A pyrazole phosphine ligand compound, preparation method and application thereof

Abstract

The application provides a pyrazine phosphine ligand compound, a preparation method and application, and relates to the technical field of catalysts. The raw material of the preparation method is subjected to a lithiation reaction, and then is reacted with different monochlorophosphine compounds to generate corresponding pyrazine phosphine ligand compounds. The preparation method is simple, has few separation steps, has high yield, and is suitable for industrial production. The application also relates to a series of pyrazine phosphine ligand compounds as ligands, which are combined with metal centers to form a catalytic system, and are used for catalyzing olefin hydroformylation, hydrocarboxylation and hydrocyanation. In particular, for the ethylene alkoxycarbonylation reaction for preparing methyl propionate, the catalytic system has good activity and selectivity.

Description

Technical Field

[0001] This invention relates to the field of catalysts, specifically to a pyrazine phosphine ligand compound, its preparation method, and its application. In particular, it relates to the design of a pyrazine phosphine ligand compound, its preparation method, and its application in the preparation of catalysts for olefin alkoxycarbonylation, olefin hydroformylation, hydrocarboxylation, or hydrocyanation reactions. Background Technology

[0002] Phosphine ligands are important catalyst ligands, widely used in transition metal catalysts and as curing accelerators for epoxy resins. For example, bisphosphine ligands such as Xphos, Sphos, and Ruphos catalyze the Suzuki coupling reaction in catalytic systems composed of palladium and rhodium. 2,2'-bisdiphenylphosphinemethyl-1,1'-biphenyl and its derivatives are catalyst ligands exhibiting good activity and selectivity in hydroformylation reactions. Currently, the most mature catalytic system for industrial olefin carbonylation is the 1,2-bis(di-tert-butylphosphine)benzene / palladium catalytic system from the Whiston research group. Its application is described in patents WO 96 / 19434, EPA04489472, and EPA0499329. Compared to traditional triphenylphosphine-modified palladium catalysts, it exhibits better catalytic performance due to its electron-rich and sterically hindered bidentate phosphine ligands (described in Chem. Commun. 2004, 1720-1721). Its greatest advantage is its ability to efficiently catalyze the alkoxycarbonylation of ethylene under relatively mild reaction conditions. (EPA04489472, EPA0499329, EPA0495547, US2005085671A1, US6284919B1, US2001051745A1, US6476255B1).

[0003] Currently, most reported organophosphorus ligands exhibiting good activity and selectivity in the catalytic alkoxycarbonylation of olefins have benzene ring skeletons, and highly efficient ligands for alkoxycarbonylation of olefins are scarce. The DTBPX ligand used by Lucent Technologies has been extensively researched and patented; using foreign catalysts and processes requires paying high patent fees and process package transfer fees. Furthermore, DTBPX ligands suffer from poor stability, are prone to hydrolysis and acid degradation, and are easily clogged in pipelines, necessitating the periodic addition of ligands to maintain catalytic activity.

[0004] This invention provides a novel pyrazine-based phosphine ligand compound, its preparation method, and its applications. Compared to DTBPX ligands, the novel pyrazine-based phosphine ligand compound and its preparation method developed in this invention are characterized by ease of synthesis and scale-up capability, high yield, good reactivity, and resistance to decomposition. Furthermore, preliminary industrial-scale studies and comparisons with DTBPX and other phosphine ligands demonstrate that the novel pyrazine-based phosphine ligand compound developed in this invention can achieve highly active and selective alkoxycarbonylation of olefins, showing great potential and practical value for the future development of alkoxycarbonylation reactions in olefins.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] One objective of this invention is to provide a pyrazine-based phosphine ligand compound. The ligand can be a monophosphine, bisphosphine, or polyphosphine compound with a novel structure, allowing for control of ligand electronic effects and steric hindrance.

[0007] A second objective of this invention is to provide a method for preparing pyrazine phosphine ligand compounds. This method is simple, environmentally friendly, involves few synthesis and separation steps, and has high production efficiency, making it suitable for industrial production.

[0008] A third objective of this invention is to provide the application of a pyrazine-based phosphine ligand compound in the preparation of catalysts for olefin alkoxycarbonylation, olefin hydroformylation, hydrocarboxylation, or hydrocyanation reactions. This compound, acting as a ligand, complexes with a metal center to form a catalytic system, exhibiting particularly high activity and product selectivity as a highly efficient catalyst for olefin alkoxycarbonylation reactions.

[0009] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0010] In a first aspect, the present invention provides a pyrazine phosphine ligand compound, wherein the structural formula of the pyrazine phosphine ligand compound comprises any one of the following formulas I to IV:

[0011]

[0012] in,

[0013] R1 and R2 are each independently selected from any one of substituted or unsubstituted alkyl, substituted or unsubstituted silyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted aryl, or substituted or unsubstituted heteroaryl.

[0014] R3, R4 and R5 are each independently selected from any one of hydrogen, substituted or unsubstituted alkyl, halogen or nitro;

[0015] Y is selected from

[0016] Preferably, R1 and R2 are each independently selected from any one of substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C3-C12 silyl, substituted or unsubstituted C3-C12 cycloalkyl, substituted or unsubstituted C6-C12 aryl, or substituted or unsubstituted C3-C12 heteroaryl.

[0017] Preferably, R1 and R2 are each independently selected from any one of isopropyl, tert-butyl, n-butyl, dimethyltert-butylsilyl, triisopropylsilyl, cyclohexyl, adamantyl, phenyl, pyridyl, N-methylpyrroleyl, N-methylimidazolyl, quinolinyl, furanyl, or thiofuranyl.

[0018] Preferably, R3, R4 and R5 are each independently selected from any one of hydrogen, unsubstituted C1-C4 alkyl, halogen or nitro.

[0019] Preferably, the pyrazine phosphine ligand compound includes any one of the following compounds L1 to L8:

[0020]

[0021] In a second aspect, the present invention provides a method for preparing pyrazine phosphine ligand compounds as described in the first aspect, the method comprising the following steps:

[0022] (1) Pyrazine compounds, N,N,N,N-tetramethylethylenediamine, basic salts and n-butyllithium react to give pyrazine metal salts;

[0023] (2) The pyrazine metal salt and the monochlorophosphine compound react to obtain the pyrazine phosphine ligand compound.

[0024] Preferably, in step (1), the pyrazine compound has the following structural formula A:

[0025]

[0026] R1', R2', R3 and R4 are each independently selected from hydrogen or substituted or unsubstituted alkyl groups.

[0027] Preferably, in step (1), the alkaline salt is selected from sodium tert-butoxide and / or potassium tert-butoxide.

[0028] Preferably, in step (1), the molar ratio of the pyrazine compound, N,N,N,N-tetramethylethylenediamine, basic salt and n-butyllithium is 1:(1.5-4):(2-9):(2-9).

[0029] Preferably, in step (1), the reaction is carried out in an alkane solvent.

[0030] Preferably, the alkane solvent is heptane.

[0031] Preferably, in step (1), the reaction is carried out in the presence of a protective gas.

