Iron complex based on biisoquinoline as well as preparation method and application of iron complex

Abstract

The invention provides a biisoquinoline-based iron complex which has a structure as shown in a formula (I), and also provides a preparation method of the biisoquinoline-based iron complex and an application of the biisoquinoline-based iron complex as a catalyst for an anisole hydroxylation reaction. The invention further provides a method for preparing p-hydroxyanisole and co-producing o-hydroxyanisole. When the biisoquinoline-based iron complex provided by the invention is used for catalyzing hydroxylation reaction of anisole, excellent reaction activity and selectivity to hydroxyl products can be obtained, a new process thought is provided for industrial production of p-hydroxyanisole, and the biisoquinoline-based iron complex has very important economic value and social value, # imgabs0 #

Description

Technical Field

[0001] The invention relates to the technical field of catalyst preparation, and in particular to an iron complex based on diisoquinoline, a preparation method thereof and application thereof in catalyzing anisole hydroxylation reaction. The invention also relates to a method for preparing p-hydroxyanisole and co-producing o-hydroxyanisole. Background Art

[0002] p-Hydroxyanisole is also known as p-methoxyphenol, and its English name is 4-methoxyphenol, or MEHQ for short. MEHQ is an important organic chemical intermediate that plays an important role in the pharmaceutical, pesticide, and fragrance industries. It can be used to synthesize stabilizers, UV absorbers, and food preservatives for certain plastic monomers. The main function of MEHQ is to act as an inhibitor and anti-aging agent in polymer production, especially in the process of generating acrylonitrile, acrylic acid, and related products. Its unique advantage is that it can directly participate in the polymerization of the final product without prior removal.

[0003] At present, there are two main processes for the industrial preparation of p-hydroxyanisole, which can be divided into p-aminoanisole diazotization method and hydroquinone etherification method according to the reaction raw materials. The p-aminoanisole diazotization method uses methoxyaniline as raw material, and p-hydroxyanisole is obtained after two steps of diazotization and hydrolysis. The reaction needs to be carried out under high temperature and concentrated acid conditions. The operation during the process is relatively cumbersome, the equipment requirements are high, and a large amount of nitrogen-containing wastewater is produced; the hydroquinone etherification method is mainly divided into dimethyl sulfate method and methanol method. Although both start from hydroquinone, dimethyl sulfate is a highly toxic chemical, which requires high equipment and personnel for operation, and a large amount of alkali is required to neutralize the by-products in the subsequent process, which increases environmental pressure and processing costs. Even the milder methanol method also faces the problem of purity control and by-product management. Therefore, both of the above-mentioned two synthesis processes have certain limitations.

[0004] In recent years, a new synthesis process using anisole and hydrogen peroxide as raw materials has gradually attracted attention. This process has the advantages of mild reaction conditions, high yield, and high value-added by-product guaiacol (o-hydroxyanisole). The most important thing is that the product of the reaction is water, which is a green synthesis process.

[0005] In order to solve the problem of low reaction conversion rate and yield in the existing anisole hydroxylation process, Chinese patent application CN 113731400A discloses a method for synthesizing p-hydroxyanisole and guaiacol by reacting anisole with hydrogen peroxide. 7 [MnV 13 O 38 ]·18H 2O as catalyst, the catalyst has higher catalytic activity, can significantly improve the conversion rate of anisole in hydroxylation reaction and the productivity of target product (p-hydroxyanisole), thereby can effectively promote the clean production of p-hydroxyanisole, the final yield of hydroxylation product is 76%, and the selectivity is 98%. Chinese patent CN115490579B discloses a preparation method of o / p-hydroxyanisole, mainly including catalyst optimization and reaction process optimization, wherein, catalyst optimization is: first prepare alkali-modified microsphere titanium silicon molecular sieve, then prepare the microsphere titanium silicon molecular sieve catalyst of load copper and cadmium by equal volume impregnation method; reaction process optimization is: reaction temperature is room temperature~150 ℃, reaction pressure is 0.1~5.0MPa, the hydroxyanisole obtained by the preparation method has excellent yield and selectivity, conversion rate is about 22%, selectivity is about 97%, and the life of catalyst reaches more than two thousand hours. However, the above two catalysts all belong to heterogeneous catalysts, are not fully contacted with reaction solution, and still have the disadvantages such as low catalyst activity. Summary of the invention

[0006] In order to make up for the deficiencies in the prior art, an object of the present invention is to provide an iron complex based on diisoquinoline, which, when used to catalyze the hydroxylation reaction of anisole, can achieve excellent catalytic activity, high substrate conversion rate, and good selectivity for the hydroxyanisole product, and thus has great application potential.

