Process for the preparation of a homogeneous catalyst and process for the hydroesterification of vinyl acetate using the homogeneous catalyst

Abstract

This invention belongs to the field of organic chemical engineering, specifically relating to a method for preparing a homogeneous catalyst and a method for preparing 3-acetoxypropionate by using the homogeneous catalyst in the hydrogen esterification reaction of vinyl acetate. The method for preparing the homogeneous catalyst of this invention includes the following steps: (1) in a first organic solvent, a dihaloalkane and a dialkylphosphine borane complex are reacted under alkaline conditions to generate a dialkylphosphine ligand borane complex; (2) in a first alcohol, the dialkylphosphine ligand borane complex is heated to remove borane, yielding a dialkylphosphine ligand; (3) in a second organic solvent, the dialkylphosphine ligand and a metal precursor are mixed to obtain a solution containing the homogeneous catalyst. The homogeneous catalyst of this invention can be applied to the hydrogen esterification reaction of vinyl acetate, and the homogeneous catalyst and its ligands are easy to synthesize. Using the homogeneous catalyst of this invention to catalyze the hydrogen esterification reaction of vinyl acetate, the conversion rate of the reaction raw materials is >99%, the yield of the straight-chain ester product can reach 62%, and the selectivity can reach 71%.

Description

Technical Field

[0001] This invention belongs to the field of organic chemical engineering, specifically relating to a homogeneous catalyst, its preparation method, and a method for using the homogeneous catalyst to carry out the hydrogen esterification reaction of vinyl acetate. Background Technology

[0002] 1,3-Propanediol (1,3-PDO) is an important chemical raw material, mainly used in the synthesis of plasticizers, detergents, preservatives, and emulsifiers, and also in the food, cosmetics, and pharmaceutical industries. Furthermore, it is an important polyester fiber monomer, its primary use being as a monomer to synthesize a novel polyester material—polypropylene terephthalate (PTT)—with terephthalic acid.

[0003] Using vinyl acetate as a raw material, a linear hydrogen esterification product is obtained through hydrogenation reaction. Subsequently, 1,3-propanediol can also be obtained through alcoholysis and hydrogenation. Among these steps, the hydrogenation reaction of vinyl acetate is a key homogeneous catalytic step, but this step has been rarely reported.

[0004] In 2003, Lucite Int.Uk.Ltd. (CN100408545C) reported a method for hydrogenating vinyl acetate with carbon monoxide at relatively low temperature and pressure using Pd(0) / DTBPMB as a catalyst, methanol as a solvent, and toluene as an additive, achieving a maximum conversion rate of 81.4% and a linear selectivity of 77.27%. However, this method requires a relatively high catalyst concentration. In 2005, the same company (CN101001827A) reported a method for hydrogenating vinyl acetate using Pd(OAc)2 / 1,2-bis(1,3,5-trimethyl-6,9,10-trioxa-2-phospha-adamantyl-2-yl-methyl)benzene as a catalyst, at 10 bar CO, methanol as a solvent, and 60°C for 3 hours, achieving a feed conversion rate of 62.07% and a linear selectivity of 86.03%.

[0005] In 2005, Masato et al. (Masato T., Chem. Commun., 2005, 1173) reported the use of supported Pd(0) / DTBPMB as a catalyst in the hydrogen esterification reaction of vinyl acetate, carbon monoxide and methanol, with a feed conversion of 70.4% and a low linear selectivity of only 38.4%.

[0006] In 2006, Boerner et al. (David, JCH; et al. Helvetica Chimica Acta., 2006, 89, 1783) reported the hydrogen esterification of vinyl acetate using Pd(0) / 1,3-di-tert-butylphosphine propane as a catalyst, with a feed conversion rate of 97% and a linear selectivity of 55.8%.

[0007] Compared to the hydroformylation of vinyl acetate to synthesize 1,3-propanediol, the hydrogen esterification route offers advantages such as similar raw material costs, lower reaction temperatures and pressures, milder conditions, relatively lower catalyst costs, and easier solvent separation and recovery. However, there are few reports on obtaining linear-chain main products from the hydrogen esterification of vinyl acetate in existing technologies, and the raw material conversion rate and linear selectivity do not meet industrialization requirements. Therefore, optimizing the reaction process and developing new, low-cost, and high-performance hydrogen esterification catalysts for use in the hydrogen esterification of vinyl acetate to synthesize linear-chain hydrogen esterification products with high chemoselectivity and high regioselectivity has significant academic and economic value. Summary of the Invention

[0008] The purpose of this invention is to provide a homogeneous catalyst for the hydrogen esterification reaction of vinyl acetate and its preparation method.

[0009] In a first aspect, the present invention provides a method for preparing a homogeneous catalyst, the method comprising the steps of:

[0010] (1) In a first organic solvent, a dialkylphosphine hydrogen borane complex is formed by reacting a dihaloalkane with a dialkylphosphine hydrogen borane complex under the action of an alkali.

[0011] (2) In a first alcohol, the dialkylphosphine ligand borane complex is heated to remove borane, thereby obtaining the dialkylphosphine ligand;

[0012] (3) The dialkylphosphine ligand and the metal precursor are mixed in a second organic solvent to prepare a solution containing a homogeneous catalyst.

[0013] In one or more embodiments, the halogenation in the dihaloalkane is selected from one or more of fluorination, chlorination, bromination, and iodination.

[0014] In one or more embodiments, the dihaloalkane is a dihalobranched alkane or a dihalolinear alkane.

[0015] In one or more embodiments, the dihaloalkane contains 3 to 10 carbon atoms.

[0016] In one or more embodiments, the two alkyl groups in the dialkylphosphine borane complex are each independently selected from C1-C10 alkyl groups and C3-C12 cycloalkyl groups, for example selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, cyclopentyl, n-hexyl, isohexyl, cyclohexyl and adamantyl, preferably tert-butyl.

[0017] In one or more embodiments, the metal precursor is selected from one or more salts of Group VIII metals and complexes of Group VIII metals; preferably, the Group VIII metal is selected from one or more of nickel, palladium, platinum, cobalt, rhodium and iridium; preferably, the metal precursor is selected from one or more of Pd(dba)2, Pd2(dba)3, Pd(PPh3)4, Pd(OAc)2, PdCl2, PdBr2, Pd(OCOCF3)2, Pd(PPh3)2Cl2, Pd(dppf)Cl2, Pd(acac)2 and Pd(CH3CN)2Cl2.

