include plural references unless the context clearly indicates otherwise. This disclosure also covers other embodiments that “comprise,” “consist of,” and “substantially consist of”: embodiments or elements presented herein, whether or not explicitly stated.

[0048] In view of the purposes defined above, the present invention provides an improved method for preparing benzonitrile compounds of formula (I).

[0049] In a first embodiment, an improved method for preparing a benzonitrile compound of formula (I) is provided, the method comprising the steps of using a suitable ammonium salt in the presence of a suitable catalyst and optionally in the presence of a suitable inert solvent at a temperature in the range of 150 to 210°C, and then treating the reaction mixture with a suitable reagent to nitrify a trichlorotoluene compound of formula (II) to provide a benzonitrile compound of formula (I).

[0050] Compound of formula (I):

[0051]

[0052] R1 and R2 are independently selected from hydrogen and cyano; when R1 and / or R2 is hydrogen, the hydrogen may be substituted by X; n is an integer from 0 to 3;

[0053] Compound of formula (I):

[0054]

[0055] R3 and R4 are independently selected from hydrogen and trichloromethyl; X is a halogen selected from fluorine and chlorine; when R3 and / or R4 is hydrogen, the hydrogen may be substituted by X; n is an integer from 0 to 3.

[0056] According to the present invention, compound (I) is obtained in a yield of 98 to 99.5%.

[0057] According to the present invention, the purity of the compound of formula (I) is greater than 99.5%.

[0058] Non-limiting examples of compounds of formula (I) include, but are not limited to, o-chlorobenzonitrile, p-chlorobenzonitrile, m-chlorobenzonitrile, o-fluorobenzonitrile, p-fluorobenzonitrile, m-fluorobenzonitrile, 2,3-dichlorobenzonitrile, 2,4-dichlorobenzonitrile, 2,5-dichlorobenzonitrile, 2,6-dichlorobenzonitrile, 3,4-dichlorobenzonitrile, 3,5-dichlorobenzonitrile, 2,3-difluorobenzonitrile, 2,4-difluorobenzonitrile, 2,5-difluorobenzonitrile, 2,6-difluorobenzonitrile, 3,4-difluorobenzonitrile, 3,5-difluorobenzonitrile, 1,3-benzanilonitrile, and 1,4-benzanilonitrile.

[0059] Non-limiting examples of compounds of formula (II) include, but are not limited to, o-chlorotrichlorotoluene, p-chlorotrichlorotoluene, m-chlorotrichlorotoluene, o-fluorotrichlorotoluene, p-fluorotrichlorotoluene, m-fluorotrichlorotoluene, 2,3-dichlorotrichlorotoluene, 2,4-dichlorotrichlorotoluene, 2,5-dichlorotrichlorotoluene, 2,6-dichlorotrichlorotoluene, 3,4-dichlorotrichlorotoluene, 3,5-dichlorotrichlorotoluene, 2,3-difluorotrichlorotoluene, 2,4-difluorotrichlorotoluene, 2,5-difluorotrichlorotoluene, 2,6-difluorotrichlorotoluene, 3,4-difluorotrichlorotoluene, 3,5-difluorotrichlorotoluene, 1,3-bis(trichloromethyl)benzene, and 1,4-bis(trichloromethyl)benzene.

[0060] Typically, ammonium salts are selected from ammonium chloride or ammonium bromide.

[0061] Non-limiting examples of suitable catalysts include, but are not limited to, p-toluenesulfonic acid, methanesulfonic acid, phosphonic acid, amberlyst-15, indion resin, sulfuric acid, phosphoric acid, metal salts (e.g., magnesium oxide (MgO), zinc chloride (ZnCl2), copper oxide (CuO), zinc acetate (Zn(OAc)2), ferric chloride (FeCl3)) or combinations thereof.

[0062] By operating under the conditions specified above, the time required to complete or nearly complete the reaction is in the range of 8 to 25 hours. More preferably, the time required to complete the reaction is in the range of 8 to 20 hours.

