CN118530276A - Phosphine ligands and their application in the synthesis of acrylic acid esters by carbonylation of acetylene - Google Patents

Abstract

The present invention relates to a phosphine ligand and its application in the synthesis of acrylic acid ester by carbonylation of acetylene. The phosphine ligand of the present invention is shown in Formula I. The phosphine ligand of the present invention can be combined with a palladium catalyst to jointly catalyze the carbonylation reaction of acetylene to synthesize acrylic acid ester. The method has the characteristics of high catalytic efficiency, high product yield, high selectivity, simple operation, etc.

Description

Phosphine ligands and their application in the synthesis of acrylic acid esters by carbonylation of acetylene

Technical Field

The invention relates to a phosphine ligand and application thereof in the synthesis of acrylic acid ester by carbonylation of acetylene.

Background Art

Acrylic acid ester is an important chemical raw material, mainly used for synthetic resin monomers, and is widely used in coatings, adhesives, textiles, rubber and other industries. Driven by the construction, textile and packaging industries, my country's consumption of acrylic acid (ester) continues to grow rapidly. Propylene oxidation has always been the main method for industrial production of acrylic acid. However, with the increasing depletion of petroleum resources and rising prices, the development of routes that replace petrochemical products as raw materials has received widespread attention. Therefore, the synthesis of acrylic acid (ester) by acetylene carbonylation, a non-petroleum route, will be more competitive and is one of the technical development trends for the production of acrylic acid (ester).

Acetylene carbonylation to acrylic acid was first invented by German W. Reppe (US2653969). In the presence of nickel tetracarbonyl, acetylene-carbon monoxide-water (alcohol) was converted into acrylic acid (ester). This reaction requires high conditions (>150°C, 1-3 MPa), serious catalyst loss, and high toxicity. After being improved by Rohmd-Hass, Dow-Badische, and BASF, it was used in industrial production (US2582911, US2964558, US3060228, US2881205, US2845451, US2886591, US2883418). So far, there are no less than hundreds of catalysts reported for this reaction, but they are basically based on nickel halides or copper halides. Although these halogen-containing catalysts have good yields and selectivities, they have problems such as long reaction time, carbon deposition during the reaction, and severe equipment corrosion.

Alper et al. found that palladium acetate can achieve the hydrogen carbonylation reaction of alkynes to synthesize α,β-unsaturated acids under the promotion of acid and phosphine ligands (Organometallics 1993, 12, 712; J.Org.Chem.1993, 58, 4739). The authors found that phosphine ligands are very important for reaction activity and selectivity. In 2009, the CN101768070A patent disclosed the use of palladium acetate as a catalyst, sulfonic acid as an auxiliary agent, and 2-pyridyldiphenylphosphine as a ligand to achieve the carbonylation of acetylene to synthesize acrylic acid under mild conditions (40°C, 5MPa), but the acetylene conversion rate of this method is not high (<42%). In 2015, Zhou Qilin et al. used the Pd(II)/Xantphos catalytic system and formic acid as a carbonyl source to achieve the carbonylation reaction of acetylene to synthesize acrylic acid, and the highest TON of the reaction reached 140 (Angew.Chem.Int.Ed.2015, 54, 6302). Although the conditions of the palladium catalytic system are relatively mild and the reaction selectivity is good, the current catalyst activity is not high enough, that is, the catalytic conversion number is low, which affects the industrial application of the process.

Summary of the invention

The object of the present invention is to provide a catalyst for preparing acrylic acid esters by carbonylation of acetylene.

Another object of the present invention is to provide a process for preparing acrylic acid ester (such as methyl acrylate, ethyl acrylate, butyl acrylate or octyl acrylate).