[0032] Preferably, the protective gas includes nitrogen and / or argon.

[0033] Preferably, in step (1), the reaction temperature is 0-5°C and the reaction time is 12-24h.

[0034] Preferably, in step (1), the specific steps of the reaction are as follows:

[0035] Under a protective gas atmosphere, pyrazine compounds, N,N,N,N-tetramethylethylenediamine, and basic salts are dissolved in an alkane solvent, cooled, and then an alkane solution of n-butyllithium is added dropwise to carry out the reaction, yielding a reaction solution.

[0036] Preferably, in step (1), the following post-processing steps are further included after the reaction is completed.

[0037] The reaction solution was filtered, washed, and dried sequentially to obtain the pyrazine metal salt.

[0038] Preferably, the structural formula of the monochlorophosphine compound is shown in Formula B below:

[0039]

[0040] R1 and R2 are each independently selected from any one of substituted or unsubstituted alkyl, substituted or unsubstituted silyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted aryl, or substituted or unsubstituted heteroaryl.

[0041] Preferably, in step (2), the molar ratio of the pyrazine metal salt and the monochlorophosphine compound is 1:(2-9), and more preferably 1:2.

[0042] Preferably, in step (2), the reaction is carried out in an alkane solvent and / or an ether solvent.

[0043] Preferably, the alkane solvent is hexane.

[0044] Preferably, the ether solvent is methyl tert-butyl ether.

[0045] Preferably, in step (2), the reaction temperature is 0–30°C and the reaction time is 12–20 h.

[0046] Preferably, in step (2), the specific steps of the reaction are as follows:

[0047] Pyrazine metal salts are dissolved in alkane solvents and / or ether solvents, cooled, and then monochlorophosphine compounds are added dropwise to carry out the reaction, resulting in a reaction solution.

[0048] Preferably, the temperature at which the monochlorophosphine compound is added is below 5°C.

[0049] Preferably, in step (2), after the reaction is completed, the following post-processing steps are further included:

[0050] The reaction solution was quenched with water, and then the mixture was separated, the organic phase was dried, and the solvent was removed under vacuum to obtain a crude product. The crude product was then pulped and filtered to obtain the pyrazine phosphine ligand compound.

[0051] Thirdly, the present invention provides the use of pyrazine phosphine ligand compounds as described in the first aspect in the preparation of catalysts for olefin alkoxycarbonylation, olefin hydroformylation, hydrocarboxylation, or hydrocyanation reactions.

[0052] Fourthly, the present invention provides a composite catalyst, the composite catalyst comprising a coordinating metal center and the pyrazine phosphine ligand compound described in the first aspect;

[0053] The coordinating metal center includes any one or a combination of at least two of iron, cobalt, nickel, ruthenium, rhodium, iridium, or palladium.

[0054] Preferably, the raw materials for preparing the composite catalyst include: the pyrazine phosphine ligand compound, the metal precursor, and the acidic auxiliaries.

[0055] Preferably, the metal precursor is selected from any one or a combination of at least two of iron-containing compounds, cobalt-containing compounds, nickel-containing compounds, ruthenium-containing compounds, rhodium-containing compounds, iridium-containing compounds, or palladium-containing compounds, preferably cobalt-containing compounds and / or palladium-containing compounds, and more preferably palladium-containing compounds.

[0056] Preferably, the palladium-containing compound is selected from any one or a combination of at least two of palladium chloride, palladium acetate, palladium acetylacetonate, or palladium dibenzylidene acetone.

[0057] Preferably, the acidic additive includes any one or a combination of at least two of methanesulfonic acid, trifluoroacetic acid, or p-toluenesulfonic acid, with p-toluenesulfonic acid being the most preferred.

[0058] Preferably, the molar ratio of the metal precursor, the pyrazine phosphine ligand compound, and the acidic auxiliaries is 1:(1-8):(0.5-1.2).

[0059] Preferably, the raw materials for preparing the composite catalyst also include a solvent.

[0060] Preferably, the solvent is methanol.

[0061] Fifthly, the present invention provides a method for alkoxycarbonylation of olefins, the method comprising the following steps:

[0062] In the presence of the composite catalyst described in the fourth aspect, olefins, carbon monoxide, and / or methanol undergo an alkoxycarbonylation reaction to yield the alkoxycarbonylated product of the olefin. (Methanol can be used as a reactant and / or as a reaction solvent.)

[0063] Preferably, the olefin is selected from any one or a combination of at least two of substituted or unsubstituted C2 to C20 olefins, preferably any one or a combination of at least two of ethylene, propylene, butene or n-hexene, preferably ethylene.

[0064] Preferably, in the alkoxycarbonylation reaction system, the concentration of the pyrazine phosphine ligand compound in the composite catalyst is 500–2500 ppm, more preferably 700–1500 ppm.

[0065] Preferably, the molar ratio of the olefin to carbon monoxide is (1-2):1.

[0066] Preferably, the temperature of the alkoxycarbonylation reaction is 70–110°C, and the pressure of the alkoxycarbonylation reaction is 1.0–2.5 MPa.

[0067]

Terminology Explanation

[0068] The various aspects and features of the present invention will be further described below.

[0069] The various terms and phrases used in this invention have their general meanings known to those skilled in the art. Nevertheless, this invention still aims to provide a more detailed explanation and interpretation of these terms and phrases. In the event of any inconsistency between the mentioned terms and their known meanings and the meanings expressed in this invention, the meanings shall prevail. Below are definitions of various terms used in this invention. These definitions apply to all terms used throughout this specification, unless otherwise specified in the specific context.

[0070] As mentioned in this invention, the terms “halogen,” “halogen,” “halogen atom,” “halogenated,” etc., refer to fluorine, chlorine, bromine, or iodine, and in particular to fluorine, chlorine, or bromine.

[0071] As mentioned in this invention, the term "alkyl" refers to an alkyl group having a specified number of carbon atoms, which can be a straight-chain alkyl group or a branched alkyl group. For example, when "C1-C12 alkyl" is mentioned, it refers to a straight-chain alkyl group or a branched alkyl group having 1 to 12 carbon atoms. Specific groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, neopentyl, n-hexyl, n-heptyl, n-octyl, and similar groups.

[0072] As mentioned in this invention, the term "silyl" encompasses the aforementioned alkyl-substituted silicon groups. For example, when "C3-C12 silyl" is mentioned, it refers to an alkyl-substituted silicon group with 3 to 12 carbon atoms. Specific groups include trimethylsilyl, triethylsilyl, methyldiethylsilyl, ethyldimethylsilyl, tripropylsilyl, tributylsilyl, triisopropylsilyl, methyldiisopropylsilyl, dimethyltert-butylsilyl, and similar groups.

[0073] As mentioned in this invention, the term "cycloalkyl" refers to a cyclic alkyl group having a specified number of cyclic carbon atoms. For example, when "C3-C12 cycloalkyl" is mentioned, it refers to a cycloalkyl group having 3 to 12 carbon atoms. Specific groups include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, adamantyl, and similar groups.