[0063] Non-limiting examples of suitable inert solvents include, but are not limited to, benzonitrile, xylene, monochlorobenzene, dichlorobenzene, sulfolane, o-chlorobenzonitrile, toluene, or combinations thereof.

[0064] Non-limiting examples of suitable reagents include, but are not limited to, thionyl chloride, phosphorus oxychloride, phosphorus trichloride, phosphorus pentachloride, cyanuryl chloride, oxalyl chloride, or combinations thereof.

[0065] By operating with the reagents specified above according to the method for preparing benzonitrile compounds of formula (I) from trichlorotoluene compounds of formula (II), the reaction yield was surprisingly and unexpectedly increased.

[0066] The method for preparing benzonitrile compounds of formula (I) from trichlorotoluene compounds of formula (II) as disclosed in this invention is shown in Scheme 1 below:

[0067]

[0068] Option 1

[0069] In an exemplary embodiment, the present invention provides an improved method for preparing o-chlorobenzonitrile, comprising the steps of using an ammonium salt in the presence of a suitable catalyst and optionally in the presence of a suitable inert solvent at a temperature in the range of 150 to 210°C, and then treating the reaction mixture with a suitable reagent to nitrify o-chlorotrichlorotoluene to provide o-chlorobenzonitrile.

[0070] In a second embodiment, the present invention provides an improved method for preparing benzonitrile compounds of formula (I), comprising the steps of using a suitable ammonium salt in the presence of a suitable initiator, a suitable catalyst, and optionally in the presence of a suitable inert solvent at a temperature in the range of 150 to 210°C, followed by treating the reaction mixture with a suitable reagent to nitrify a trichlorotoluene compound of formula (II) to provide a benzonitrile compound of formula (I).

[0071] Compound of formula (I):

[0072]

[0073] R1 and R2 are independently selected from hydrogen and cyano; when R1 and / or R2 is hydrogen, the hydrogen may be substituted by X; n is an integer from 0 to 3;

[0074] Compound of formula (II):

[0075]

[0076] R3 and R4 are independently selected from hydrogen and trichloromethyl; X is a halogen selected from fluorine and chlorine; when R3 and / or R4 is hydrogen, the hydrogen may be substituted by X; n is an integer from 0 to 3.

[0077] According to the present invention, compound (I) is obtained in a yield of 98 to 99.5%.

[0078] According to the present invention, the purity of the compound of formula (I) is greater than 99.5%.

[0079] Non-limiting examples of compounds of formula (I) include, but are not limited to, o-chlorobenzonitrile, p-chlorobenzonitrile, m-chlorobenzonitrile, o-fluorobenzonitrile, p-fluorobenzonitrile, m-fluorobenzonitrile, 2,3-dichlorobenzonitrile, 2,4-dichlorobenzonitrile, 2,5-dichlorobenzonitrile, 2,6-dichlorobenzonitrile, 3,4-dichlorobenzonitrile, 3,5-dichlorobenzonitrile, 2,3-difluorobenzonitrile, 2,4-difluorobenzonitrile, 2,5-difluorobenzonitrile, 2,6-difluorobenzonitrile, 3,4-difluorobenzonitrile, 3,5-difluorobenzonitrile, 1,3-benzanilonitrile, and 1,4-benzanilonitrile.

[0080] Non-limiting examples of compounds of formula (II) include, but are not limited to, o-chlorotrichlorotoluene, p-chlorotrichlorotoluene, m-chlorotrichlorotoluene, o-fluorotrichlorotoluene, p-fluorotrichlorotoluene, m-fluorotrichlorotoluene, 2,3-dichlorotrichlorotoluene, 2,4-dichlorotrichlorotoluene, 2,5-dichlorotrichlorotoluene, 2,6-dichlorotrichlorotoluene, 3,4-dichlorotrichlorotoluene, 3,5-dichlorotrichlorotoluene, 2,3-difluorotrichlorotoluene, 2,4-difluorotrichlorotoluene, 2,5-difluorotrichlorotoluene, 2,6-difluorotrichlorotoluene, 3,4-difluorotrichlorotoluene, 3,5-difluorotrichlorotoluene, 1,3-bis(trichloromethyl)benzene, and 1,4-bis(trichloromethyl)benzene.