In a first aspect of the present invention, a phosphine ligand for acetylene-catalyzed preparation of acrylic acid ester is provided, wherein the ligand has a structure selected from the group consisting of:

in,

^R1 and ^R4 are each independently selected from the group consisting of a substituted or unsubstituted _C1-10 alkyl group, a substituted or unsubstituted _C3-10 cycloalkyl group, or a substituted or unsubstituted _C6-30 aryl group;

R ² and R ³ are each independently selected from the group consisting of a substituted or unsubstituted 5-20 membered heteroaryl group;

R ⁵ and R ⁶ are each independently one or more substituents located on the corresponding ring selected from the group consisting of H, C _1-10 alkyl, C _1-10 alkoxy, C _2-10 ester, cyano, COOH, benzenesulfonyl, trialkylsilyl (wherein the alkyl is C _1-4 alkyl), nitro, C _6-30 aryl, 5-30 membered heteroaryl; or two R ⁵ and R ⁶ located on adjacent ring atoms and the ring atoms to which they are connected together form a 5-7 membered carbocyclic or heterocyclic ring, wherein the heterocyclic ring may have 1-3 heteroatoms selected from the group consisting of N, O or S;

Unless otherwise specified, the substitution refers to that one or more hydrogen atoms on the group are replaced by a substituent selected from the group consisting of C _1-10 alkyl, C _1-10 alkoxy, C _2-10 ester, cyano, COOH, benzenesulfonyl, trialkylsilyl (wherein the alkyl is C _1-4 alkyl), nitro, C _6-30 aryl, and 5-30 membered heteroaryl.

In another preferred embodiment, in the ligand, R ¹ and R ⁴ are each independently selected from the following group: substituted or unsubstituted C _1-4 alkyl, substituted or unsubstituted C _3-6 cycloalkyl, substituted or unsubstituted C _6-14 aryl;

R ² and R ³ are each independently selected from the group consisting of a substituted or unsubstituted 5-10 membered heteroaryl group;

Wherein, R ¹ , R ² , R ³ and R ⁴ are each independently unsubstituted or substituted by 1-2 substituents selected from the group consisting of methyl, methoxy, cyano, COOH, benzenesulfonyl, and trimethylsilyl.

In another preferred embodiment, in the ligand,

^R1 and ^R4 are each independently selected from the group consisting of methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, isobutyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl or phenyl or adamantyl;

^R2 and ^R3 are each independently selected from the group consisting of pyridyl, pyrazinyl, pyrimidinyl, pyridazinyl, pyrrolyl, imidazolyl, pyrazolyl, thienyl, furanyl, thiazolyl, triazolyl;

R ⁵ and R ⁶ are each independently selected from the following group: H, C _1-10 alkyl, C _1-10 alkoxy, C _2-10 ester, cyano, COOH, benzenesulfonyl, trialkylsilyl (wherein the alkyl is C _1-4 alkyl), nitro, C _6-30 aryl, 5-30 membered heteroaryl; or two R ⁵ and R ⁶ located on adjacent ring atoms and the ring atoms to which they are connected together form a 5-7 membered carbocyclic or heterocyclic ring.

In another preferred embodiment, the ligand in the ligand is selected from the following group:

In a second aspect of the present invention, there is provided a method for synthesizing acrylic acid ester by carbonylation of acetylene catalyzed by palladium, the method comprising the steps of:

a) dissolving a palladium catalyst, a phosphine ligand and an acid in an alcohol and an optional solvent in a reaction vessel; wherein the phosphine ligand is the phosphine ligand of formula I as described in the first aspect;

b) introducing acetylene into the kettle and then introducing carbon monoxide to react;

c) End the reaction and separate the product.

In another preferred embodiment, the reaction kettle is an autoclave.

In another preferred embodiment, the amount of the phosphine ligand used is 0.00001 to 10% molar equivalent of the acetylene, and more preferably 0.0001 to 1% molar equivalent.

In another preferred embodiment, the reaction temperature is 0-200°C, preferably room temperature to 130°C.

In another preferred embodiment, the reaction is carried out under the protection of an inert gas; preferably, the inert gas is nitrogen and/or argon.

In another preferred embodiment, the reaction is carried out at 1-10 MPa; preferably, the reaction is carried out at 2-8 MPa.