[0018] In one or more embodiments, the homogeneous catalyst is formed by coordination of the metal precursor and the dialkylphosphine ligand, the metal precursor being as described in any embodiment herein, and the dialkylphosphine ligand having the structure shown in Formula I:

[0019]

[0020] In formula I, R 1 R 2 R 3 and R 4 Each is independently selected from C1-C10 alkyl and C3-C12 cycloalkyl, and n is an integer selected from 1 to 8.

[0021] In one or more embodiments, in step (1), the base is selected from one or more of lithium hydroxide, sodium hydroxide, potassium hydroxide, cesium hydroxide, calcium hydroxide, magnesium hydroxide, sodium carbonate, potassium carbonate, triethylamine, diethylisopropylamine, sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, sodium tert-butoxide, potassium tert-butoxide, n-butyllithium, tert-butyllithium, diisopropylaminolithium, phenyllithium, and hexamethyldisilaminolithium, preferably selected from one or more of sodium tert-butoxide, potassium tert-butoxide, and n-butyllithium.

[0022] In one or more embodiments, in step (1), the first organic solvent is selected from one or more of aprotic polar solvents and protic polar solvents, wherein the aprotic polar solvent is selected from one or more of acetonitrile, propionitrile, butyronitrile, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, sulfolane, 1,4-dioxane, tetrahydrofuran, and dichloromethane, and the protic polar solvent is selected from one or more of alcohol compounds, and the first organic solvent is preferably selected from one or more of acetonitrile, propionitrile, and butyronitrile.

[0023] In one or more embodiments, in step (1), the molar ratio of the dialkylphosphine hydrogen borane complex to the dihaloalkane is (0.1-10):1, preferably (1-4):1.

[0024] In one or more embodiments, in step (1), the molar ratio of the alkali to the dihaloalkane is (0.05-50):1, preferably (0.2-10):1.

[0025] In one or more embodiments, in step (1), 0.1 to 10 L of the first organic solvent is used per mole of dihaloalkane, preferably 0.5 to 4 L.

[0026] In one or more embodiments, in step (1), the reaction temperature is 0 to 90°C, preferably 40 to 60°C.

[0027] In one or more embodiments, in step (1), the reaction time is 1 to 24 hours, preferably 3 to 8 hours.

[0028] In one or more embodiments, in step (2), the first alcohol is selected from one or more of methanol, ethanol, propanol and tert-butanol.

[0029] In one or more embodiments, in step (2), the amount of the first alcohol is 0.1 to 100 L, preferably 0.5 to 5 L, relative to each mole of dihaloalkane used in step (1).

[0030] In one or more embodiments, in step (2), the reaction temperature is 30 to 200°C, preferably 70 to 120°C.

[0031] In one or more embodiments, in step (2), the reaction time is 1 to 48 hours, preferably 6 to 12 hours.

[0032] In one or more embodiments, in step (3), the mixing is carried out at 10–40°C.

[0033] In one or more embodiments, in step (3), the second organic solvent is selected from one or more of nonpolar solvents, polar aprotic solvents, and protic solvents. The nonpolar solvent is selected from one or more of benzene, toluene, xylene, and ethylbenzene. The polar aprotic solvent is selected from one or more of dimethyl sulfoxide, N-methylpyrrolidone, sulfolane, N,N-dimethylformamide, N,N-dimethylacetamide, 1,4-dioxane, and tetrahydrofuran. The protic solvent is selected from one or two of methanol and ethanol. Preferably, the second organic solvent is selected from one or more of protic solvents.

[0034] In one or more embodiments, in step (3), the molar ratio of the group VIII metal to the dialkylphosphine ligand in the metal precursor is 1:(1 to 50), preferably 1:(5 to 20).

[0035] In one or more embodiments, in step (3), 100 to 5000 L of the second organic solvent is used per mole of the metal precursor.

[0036] A second aspect of the present invention provides a method for preparing 3-acetoxypropionate using a vinyl acetate hydrogen esterification reaction, the method comprising:

[0037] A solution containing a homogeneous catalyst, vinyl acetate, an acid, and a second alcohol are added to a third organic solvent, and carbon monoxide and optionally another gas are introduced to carry out a hydrogen esterification reaction to give 3-acetoxypropionate, wherein the homogeneous catalyst is formed by coordination of a metal precursor and a dialkylphosphine ligand as described in any embodiment herein; or

[0038] In a third organic solvent, the metal precursor, dialkylphosphine ligand, vinyl acetate, acid, and second alcohol described in any of the embodiments herein are added, and carbon monoxide and optional other gases are introduced to generate a homogeneous catalyst in situ from the metal precursor and the dialkylphosphine ligand, thereby carrying out a hydrogen esterification reaction to obtain 3-acetoxypropionate.

[0039] The dialkylphosphine ligand has the structure shown in Formula I:

[0040]

[0041] In formula I, R 1 R 2 R 3 and R 4 Each is independently selected from C1-C10 alkyl and C3-C12 cycloalkyl, and n is an integer selected from 3 to 8.

[0042] In one or more embodiments, the solution containing the homogeneous catalyst is obtained by mixing a metal precursor and a dialkylphosphine ligand in a molar ratio of 1:(5-20) in a third organic solvent.

[0043] In one or more embodiments, during the in-situ generation of the homogeneous catalyst, the molar ratio of the metal precursor to the dialkylphosphine ligand is 1:(5-20).

[0044] In one or more embodiments, the volume ratio of vinyl acetate to the second alcohol is 1:(0.1 to 10), preferably 1:(0.5 to 2); and the number of moles of the second alcohol is greater than the number of moles of vinyl acetate.

[0045] In one or more embodiments, the amount of homogeneous catalyst added is such that the molar ratio of the Group VIII metal to vinyl acetate is (10:1). -8 ~10 -1 ): 1, preferably (10) -6 ~10 -3 ): 1.

[0046] In one or more embodiments, the molar ratio of the acid to the Group VIII metal in the homogeneous catalyst is (0.1 to 100):1, preferably (1 to 10):1.

[0047] In one or more embodiments, the reaction temperature is between -10 and 160°C, preferably between 60 and 120°C.

[0048] In one or more embodiments, the partial pressure of carbon monoxide is between 1 and 60 bar, preferably between 3 and 40 bar.

[0049] In one or more embodiments, the reaction time is 0.1 to 48 hours, preferably 2 to 16 hours.

[0050] The present invention has the following beneficial effects:

[0051] (1) The homogeneous catalyst of the present invention can be applied to the hydrogen esterification reaction of vinyl acetate, and the homogeneous catalyst and its ligands are easy to synthesize.