[0081] Non-limiting examples of initiators are selected from benzoic acids, such as o-chlorobenzoic acid, p-chlorobenzoic acid, m-chlorobenzoic acid, o-fluorobenzoic acid, p-fluorobenzoic acid, m-fluorobenzoic acid, halogen-substituted or unsubstituted 1,4-phthalic acid, halogen-substituted or unsubstituted 1,3-phthalic acid; benzoyl groups, such as o-chlorobenzoyl chloride, p-chlorobenzoyl chloride, m-chlorobenzoyl chloride, o-fluorobenzoyl chloride, p-fluorobenzoyl chloride, m-fluorobenzoyl chloride; halogen-substituted or unsubstituted 1,4-phthalicyl chloride, halogen-substituted or unsubstituted 1,3-phthalicyl chloride; benzamides, such as o-chlorobenzoamide, p-chlorobenzoamide, m-chlorobenzoamide, o-fluorobenzoamide, p-fluorobenzoamide, m-fluorobenzoamide, halogen-substituted or unsubstituted 1,4-phthalamide, halogen-substituted or unsubstituted 1,3-phthalamide, or combinations thereof.

[0082] Typically, ammonium salts are selected from ammonium chloride or ammonium bromide.

[0083] Non-limiting examples of suitable catalysts include, but are not limited to, p-toluenesulfonic acid, methanesulfonic acid, phosphonic acid, amberlyst-15, indion resin, sulfuric acid, phosphoric acid, metal salts (e.g., magnesium oxide (MgO), zinc chloride (ZnCl2), copper oxide (CuO), zinc acetate (Zn(OAc)2), ferric chloride (FeCl3)) or combinations thereof.

[0084] The reaction yield is improved by operating with the reagents specified above according to the method for preparing benzonitrile compounds of formula (I) from trichlorotoluene compounds of formula (II).

[0085] In an exemplary embodiment, the present invention provides an improved method for preparing o-chlorobenzonitrile, comprising the steps of using an ammonium salt in the presence of o-chlorobenzoic acid as an initiator, a suitable catalyst, and optionally in the presence of a suitable inert solvent at a temperature in the range of 150 to 210°C, followed by treating the reaction mixture with a suitable reagent to nitrify o-chlorotrichlorotoluene to provide o-chlorobenzonitrile.

[0086] In another exemplary embodiment, the present invention provides an improved method for preparing o-chlorobenzonitrile, comprising the steps of using an ammonium salt in the presence of o-chlorobenzoyl chloride as an initiator, a suitable catalyst, and optionally in the presence of a suitable inert solvent at a temperature in the range of 150 to 210°C, and then treating the reaction mixture with a suitable reagent to nitrify o-chlorotrichlorotoluene to provide o-chlorobenzonitrile.

[0087] Typically, the amount of initiator, relative to the compound of formula (II), ranges from 1 to 10 w / w%.

[0088] Typically, the amount of catalyst is between 0.1 and 0.5 w / w% relative to the compound of formula (II).

[0089] In one embodiment, the molar ratio of compound (II) to a suitable ammonium salt is in the range of 1:1 to 1:2.

[0090] Non-limiting examples of suitable inert solvents include, but are not limited to, xylene, monochlorobenzene, dichlorobenzene, sulfolane, o-chlorobenzonitrile, benzonitrile, toluene, or combinations thereof.

[0091] Non-limiting examples of suitable reagents include, but are not limited to, thionyl chloride, phosphorus oxychloride, phosphorus trichloride, phosphorus pentachloride, cyanuryl chloride, oxalyl chloride, or combinations thereof.