In another preferred embodiment, the reaction time is 0.5 to 72 hours, preferably 0.5 to 24 hours.

In another preferred embodiment, the alcohol is a C _1-12 alkyl alcohol; preferably, the alcohol is selected from the following group: methanol, ethanol, propanol, butanol, octanol, or a combination thereof.

In another preferred embodiment, in the reaction, the amount of the alcohol used is 1-100 molar equivalents of the acetylene, preferably 1-10 molar equivalents.

In another preferred embodiment, the palladium catalyst is selected from the following group: palladium acetate, palladium trifluoroacetate, palladium pentanoate, palladium tetraacetonitrile tetrafluoroborate, palladium hexafluoroacetylacetonate, palladium di(acetylacetone), palladium tetraacetonitrile trifluoromethanesulfonate, palladium pivalate, bis(dibenzylideneacetone)palladium, tris(dibenzylideneacetone)dipalladium, palladium chloride, diacetonitrile palladium dichloride, dibenzonitrile palladium dichloride, or a combination thereof.

In another preferred embodiment, the palladium catalyst is selected from the following group: palladium acetate, palladium trifluoroacetate, palladium pentanoate, tris(dibenzylideneacetone)dipalladium, palladium chloride or a combination thereof.

In another preferred embodiment, the amount of the palladium catalyst used is 0.00001 to 10% molar equivalent of the acetylene, and more preferably 0.0001 to 1% molar equivalent.

In another preferred embodiment, in the reaction, when the phosphine ligand is a bisphosphine ligand (ie, a compound of formula I), the molar ratio of the palladium catalyst to the bisphosphine ligand is 1:1 to 1:30, more preferably 1:1 to 1:5.

In another preferred embodiment, the acid is selected from the following group: perchloric acid, sulfuric acid, phosphoric acid, sulfonic acid, alkylphosphonic acid, alkylsulfonic acid, alkylcarboxylic acid, perfluoroalkylsulfonic acid, perfluoroalkylcarboxylic acid, arylsulfonic acid, wherein the alkyl is C _1-12 alkyl, and the aryl is C ₆ -C ₁₀ aryl.

In another preferred embodiment, the acid is selected from the group consisting of methanesulfonic acid, trifluoromethanesulfonic acid, tert-butanesulfonic acid, p-toluenesulfonic acid (PTSA), 2-hydroxypropane-2-sulfonic acid, 2,4,6-trimethylbenzenesulfonic acid, dodecylsulfonic acid, sulfuric acid, sulfonic acid, formic acid and trifluoroacetic acid.

In another preferred embodiment, the amount of the acid used is 0.00004 to 100% molar equivalent of the acetylene, preferably 0.0004 to 4% molar equivalent.

In another preferred embodiment, the inert solvent is selected from the following group: alkane solvents, substituted aromatic solvents, ether solvents, ketone solvents, nitrile solvents, ester solvents, or a combination thereof.

In another preferred embodiment, the alkane solvent is selected from the following group: n-hexane, cyclohexane, or a combination thereof.

In another preferred embodiment, the substituted aromatic hydrocarbon solvent is selected from the group consisting of chlorobenzene, toluene and trifluorotoluene.

In another preferred embodiment, the ether solvent is selected from the following group: tetrahydrofuran, diethyl ether, methyl tert-butyl ether, ethyl tert-butyl ether, anisole, ethylene glycol dimethyl ether, 1,4-dioxane, or a combination thereof.

In another preferred embodiment, the ketone solvent is selected from the following group: acetone.

In another preferred embodiment, the nitrile solvent is selected from the following group: acetonitrile, propionitrile, benzonitrile, or a combination thereof.

In another preferred embodiment, the ester solvent is selected from the following group: ethyl acetate, methyl acrylate, ethyl acrylate, butyl acrylate, octyl acrylate, or a combination thereof.