[0052] (2) When the homogeneous catalyst of the present invention is used to catalyze the hydrogen esterification reaction of vinyl acetate, the conversion rate of the reaction raw materials is >99%, the yield of straight-chain ester products can reach 62%, and the selectivity can reach 71%. Detailed Implementation

[0053] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0054] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0055] In this document, the terms “contains,” “includes,” “containing,” and similar terms encompass the meanings of “basically composed of” and “composed of.” For example, when this document discloses “A contains B and C,” “A is basically composed of B and C” and “A is composed of B and C” should be considered as having been disclosed in this document.

[0056] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0057] Unless otherwise specified, percentages refer to mass percentages and proportions refer to mass ratios in this article.

[0058] In this document, when describing embodiments or examples, it should be understood that it is not intended to limit the invention to those embodiments or examples. Rather, all alternatives, modifications, and equivalents of the methods and materials described herein are covered within the scope defined by the claims.

[0059] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0060] In this document, the terms "Ci~Cj" represent the range of carbon atoms, where i and j are integers, and the range includes the endpoints (i.e., i and j) and every integer point between the endpoints, where j is greater than i. For example, C1~C6 represents the range of 1 to 6 carbon atoms, including 1 carbon atom, 2 carbon atoms, 3 carbon atoms, 4 carbon atoms, 5 carbon atoms, and 6 carbon atoms. Similarly, the terms "C1~C12" represent 1 to 12, particularly 1 to 10, particularly 1 to 8, particularly 1 to 6, particularly 1 to 5, particularly 1 to 4, particularly 1 to 3, or particularly 1 to 2 carbon atoms.

[0061] As used herein, "alkyl" refers to a straight-chain or branched monovalent saturated hydrocarbon group having a specified number of carbon atoms. Specifically, alkyl groups are those having 1 to 10 carbon atoms ("C1 to C10 alkyl"), typically containing 1 to 8 carbon atoms (C1 to C8 alkyl), preferably containing 1 to 6 carbon atoms (C1 to C6 alkyl), and more preferably containing 1 to 4 carbon atoms (C1 to C4 alkyl). Examples of alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, etc.

[0062] As used herein, the term "cycloalkyl" refers to a saturated, non-aromatic monocyclic or polycyclic alkyl group or portion consisting only of carbon and hydrogen atoms, which may be linked to the remainder of the molecule via any suitable carbon atom. In some embodiments, the cycloalkyl group may comprise a fused ring system, a bridged ring system, or a spirocyclic system. In some embodiments, the cycloalkyl group contains 3 to 12 carbon atoms, 3 to 11 carbon atoms, 3 to 10 carbon atoms, 3 to 9 carbon atoms, or 3 to 8 carbon atoms. In some embodiments, the cycloalkyl group has 3, 4, 5, 6, 7, or 8 carbon atoms. Unless otherwise specifically indicated in this specification, the carbon atoms in the cycloalkyl group may optionally be oxidized. Non-limiting examples of cycloalkyl groups include, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclopentenyl, cyclohexyl, cyclohexenyl, cyclohexadienyl, cycloheptyl, cyclooctyl, 1H-indenyl, 2,3-dihydroindenyl, 1,2,3,4-tetrahydro-naphthyl, 5,6,7,8-tetrahydro-naphthyl, 8,9-dihydro-7H-benzocyclohepten-6-yl, 6,7,8,9-tetrahydro-5H-benzocycloheptenyl, and 5,6,7,8,9,10-hexahydro-benzene. Cyclooctenyl, fluorenyl, bicyclo[2.2.1]heptyl, 7,7-dimethyl-bicyclo[2.2.1]heptyl, bicyclo[2.2.1]heptyl, bicyclo[2.2.2]octyl, bicyclo[3.1.1]heptyl, bicyclo[3.2.1]octyl, bicyclo[2.2.2]octenyl, bicyclo[3.2.1]octenyl, adamantyl, octahydro-4,7-methylene-1H-indenyl and octahydro-2,5-methylene-cyclopentadienyl, etc.

[0063] In this document, "optionally" or "optionally" means that the event or condition described below may or may not occur, and the description includes both the occurrence and non-occurrence of the event or condition. For example, "optionally halogenated alkanes" means that alkanes are substituted or unsubstituted, and the description includes both substituted and unsubstituted alkanes.

[0064] In this document, the term “substitution,” regardless of whether the term “optional” (i.e., equivalent to substituted or unsubstituted) is used, refers to the substitution of one or more hydrogen atoms of a specified group or portion by a “suitable substituent.” The number of substituents may be one or more, i.e., 1, 2, 3, 4, 5, or 6 or more, depending on the substituted group and the nature of the substituents. For example, when the substituent of an ethyl group is a halogen, the group may be substituted by 1, 2, 3, 4, or 5 substituents, such as trifluoroethyl, pentafluoroethyl, etc., depending on the structure of the substituted group. In some embodiments, the number of substituents is 1, 2, or 3. In some embodiments, the number of substituents is 1 or 2. In some embodiments, the number of substituents is 1. It will be understood that “substitution” or “replaced by” includes the implicit condition that such substitution is based on the permissible valence of the substituted atom and that the substitution produces a stable or chemically viable compound, such as a compound that does not spontaneously transform, for example, through rearrangement, cyclization, elimination, etc. Unless otherwise stated, an "optionally substituted" group may have suitable substituents at each substituted position of the group, and when more than one position in any given structure can be substituted by more than one substituent selected from the specified group, the substituents may be the same or different at each position. Those skilled in the art will understand that the substituent itself may be substituted if appropriate.

[0065] This invention provides a ligand having the structure shown in Formula I:

[0066]

[0067] In formula I, R 1 R 2 R 3 and R 4 Each is independently selected from C1-C10 alkyl and C3-C12 cycloalkyl, and n is an integer selected from 1 to 8.

[0068] In some implementation schemes, R 1 R 2 R 3 and R 4 Each is independently selected from C1-C6 alkyl and C3-C10 cycloalkyl. In some embodiments, R 1 R 2 R 3and R 4 Each is independently selected from C1 to C4 alkyl groups, such as tert-butyl, isopropyl, cycloalkyl, and adamantyl; preferably tert-butyl.

[0069] In some implementations, n is selected from 1, 2, 3, 4, 5, and 6.

[0070] In some implementations, the ligand is

[0071] The present invention also provides a homogeneous catalyst formed by coordination of a metal precursor and a dialkylphosphine ligand of the present invention. In some embodiments, the dialkylphosphine ligand is a ligand of the present invention having the structure shown in Formula I.

[0072] In some embodiments, the metal precursor is selected from one or more salts of Group VIII metals and complexes of Group VIII metals. Preferably, the Group VIII metal is selected from one or more of nickel, palladium, platinum, cobalt, rhodium, and iridium. Exemplarily, the metal precursor is selected from one or more of Pd(dba)2, Pd2(dba)3, Pd(PPh3)4, Pd(OAc)2, PdCl2, PdBr2, Pd(OCOCF3)2, Pd(PPh3)2Cl2, Pd(dppf)Cl2, Pd(acac)2, and Pd(CH3CN)2Cl2.