[0007] Another object of the present invention is to provide a preparation method and application of the diisoquinoline-based iron complex.

[0008] Another object of the present invention is to provide a method for preparing p-hydroxyanisole and co-producing o-hydroxyanisole.

[0009] The first aspect of the present invention provides an iron complex based on biisoquinoline, which has a structure shown in formula (I):

[0010]

[0011] Here, R is the same or different and each independently represents hydrogen, C1-C6 alkyl, C1-C6 alkoxy or C3-C8 cycloalkyl.

[0012] In some preferred embodiments, R may each independently represent hydrogen, C1-C4 alkyl or C1-C4 alkoxy. In some more preferred embodiments, R may each independently represent hydrogen, methyl, ethyl, n-propyl or isopropyl. In some most preferred embodiments, the biisoquinoline-based iron complex may be the following compound:

[0013]

[0014] The second aspect of the present invention provides a method for preparing the iron complex based on biisoquinoline according to any one of the above technical solutions, the preparation method comprising the following steps:

[0015] S1: an isoquinoline derivative of the structure shown in formula (I-1) reacts with an alkyltin chloride reagent to obtain a first intermediate of the structure shown in formula (I-2);

[0016]

[0017] S2: The first intermediate reacts with a halogenated isoquinoline of the structure shown in formula (I-3) (i.e., Stile coupling reaction) to obtain a second intermediate of the structure shown in formula (I-4);

[0018]

[0019] S3: The second intermediate contains Fe 2+ The iron source is reacted (i.e., complexation reaction) to obtain the diisoquinoline-based iron complex;

[0020]

[0021] Among them, R 1 represents a C1-C6 alkyl group, for example, it may represent a methyl group, an ethyl group, an n-propyl group, an isopropyl group or a tert-butyl group;

[0022] X represents a halogen atom, for example, it may represent Br;

[0023] R is the same or different, and each is independently defined as in any one of the above technical solutions.

[0024] In the preparation method provided by the present invention, the iron source can be one or more of ferrous sulfate, ferrous nitrate, ferrous chloride, and ferrous hydroxide.

[0025] In the preparation method provided by the present invention, the mass ratio of the second intermediate to the iron source can be 1:1-6, for example, 1:2-4.

[0026] In the preparation method provided by the present invention, in step S1, the isoquinoline derivative and the alkyltin chloride reagent can be reacted in the presence of a butyllithium catalyst (e.g., n-butyllithium) in a first organic solvent. In some preferred embodiments, the reaction temperature in step S1 can be 20 to 100° C., for example, 30 to 60° C.

[0027] In the preparation method provided by the present invention, in step S1, the alkyl tin chloride reagent may be trimethyltin chloride. In some preferred embodiments, the mass ratio of the isoquinoline derivative to trimethyltin chloride may be 1:0.4-2, for example, 1:0.6-1.5, and further 1:0.6-1.2.

[0028] In the preparation method provided by the present invention, in the step S1, the mass ratio of the isoquinoline derivative to the butyl lithium catalyst can be 1:0.05-0.8, for example, can be 1:0.1-0.4, and can further be 1:0.2-0.3.

[0029] In the preparation method provided by the present invention, in step S1, the first organic solvent can be one or more of toluene, ethylbenzene, tetrahydrofuran, N,N-dimethylformamide (DMF), and diethyl ether. In some preferred embodiments, the mass ratio of the isoquinoline derivative to the first organic solvent can be 1:2 to 10, for example, 1:3 to 8.

[0030] In the preparation method provided by the present invention, the reaction environment in step S1 is an anhydrous and oxygen-free environment, which can be achieved by common operations or means in the art.

[0031] In the preparation method provided by the present invention, in step S1, the addition (e.g., dropwise addition) of the butyl lithium catalyst needs to maintain a low temperature environment of -100 to -50°C, and after the butyl lithium catalyst is added, the temperature is slowly raised to the desired reaction temperature. The low temperature environment can be achieved by common operations or means in the art.