In another preferred embodiment, the alcohol is methanol, and the reaction is carried out under the following conditions:

a) dissolving palladium acetate, a phosphine ligand and an acid in methanol or a mixed solvent with an optional solvent;

b) introducing acetylene into the kettle and then introducing carbon monoxide to react, wherein the reaction is carried out at room temperature to 120° C.;

c) End the reaction and separate the product.

In another preferred embodiment, the alcohol is ethanol, and the reaction is carried out under the following conditions:

a) dissolving palladium acetate, a phosphine ligand and an acid in ethanol or a mixed solvent with an optional solvent;

b) introducing acetylene into the kettle and then introducing carbon monoxide to react, wherein the reaction is carried out at room temperature to 120° C.;

c) End the reaction and separate the product.

In another preferred embodiment, the alcohol is butanol, and the reaction is carried out under the following conditions:

a) dissolving palladium acetate, phosphine ligand and acid in butanol or a mixed solvent with an inert solvent,

b) introducing acetylene into the kettle and then introducing carbon monoxide to react, wherein the reaction is carried out at room temperature to 120° C.;

c) End the reaction and separate the product.

In another preferred embodiment, the alcohol is octanol, and the reaction is carried out under the following conditions:

a) dissolving palladium acetate, phosphine ligand and acid in octanol or a mixed solvent with an inert solvent,

b) introducing acetylene into the kettle and then introducing carbon monoxide to react, wherein the reaction is carried out at room temperature to 120° C.;

c) End the reaction and separate the product.

It should be understood that within the scope of the present invention, the above-mentioned technical features of the present invention and the technical features specifically described below (such as embodiments) can be combined with each other to form a new or preferred technical solution. Due to space limitations, they will not be described one by one here.

DETAILED DESCRIPTION

Based on long-term and in-depth research, the inventors have prepared a series of novel phosphine ligands and a method for synthesizing acrylic esters by carbonylation of acetylene based on the ligands. The method can improve the catalytic efficiency of the carbonylation reaction of acetylene, improve the conversion rate of acetylene and product selectivity, and the reaction conditions are mild and the operation is simple. Based on the above findings, the inventors have completed the present invention.

definition

In the present invention, "room temperature" means 10 to 30°C.

In the present invention, the term "alkyl" refers to a linear or branched saturated hydrocarbon group, preferably a C _1-10 alkyl group (eg, a C _1-8 alkyl group, a C _1-6 alkyl group, a C _1-4 alkyl group).

In the present invention, the term "cycloalkyl" refers to a saturated monocyclic or carbon ring substituent containing a fused, bridged or spiro polycyclic system, preferably a C _3-8 cycloalkyl (eg C _3-6 cycloalkyl).

In the present invention, the term "alkoxy" refers to a cyclic or non-cyclic alkyl group connected by an oxygen bridge, and the definitions of alkyl and cycloalkyl are as described above, preferably a C _1-10 alkoxy group (e.g., a C _1-8 alkoxy group, a C _1-6 alkoxy group, a C _1-4 alkoxy group).

Unless otherwise specified, in the present invention, "aryl" refers to a group having 6-30 (preferably 6-14) ring carbon atoms and zero heteroatoms, a monocyclic or polycyclic (e.g., bicyclic or tricyclic) 4n+2 aromatic ring system (e.g., having 6, 10, or 14 shared p electrons in a cyclic array), preferably a _C6 - _C14 aryl group, and more preferably a _C6 - _C10 aryl group).

Unless otherwise specified, in the present invention, "heteroaryl" refers to a group having a monocyclic or polycyclic (e.g., bicyclic or tricyclic) 4n+2 aromatic ring system (e.g., having 6, 10, or 14 shared p electrons in a cyclic array) having 5-30 (preferably 5-20, more preferably 5-14) ring atoms (the ring atoms may be carbon atoms or heteroatoms), preferably a 5-15 membered heteroaryl, and more preferably a 5-9 membered heteroaryl.

Without violating the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

The reagents and raw materials used in the present invention are commercially available.