[0073] This invention provides a method for preparing a homogeneous catalyst, the method comprising the steps of:

[0074] (1) In a first organic solvent, a dialkylphosphine hydrogen borane complex is formed by reacting a dihaloalkane with a dialkylphosphine hydrogen borane complex under the action of an alkali.

[0075] (2) In a first alcohol, the dialkylphosphine ligand borane complex is heated to remove borane, thereby obtaining the dialkylphosphine ligand;

[0076] (3) The dialkylphosphine ligand and the metal precursor are mixed in a second organic solvent to prepare a solution containing a homogeneous catalyst.

[0077] In some embodiments, the halogenation in the dihaloalkane is selected from one or more of fluorination, chlorination, bromination, and iodination; preferably chlorination.

[0078] In some embodiments, the dihaloalkane is a dihalobranched alkane or a dihalolinear alkane, preferably a dihalobranched alkane.

[0079] In some embodiments, the dihaloalkane contains 3 to 10 carbon atoms, such as 4, 5, or 6 carbon atoms.

[0080] In some embodiments, the two alkyl groups in the dialkylphosphine borane complex are each independently selected from C1-C10 alkyl groups and C3-C12 cycloalkyl groups, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, cyclopentyl, n-hexyl, isohexyl, cyclohexyl, and adamantyl, preferably tert-butyl.

[0081] In step (1), the base can be an organic base or an inorganic base. The base suitable for step (1) of the present invention can be selected from one or more of lithium hydroxide, sodium hydroxide, potassium hydroxide, cesium hydroxide, calcium hydroxide, magnesium hydroxide, sodium carbonate, potassium carbonate, triethylamine, diethylisopropylamine, sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, sodium tert-butoxide, potassium tert-butoxide, n-butyllithium, tert-butyllithium, diisopropylaminolithium, phenyllithium, and hexamethyldisilaminolithium, preferably selected from one or more of sodium tert-butoxide, potassium tert-butoxide, and n-butyllithium.

[0082] In step (1), the first organic solvent is selected from one or more of aprotic polar solvents and protic polar solvents. Exemplary aprotic polar solvents are selected from one or more of acetonitrile, propionitrile, butyronitrile, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, sulfolane, 1,4-dioxane, tetrahydrofuran, and dichloromethane. Exemplary protic polar solvents are selected from one or more of alcohols. Preferably, the first organic solvent is selected from one or more of acetonitrile, propionitrile, and butyronitrile.

[0083] In step (1), the molar ratio of the dialkylphosphine hydrogen borane complex to the dihaloalkanes is (0.1-10):1, for example (0.8-3):1, (2-6):1, preferably (2-4):1.

[0084] In step (1), the molar ratio of the alkali to the dihaloalkane is (0.05-50):1, for example (0.1-20):1, (2-15):1, preferably (4-10):1.

[0085] In step (1), the first organic solvent is used in 0.1 to 10 L per mole of dihaloalkane, for example 1 to 5 L, 3 to 8 L, preferably 0.5 to 4 L.

[0086] In step (1), the reaction temperature is 0 to 90°C, for example 20 to 80°C, 30 to 50°C, preferably 40 to 60°C.

[0087] In step (1), the reaction time can be 1 to 24 hours, preferably 3 to 8 hours.

[0088] In some embodiments, the dialkylphosphine hydrogen borane complex is prepared by reacting dialkylphosphine hydrogen with borane. This reaction can be carried out in a fourth organic solvent. The fourth organic solvent can be a conventional organic solvent in the art, as long as it does not adversely affect the reaction. The fourth organic solvent can be selected from one or more of acetonitrile, propionitrile, butyronitrile, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, sulfolane, 1,4-dioxane, tetrahydrofuran, and dichloromethane, preferably tetrahydrofuran. The two alkyl groups in the dialkylphosphine hydrogen are each independently selected from C1-C10 alkyl groups and C3-C12 cycloalkyl groups, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, cyclopentyl, n-hexyl, isohexyl, cyclohexyl, and adamantyl, preferably tert-butyl. The molar ratio of borane to dialkylphosphine hydrogen can be (2-5):1, preferably (3-5):1. In some embodiments, dialkylphosphine hydrogen is added to a fourth organic solvent of borane. The concentration of borane in the fourth organic solvent of borane can be 0.5-5 mol / L, for example, 1-2 mol / L.

[0089] In step (2), the first alcohol is selected from one or more of methanol, ethanol, propanol and tert-butanol, preferably methanol.

[0090] In step (2), the amount of the first alcohol is 0.1 to 100 L, preferably 2 to 10 L, relative to the amount of dihaloalkane used in step (1).

[0091] In step (2), the reaction temperature is 30–200°C, preferably 70–120°C;

[0092] In step (2), the reaction time is 1 to 48 hours, preferably 6 to 12 hours.

[0093] In step (3), the mixing is carried out at 10–40°C, for example at room temperature (25°C).

[0094] In step (3), the second organic solvent is selected from one or more of nonpolar solvents, polar aprotic solvents, and protic solvents. Exemplary nonpolar solvents are selected from one or more of benzene, toluene, xylene, and ethylbenzene. Exemplary polar aprotic solvents are selected from one or more of dimethyl sulfoxide, N-methylpyrrolidone, sulfolane, N,N-dimethylformamide, N,N-dimethylacetamide, 1,4-dioxane, and tetrahydrofuran. Exemplary protic solvents are selected from one or both of methanol and ethanol. Preferably, the second organic solvent is selected from one or more protic solvents, such as methanol.

[0095] In step (3), the molar ratio of the metal precursor to the dialkylphosphine ligand is 1:(1-50), preferably 1:(5-20).

[0096] In step (3), 100 to 5000 L of the second organic solvent is used per mole of the metal precursor, preferably 500 to 2000 L.

[0097] In some embodiments, the solution containing the homogeneous catalyst is pre-prepared before the start of the homogeneous catalyst-catalyzed reaction. In other embodiments, the homogeneous catalyst is generated in situ during the homogeneous catalyst-catalyzed reaction.