[0032] In the preparation method provided by the present invention, the reaction time in step S1 can be monitored and controlled in real time according to conditions such as the reaction scale and the actual reaction situation, for example, it can be 2 to 30 hours, and further can be 5 to 20 hours.

[0033] In the preparation method provided by the present invention, in step S1, distilled water or deionized water can be added after the reaction is completed to quench the reaction, and after removing the first organic solvent, the obtained residue can be purified by a silica gel chromatography column, wherein the elution system can include solvents such as n-hexane, ethyl acetate, dichloromethane, or mixtures thereof.

[0034] In the preparation method provided by the present invention, in step S2, the first intermediate and the halogenated isoquinoline can react in a second organic solvent. In some preferred embodiments, the reaction temperature in step S2 can be 60 to 200°C, for example, 60 to 120°C.

[0035] In the preparation method provided by the present invention, in step S2, the halogenated isoquinoline may be 2-bromoisoquinoline. In some preferred embodiments, the mass ratio of the first intermediate to 2-bromoisoquinoline may be 1:1 to 3, for example, 1:1 to 1.5.

[0036] In the preparation method provided by the present invention, in step S2, the second organic solvent can be one or more of toluene, chloroform, dichloromethane, and tetrahydrofuran. In some preferred embodiments, the mass ratio of the first intermediate to the second organic solvent can be 1:2 to 10, for example, 1:4 to 6.

[0037] In the preparation method provided by the present invention, the reaction environment in step S2 is an anhydrous and oxygen-free environment, which can be achieved by common operations or means in the art.

[0038] In the preparation method provided by the present invention, the reaction time in step S2 can be monitored and controlled in real time according to conditions such as the reaction scale and the actual reaction situation, for example, it can be 2 to 30 hours, and further can be 5 to 20 hours.

[0039] In the preparation method provided by the present invention, in step S2, the second organic solvent can be removed after the reaction is completed, and the obtained residue can be separated and purified by a silica gel chromatography column, wherein the elution system can include solvents such as dichloromethane, ethyl acetate, petroleum ether, n-hexane, or mixtures thereof.

[0040] In the preparation method provided by the present invention, in step S3, the second intermediate is reacted with a Fe 2+ The iron source can be reacted in a third organic solvent. In some preferred embodiments, the reaction temperature in step S3 can be 10 to 80° C., for example, 20 to 40° C., and further can be room temperature.

[0041] In the preparation method provided by the present invention, in step S3, the third organic solvent can be one or more of N,N-dimethylformamide, dimethyl sulfoxide (DMSO), methanol, and acetonitrile. In some preferred embodiments, the mass ratio of the second intermediate to the third organic solvent can be 1:1 to 10, for example, 1:2 to 4.

[0042] In the preparation method provided by the present invention, the reaction time in step S3 can be monitored and controlled in real time according to conditions such as the reaction scale and the actual reaction situation, for example, it can be 0.5 to 10 hours, and further can be 0.5 to 5 hours.

[0043] In the preparation method provided by the present invention, in the step S3, after the reaction is completed, the precipitated solid can be separated, washed and dried to obtain the iron complex.

[0044] In the preparation method provided by the present invention, the desired material can be obtained through a separation step, and the separation equipment or method can be a common equipment or method in the art, including but not limited to natural sedimentation, (normal pressure or vacuum) filtration, centrifugation and the like and their common equipment.

[0045] In the preparation method provided by the present invention, the solvent can be removed by common equipment or methods in the art, for example, the solvent can be removed by reduced pressure evaporation using a rotary evaporator.

[0046] In the preparation method provided by the present invention, the washing step refers to washing the material with distilled water or deionized water until the surface of the material is close to or neutral, and the number of washing times can be adjusted according to actual conditions, for example, it can be 2 to 5 times, usually 3 times.

[0047] In the preparation method provided by the present invention, the drying step refers to removing the residual solvent or moisture on the surface of the material by heating or the like, and the drying time and temperature can be adjusted according to actual conditions without affecting the properties of the material itself.

[0048] In the preparation method provided by the present invention, room temperature refers to 25±5°C.