[0074] As used in this invention, the term "aryl" refers to a monocyclic or polycyclic aromatic hydrocarbon (e.g., having 2, 3, or 4 fused rings), such as phenyl, naphthyl, anthracene, phenanthryl, indene, and similar groups.

[0075] As used in this invention, the term "heteroaryl" refers to an aromatic heterocycle having at least one heteroatom ring member such as O, N, or S. Heteroaryl groups include monocyclic or polycyclic ring systems (such as those having 2, 3, or 4 fused rings). Any N atom cyclic in the heterocyclic group can also be oxidized to form an N-oxide. Examples of preferred "heteroaryl" groups include, but are not limited to: pyridinyl, pyrimidinyl, pyrazinyl, pyridazinyl, triazinyl, furanyl, thiofuranyl, thiopheneyl, imidazolyl, N-methylimidazolyl, triazolyl, tetrazolyl, thiazolyl, isothiazolyl, 1,2,4-thiadiazolyl, pyrroleyl, N-methylpyrroleyl, pyrazolyl, oxazolyl, isoxazolyl, oxadiazolyl, benzofuranyl, benzothiopheneyl, benzothiazolyl, indolyl, inazolyl, quinolinyl, isoquinolinyl, purineyl, carbazolyl, benzimidazolyl, pyrrolopyridinyl, pyrrolopyrimidinyl, pyrazolopyridinyl, pyrazolopyrimidinyl, and similar groups.

[0076] As used herein, the term "compound" means, as is used herein, all stereoisomers, geometric isomers, tautomers, and isotopes.

[0077] Compared with the prior art, the present invention has the following beneficial effects:

[0078] (1) The phosphine ligand compounds of the present invention, using substituted pyrazine as the initial raw material, can be obtained by lithiation reaction and metathesis reaction to obtain pyrazine-type monophosphine, bisphosphine or polyphosphine compounds with novel structure and controllable ligand electronic effect and steric hindrance.

[0079] (2) The preparation method of the pyrazine-type phosphine ligand compound of the present invention has a simple synthetic route, high economic efficiency, few separation steps, and good environmental performance, and is suitable for industrial production.

[0080] (3) The application of the pyrazine-type phosphine ligand compound of the present invention in olefin catalytic reactions, wherein the compound, as a ligand, complexes with the metal center to form a catalytic system, catalyzing the hydroformylation, alkoxycarbonylation and hydrocyanation of olefins. Attached Figure Description

[0081] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0082] Figure 1 A diagram of the continuous reaction apparatus for ethylene alkoxycarbonylation provided by the present invention. Detailed Implementation

[0083] Unless otherwise defined herein, scientific and process terms used in conjunction with this invention should have the meanings commonly understood by one of ordinary skill in the art. The meaning and scope of terms should be clear; however, in any case of potential ambiguity, the definitions provided herein take precedence over any dictionary or foreign definitions. In this application, unless otherwise stated, the use of "or" means "and / or". Furthermore, the use of the term "comprising" and other forms is non-limiting.

[0084] It should be noted that specific details are set forth in the following description to provide a full understanding of the invention. However, the invention can be practiced in many ways other than those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0085] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0086] In a first aspect, the present invention provides a pyrazine phosphine ligand compound, wherein the structural formula of the pyrazine phosphine ligand compound comprises any one of the following formulas I to IV:

[0087]

[0088] in,

[0089] R1 and R2 are each independently selected from any one of substituted or unsubstituted alkyl, substituted or unsubstituted silyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted aryl, or substituted or unsubstituted heteroaryl.

[0090] R3, R4 and R5 are each independently selected from any one of hydrogen, substituted or unsubstituted alkyl, halogen or nitro;

[0091] Y is selected from

[0092] As an optional implementation, R1 and R2 are each independently selected from any one of substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C3-C12 silyl, substituted or unsubstituted C3-C12 cycloalkyl, substituted or unsubstituted C6-C12 aryl, or substituted or unsubstituted C3-C12 heteroaryl.

[0093] As an optional implementation, R1 and R2 are each independently selected from any one of isopropyl, tert-butyl, n-butyl, dimethyltert-butylsilyl, triisopropylsilyl, cyclohexyl, adamantyl, phenyl, pyridyl, N-methylpyrroleyl, N-methylimidazolyl, quinolinyl, furanyl, or thiofuranyl.

[0094] As an optional implementation, R3, R4 and R5 are each independently selected from any one of hydrogen, unsubstituted C1-C4 alkyl, halogen or nitro.

[0095] As an optional implementation, the pyrazine phosphine ligand compound includes any one of the following compounds L1 to L8:

[0096]

[0097] In a second aspect, the present invention provides a method for preparing pyrazine phosphine ligand compounds as described in the first aspect, the method comprising the following steps:

[0098] (1) Pyrazine compounds, N,N,N,N-tetramethylethylenediamine, basic salts and n-butyllithium react to give pyrazine metal salts;

[0099] (2) The pyrazine metal salt and the monochlorophosphine compound react to obtain the pyrazine phosphine ligand compound.

[0100] As an optional implementation, in step (1), the pyrazine compound has the following structural formula A:

[0101]

[0102] R1', R2', R3 and R4 are each independently selected from hydrogen or substituted or unsubstituted alkyl groups.

[0103] As an optional implementation, in step (1), the alkaline salt is selected from sodium tert-butoxide and / or potassium tert-butoxide.

[0104] As an optional implementation, in step (1), the molar ratio of the pyrazine compound, N,N,N,N-tetramethylethylenediamine, basic salt and n-butyllithium is 1:(1.5-4):(2-9):(2-9);

[0105] Among them, "1.5~4" can be, for example, 1.5, 2, 2.5, 3, 3.5, 4, etc.;

[0106] The first "2-9" can be, for example, 2, 3, 4, 5, 6, 7, 8, 9, etc.

[0107] The second "2-9" can be, for example, 2, 3, 4, 5, 6, 7, 8, 9, etc.

[0108] As an optional implementation, in step (1), the reaction is carried out in an alkane solvent.

[0109] As an optional implementation, in step (1), the alkane solvent is heptane.

[0110] As an optional implementation, in step (1), the reaction is carried out in the presence of a protective gas.

[0111] As an optional implementation, in step (1), the protective gas includes nitrogen and / or argon.

[0112] As an optional implementation, in step (1), the reaction temperature is 0 to 5°C, for example, 0°C, 1°C, 2°C, 3°C, 4°C, 5°C, etc., and the reaction time is 12 to 24 hours, for example, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours, 24 hours, 26 hours, 28 hours, 30 hours, etc.

[0113] As an optional implementation, in step (1), the specific steps of the reaction are as follows:

[0114] Under a protective gas atmosphere, pyrazine compounds, N,N,N,N-tetramethylethylenediamine, and basic salts are dissolved in an alkane solvent, cooled, and then an alkane solution of n-butyllithium is added dropwise to carry out the reaction, yielding a reaction solution.

[0115] As an optional implementation, step (1) further includes the following post-processing steps after the reaction is completed.