[0098] The present invention also provides a method for preparing 3-acetoxypropionate using a vinyl acetate hydrogen esterification reaction, the method comprising:

[0099] A solution containing a homogeneous catalyst, vinyl acetate, an acid, and a second alcohol are added to a third organic solvent, and carbon monoxide and optionally other gases are introduced to carry out a hydrogen esterification reaction to obtain 3-acetoxypropionate ester. The homogeneous catalyst is formed by coordination of the metal precursor of the present invention and a dialkylphosphine ligand. Alternatively, the metal precursor of the present invention, a dialkylphosphine ligand, vinyl acetate, an acid, and a second alcohol are added to a third organic solvent, and carbon monoxide and optionally other gases are introduced to allow the metal precursor and the dialkylphosphine ligand to generate a homogeneous catalyst in situ, thereby carrying out a hydrogen esterification reaction to obtain 3-acetoxypropionate ester.

[0100] The dialkylphosphine ligand has the structure shown in Formula I:

[0101]

[0102] In formula I, R 1 R 2 R 3 and R 4 Each is independently selected from C1-C10 alkyl and C3-C12 cycloalkyl, and n is an integer selected from 3 to 8.

[0103] In some embodiments, a pre-prepared solution containing a homogeneous catalyst is added to a third organic solvent. The solution containing the homogeneous catalyst is obtained by mixing a metal precursor and a dialkylphosphine ligand in a molar ratio of 1:(5–20) in the third organic solvent, preferably 1:(8–15), for example 1:10.

[0104] In other embodiments, a homogeneous catalyst is prepared in situ by adding a metal precursor and a dialkylphosphine ligand to a third organic solvent. During the in-situ generation of the homogeneous catalyst, the molar ratio of the metal precursor to the dialkylphosphine ligand is 1:(5–20), preferably 1:(8–15), for example 1:10.

[0105] In the hydrogen esterification reaction, the acid is selected from one or more of sulfuric acid, hydrochloric acid, nitric acid, methanesulfonic acid, chlorosulfonic acid, fluorosulfonic acid, trifluoromethanesulfonic acid, benzenesulfonic acid, naphthalenesulfonic acid, toluenesulfonic acid, tert-butylsulfonic acid, 2-hydroxypropanesulfonic acid, sulfonated ion exchange resin, perchloric acid, halogenated carboxylic acids, orthophosphoric acid, and phosphonic acid. The halogenated carboxylic acids include perhalogenated carboxylic acids. The perhalogenated carboxylic acids include trichloroacetic acid and trifluoroacetic acid. The phosphonic acid includes phenylphosphonic acid.

[0106] In the hydrogen esterification reaction, the alcohol can be a monohydric alcohol, such as a monohydric chain alcohol, or a polyhydric alcohol, such as one or more selected from dihydric alcohols, trihydric alcohols, tetrahydric alcohols, pentahydric alcohols, hexahydric alcohols, heptahydric alcohols, and octahydric alcohols, preferably selected from dihydric alcohols, trihydric alcohols, tetrahydric alcohols, and sugars. Exemplary monohydric alcohols can be selected from one or more selected from methanol, ethanol, propanol, isopropanol, isobutanol, tert-butanol, n-butanol, and chlorooctanol. Exemplary polyhydric alcohols can be selected from one or more selected from 1,2-ethylene glycol, 1,3-propanediol, glycerol, 1,2,4-butanetriol, 2-(hydroxymethyl)-1,3-propanediol, 1,2,6-trihydroxyhexane, pentaerythritol, 1,1,1-tris(hydroxymethyl)ethane, mannose, sorbitol, galactose, sucrose, fructose, and glucose. Preferably, the sugar can be selected from one or more selected from sucrose, fructose, and glucose. Preferably, the second alcohol is selected from one or both of methanol and ethanol. The second alcohol is more preferably methanol.

[0107] In this invention, no particular limitation is placed on the amount of the second alcohol used. Generally speaking, the amount of the second alcohol used should exceed the amount of vinyl acetate to be carbonylated; that is, theoretically, the molar number of the second alcohol should be greater than the molar number of vinyl acetate. The second alcohol can be used alone as a solvent for the hydrogen esterification reaction, or it can be used as a mixed solvent with other conventional organic solvents in the art. Alternatively, the hydrogen esterification reaction in this invention can also use other conventional organic solvents, with the addition of a sufficient amount of second alcohol to proceed with the reaction. Therefore, the volume ratio of vinyl acetate to the second alcohol can be varied within a wide range. For example, when the second alcohol is used as the reaction solvent, the maximum volume ratio of vinyl acetate to the second alcohol can be 1:50. In some embodiments, the volume ratio of vinyl acetate to the second alcohol is 1:(0.1 to 10), preferably 1:(0.5 to 2); and the molar number of the second alcohol is greater than the molar number of vinyl acetate.

[0108] In the hydrogen esterification reaction of this invention, carbon monoxide can be used in pure form or diluted with other gases. Other gases can be selected from one or more protective gases that do not participate in the reaction, such as nitrogen, carbon dioxide, and inert gases (e.g., argon). Other gases can also be hydrogen, provided that the volume fraction of hydrogen is less than 5%.

[0109] In the hydrogen esterification reaction of this invention, there is no particular limitation on the amount of homogeneous catalyst used. Those skilled in the art can choose conventional catalyst amounts within the field of catalysts, as long as they do not adversely affect the reaction. In some embodiments, the amount of homogeneous catalyst added is such that the molar ratio of the Group VIII metal to vinyl acetate is (10:1). -8 ~10 -1 ): 1, preferably (10) -6 ~10 -3 ): 1.

[0110] In the hydrogen esterification reaction of this invention, there is no particular limitation on the amount of acid used. Those skilled in the art can choose the amount of acid conventional in the field of hydrogen esterification reactions, as long as it does not adversely affect the reaction. In some embodiments, the molar ratio of the acid to the Group VIII metal in the homogeneous catalyst is (0.1 to 100):1, preferably (1 to 10):1.

[0111] Although not essential to this invention, the hydrogen esterification reaction of this invention can be carried out in one or more aprotic solvents. The third organic solvent is selected from one or more of the following: alcohols, ketones, ethers, esters, amides, sulfoxides, sulfones, optionally halogenated C6-C14 aromatic compounds, optionally halogenated C5-C10 alkanes, and nitrile compounds; preferably, the third organic solvent is selected from: methanol, ethanol, propanol, isopropanol, isobutanol, tert-butanol, n-butanol, chlorooctanol, 1,2-ethylene glycol, 1,3-propanediol, glycerol, 1,2,4-butanetriol, 2-(hydroxymethyl)-1,3-propanediol, 1,2,6-trihydroxyhexane, pentaerythritol, 1,1,1-tris(hydroxymethyl)ethane, mannose, sorbitol, galactose, sucrose, fructose, glucose, methyl butyl ketone, anisole (methyl phenyl ether), 2,5,8-trioxane... Nonane (diethylene glycol dimethyl ether), diethyl ether, dimethyl ether, tetrahydrofuran, diphenyl ether, diisopropyl ether, dimethyl ether of diethylene glycol, methyl acetate, dimethyl adipate, methyl benzoate, dimethyl phthalate, butyrolactone, dimethylacetamide, N-methylpyrrolidone, N,N-dimethylformamide, dimethyl sulfoxide, di-isopropyl sulfone, sulfolane (tetrahydrothiophene-2,2-dioxide), 2-methylsulfolane, diethyl sulfone, tetrahydrothiophene-1,1-dioxide, 2-methyl-4-ethylsulfolane, benzene, toluene, ethylbenzene, o-xylene, m-xylene, p-xylene, chlorobenzene, o-dichlorobenzene, m-dichlorobenzene, hexane, heptane, 2,2,3-trimethylpentane, dichloromethane, carbon tetrachloride, benzyl nitrile, and acetonitrile. In some embodiments, if the second alcohol is an alkanol, an aprotic solvent can be generated by reaction because the hydrogen esterification product of vinyl acetate, carbon monoxide, and the second alcohol is an aprotic solvent.