[0049] The third aspect of the present invention provides the use of the diisoquinoline-based iron complex described in any one of the above technical solutions as a catalyst for the hydroxylation reaction of anisole.

[0050] In some preferred embodiments, the anisole hydroxylation reaction can be a hydroxylation reaction of anisole reacting with an oxidant to prepare p-hydroxyanisole and co-produce o-hydroxyanisole. In some more preferred embodiments, the oxidant can be hydrogen peroxide with a mass concentration of 20 to 60%.

[0051] A fourth aspect of the present invention provides a method for preparing p-hydroxyanisole and co-producing o-hydroxyanisole, the method comprising: in the presence of a catalyst, anisole and an oxidant undergo a hydroxylation reaction to prepare p-hydroxyanisole and co-produce o-hydroxyanisole, wherein the catalyst is the diisoquinoline-based iron complex described in any one of the above technical solutions.

[0052] In some preferred embodiments, the amount of the catalyst used may be 0.1 to 1.5% of anisole, for example, 0.2 to 0.8%, or further 0.3 to 0.5%, by mass percentage.

[0053] In some preferred embodiments, the oxidant may be hydrogen peroxide with a mass concentration of 20 to 60%, for example, hydrogen peroxide with a mass concentration of 30 to 50%.

[0054] In some preferred embodiments, the hydroxylation reaction can be carried out in a reaction solvent, for example, the reaction is one or more of acetone, methanol, water, and ethanol, and the mass ratio of anisole to the reaction solvent can be 1:0.5-5, for example, 1:0.5-1.5.

[0055] In some preferred embodiments, the reaction temperature of the hydroxylation reaction may be 50-80° C., and the reaction pressure may be normal pressure.

[0056] In some preferred embodiments, the reaction time of the hydroxylation reaction may be 2 to 20 hours, for example, 5 to 10 hours.

[0057] The technical solution provided by the present invention has the following advantages:

[0058] (1) The iron complex based on biisoquinoline provided by the present invention is directed to active Fe 2+ A large-volume cycloconjugated ligand structure is introduced, which can effectively pair with anisole when used in the hydroxylation reaction of anisole, thereby significantly improving the reaction activity; the large-volume diisoquinoline ligand structure can also form a steric hindrance to the ortho-position side reaction of the methoxy group, thereby reducing the occurrence of ortho-position reactions, which can significantly improve the selectivity of parahydroxyanisole and provide a higher added value product.

[0059] (2) The iron complex provided by the present invention can be dissolved in common reaction solvents, so the hydroxylation reaction of anisole catalyzed by the iron complex can be a homogeneous reaction. Compared with traditional heterogeneous catalysts, the contact between the catalyst and the reaction materials is more complete, so the catalytic activity is higher, thereby greatly improving the reaction rate.

[0060] (3) The preparation method of the iron complex provided by the present invention is simple, easy to operate and easy to control, does not require high costs, has strong industrial applicability, and provides a new process idea for the industrial production of p-hydroxyanisole, and therefore has very important economic and social value. DETAILED DESCRIPTION

[0061] The specific embodiments of the catalyst of the present invention will be described below. First of all, it should be clear that the catalyst disclosed in the present invention has different forms and should not be understood or interpreted as being limited to the specific embodiments described in the present invention. At the same time, the purpose of providing the embodiments is to make the disclosure of the present invention more thorough and complete, and to fully convey the intention and scope of the subject matter to those skilled in the art. Therefore, any other embodiments without creative premises should belong to the scope of protection of the present invention.

[0062] Unless otherwise defined, the terms used in the present invention should be considered to be consistent with the common meanings that can be understood by those skilled in the art. Some common terms are introduced and explained below:

[0063] As used herein, the singular forms "a," "an," "the," "said," and "above" include both singular and plural referents.

[0064] The terms “include” or “including” used in this document are open and non-restrictive, that is, they do not exclude unlisted species, elements, or method steps.

[0065] The "one (one) embodiment" used in this article specifically refers to the specific features, structures or properties of the subject being described when the phrase appears. Therefore, the "one (one) embodiment" appearing in different places in this article does not all refer to the same embodiment. On the other hand, in some specific embodiments, it may contain some features of other embodiments but not other features of other embodiments. At this time, the combination of embodiments with different features, although not listed in this article, should be assumed to be included in the claims and statements of this article.