[0116] The reaction solution was filtered, washed, and dried sequentially to obtain the pyrazine metal salt.

[0117] As an optional implementation, the structural formula of the monochlorophosphine compound is shown in Formula B below:

[0118]

[0119] R1 and R2 are each independently selected from any one of substituted or unsubstituted alkyl, substituted or unsubstituted silyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted aryl, or substituted or unsubstituted heteroaryl.

[0120] As an optional implementation, in step (2), the molar ratio of the pyrazine metal salt and the monochlorophosphine compound is 1:(2-9), for example, it can be 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, etc., preferably 1:2.

[0121] As an optional implementation, in step (2), the reaction is carried out in an alkane solvent and / or an ether solvent.

[0122] As an optional implementation, in step (2), the alkane solvent is hexane.

[0123] As an optional implementation, in step (2), the ether solvent is methyl tert-butyl ether.

[0124] As an optional implementation, in step (2), the reaction temperature is 0 to 30°C, for example, it can be 0°C, 2°C, 4°C, 6°C, 8°C, 10°C, 12°C, 14°C, 16°C, 18°C, 20°C, 22°C, 24°C, 26°C, 28°C, 30°C, etc., and the reaction time is 12 to 20 hours, for example, it can be 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours, etc.

[0125] As an optional implementation, in step (2), the specific steps of the reaction are as follows:

[0126] Pyrazine metal salts are dissolved in alkane solvents and / or ether solvents, cooled, and then monochlorophosphine compounds are added dropwise to carry out the reaction, resulting in a reaction solution.

[0127] As an optional implementation, the temperature at which the monochlorophosphine compound is added is below 5°C, for example, it can be 5°C, 4°C, 3°C, 2°C, 1°C, 0°C, -1°C, -2°C, -3°C, -4°C, -5°C, etc.

[0128] As an optional implementation, step (2) further includes the following post-processing steps after the reaction is completed:

[0129] The reaction solution was quenched with water, and then the mixture was separated, the organic phase was dried, and the solvent was removed under vacuum to obtain a crude product. The crude product was then pulped and filtered to obtain the pyrazine phosphine ligand compound.

[0130] Thirdly, the present invention provides the use of pyrazine phosphine ligand compounds as described in the first aspect in the preparation of catalysts for olefin alkoxycarbonylation, olefin hydroformylation, hydrocarboxylation, or hydrocyanation reactions.

[0131] Fourthly, the present invention provides a composite catalyst, the composite catalyst comprising a coordinating metal center and the pyrazine phosphine ligand compound described in the first aspect;

[0132] The coordinating metal center includes any one or a combination of at least two of iron, cobalt, nickel, ruthenium, rhodium, iridium, or palladium.

[0133] As an optional implementation, the raw materials for preparing the composite catalyst include: the pyrazine phosphine ligand compound, the metal precursor, and the acidic auxiliaries.

[0134] As an optional implementation, the metal precursor is selected from any one or a combination of at least two of iron-containing compounds, cobalt-containing compounds, nickel-containing compounds, ruthenium-containing compounds, rhodium-containing compounds, iridium-containing compounds, or palladium-containing compounds, preferably cobalt-containing compounds and / or palladium-containing compounds, and more preferably palladium-containing compounds.

[0135] As an optional implementation, the palladium-containing compound is selected from any one or a combination of at least two of palladium chloride, palladium acetate, palladium acetylacetonate, or palladium dibenzylidene acetone.

[0136] As an optional implementation, the acidic additive includes any one or a combination of at least two of methanesulfonic acid, trifluoroacetic acid, or p-toluenesulfonic acid, preferably p-toluenesulfonic acid.

[0137] As an optional implementation, the molar ratio of the metal precursor, pyrazine phosphine ligand compound, and acidic auxiliaries is 1:(1-8):(0.5-1.2);

[0138] Among them, "1 to 8" can be, for example, 1, 2, 3, 4, 5, 6, 7, 8, etc.;

[0139] Among them, "0.5~1.2" can be, for example, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, etc.

[0140] As an optional implementation, the raw materials for preparing the composite catalyst also include a solvent.

[0141] As an optional implementation, the solvent is methanol.

[0142] Fifthly, the present invention provides a method for alkoxycarbonylation of olefins, the method comprising the following steps:

[0143] In the presence of the composite catalyst described in the fourth aspect, olefins, carbon monoxide, and / or methanol undergo an alkoxycarbonylation reaction to yield alkoxycarbonylated olefin products. (Where methanol is used as a ligand solvent and / or as a reactant.)

[0144] As an optional implementation, the present invention provides an application based on a novel pyrazine phosphine ligand compound. The method involves dissolving a metal precursor and the novel pyrazine phosphine ligand compound in a solvent in a certain proportion to prepare a metal / pyrazine phosphine ligand catalytic system. The prepared catalytic system undergoes a highly active and selective reaction with a certain proportion of olefins, carbon monoxide, and methanol under certain temperature and pressure.

[0145] As an optional embodiment, the olefin is selected from any one or a combination of at least two of substituted or unsubstituted C2 to C20 olefins, preferably any one or a combination of at least two of ethylene, propylene, butene or n-hexene, preferably ethylene.

[0146] As an optional embodiment, in the alkoxycarbonylation reaction system, the concentration of the pyrazine phosphine ligand compound in the composite catalyst is 500 to 2500 ppm, for example, it can be 500 ppm, 600 ppm, 800 ppm, 1000 ppm, 1200 ppm, 1400 ppm, 1500 ppm, 1600 ppm, 1800 ppm, 2000 ppm, 2200 ppm, 2400 ppm, 2500 ppm, etc., preferably 700 to 1500 ppm.

[0147] As an optional implementation, the temperature of the alkoxycarbonylation reaction is 70–110°C, for example, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, etc., and the pressure of the alkoxycarbonylation reaction is 1.0–2.5 MPa, for example, 1.0 MPa, 1.2 MPa, 1.4 MPa, 1.6 MPa, 1.8 MPa, 2 MPa, 2.2 MPa, 2.4 MPa, 2.5 MPa, etc.

[0148] In this invention, the olefin alkoxycarbonylation method can be carried out intermittently or continuously. In the continuous industrial method, a pre-prepared metal catalyst, pyrazinephosphine ligand, acidic auxiliaries, and reaction solvents are added to a reactor to initiate the continuous synthesis process. After heating to the desired reaction temperature, olefins, carbon monoxide, and methanol are introduced into the reaction mixture continuously or intermittently. The reactor effluent contains carbonylation products, metal / pyrazinephosphine ligands, acidic auxiliaries, unreacted olefins, carbon monoxide, and reaction solvents, and can be discharged from the reactor to an evaporator / separator. By reducing pressure, the gaseous reactants carbon monoxide and olefins are separated from the mixture, while the carbonylation products can be collected by molecular distillation. The remaining metal / pyrazinephosphine ligand-containing catalyst and all unseparated byproducts are recycled back to the reactor and reused in the method of this invention.