[0112] In the hydrogen esterification reaction of the present invention, the reaction temperature is between -10 and 160°C, preferably between 60 and 120°C.

[0113] In the hydrogen esterification reaction of the present invention, the partial pressure of carbon monoxide is 1 to 60 bar, preferably 3 to 40 bar.

[0114] In the hydrogen esterification reaction of the present invention, the reaction time is 0.1 to 48 hours, preferably 2 to 16 hours.

[0115] In this invention, the products of the hydrogen esterification reaction can be separated from other components by any suitable method. One advantage of the hydrogen esterification method of this invention is the formation of significantly fewer byproducts, thus reducing the need for further purification after initial product separation. The hydrogen esterification method of this invention also allows for the recycling and / or reuse of other components containing the homogeneous catalyst of this invention in another reaction, thereby replenishing a minimal amount of homogeneous catalyst in new reactions.

[0116] This invention also provides the application of the homogeneous catalyst of this invention in the catalytic hydrogen esterification reaction of vinyl acetate. In some embodiments, the hydrogen esterification reaction of vinyl acetate is as described in any embodiment herein.

[0117] The present invention also provides a method for improving the selectivity of straight-chain ester products in the hydrogen esterification reaction of vinyl acetate, the method comprising:

[0118] A solution containing a homogeneous catalyst, vinyl acetate, an acid, and a second alcohol are added to a third organic solvent, and carbon monoxide and optionally other gases are introduced to carry out a hydrogen esterification reaction to obtain 3-acetoxypropionate ester. The homogeneous catalyst is formed by coordination of the metal precursor of the present invention and a dialkylphosphine ligand. Alternatively, the metal precursor of the present invention, a dialkylphosphine ligand, vinyl acetate, an acid, and a second alcohol are added to a third organic solvent, and carbon monoxide and optionally other gases are introduced to allow the metal precursor and the dialkylphosphine ligand to generate a homogeneous catalyst in situ, thereby carrying out a hydrogen esterification reaction to obtain 3-acetoxypropionate ester.

[0119] The dialkylphosphine ligand has the structure shown in Formula I:

[0120]

[0121] In formula I, R 1 R 2 R 3 and R 4 Each component is independently selected from C1-C10 alkyl and C3-C12 cycloalkyl, where n is an integer selected from 3 to 8. The various features of this method are as described in any embodiment herein.

[0122] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. Percentages and parts are by weight unless otherwise stated.

[0123] In this paper, the raw material conversion rate = (1 - remaining raw material content / initial raw material content) × 100%.

[0124] In this paper, L / B = straight-chain ester yield / branched-chain ester yield, and normalized (L+B = 100%).

[0125] In this paper, the reaction solution obtained from the reaction was analyzed by GC to determine the conversion rate, yield of straight-chain esters, and yield of branched-chain esters.

[0126] In this paper, the selectivity of straight-chain ester products = yield of straight-chain esters / (yield of straight-chain esters + yield of branched-chain esters).

[0127] Preparation Example 1: Synthesis of di-tert-butylphosphine hydrogen borane complex

[0128] In an anaerobic environment under an ice-water bath, 29.2 g (200 mmol) of di-tert-butylphosphine hydrogen and 200 mL of THF were added to a dry Schleck flask, followed by the slow addition of a tetrahydrofuran solution of borane (1.0 mol / L, 600 mL). After the addition was complete, the mixture was slowly brought back to room temperature and the reaction was allowed to proceed for 2 hours.

[0129] Most of the solvent was removed under reduced pressure, methanol was added to precipitate the solid, the solution was filtered off, and the solid was washed with a small amount of methanol to obtain 28.8 g of the target product, di-tert-butylphosphine hydrogen borane complex, with a separation yield of 90%.

[0130] Preparation Example 2: Synthesis of 1,5-bis(di-tert-butylphosphine)pentaneborane complex

[0131] In a dry Schleck flask, add di-tert-butylphosphine hydroborane complex (16 g, 100 mmol), sodium tert-butoxide (28.8 g, 300 mmol), purge with nitrogen three times, then add acetonitrile (180 mL) and 1,5-dichloropentane (7.0 g, 50 mmol). React at 50 °C for 6 hours.

[0132] After cooling to room temperature, the insoluble matter was filtered off, most of the solvent was removed under reduced pressure, water was added to precipitate the solid, the solution was filtered off, and the solid was washed with a small amount of methanol to obtain 17.8 g of the target product 1,5-bis(di-tert-butylphosphine)pentaneborane complex, with a separation yield of 92%.

[0133] Preparation Example 3: Synthesis of 1,5-bis(di-tert-butylphosphine)pentane

[0134] The 1,5-bis(di-tert-butylphosphine)pentaneborane complex (10 g, 25.8 mmol) prepared in Preparation Example 1 and methanol (50 mL) were added to a dry reaction vessel, and nitrogen was purged three times. The reaction was carried out at 100 °C for 6 hours. After cooling, the hydrogen gas generated in the vessel was released, and the reaction was reheated to 100 °C. The above steps were repeated until no more gas was generated.

[0135] Under nitrogen atmosphere, the solvent and borate ester were removed by reduced pressure to obtain 9.2 g of the target product 1,5-bis(di-tert-butylphosphine)pentane, with a separation yield of 99%.

[0136] Preparation Example 4: Preparation of Pd(0) / 1,5-bis(di-tert-butylphosphine)pentane catalyst

[0137] Under anhydrous and oxygen-free conditions, Pd2(dba)3 (0.458 g, 0.5 mmol), 1,5-bis(di-tert-butylphosphine)pentane (1.801 g, 5 mmol) and methanol (50 mL) were mixed at room temperature and stirred for 10 min to obtain a catalyst methanol solution with a concentration of 10 mmol / L.