[0066] "C1-Cn" used herein includes C1-C2, C1-C3, ... C1-Cn. For example, the "C1-C6" group refers to a group having 1 to 6 carbon atoms in the portion, i.e., the group contains 1 carbon atom, 2 carbon atoms, 3 carbon atoms, 4 carbon atoms, 5 carbon atoms or 6 carbon atoms. Therefore, for example, "C1-C4 alkyl" refers to an alkyl group containing 1 to 4 carbon atoms, i.e., the alkyl group is selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, etc. The numerical range herein, such as "1-6", refers to each integer in the given range.

[0067] The term "alkyl" as used herein, alone or in combination, refers to a molecule having the formula C n H 2n+1 The hydrocarbon group of the general formula is wherein n is an integer greater than or equal to 1. The alkyl group may be linear or branched. The alkyl groups of the present invention contain from 1 to 6 carbon atoms. Non-limiting examples of alkyl groups include methyl, ethyl, n-propyl, isopropyl, 2-methyl-1-propyl, 2-methyl-2-propyl, 2-methyl-1-butyl, 3-methyl-1-butyl, 2-methyl-3-butyl, 2,2-dimethyl-1-propyl, 2-methyl-1-pentyl, 3-methyl-1-pentyl, 4-methyl-1-pentyl, 2-methyl-2-pentyl, 3-methyl-2-pentyl, 4-methyl-2-pentyl, 2,2-dimethyl-1-butyl, 3,3-dimethyl-1-butyl, 2-ethyl-1-butyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, neopentyl, tert-pentyl, hexyl, and the like, and isomers thereof.

[0068]

[0046] "Alkyl" as used herein in combination refers to an alkyl group attached to another group, for example, an alkyl group in an alkoxy group, and has the same definition as when used alone.

[0069] The term "alkoxy" as used herein, alone or in combination, refers to an alkyl ether radical, represented as "alkyl-O-." Non-limiting examples of alkoxy include methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, sec-butoxy, tert-butoxy, and the like.

[0070] The term "cycloalkyl" as used herein alone or in combination refers to a non-aromatic saturated carbocyclic ring, which may include a monocyclic carbocyclic ring (having one ring), a bicyclic carbocyclic ring (having two rings), or a polycyclic carbocyclic ring (having more than two rings), and the rings may be bridged or spirocyclic. The cycloalkyl group may have 3 to 8 ring-forming carbon atoms, for example, 3 to 6 ring-forming carbon atoms. Non-limiting examples of cycloalkyl groups include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and the like.

[0071] The term "halogen atom" as used herein, alone or in combination, refers to fluorine (F), chlorine (Cl), bromine (Br) or iodine (I).

[0072] The technical solution of the present invention is further described in detail below in conjunction with specific embodiments.

[0073] In the embodiments of the present invention, an Agilent liquid chromatograph is used to calibrate the contents of anisole, o-hydroxyanisole and p-hydroxyanisole in the system by an external standard method, and a potentiometric titrator is used to measure the hydrogen peroxide.

[0074] The silica gel chromatographic column used in the examples of the present invention is filled with 30 mesh silica gel, and the raw materials or reagents used are all commercially available products unless otherwise specified.

[0075] The percentages used in the embodiments of the present invention are all by mass unless otherwise specified.

[0076] Example 1

[0077] 1. Preparation of Catalyst Cat-1

[0078] Into an anhydrous, oxygen-free sealed three-necked flask, 40 g of isoquinoline and 250 g of tetrahydrofuran were injected. At -78 °C, 80 g of 1.6 mol / L n-butyllithium solution was slowly added dropwise to the reaction system. After the addition was completed, the temperature was raised to room temperature and the reaction was continued for 3 h. Then, 50 g of trimethyltin chloride solution (the mass concentration of trimethyltin chloride was 65%) was quickly added to the reaction system. The temperature was raised to 60 °C and the reaction was carried out for 6 h. Water was added to quench the reaction. The solvent was removed by rotary evaporation. The obtained residue was purified by silica gel chromatography. The eluent was a mixed solution of ethyl acetate and n-hexane (mass ratio was 1:4) to obtain compound 1-1.