[0149] In this invention, the concentration of the novel pyrazine phosphine ligand needs to be monitored periodically or continuously for the continuously operating reaction system. If the concentration is found to be lower than the specified value, the compound may be lost due to degradation or other reasons. In this case, the novel pyrazine phosphine ligand compound is added to the mixture of the reaction system.

[0150] In this invention, the pyrazine phosphine ligand compounds are also suitable for hydroformylation, hydrocarboxylation, and hydrocyanation reactions.

[0151] The present invention will be further illustrated by the following examples. Unless otherwise specified, the materials in the examples are prepared according to existing methods or purchased directly from the market.

[0152] Example 1

[0153] This embodiment provides a pyrazine phosphine ligand compound, wherein the pyrazine phosphine ligand compound is the following pyrazine phosphine ligand compound L1:

[0154]

[0155] The synthetic route for the pyrazine phosphine ligand compound L1 is shown below:

[0156]

[0157] The preparation method of the pyrazine phosphine ligand compound L1 is as follows:

[0158] (1) Under a nitrogen or argon atmosphere, 2-dimethylpyrazine (9.4 g, 0.1 mol), N,N,N,N-tetramethylethylenediamine (23.2 g, 0.2 mol), sodium tert-butoxide (19.2 g, 0.4 mol), and heptane (200 mL) were added to a reactor and stirred. The mixture was cooled to 5 °C, and a hexane solution of n-butyllithium (68 mL, 1.6 M, 0.11 mol) was added dropwise. The mixture was reacted for 12 h, filtered, washed, and dried to obtain the pyrazine metal salt.

[0159] (2) Add pyrazine metal salt to the reactor, add hexane (200 mL), cool down to 5 °C, add di-tert-butylphosphine chloride (19.8 g, 0.11 mol) dropwise, and after the addition is complete, restore to room temperature and react for 24 h. A white substance is generated. Add degassed water to quench the reaction, separate the liquids, dry the hexane phase, filter, remove the solvent under vacuum to obtain the crude product, slurry with cold methanol, filter to obtain the product, yield (19.1 g, 80%).

[0160] The proton NMR spectra of the obtained product are as follows:

[0161] 1 HNMR (C6D6, 400MHz, 298K) δ, ppm: 8.51 (s, 2H, CH on pyrazine), 8.45 (s, H, CH on pyrazine), 3.02 (s, 6H, C6H6,), 1.06 (s, 18H, C (CH3) 3).

[0162] Example 2

[0163] This embodiment provides a pyrazine phosphine ligand compound, wherein the pyrazine phosphine ligand compound is the following pyrazine phosphine ligand compound L2:

[0164]

[0165] The synthetic route for the pyrazine phosphine ligand compound L2 is shown below:

[0166]

[0167] The preparation method of the pyrazine phosphine ligand compound L2 is as follows:

[0168] (1) Under a nitrogen or argon atmosphere, 2-dimethylpyrazine (9.4 g, 0.1 mol), N,N,N,N-tetramethylethylenediamine (23.2 g, 0.2 mol), sodium tert-butoxide (19.2 g, 0.4 mol), and heptane (200 mL) were added to a reactor and stirred. The mixture was cooled to 5 °C, and a hexane solution of n-butyllithium (68 mL, 1.6 M, 0.11 mol) was added dropwise. The mixture was reacted for 12 h, filtered, washed, and dried to obtain the pyrazine metal salt.

[0169] (2) Add pyrazine metal salt to the reactor, add hexane (200 mL), cool down to 5 °C, add diphenylphosphine chloride (26.5 g, 0.12 mol) dropwise, after the addition is complete, restore to room temperature and react for 24 h. A white substance is generated. Add degassed water to quench the reaction, separate the liquids, dry the hexane phase, filter, remove the solvent under vacuum to obtain the crude product, slurry with cold methanol, filter to obtain the product, yield (18 g, 78%).

[0170] The proton NMR spectra of the obtained product are as follows:

[0171] 1 HNMR (C6D6, 400MHz, 298K) δ, ppm: 8.52 (s, 2H, CH on pyrazine), 8.47 (s, H, CH on pyrazine), 7.45 (s, 6H, C6H6,) 7.08 (s, 4H, C6H6), 3.02 (s, 2H, CH2).

[0172] Example 3

[0173] This embodiment provides a pyrazine phosphine ligand compound, wherein the pyrazine phosphine ligand compound is the following pyrazine phosphine ligand compound L3:

[0174]

[0175] The synthetic route for the pyrazine phosphine ligand compound L3 is shown below:

[0176]

[0177] The preparation method of the pyrazine phosphine ligand compound L3 is as follows:

[0178] (1) Under a nitrogen or argon atmosphere, 2,3-dimethylpyrazine (10.8 g, 0.1 mol), N,N,N,N-tetramethylethylenediamine (34.8 g, 0.3 mol), sodium tert-butoxide (28.8 g, 0.6 mol), and heptane (200 mL) were added to a reactor and stirred. The mixture was cooled to 5 °C, and a hexane solution of n-butyllithium (136 mL, 1.6 M, 0.2 mol) was added dropwise. The reaction was carried out for 12 h. After filtration, washing, and drying, the pyrazine metal salt was obtained.

[0179] (2) Add pyrazine metal salt to the reactor, add hexane (300 mL), cool down to 5 °C, add diphenylphosphine chloride (52.8 g, 0.22 mol) dropwise, and after the addition is complete, restore to room temperature and react for 24 h. A white substance is generated. Add degassed water to quench the reaction, separate the liquids, dry the hexane phase, filter, remove the solvent under vacuum to obtain the crude product, slurry with cold methanol, filter to obtain the product, yield (36.2 g, 76%).

[0180] The proton NMR spectra of the obtained product are as follows:

[0181] 1 HNMR (C6D6, 400MHz, 298K) δ, ppm: 8.50 (s, H, CH on pyrazine), 8.45 (s, H, CH on pyrazine), 7.43 (s, 12H, C6H6,) 7.06 (s, 8H, C6H6), 3.01 (s, 4H, CH2).

[0182] Example 4

[0183] This embodiment provides a pyrazine phosphine ligand compound, wherein the pyrazine phosphine ligand compound is the following pyrazine phosphine ligand compound L4:

[0184]

[0185] The synthetic route for the pyrazine phosphine ligand compound L4 is shown below:

[0186]

[0187] The preparation method of the pyrazine phosphine ligand compound L4 is as follows:

[0188] (1) Under a nitrogen or argon atmosphere, 2,3-dimethylpyrazine (10.8 g, 0.1 mol), N,N,N,N-tetramethylethylenediamine (34.8 g, 0.3 mol), sodium tert-butoxide (28.8 g, 0.6 mol), and heptane (300 mL) were added to a reactor and stirred. The mixture was cooled to 5 °C, and a hexane solution of n-butyllithium (136 mL, 1.6 M, 0.2 mol) was added dropwise. The mixture was reacted for 12 h, filtered, washed, and dried to obtain the pyrazine metal salt.