[0138] Example 1, Comparative Examples 1-3

[0139] Under anhydrous and oxygen-free conditions, vinyl acetate (1.86 g, 21.6 mmol), Pd₂(dba)₃ (45.7 mg, 0.05 mmol), a ligand (0.5 mmol), methanesulfonic acid (48.0 mg, 0.5 mmol), and methanol (30 mL) were added to a reaction vessel. The carbon monoxide was replaced three times, and the vessel was then charged with carbon monoxide (30 bar). The reaction was carried out at 80 °C for 6 h. The reaction conditions are shown in the following formulas and Table 1. The ligands used in Table 1 can be commercially available or synthesized according to Preparation Examples 1–3.

[0140]

[0141] Table 1: Ligand (L) Screening Experiment

[0142]

[0143] Examples 2-4

[0144] Under anhydrous and oxygen-free conditions, vinyl acetate (1.86 g, 21.6 mmol), [Pd] metal precursor ([Pd] element added in an amount of 0.10 mmol), 1,5-bis(di-tert-butylphosphine)pentane (0.5 mmol), methanesulfonic acid (48.0 mg, 0.5 mmol), and methanol (30 mL) were added to the reactor. Carbon monoxide was replaced three times, and the reactor was then charged with carbon monoxide (30 bar). The reaction was carried out at 80 °C for 6 h. The reaction conditions are shown in the following formula and Table 2.

[0145]

[0146] Table 2: Screening Experiments for Metal Precursors ([Pd])

[0147]

[0148]

[0149] Examples 5-10

[0150] Under anhydrous and oxygen-free conditions, vinyl acetate (1.86 g, 21.6 mmol), Pd₂(dba)₃ (45.7 mg, 0.05 mmol), 1,5-bis(di-tert-butylphosphine)pentane (180 mg, 0.5 mmol), methanesulfonic acid (48.0 mg, 0.5 mmol), and methanol (30 mL) were added to the reactor. Carbon monoxide was replaced three times, and the reactor was then charged with carbon monoxide (30 bar). The reaction was carried out at a specific temperature (T) for 6 hours. The reaction conditions are shown in the following formula and Table 3. As shown in Table 3, when the temperature was increased to 120 °C, the yields of both straight-chain and branched-chain esters decreased significantly. This is because the straight-chain and branched-chain ester products react with methanol at high temperatures to produce byproducts such as methyl propionate and acetic acid, while the methanol itself is oxidized to formaldehyde.

[0151]

[0152] Table 3: Temperature (T) Screening Test

[0153] Temperature / °C Raw material conversion rate / % Straight-chain ester yield / % Branched ester yield / % L / B Example 5 60 98.09 52.37 43.93 54 / 46 Example 6 80 >99 58.85 40.09 59 / 41 Example 7 90 >99 57.44 29.71 66 / 34 Example 8 100 >99 57.96 24.14 71 / 29 Example 9 110 >99 33.57 14.89 69 / 31 Example 10 120 >99 23.06 10.27 69 / 31

[0154] Examples 11-14

[0155] Under anhydrous and oxygen-free conditions, vinyl acetate (1.86 g, 21.6 mmol), Pd2(dba)3 (45.7 mg, 0.05 mmol), 1,5-bis(di-tert-butylphosphine)pentane (L), methanesulfonic acid (48.0 mg, 0.5 mmol), and methanol (30 mL) were added to the reactor. The carbon monoxide was replaced three times, and carbon monoxide (30 bar) was introduced. The reaction was carried out at 100 °C for 6 h.

[0156] The reaction conditions are shown in the following formula and Table 4.

[0157]

[0158] Table 4: L / [Pd] ratio screening test

[0159] L / mmol L / [Pd] Raw material conversion rate / % Straight-chain ester yield / % Branched ester yield / % L / B Example 11 0.35 3.5 98.7 6.44 4.28 60 / 40 Example 12 0.4 4 97.0 61.67 26.07 70 / 30 Example 13 0.5 5 >99 57.96 24.14 71 / 29 Example 14 0.75 7.5 >99 58.97 24.97 70 / 30

[0160] Examples 15-17

[0161] Under anhydrous and oxygen-free conditions, vinyl acetate (1.86 g, 21.6 mmol), Pd2(dba)3 (45.7 mg, 0.05 mmol), 1,5-bis(di-tert-butylphosphine)pentane, methanesulfonic acid (48.0 mg, 0.5 mmol), and methanol (30 mL) were added to the reactor. The carbon monoxide was replaced three times, and carbon monoxide (30 bar) was introduced. The reaction was carried out at 100 °C for 6 h.

[0162] The reaction conditions are shown in the following formula and Table 5.

[0163]

[0164] Table 5: Screening Tests for Acid Types

[0165] acid Raw material conversion rate / % Straight-chain ester yield / % Branched ester yield / % L / B Example 15 mesylate >99 57.96 24.14 71 / 29 Example 16 p-Toluenesulfonic acid 34.4 3.36 2.49 57 / 43 Example 17 Trifluoromethanesulfonic acid >99 1.12 0.90 55 / 45

[0166] Based on the above research results, the homogeneous catalyst composed of [Pd] / dialkyl tert-butylphosphine ligands catalyzes the hydrogen esterification of vinyl acetate, achieving excellent feed conversion and linear ester product selectivity to 3-acetoxypropionate. Different palladium metal precursors have relatively little effect on the feed conversion and linear ester product selectivity of this reaction. Reacting at 80-100℃ is more favorable for obtaining the linear ester product. Using 0.05 mmol of Pd2(dba)3,1,5-di(di-tert-butylphosphine)pentane in amounts between 0.4 and 0.75 mmol, for example, a [Pd] / 1,5-di(di-tert-butylphosphine)pentane ratio between 0.1 / (0.4-0.75), exhibits good linear ester product selectivity. Using methanesulfonic acid as the acid further enhances the selectivity of the linear ester product.

Claims

1. A method for preparing a homogeneous catalyst, characterized in that, The method includes the following steps: (1) In a first organic solvent, a dialkylphosphine hydrogen borane complex is formed by reacting a dihaloalkane with a dialkylphosphine hydrogen borane complex under the action of an alkali. (2) In a first alcohol, the dialkylphosphine ligand borane complex is heated to remove borane, thereby obtaining the dialkylphosphine ligand; (3) The dialkylphosphine ligand and the metal precursor are mixed in a second organic solvent to prepare a solution containing a homogeneous catalyst.