[0079] Take 40g of compound 1-1 and dissolve it in 180g of toluene, add 60g of 2-bromoisoquinoline, heat to 110°C and reflux for 12h. After the reaction is completed, the reaction solution is evaporated to remove the solvent, and the obtained residue is purified by silica gel column chromatography with dichloromethane as the eluent to obtain compound 1-2.

[0080] 20 g of compound 1-2 and 40 g of ferrous sulfate solid were mixed and dissolved in 80 g of DMF, and stirred at room temperature for 3 h to precipitate flocculent solids, which were filtered, washed, and dried to obtain the iron ion ligand catalyst Cat-1.

[0081] Elemental analysis: C 76.04%, H 4.26%, Fe 9.82%, N 9.86% (measured values).

[0082] H NMR spectrum analysis: 1 H NMR (400 MHz, CDCl 3 )δ7.16(2H), 7.42(4H), 7.49(4H), 7.63(4H), 7.92(4H), 8.21(2H), 8.54(2H), 8.91(2H).

[0083] 2. Catalyst performance evaluation

[0084] 0.2g Cat-1 was mixed with 100g reaction raw materials (anisole: 27.5% hydrogen peroxide: acetone = 1: 0.3: 0.8, mass ratio), and the reaction was stopped after 6h at 60°C. The reaction solution was subjected to liquid chromatography and titration analysis. The hydrogen peroxide conversion was greater than 99%, the total selectivity of hydroxyanisole was greater than 95%, and p-hydroxyanisole / o-hydroxyanisole = 3.65 (molar ratio).

[0085] Example 2

[0086] 1. Preparation of Catalyst Cat-2

[0087] Into an anhydrous, oxygen-free sealed three-necked flask, 40 g of 6-methylisoquinoline and 320 g of toluene were injected. At -98 °C, 120 g of 1.6 mol / L n-butyllithium solution was slowly added dropwise to the reaction system. After the addition was completed, the temperature was raised to room temperature and the reaction was continued for 2 h. Then, 60 g of trimethyltin chloride solution (the mass concentration of trimethyltin chloride was 70%) was quickly added to the reaction system. The temperature was raised to 50 °C and the reaction was carried out for 10 h. Water was added to quench the reaction. The solvent was removed by rotary evaporation. The obtained residue was purified by silica gel chromatography, and the eluent was a mixed solution of ethyl acetate and n-hexane (mass ratio was 1:4) to obtain compound 2-1.

[0088] Take 40g of compound 2-1 and dissolve it in 240g of dichloromethane, add 60g of 2-bromoisoquinoline, heat to 120℃ and reflux for 16h. After the reaction is completed, the reaction solution is evaporated to remove the solvent, and the obtained residue is purified by silica gel column chromatography with dichloromethane as the eluent to obtain compound 2-2.

[0089] 20 g of compound 2-2 and 60 g of ferrous nitrate solid were mixed and dissolved in 40 g of methanol, and stirred at room temperature for 3 h to precipitate flocculent solids, which were filtered, washed, and dried to obtain the iron ion ligand catalyst Cat-2.

[0090] Elemental analysis: C 76.51%, H 4.73%, Fe 9.36%, N 9.39% (measured values).

[0091] H NMR spectrum analysis: 1 H NMR (400 MHz, CDCl 3 )δ2.34(6H), 7.16(2H), 7.28(2H), 7.42(4H), 7.49(4H), 7.63(4H), 7.86(2H), 7.92(4H), 8.21(2H), 8.51(2H), 8.92(2H).

[0092] 2. Catalyst performance evaluation

[0093] 0.2g Cat-2 was mixed with 100g reaction raw materials (anisole: 27.5% hydrogen peroxide: methanol = 1: 0.4: 1.2, mass ratio), and the reaction was stopped after 5h at 80°C. The reaction solution was subjected to liquid chromatography and titration analysis. The hydrogen peroxide conversion was greater than 99%, the total selectivity of hydroxyanisole was greater than 96%, and p-hydroxyanisole / o-hydroxyanisole = 4.03 (molar ratio).