[0189] (2) Add pyrazine metal salt to the reactor, add hexane (350 mL), cool down to 5 °C, add tert-butylchloro(cyclohexyl)phosphine (45.3 g, 0.22 mol) dropwise, and after the addition is complete, restore to room temperature and react for 24 h. A white substance is generated. Add degassed water to quench the reaction, separate the liquids, dry the hexane phase, filter, remove the solvent under vacuum to obtain the crude product, slurry with cold methanol, filter to obtain the product, yield (32.7 g, 73%).

[0190] The proton NMR spectra of the obtained product are as follows:

[0191] 1 HNMR (C6D6, 400MHz, 298K) δ, ppm: 8.40 (s, 2H, CH on pyrazine), 3.01 (s, 4H, CH2), 1.61-1.30 (m, 20H, CH on cyclohexane), 1.05 (s, 18H, C (CH3)3).

[0192] Example 5

[0193] This embodiment provides a pyrazine phosphine ligand compound, wherein the pyrazine phosphine ligand compound is the following pyrazine phosphine ligand compound L5:

[0194]

[0195] The synthetic route for the pyrazine phosphine ligand compound L5 is shown below:

[0196]

[0197] The preparation method of the pyrazine phosphine ligand compound L5 is as follows:

[0198] (1) Under a nitrogen or argon atmosphere, 2,3,5-trimethylpyrazine (12.2 g, 0.1 mol), N,N,N,N-tetramethylethylenediamine (52.2 g, 0.45 mol), sodium tert-butoxide (43.2 g, 0.9 mol), and heptane (400 mL) were added to a reactor and stirred. The mixture was cooled to 5 °C, and a hexane solution of n-butyllithium (211 mL, 1.6 M, 0.31 mol) was added dropwise. The mixture was reacted for 12 h, filtered, washed, and dried to obtain the pyrazine metal salt.

[0199] (2) Add pyrazine metal salt to the reactor, add hexane (450 mL), cool down to 5 °C, add di-tert-butylphosphine chloride (61.2 g, 0.34 mol) dropwise, and after the addition is complete, restore to room temperature and react for 24 h. A white substance is generated. Add degassed water to quench the reaction, separate the liquids, dry the hexane phase, filter, remove the solvent under vacuum to obtain the crude product, slurry with cold methanol, filter to obtain the product, yield (42.5 g, 78%).

[0200] The proton NMR spectra of the obtained product are as follows:

[0201] 1 HNMR (C6D6, 400MHz, 298K) δ, ppm: 8.39 (s, H, CH on pyrazine), 3.01 (s, 6H, CH2), 1.03 (s, 18H, C (CH3) 3).

[0202] Example 6

[0203] This embodiment provides a pyrazine phosphine ligand compound, wherein the pyrazine phosphine ligand compound is the following pyrazine phosphine ligand compound L6:

[0204]

[0205] The synthetic route for the pyrazine phosphine ligand compound L6 is shown below:

[0206]

[0207] The preparation method of the pyrazine phosphine ligand compound L6 is as follows:

[0208] (1) Under a nitrogen or argon atmosphere, 2,3,5,6-tetramethylpyrazine (13.6 g, 0.1 mol), N,N,N,N-tetramethylethylenediamine (69.6 g, 0.6 mol), sodium tert-butoxide (57.6 g, 0.9 mol), and heptane (500 mL) were added to a reactor and stirred. The mixture was cooled to 5 °C, and a hexane solution of n-butyllithium (272 mL, 1.6 M, 0.41 mol) was added dropwise. The mixture was reacted for 12 h, filtered, washed, and dried to obtain the pyrazine metal salt.

[0209] (2) Add pyrazine metal salt to the reactor, add hexane (600 mL), cool down to 5 °C, add tert-butyl(phenyl)phosphine chloride (88 g, 0.44 mol) dropwise, and after the addition is complete, restore to room temperature and react for 24 h. A white substance is generated. Add degassed water to quench the reaction, separate the liquids, dry the hexane phase, filter, remove the solvent under vacuum to obtain the crude product, slurry with cold methanol, filter to obtain the product, yield (58.6 g, 76%).

[0210] The proton NMR spectra of the obtained product are as follows:

[0211] 1 HNMR (C6D6, 400MHz, 298K) δ, ppm: 7.46-7.40 (m, 8H, C6H6), 7.33-7.30 (m, 12H, C6H6), 3.02 (s, 8H, CH2), 1.02 (s, 36H, C(CH3)3).

[0212] Example 7

[0213] This embodiment provides a pyrazine phosphine ligand compound, wherein the pyrazine phosphine ligand compound is the following pyrazine phosphine ligand compound L7:

[0214]

[0215] The synthetic route for the pyrazine phosphine ligand compound L7 is shown below:

[0216]

[0217] The preparation method of the pyrazine phosphine ligand compound L7 is as follows:

[0218] (1) Under a nitrogen or argon atmosphere, 2,3,5,6-tetramethylpyrazine (13.6 g, 0.1 mol), N,N,N,N-tetramethylethylenediamine (69.6 g, 0.6 mol), sodium tert-butoxide (57.6 g, 0.9 mol), and heptane (500 mL) were added to a reactor and stirred. The mixture was cooled to 5 °C, and a hexane solution of n-butyllithium (272 mL, 1.6 M, 0.41 mol) was added dropwise. The mixture was reacted for 12 h, filtered, washed, and dried to obtain the pyrazine metal salt.

[0219] (2) Add pyrazine metal salt to the reactor, add hexane (550 mL), cool down to 5 °C, add tert-butylchloro(cyclohexyl)phosphine (88.58 g, 0.43 mol) dropwise, and after the addition is complete, restore to room temperature and react for 24 h. A white substance is generated. Add degassed water to quench the reaction, separate the liquids, dry the hexane phase, filter, remove the solvent under vacuum to obtain the crude product, slurry with cold methanol, filter to obtain the product, yield (58.8 g, 72%).

[0220] The proton NMR spectra of the obtained product are as follows:

[0221] 1 HNMR (C6D6, 400MHz, 298K) δ, ppm: 3.02 (s, 8H, CH2), 1.62-1.36 (m, 20H, CH oncyclohexane) 1.02 (s, 36H, C (CH3)3).

[0222] Example 8

[0223] This embodiment provides a pyrazine phosphine ligand compound, wherein the pyrazine phosphine ligand compound is the following pyrazine phosphine ligand compound L8:

[0224]

[0225] The synthetic route for the pyrazine phosphine ligand compound L8 is shown below:

[0226]

[0227] The preparation method of the pyrazine phosphine ligand compound L8 is as follows:

[0228] (1) Under a nitrogen or argon atmosphere, 2,3,5,6-tetramethylpyrazine (13.6 g, 0.1 mol), N,N,N-tetramethylethylenediamine (69.6 g, 0.6 mol), sodium tert-butoxide (57.6 g, 0.9 mol), and heptane (500 mL) were added to a reactor and stirred. The mixture was cooled to 5 °C, and a hexane solution of n-butyllithium (272 mL, 1.6 M, 0.41 mol) was added dropwise. The mixture was reacted for 12 h, filtered, washed, and dried to obtain the pyrazine metal salt.