The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. The experimental methods in the following examples without specifying specific conditions are usually based on conventional conditions or the conditions recommended by the manufacturer. Unless otherwise stated, percentages and parts are calculated by weight.

Example 1 Preparation of the ligand represented by formula I

In a 100mL three-necked flask equipped with a thermometer, a magnetic stirrer and a reflux cooler, dibromide II (10mmol) was dissolved in 50mL of dry tetrahydrofuran. After cooling to -78°C, n-butyl lithium (25mL, 1.6M n-hexane solution) was added by injection. After stirring at low temperature for 3 hours, chlorophosphine (20mmol) dissolved in 20mL of dry tetrahydrofuran was then added dropwise, and the mixture was naturally returned to room temperature to react overnight. After the reaction was completed, 2mL of degassed water was added to quench the reaction, the mixture was concentrated, the solvent was removed, oxygen-free water was added, ether was extracted, the liquids were separated, and after drying over anhydrous magnesium sulfate, the ether was removed and the obtained sample was recrystallized in methanol to obtain a white or light yellow solid powder.

Some ligand data are as follows:

¹ H NMR (400MHz, CDCl ₃ ) δ8.59–8.48(m,2H),7.60(d,J＝8.0Hz,2H),7.53(d,J＝7.6Hz,2H),7.45–7.36(m, 2H),7.30–7.25(m,6H),6.99–6.90(m,2H),1.17–0.97(m,18H).

¹ H NMR (400 MHz, CDCl ₃ ) δ8.60 (d, J = 7.6 Hz, 4H), 7.55 (d, J = 7.6 Hz, 2H), 7.45–7.38 (m, 2H), 7.30–7.26 (m ,4H),7.02–6.97(m,2H),1.18–0.99(m,18H).

¹ H NMR (400 MHz, CDCl ₃ )7.45–7.38(m,2H),7.30–7.26(m,4H),7.02–6.97(m,2H),6.75–6.67(m,2H),6.55–6.50( m,2H),6.38–6.30(m,2H),3.55(s,6H),1.20–0.99(m,18H).

¹ H NMR (400 MHz, CDCl ₃ )7.75–7.70(m,2H),7.45–7.38(m,2H),7.30–7.26(m,4H),7.15–7.10(m,2H),6.55–6.50( m,2H),3.72(s,3H),3.68(s,3H),1.20–0.99(m,18H).

¹ H NMR (400 MHz, CDCl ₃ )8.32–8.27(m,4H),7.78–7.70(m,6H),7.56–7.36(m,6H),7.30–7.26(m,4H),1.17–1.00( m,18H).

¹ H NMR (400 MHz, CDCl ₃ ) δ7.62 (d, J = 8.0 Hz, 2H), 7.45–7.38 (m, 2H), 7.30–7.26 (m, 4H), 7.02–6.97 (m, 2H) ,6.45(d,J＝8.0 Hz,2H),3.55(s,6H),1.20–0.99(m,18H).

¹ H NMR (400 MHz, CDCl ₃ ) δ7.78–7.60 (m, 2H), 7.53 (d, J = 7.6 Hz, 2H), 7.45–7.36 (m, 2H), 7.30–7.25 (m, 4H) ,6.93–6.89(m,2H),6.54–6.49(m,2H),1.10–0.95(m,18H).

¹ H NMR (400 MHz, CDCl ₃ ) δ7.96–7.90(m,2H),7.60–6.55(m,4H),7.45–7.36(m,2H),7.30–7.25(m,6H),1.10– 0.91(m,18H).

¹ H NMR (400 MHz, CDCl ₃ ) δ8.85–8.75(m,6H),7.60–6.55(m,2H),7.45–7.36(m,2H),7.30–7.25(m,4H),1.78– 1.70(m,2H),1.03–0.90(m,12H).