2. The method as described in claim 1, characterized in that, The dihaloalkane has one or more of the following characteristics: The halogenation in the dihaloalkane is selected from one or more of fluorination, chlorination, bromination, and iodination; The dihaloalkane is a dihalobranched alkane or a dihalolinear alkane. The dihaloalkanes contain 3 to 10 carbon atoms.

3. The method as described in claim 1, characterized in that, The two alkyl groups in the dialkylphosphine borane complex are each independently selected from C1-C10 alkyl groups and C3-C12 cycloalkyl groups, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, cyclopentyl, n-hexyl, isohexyl, cyclohexyl and adamantyl, preferably tert-butyl.

4. The method as described in claim 1, characterized in that, The metal precursor is selected from one or more salts of Group VIII metals and complexes of Group VIII metals; preferably, the Group VIII metal is selected from one or more of nickel, palladium, platinum, cobalt, rhodium and iridium; preferably, the metal precursor is selected from one or more of Pd(dba)2, Pd2(dba)3, Pd(PPh3)4, Pd(OAc)2, PdCl2, PdBr2, Pd(OCOCF3)2, Pd(PPh3)2Cl2, Pd(dppf)Cl2, Pd(acac)2 and Pd(CH3CN)2Cl2.

5. The method as described in claim 1, characterized in that, The homogeneous catalyst is formed by coordination of the metal precursor and the dialkylphosphine ligand, wherein the metal precursor is as described in claim 4, and the dialkylphosphine ligand has the structure shown in Formula I: In formula I, R 1 R 2 R 3 and R 4 Each is independently selected from C1-C10 alkyl and C3-C12 cycloalkyl, and n is an integer selected from 1 to 8.

6. The method as described in claim 1, characterized in that, Step (1) has one or more of the following characteristics: The alkali is selected from one or more of lithium hydroxide, sodium hydroxide, potassium hydroxide, cesium hydroxide, calcium hydroxide, magnesium hydroxide, sodium carbonate, potassium carbonate, triethylamine, diethylisopropylamine, sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, sodium tert-butoxide, potassium tert-butoxide, n-butyllithium, tert-butyllithium, diisopropylaminolithium, phenyllithium, and hexamethyldisilaminolithium, preferably selected from one or more of sodium tert-butoxide, potassium tert-butoxide, and n-butyllithium; The first organic solvent is selected from one or more of aprotic polar solvents and protic polar solvents. The aprotic polar solvent is selected from one or more of acetonitrile, propionitrile, butyronitrile, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, sulfolane, 1,4-dioxane, tetrahydrofuran, and dichloromethane. The protic polar solvent is selected from one or more of alcohols. The first organic solvent is preferably selected from one or more of acetonitrile, propionitrile, and butyronitrile. The molar ratio of the dialkylphosphine borohydride complex to the dihaloalkane is (0.1-10):1, preferably (1-4):1; The molar ratio of the alkali to the dihaloalkane is (0.05–50):1, preferably (0.2–10):1; The first organic solvent is used for each mole of dihaloalkane at a rate of 0.1 to 10 L, preferably 0.5 to 4 L; The reaction temperature is 0–90℃, preferably 40–60℃; The reaction time is 1 to 24 hours, preferably 3 to 8 hours.

7. The method as described in claim 1, characterized in that, Step (2) has one or more of the following characteristics: The first alcohol is selected from one or more of methanol, ethanol, propanol, and tert-butanol; The amount of the first alcohol is 0.1 to 100 L, preferably 0.5 to 5 L, relative to the amount of dihaloalkane used in step (1); The reaction temperature is 30–200℃, preferably 70–120℃; The reaction time is 1 to 48 hours, preferably 6 to 12 hours.

8. The method as described in claim 4, characterized in that, Step (3) has one or more of the following characteristics: The mixing is carried out at 10–40°C; The second organic solvent is selected from one or more of nonpolar solvents, polar aprotic solvents, and protic solvents. The nonpolar solvent is selected from one or more of benzene, toluene, xylene, and ethylbenzene. The polar aprotic solvent is selected from one or more of dimethyl sulfoxide, N-methylpyrrolidone, sulfolane, N,N-dimethylformamide, N,N-dimethylacetamide, 1,4-dioxane, and tetrahydrofuran. The protic solvent is selected from one or two of methanol and ethanol. Preferably, the second organic solvent is selected from one or more of protic solvents. The molar ratio of the Group VIII metal to the dialkylphosphine ligand in the metal precursor is 1:(1-50), preferably 1:(5-20); Each mole of the metal precursor is produced using 100–5000 L of the second organic solvent.

9. A method for preparing 3-acetoxypropionate using the hydrogen esterification reaction of vinyl acetate, characterized in that, The method includes: A solution containing a homogeneous catalyst, vinyl acetate, an acid, and a second alcohol are added to a third organic solvent, and carbon monoxide and optionally another gas are introduced to carry out a hydrogen esterification reaction to give 3-acetoxypropionate, wherein the homogeneous catalyst is formed by coordination of the metal precursor and a dialkylphosphine ligand as described in claim 4; or The metal precursor, dialkylphosphine ligand, vinyl acetate, acid, and second alcohol described in claim 4 are added to a third organic solvent, and carbon monoxide and optional other gases are introduced to generate a homogeneous catalyst in situ from the metal precursor and the dialkylphosphine ligand, thereby carrying out a hydrogen esterification reaction to obtain 3-acetoxypropionate. The dialkylphosphine ligand has the structure shown in Formula I: In formula I, R 1 R 2 R 3 and R 4 Each is independently selected from C1-C10 alkyl and C3-C12 cycloalkyl, and n is an integer selected from 3 to 8.

10. The method as described in claim 9, characterized in that, The method has one or more of the following characteristics: The solution containing the homogeneous catalyst is obtained by mixing a metal precursor and a dialkylphosphine ligand in a molar ratio of 1:(5-20) in a third organic solvent; During the in-situ generation of the homogeneous catalyst, the molar ratio of the metal precursor to the dialkylphosphine ligand is 1:(5-20); The volume ratio of vinyl acetate to the second alcohol is 1:(0.1-10), preferably 1:(0.5-2); and the number of moles of the second alcohol is greater than the number of moles of vinyl acetate. The amount of homogeneous catalyst added is such that the molar ratio of the Group VIII metal to vinyl acetate is (10) -8 ~10 -1 ): 1, preferably (10) -6 ~10 -3 ): 1; The molar ratio of the acid to the group VIII metal in the homogeneous catalyst is (0.1-100):1, preferably (1-10):1; The reaction temperature is between -10 and 160°C, preferably between 60 and 120°C; The partial pressure of carbon monoxide is 1–60 bar, preferably 3–40 bar; The reaction time is 0.1 to 48 hours, preferably 2 to 16 hours.

Images