[0094] Example 3

[0095] 1. Preparation of Catalyst Cat-3

[0096] Into an anhydrous, oxygen-free sealed three-necked flask, inject 40g of 6-n-propylisoquinoline and 150g of ether, slowly add 80g of 1.6mol / L n-butyllithium solution to the reaction system at -50°C, warm to room temperature after the addition is complete and continue to react for 2h, then quickly add 40g of trimethyltin chloride solution (the mass concentration of trimethyltin chloride is 60%) to the reaction system, heat to 30°C and react for 18h, add water to quench the reaction, and remove the solvent by rotary evaporation. The obtained residue is purified by silica gel chromatography, and the eluent is a mixed solution of ethyl acetate and n-hexane (mass ratio is 1:4) to obtain compound 3-1.

[0097] Take 40g of compound 3-1 and dissolve it in 160g of tetrahydrofuran, add 40g of 2-bromoisoquinoline, heat to 70°C and reflux for 6h. After the reaction is completed, the reaction solution is evaporated to remove the solvent, and the obtained residue is purified by silica gel column chromatography with dichloromethane as the eluent to obtain compound 3-2.

[0098] 20 g of compound 3-2 and 40 g of ferrous chloride solid were mixed and dissolved in 40 g of DMSO, and stirred at room temperature for 0.5 h to precipitate flocculent solids, which were filtered and washed to obtain the iron ion ligand catalyst Cat-3.

[0099] Elemental analysis: C 77.30%, H 5.56%, Fe 8.56%, N 8.59% (measured values).

[0100] H-NMR spectrum analysis: 1 H NMR (400 MHz, CDCl 3 )δ0.90(6H), 1.65(4H), 2.62(4H), 7.16(2H), 7.28(2H), 7.42(4H), 7.4 9(4H), 7.63(4H), 7.86(2H), 7.92(4H), 8.21(2H), 8.51(2H), 8.92(2H).

[0101] 2. Catalyst performance evaluation

[0102] Take 0.2g Cat-3 and 100g reaction raw materials (anisole: 50% hydrogen peroxide: acetone = 1: 0.2: 0.5, mass ratio) and mix, react at 50 ℃ for 10h before stopping the reaction, take the reaction solution for liquid chromatography analysis and titration analysis, the hydrogen peroxide conversion rate is greater than 99%, the total selectivity of hydroxyanisole is greater than 95.8%, and p-hydroxyanisole / o-hydroxyanisole = 3.44 (molar ratio).

[0103] Comparative Example

[0104] 0.2 g of ferrocene was mixed with 100 g of reaction raw materials (anisole: 50% hydrogen peroxide: acetone = 1: 0.2: 0.5, mass ratio), and the reaction was stopped after reacting at 50 ° C for 10 hours. The reaction solution was subjected to liquid chromatography analysis and titration analysis. The hydrogen peroxide conversion rate was about 95%, the total selectivity of hydroxyanisole was about 85.3%, and p-hydroxyanisole / o-hydroxyanisole = 2.58 (molar ratio).

[0105] It can be seen from the comparative examples that, compared with ferrocene, the iron complex of the present invention has better catalytic performance due to the large-volume biisoquinoline ligand structure, the product yield is higher, and the selectivity of the p-hydroxyanisole product is significantly improved.

[0106] Unless otherwise defined, the terms used in the present invention have the meanings commonly understood by those skilled in the art.

[0107] The embodiments described in the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Those skilled in the art may make various other substitutions, changes and improvements within the scope of the present invention. Therefore, the present invention is not limited to the above embodiments, but is only limited by the claims.

Claims

1. An iron complex based on biisoquinoline, characterized in that: The iron complex has a structure shown in formula (I): Here, R is the same or different and each independently represents hydrogen, C1-C6 alkyl, C1-C6 alkoxy or C3-C8 cycloalkyl.

2. The iron complex according to claim 1, characterized in that The R are the same or different, and each independently represents hydrogen, C1-C4 alkyl or C1-C4 alkoxy, preferably hydrogen, methyl, ethyl, n-propyl or isopropyl; Preferably, the iron complex is the following compound:

3. The method for preparing the biisoquinoline-based iron complex according to claim 1 or 2, characterized in that: The following steps are involved: S1: an isoquinoline derivative of the structure shown in formula (I-1) reacts with an alkyltin chloride reagent to obtain a first intermediate of the structure shown in formula (I-2); S2: The first intermediate reacts with a halogenated isoquinoline of formula (I-3) to obtain a second intermediate of formula (I-4); S3: The second intermediate contains Fe 2+ The iron source is reacted to obtain the diisoquinoline-based iron complex; Wherein, R1 represents a C1-C6 alkyl group, preferably a methyl group, an ethyl group, a n-propyl group, an isopropyl group or a tert-butyl group; X represents a halogen atom, preferably a Br group; R are the same or different, and are each independently defined as in claim 1 or 2.