[0092] By operating according to the conditions specified above, the time required to complete or nearly complete the reaction is in the range of 8 to 20 hours.

[0093] By operating according to the method of the invention, almost complete conversion of compound (II) was achieved with high selectivity, thereby unexpectedly increasing the yield of the product.

[0094] The benzonitrile obtained according to the invention can be readily separated from the reaction mixture by known techniques (e.g., distillation and solvent treatment), and in particular from the catalyst, reagent and excess ammonium salt.

[0095] Specifically, benzonitrile can be distilled directly from the reaction mixture, or it can be extracted by dissolving it in a suitable organic solvent.

[0096] In any case, the catalyst, initiator, reagent, or ammonium salt can be readily recovered and recycled into subsequent reaction cycles, which is ideal and is the intended result of the present invention. Example

[0097] Example 1:

[0098] 400 g of o-chlorotrichlorotoluene, 16 g of o-chlorobenzoic acid (OCBA), 0.8 g of sulfuric acid (98%), and 112 g of ammonium chloride were charged into a reactor. The reaction mixture was heated to 180–195 °C and maintained for 17 hours. When the o-chlorotrichlorotoluene content was <0.2%, the reaction mixture was cooled. 40 g of oxalyl chloride was slowly added. The temperature was maintained at 195–200 °C for 1 hour. The crude o-chlorobenzonitrile obtained was then purified by distillation. (Yield: 99.1%; Purity: >99.5%)

[0099] Example 2:

[0100] 400 g of o-chlorotrichlorotoluene, 36 g of o-chlorobenzoyl chloride (OCBOC), 1 g of phosphoric acid, 0.01 g of copper oxide, and 112 g of ammonium chloride were charged into a reactor. The reaction mixture was heated to 180-195 °C and maintained for 12 hours. When the o-chlorotrichlorotoluene content was <0.2%, the reaction mixture was cooled. 21 g of cyanuryl chloride was slowly added. The temperature was maintained at 195-200 °C for 2 hours. The crude o-chlorobenzonitrile obtained was purified by distillation. (Yield: 99.05%; Purity: >99.5%)

[0101] Example 3:

[0102] 376 g of o-chlorotrichlorotoluene, 36 g of o-chlorobenzoyl chloride (OCBOC), 0.8 g of p-toluenesulfonic acid, 0.01 g of zinc chloride, and 112 g of ammonium chloride were charged into a reactor. The reaction mixture was heated to 180-195 °C and maintained for 18 hours. When the o-chlorotrichlorotoluene content was <0.2%, the reaction mixture was cooled. 40 g of thionyl chloride was slowly added. The temperature was maintained at 195-200 °C for 1 hour. The crude o-chlorobenzonitrile obtained was purified by distillation. (Yield: 99.2%; Purity: >99.5%)

[0103] Example 4:

[0104] 200 g of o-chlorotrichlorotoluene, 6 g of o-chlorobenzoic acid (OCBA), 0.010 g of zinc chloride, 0.6 g of sulfuric acid (98%), and 57 g of ammonium chloride were charged into a reactor. The reaction mixture was heated to 180-185 °C and maintained for 20 hours. When the o-chlorotrichlorotoluene content was <0.2%, the reaction mixture was cooled. 20 g of thionyl chloride was slowly added. The temperature was maintained at 195-200 °C for 1 hour. The crude o-chlorobenzonitrile obtained was purified by distillation. (Yield: 99.12%; Purity: >99.5%)

[0105] Example 5:

[0106] 400 g of o-chlorotrichlorotoluene, 16 g of o-chlorobenzamide (OCBAM), 1 gamberlyst-15, and 112 g of ammonium chloride were charged into a reactor. The reaction mixture was heated to 180-195 °C and maintained for 15 hours. When the o-chlorotrichlorotoluene content was <0.2%, the reaction mixture was cooled. 40 g of thionyl chloride was slowly added. The temperature was maintained at 195-200 °C for 1 hour. The crude o-chlorobenzonitrile obtained was purified by distillation. (Yield: 99.23%; Purity: >99.5%)