[0229] (2) Add pyrazine metal salt to the reactor, add hexane (600 mL), cool down to 5 °C, add di-tert-butylphosphine chloride (81.1 g, 0.45 mol) dropwise, and after the addition is complete, restore to room temperature and react for 24 h. A white substance is generated. Add degassed water to quench the reaction, separate the liquids, dry the hexane phase, filter, remove the solvent under vacuum to obtain the crude product, slurry with cold methanol, filter to obtain the product, yield (55.5 g, 78%).

[0230] The proton NMR spectra of the obtained product are as follows:

[0231] 1 HNMR (C6D6, 400MHz, 298K) δ, ppm: 3.02(s,8H,CH),, 1.03(s,36H,C(CH3)3), 1.01(s,36H,C(CH3)3).

[0232] Comparative Example 1

[0233] This embodiment provides a phosphine ligand compound having the following structure:

[0234]

[0235] Comparative Example 2

[0236] This embodiment provides a phosphine ligand compound with the following structure:

[0237]

[0238] Test Example 1

[0239] Test samples: Pyrazine phosphine ligand compounds provided in Examples 1-8;

[0240] Test method:

[0241] (1) In a nitrogen atmosphere, add Pd(OAc)2 (29 mg, 0.16 mol%) and one of the novel pyrazine phosphine ligand compounds L1-L8 (0.38 mmol) specified in Table 1 to a 500 mL stainless steel autoclave equipped with a pressure gauge, along with 70 mL of anhydrous methanol and p-toluenesulfonic acid (0.227 g, 1.5 mol%), and replace the gas in the autoclave with nitrogen three times.

[0242] (2) Introduce a mixture of ethylene and CO (molar ratio 1:1) to a total pressure of 2.5 MPa. Heat to the required temperature (80°C) under magnetic stirring. Add gas several times during the reaction to maintain a total pressure of 2.5 MPa. After the specified reaction time, cool the reactor, vent the residual gas in a fume hood, open the reactor, weigh the product, and take a sample for gas chromatography (GC) analysis.

[0243] The test results are shown in Table 1 below:

[0244] Table 1

[0245]

[0246]

[0247] As shown in Table 1, the pyrazine phosphine ligand compounds provided in Examples 1-8, when used as catalysts, achieved an ethylene conversion rate of over 95% and a selectivity of over 99% in the alkoxycarbonylation reaction of olefins.

[0248] Test Example 2

[0249] Test sample: L3, a pyrazine phosphine ligand compound provided in Example 3;

[0250] Test method:

[0251] (1) Under a nitrogen atmosphere, a palladium source (0.13 mmol) and the specified pyrazine novel phosphine ligand compound L3 (0.38 mmol) were added to a 500 mL stainless steel autoclave equipped with a pressure gauge, along with 70 mL of anhydrous methanol (70 g) and p-toluenesulfonic acid (1.5 mol%).

[0252] (2) Replace the gas in the reactor with nitrogen three times, and introduce a mixture of ethylene and CO (1:1) until the total pressure is 2.5 MPa. Heat to the required temperature (80°C) under magnetic stirring. When the pressure in the reactor drops to 0.2 MPa during the reaction process, add gas and pressurize to 2.5 MPa. Repeat this process several times. After the reaction has been carried out for a specified time, cool the reactor, vent the residual gas in a fume hood, open the reactor, weigh the product, and take a sample for gas chromatography (GC) analysis.

[0253] The test results are shown in Table 2 below:

[0254] Table 2

[0255]

[0256]

[0257] As shown in Table 2, in the composite catalyst of the present invention, the metal precursor is preferably a palladium-containing compound, the initiation temperature of which is below 83°C, and the system activity and stability are above 3 times; among them, palladium chloride is the most preferred option, the initiation temperature of which can be reduced to below 70°C, and the system activity and stability are as high as 10 times or more.

[0258] Application Example 1

[0259] This application example provides an apparatus and a method for the ethylene alkoxycarbonylation reaction:

[0260] like Figure 1The diagram shows a continuous ethylene alkoxycarbonylation reaction apparatus. The feed tower, reactor, separator, and evaporator are purged with nitrogen. In the feed tower, Pd(OAc)₂ and a novel pyrazine phosphine ligand L₃ are dissolved in 10L of methanol, resulting in a Pd(II) concentration of 100 mg / L and a Pd / L₃ molar ratio of 1:4. This 10L solution is pumped through a pipeline into a 15L reactor; and the separator and evaporator are each maintained with 2L of solution. Ethylene, carbon monoxide, and methanol are supplied at 120 NL / h, 110 NL / h reactor, and 200 g / h, respectively. The reactor temperature is 80 ± 1℃, and the total gas pressure of ethylene and carbon monoxide is 2.5 ± 0.1 MPa. Ethylene, carbon monoxide, and methanol react under the catalysis of Pd / L3 to produce methyl propionate. The mixed solution containing the reaction products and catalyst flows from the reactor into a separator, where the pressure is reduced to 0.6 MPa, and the solution and a small amount of unreacted tail gas are discharged. The gas-liquid separated solution enters an evaporator for evaporation, distilling off some of the product, while the remaining product and the catalytic system are returned to the reactor to continue participating in the reaction.

[0261] The novel pyrazine phosphine ligand compound L3 was dissolved in methanol in a feed tower. The ligand concentration in the reactor was monitored at regular intervals. When the ligand concentration fell below 800 ppm, the feed tower was opened, and the novel pyrazine phosphine ligand was pumped into the reactor, maintaining the concentration of the novel pyrazine phosphine ligand between 800 and 1600 ppm. The liquid levels at the bottom of the reactor, separator, and evaporator were kept constant.

[0262] The concentration of the novel pyrazine phosphine ligand L3 in the reactor was monitored by liquid chromatography, and the percentage content of methyl propionate was determined by gas chromatography (GC). The reaction was carried out continuously for 1000 h. The molar ratio of methyl propionate to methanol received at the top of the evaporator remained constant after 150 h of the reaction and remained at approximately 65%.

[0263] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A pyrazine phosphine ligand compound, characterized in that, The pyrazine phosphine ligand compound is selected from any one of compounds L5, L7, and L8: 。 2. A method for preparing a pyrazine phosphine ligand compound according to claim 1, characterized in that, The preparation method includes the following steps: (1) Pyrazine compounds, N,N,N,N -Tetramethylethylenediamine, basic salt and n-butyllithium react to give pyrazine metal salt; In step (1), the structural formula of the pyrazine compound is shown in formula A below: Formula A Wherein, R1', R2', R3' and R4' are defined in the same position as the specific compound of claim 1; (2) The pyrazine metal salt and the monochlorophosphine compound react to obtain the pyrazine phosphine ligand compound; In step (2), the structural formula of the monochlorophosphine compound is shown in formula B below: Formula B; Wherein, R1 and R2 are defined at the corresponding positions of the specific compound as claimed in claim 1.