4. The preparation method according to claim 3, characterized in that: The iron source is one or more of ferrous sulfate, ferrous nitrate, ferrous chloride, and ferrous hydroxide; Preferably, the mass ratio of the second intermediate to the iron source is 1:1-6, preferably 1:2-4.

5. The preparation method according to claim 3 or 4, characterized in that: In the step S1, the isoquinoline derivative and the alkyltin chloride reagent are reacted in the presence of a butyl lithium catalyst in a first organic solvent, preferably at a reaction temperature of 20 to 100° C., preferably 30 to 60° C.; Preferably, the alkyl tin chloride reagent is trimethyltin chloride, and more preferably, the mass ratio of the isoquinoline derivative to trimethyltin chloride is 1:0.4-2, preferably 1:0.6-1.5; Preferably, the mass ratio of the isoquinoline derivative to the butyl lithium catalyst is 1:0.05-0.8, preferably 1:0.1-0.4; Preferably, the first organic solvent is one or more of toluene, ethylbenzene, tetrahydrofuran, N,N-dimethylformamide, and diethyl ether. More preferably, the mass ratio of the isoquinoline derivative to the first organic solvent is 1:2-10, preferably 1:3-8.

6. The preparation method according to any one of claims 3 to 5, characterized in that: In the step S2, the first intermediate reacts with halogenated isoquinoline in a second organic solvent, preferably at a reaction temperature of 60 to 200° C., preferably 60 to 120° C.; Preferably, the halogenated isoquinoline is 2-bromoisoquinoline, and more preferably, the mass ratio of the first intermediate to 2-bromoisoquinoline is 1:1 to 3, preferably 1:1 to 1.5; Preferably, the second organic solvent is one or more of toluene, chloroform, dichloromethane, tetrahydrofuran, and more preferably, the mass ratio of the first intermediate to the second organic solvent is 1:2-10, preferably 1:4-6.

7. The preparation method according to any one of claims 3 to 6, characterized in that: In step S3, the second intermediate is reacted with a Fe 2+ The iron source is reacted in a third organic solvent, preferably, the reaction temperature is 10 to 80° C., preferably 20 to 40° C.; Preferably, the third organic solvent is one or more of N,N-dimethylformamide, dimethyl sulfoxide, methanol, and acetonitrile. More preferably, the mass ratio of the third intermediate to the second organic solvent is 1:1-10, preferably 1:2-4.

8. Use of the diisoquinoline-based iron complex according to claim 1 or 2 as a catalyst for the hydroxylation reaction of anisole; Preferably, the anisole hydroxylation reaction is a hydroxylation reaction in which anisole reacts with an oxidant to prepare p-hydroxyanisole and co-produce o-hydroxyanisole; More preferably, the oxidant is hydrogen peroxide with a mass concentration of 20 to 60%.

9. A method for preparing p-hydroxyanisole and co-producing o-hydroxyanisole, characterized in that: In the presence of a catalyst, anisole and an oxidant undergo a hydroxylation reaction to prepare p-hydroxyanisole and co-produce o-hydroxyanisole, wherein the catalyst is the diisoquinoline-based iron complex according to claim 1 or 2; Preferably, the amount of the catalyst used is 0.1-1.5% of anisole, preferably 0.2-0.8%, by mass percentage.

10. The method according to claim 9, characterized in that The oxidant is hydrogen peroxide with a mass concentration of 20 to 60%; Preferably, the hydroxylation reaction is carried out in a reaction solvent, more preferably, the reaction solvent is one or more of acetone, methanol, water, and ethanol, and the mass ratio of anisole to the reaction solvent is 1:0.5-5, preferably 1:0.5-1.5; More preferably, the reaction temperature of the hydroxylation reaction is 50-80° C., and the reaction pressure is normal pressure.

Images