[0107] Example 6:

[0108] 20 g of o-chlorotrichlorotoluene, 50 g of o-chlorobenzonitrile (OCBN), and 0.01 g of magnesium oxide were charged into a reactor at room temperature. The reaction mixture was heated to 150-155°C. 1.4 g of 30.0% sulfuric acid solution was added to the reaction mixture. 55.8 g of ammonium chloride was added, and the reaction mixture was heated to 170-175°C. 190 g of o-chlorotrichlorotoluene was added to the reactor at 170-195°C, and the mixture was maintained for 6 hours. After the addition was complete, a sample was sent for GC analysis. If the o-chlorotrichlorotoluene content was <0.2%, the mixture was cooled. 20 g of thionyl chloride was slowly added. The temperature was maintained at 195-200°C for 1 hour. Pure o-chlorobenzonitrile was obtained by distillation. (Yield: 99.14%; Purity: >99.5%)

[0109] Example 7:

[0110] 400 g of 1,4-bis-trichloromethylbenzene, 36 g of terephthaloyl chloride, 1.6 g of sulfuric acid (98%), 0.02 g of zinc acetate, and 224 g of ammonium chloride were charged into a reactor. The reaction mixture was heated to 180-195 °C and maintained for 21 hours. When the content of 1,3-bis-trichloromethylbenzene was <0.2%, the reaction mixture was cooled. 42 g of cyanuric chloride was slowly added. The temperature was maintained at 195-200 °C for 2 hours. The crude terephthalonitrile obtained was purified by distillation. (Yield: 99.03%; Purity: >99.0%)

[0111] Example 8:

[0112] 200 g of p-chlorotrichlorotoluene, 6 g of p-chlorobenzoic acid (OCBA), 0.010 g of zinc chloride, 0.6 g of sulfuric acid (98%), and 57 g of ammonium chloride were charged into a reactor. The reaction mixture was heated to 180–185 °C and maintained for 20 hours. When the p-chlorotrichlorotoluene content was <0.2%, the reaction mixture was cooled. 20 g of thionyl chloride was slowly added. The temperature was maintained at 195–200 °C for 1 hour. The crude p-chlorobenzonitrile obtained was purified by distillation. (Yield: 98.7%; Purity: >99.5%)

[0113] Comparative Example 1:

[0114] 400 g of o-chlorotrichlorotoluene, 16 g of o-chlorobenzoic acid (OCBA), 0.8 g of sulfuric acid (98%), and 112 g of ammonium chloride were charged into a reactor. The reaction mixture was heated to 180-195 °C and maintained for 12 hours. When the o-chlorotrichlorotoluene content was <0.2%, the reaction mixture was cooled. The crude o-chlorobenzonitrile obtained was purified by distillation. (Yield: 90%; Purity: >99.5%)

[0115] Comparative Example 2:

[0116] 376 g of o-chlorotrichlorotoluene, 36 g of o-chlorobenzoyl chloride (OCBOC), 0.8 g of sulfuric acid (98%), and 112 g of ammonium chloride were charged into a reactor. The reaction mixture was heated to 180-195 °C and maintained for 12 hours. When the o-chlorotrichlorotoluene content was <0.2%, the reaction mixture was cooled. The crude o-chlorobenzonitrile obtained was purified by distillation (yield: 89%; purity: >99.5%).

[0117] Comparative Example 3:

[0118] 200 g of o-chlorotrichlorotoluene and 0.4 g of sulfuric acid (98%) were added to a reactor at room temperature, and the reaction mixture was heated to 150-155 °C. 1.0 g of water was added to the reaction mixture at 155-160 °C over 20 minutes, followed by the addition of 55.8 g of ammonium chloride. The reaction mixture was heated to 180-185 °C. The resulting reaction mixture was heated at 180-185 °C for 25 hours. After the reaction was complete, when the o-chlorotrichlorotoluene content was <0.2%, the reaction mixture was cooled to 110 °C. The crude o-chlorobenzonitrile obtained was purified by distillation (yield: 89.5%; purity: >99.5%).