3. The method for preparing pyrazine phosphine ligand compounds according to claim 2, characterized in that, In step (1), the alkaline salt is selected from sodium tert-butoxide and / or potassium tert-butoxide.

4. The method for preparing pyrazine phosphine ligand compounds according to claim 2, characterized in that, In step (1), the pyrazine compound, N,N,N,N The molar ratio of tetramethylethylenediamine, basic salt and n-butyllithium is 1:(1.5~4):(2~9):(2~9).

5. The method for preparing pyrazine phosphine ligand compounds according to claim 2, characterized in that, In step (1), the reaction is carried out in an alkane solvent; the alkane solvent is heptane.

6. The method for preparing pyrazine phosphine ligand compounds according to claim 2, characterized in that, In step (1), the reaction is carried out in the presence of a protective gas.

7. The method for preparing pyrazine phosphine ligand compounds according to claim 6, characterized in that, In step (1), the protective gas is selected from nitrogen and / or argon.

8. The method for preparing the pyrazine phosphine ligand compound according to claim 2, characterized in that, In step (1), the reaction temperature is 0~5℃ and the reaction time is 12~24 h.

9. The method for preparing pyrazine phosphine ligand compounds according to claim 2, characterized in that, In step (1), the specific steps of the reaction are as follows: Under a protective gas atmosphere, pyrazine compounds, N,N,N,N - Tetramethylethylenediamine and its basic salt are dissolved in an alkane solvent, cooled, and then an alkane solution of n-butyllithium is added dropwise to carry out the reaction, thereby obtaining a reaction solution; wherein the alkane solvent is heptane.

10. The method for preparing pyrazine phosphine ligand compounds according to claim 2, characterized in that, In step (1), the following post-processing steps are also included after the reaction is completed: The reaction solution was filtered, washed, and dried sequentially to obtain the pyrazine metal salt.

11. The method for preparing pyrazine phosphine ligand compounds according to claim 2, characterized in that, In step (2), the molar ratio of the pyrazine metal salt and the monochlorophosphine compound is 1:(2~9).

12. The method for preparing pyrazine phosphine ligand compounds according to claim 2, characterized in that, In step (2), the reaction is carried out in an alkane solvent and / or an ether solvent; the alkane solvent is hexane; and the ether solvent is methyl tert-butyl ether.

13. The method for preparing the pyrazine phosphine ligand compound according to claim 2, characterized in that, In step (2), the reaction temperature is 0~30℃ and the reaction time is 12~20 h.

14. The method for preparing pyrazine phosphine ligand compounds according to claim 2, characterized in that, In step (2), the specific steps of the reaction are as follows: A pyrazine metal salt is dissolved in an alkane solvent and / or an ether solvent, cooled, and then a chlorophosphine compound is added dropwise to carry out the reaction, yielding a reaction solution; the alkane solvent is hexane; and the ether solvent is methyl tert-butyl ether.

15. The method for preparing pyrazine phosphine ligand compounds according to claim 14, characterized in that, The temperature at which the monochlorophosphine compound is added is below 5°C.

16. The method for preparing pyrazine phosphine ligand compounds according to claim 2, characterized in that, In step (2), after the reaction is completed, the following post-processing steps are also included: The reaction solution was quenched with water, and then the mixture was separated, the organic phase was dried, and the solvent was removed under vacuum to obtain a crude product. The crude product was then pulped and filtered to obtain the pyrazine phosphine ligand compound.

17. The use of a pyrazine phosphine ligand compound according to claim 1 in the preparation of a catalyst for alkoxycarbonylation of olefins.

18. A compound catalyst, characterized in that, The composite catalyst comprises a coordinating metal center and the pyrazine phosphine ligand compound as described in claim 1; The coordinating metal center includes any one or a combination of at least two of iron, cobalt, nickel, ruthenium, rhodium, iridium, or palladium.

19. The compound catalyst according to claim 18, characterized in that, The raw materials for preparing the composite catalyst include: the pyrazine phosphine ligand compound, the metal precursor, and the acidic auxiliary agent.

20. The compound catalyst according to claim 19, characterized in that, The metal precursor is selected from any one or a combination of at least two of the following: iron-containing compounds, cobalt-containing compounds, nickel-containing compounds, ruthenium-containing compounds, rhodium-containing compounds, iridium-containing compounds, or palladium-containing compounds.

21. The compound catalyst according to claim 20, characterized in that, The metal precursor is selected from cobalt-containing compounds and / or palladium-containing compounds.

22. The compound catalyst according to claim 21, characterized in that, The metal precursor is a palladium-containing compound.

23. The compound catalyst according to claim 22, characterized in that, The palladium-containing compound is selected from any one or a combination of at least two of palladium chloride, palladium acetate, palladium acetylacetonate, or palladium dibenzylidene acetone.

24. The compound catalyst according to claim 19, characterized in that, The acidic additives include any one or a combination of at least two of methanesulfonic acid, trifluoroacetic acid, or p-toluenesulfonic acid.

25. The compound catalyst according to claim 24, characterized in that, The acidic additive is p-toluenesulfonic acid.

26. The compound catalyst according to claim 19, characterized in that, The molar ratio of the metal precursor, pyrazine phosphine ligand compound, and acidic auxiliaries is 1:(1~8):(0.5~1.2).

27. The compound catalyst according to claim 19, characterized in that, The raw materials for preparing the composite catalyst also include solvents.

28. The compound catalyst according to claim 27, characterized in that, The solvent is methanol.

29. A method for alkoxycarbonylation of olefins, characterized in that, The olefin alkoxycarbonylation method includes the following steps: In the presence of any one of the compound catalysts according to claims 18 to 28, olefins, carbon monoxide, and / or methanol undergo alkoxycarbonylation to obtain alkoxycarbonylated olefin products.

30. The olefin alkoxycarbonylation method according to claim 29, characterized in that, The olefin is selected from any one or a combination of at least two of substituted or unsubstituted C2-C20 olefins.

31. The olefin alkoxycarbonylation method according to claim 30, characterized in that, The olefin is any one or a combination of at least two of ethylene, propylene, butene or n-hexene.

32. The olefin alkoxycarbonylation method according to claim 31, characterized in that, The olefin is ethylene.

33. The olefin alkoxycarbonylation method according to claim 31, characterized in that, In the alkoxycarbonylation reaction system, the concentration of the pyrazine phosphine ligand compound in the composite catalyst is 500~2500 ppm.

34. The olefin alkoxycarbonylation method according to claim 33, characterized in that, In the alkoxycarbonylation reaction system, the concentration of the pyrazine phosphine ligand compound in the composite catalyst is 700~1500 ppm.

35. The olefin alkoxycarbonylation method according to claim 29, characterized in that, The molar ratio of the olefin to carbon monoxide is (1~2):

1.

36. The olefin alkoxycarbonylation method according to claim 29, characterized in that, The alkoxycarbonylation reaction is carried out at a temperature of 70~110℃ and at a pressure of 1.0~2.5 MPa.

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