[0119] The above description of the present invention is merely illustrative and is not intended to be limiting. Since those skilled in the art will conceive of embodiments disclosed that incorporate the spirit and substance of the invention, the present invention should be construed as including all contents within the scope of this disclosure.

[0120] The embodiments described herein, along with their various features and advantageous details, are explained with reference to the non-limiting embodiments in the description. Descriptions of well-known components and processing techniques have been omitted to avoid unnecessarily obscuring the embodiments herein. The embodiments used herein are intended only to facilitate an understanding of how the embodiments described herein can be practiced, and further to enable those skilled in the art to practice the embodiments. Therefore, the embodiments should not be construed as limiting the scope of the embodiments described herein.

[0121] The description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can readily modify and / or adapt these specific embodiments to various applications by applying present knowledge without departing from the general conception, and therefore, such adaptations and modifications should and are intended to be understood within the meaning and scope of equivalents of the disclosed embodiments. It should be understood that the wording or terminology used herein is for descriptive rather than limiting purposes. Therefore, while embodiments herein have been described according to preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modifications to the spirit and scope of the embodiments described herein.

[0122] While specific features of the invention have been emphasized herein, it should be understood that various modifications and numerous alterations can be made to the preferred embodiments without departing from the principles of the invention. These and other modifications to the nature of the invention or its preferred embodiments will be apparent to those skilled in the art from the invention described herein, and it will be clearly understood that the foregoing description is to be interpreted merely as illustrative and not limiting.

[0123] Various features and embodiments of the present invention are described in the following representative embodiments, which are intended to be illustrative and not restrictive.

[0124] The embodiments were selected and described in order to best explain the principles of the invention and its practical application, thereby enabling those skilled in the art to best utilize the invention and its various embodiments with various modifications suitable for the intended particular use.

[0125] It should be understood that various omissions and equivalents may be contemplated as appropriate, depending on the circumstances, but this is intended to cover the application or implementation without departing from the scope of the invention.

Claims

1. An improved method for preparing benzonitrile compounds of formula (I), comprising the steps of using a suitable ammonium salt in the presence of a suitable catalyst and optionally in the presence of a suitable inert solvent and a suitable initiator at a temperature in the range of 150 to 210°C, and then treating the reaction mixture with a suitable reagent to nitrify the corresponding trichlorotoluene compound of formula (II) to provide benzonitrile compounds of formula (I). Compound of formula (I): R1 and R2 are independently selected from hydrogen and cyano; when R1 and / or R2 is hydrogen, the hydrogen may be substituted by X; X is selected from fluorine and chlorine; n is an integer from 0 to 3; Compound of formula (II): R3 and R4 are independently selected from hydrogen and trichloromethyl; the condition is that R3 and R4 cannot both be trichloromethyl. And when R3 and / or R4 are hydrogen, the hydrogen may be replaced by X; X is selected from fluorine and chlorine; n is an integer between 0 and 3.

2. The method according to claim 1, wherein the suitable ammonium salt is selected from ammonium chloride or ammonium bromide or a mixture thereof, and the molar ratio of the trichlorotoluene compound of formula (II) to the suitable ammonium salt is in the range of 1:1 to 1:

2.

3. The method according to claim 1, wherein the suitable catalyst is selected from p-toluenesulfonic acid, methanesulfonic acid, phosphonic acid, amberlyst-15, indion resin, sulfuric acid, phosphoric acid, metal salts such as magnesium oxide (MgO), zinc chloride (ZnCl2), copper oxide (CuO), zinc acetate (Zn(OAc)2), ferric chloride (FeCl3), or mixtures thereof, and the amount of suitable catalyst is in the range of 0.5 w / w% of the trichlorotoluene compound of formula (II).

4. The method according to claim 1, wherein the suitable reagent is selected from oxalyl chloride, thionyl chloride, phosphorus oxychloride, phosphorus trichloride, phosphorus pentachloride, cyanuryl chloride, or a mixture thereof.

5. The method according to claim 1, wherein the suitable inert solvent is selected from benzonitrile, xylene, monochlorobenzene, dichlorobenzene, sulfolane, o-chlorobenzonitrile, toluene, or mixtures thereof.

6. The method according to claim 1, wherein the initiator is selected from benzoic acid, such as o-chlorobenzoic acid, p-chlorobenzoic acid, m-chlorobenzoic acid, o-fluorobenzoic acid, p-fluorobenzoic acid, m-fluorobenzoic acid, halogen-substituted or unsubstituted 1,4-phthalic acid, halogen-substituted or unsubstituted 1,3-phthalic acid; benzoyl group, such as o-chlorobenzoyl chloride, p-chlorobenzoyl chloride, m-chlorobenzoyl chloride, o-fluorobenzoyl chloride, p-fluorobenzoyl chloride, m-fluorobenzoyl chloride, halogen-substituted Or unsubstituted 1,4-phthaloyl chloride, halogenated or unsubstituted 1,3-phthaloyl chloride; benzamide, such as o-chlorobenzamide, p-chlorobenzamide, m-chlorobenzamide, o-fluorobenzamide, p-fluorobenzamide, m-fluorobenzamide, halogenated or unsubstituted 1,4-phthaloyl chloride, halogenated or unsubstituted 1,3-phthaloyl chloride or mixtures thereof, and a suitable initiator in an amount ranging from 1 to 10 w / w% of the trichlorotoluene compound of formula (II).

7. The method according to claim 1, wherein the yield of the benzonitrile compound of formula (I) is in the range of 98% to 99.5%.

8. The method according to claim 1, wherein the benzonitrile compound of formula (I) has a purity greater than 99.5%.

9. The method according to claim 1, wherein the compound of formula (I) is selected from o-chlorobenzonitrile, p-chlorobenzonitrile, m-chlorobenzonitrile, o-fluorobenzonitrile, p-fluorobenzonitrile, m-fluorobenzonitrile, 2,3-dichlorobenzonitrile, 2,4-dichlorobenzonitrile, 2,5-dichlorobenzonitrile, 2,6-dichlorobenzonitrile, 3,4-dichlorobenzonitrile, 3,5-dichlorobenzonitrile, 2,3-difluorobenzonitrile, 2,4-difluorobenzonitrile, 2,5-difluorobenzonitrile, 2,6-difluorobenzonitrile, 3,4-difluorobenzonitrile, 3,5-difluorobenzonitrile, 1,3-benzanilonitrile, and 1,4-benzanilonitrile.

10. The method according to claim 1, wherein the compound of formula (II) is selected from o-chlorotrichlorotoluene, p-chlorotrichlorotoluene, m-chlorotrichlorotoluene, o-fluorotrichlorotoluene, p-fluorotrichlorotoluene, m-fluorotrichlorotoluene, 2,3-dichlorotrichlorotoluene, 2,4-dichlorotrichlorotoluene, 2,5-dichlorotrichlorotoluene, 2,6-dichlorotrichlorotoluene, 3,4-dichlorotrichlorotoluene, 3,5-dichlorotrichlorotoluene, 2,3-difluorotrichlorotoluene, 2,4-difluorotrichlorotoluene, 2,5-difluorotrichlorotoluene, 2,6-difluorotrichlorotoluene, 3,4-difluorotrichlorotoluene, 3,5-difluorotrichlorotoluene, 1,3-bis(trichloromethyl)benzene, and 1,4-bis(trichloromethyl)benzene.

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