¹ H NMR (400MHz, CDCl ₃ ) δ8.60 (d, J = 7.6 Hz, 4H), 8.02 (s, 2H), 7.87–7.83 (m, 2H), 7.78–7.73 (m, 4H), 7.62– 7.51(m,10H),1.16–1.02(m,18H).

¹ H NMR (400 MHz, CDCl ₃ ) δ7.45–7.37(m,4H),7.27–7.24(m,2H),7.16–7.14(m,2H),6.56–6.50(m,2H),3.67- 3.65(m,6H),2.58–2.54(m,6H),2.03–1.96(m,6H),1.73–1.58(m,24H).

¹ H NMR (400 MHz, CDCl ₃ ) δ8.60–8.52(m,4H),7.72–7.67(m,2H),7.12–7.06(m,4H),6.03(s,4H),2.03–1.96( m,6H),1.75–1.55(m,24H).

¹ H NMR (400 MHz, CDCl ₃ ) δ8.60–8.52(m,4H),7.72–7.67(m,4H),7.21–7.18(m,2H),7.12–7.06(m,2H),3.82( s,6H),2.03–1.96(m,6H),1.83–1.71(m,24H).

¹ H NMR (400MHz, CDCl ₃ ) δ8.63–8.54(m,4H),7.72–7.62(m,4H),7.41–7.32(m,2H),7.27–7.22(m,2H),2.03–1.96 (m,6H),1.83–1.71(m,24H),0.13(s,18H).

¹ H NMR (400MHz, CDCl ₃ ) δ8.56–8.51(m,4H),7.70–7.66(m,4H),7.38–7.28(m,4H),2.03–1.96(m,6H),1.36–1.32 (m,18H),1.83–1.71(m,24H).

Example 2

PdCl ₂ (1.8 mg, 0.01 mmol), bisphosphine ligand L1 (19.4 mg, 0.04 mmol), trifluoromethanesulfonic acid (14.2 μL, 0.16 mmol), butanol (10 mL), tetrahydrofuran (10 mL) and a stirrer were added to a 300 mL Parr autoclave under nitrogen protection, and acetylene gas was replaced. Acetylene gas (62 mmol) was added through a flow meter under cooling, and then carbon monoxide was added until the pressure in the autoclave reached 4 MPa. The temperature was quickly raised to 120°C and stirred for reaction for 5 hours. After the reaction was completed, the temperature was lowered, and the yield of butyl acrylate was 83% and the selectivity was greater than 90% as determined by nuclear magnetic resonance.

Example 3

Pd(OAc) ₂ (2.2 mg, 0.01 mmol), bisphosphine ligand L2 (9.7 mg, 0.02 mmol), methanesulfonic acid (6.5 μL, 0.10 mmol), methanol (20 mL) and a stirrer were added to a 300 mL Parr autoclave under nitrogen protection, and acetylene gas was replaced. Acetylene gas (62 mmol) was added through a flow meter under cooling, and then carbon monoxide was added until the pressure in the autoclave reached 4 MPa. The temperature was quickly raised to 120°C and stirred for 5 hours. After the reaction was completed, the temperature was lowered, and the yield of methyl acrylate was 91% by nuclear magnetic resonance, and the selectivity was greater than 90%.

Example 4

Pd(CF ₃ COO) ₂ (palladium trifluoroacetate) (4.0 mg, 0.01 mmol), bisphosphine ligand L3 (19.5 mg, 0.04 mmol), methanesulfonic acid (6.5 μL, 0.10 mmol), methanol (10 mL) and a stirrer were added to a 300 mL Parr autoclave under nitrogen protection, and acetylene gas was replaced. Acetylene gas (62 mmol) was added through a flow meter under cooling, and then carbon monoxide was added until the pressure in the autoclave reached 4 MPa. The temperature was quickly raised to 120°C and stirred for reaction for 5 hours. After the reaction was completed, the temperature was lowered, and the yield of methyl acrylate was 82% and the selectivity was greater than 90% as determined by nuclear magnetic resonance.

Example 5

Pd(OPiv) ₂ (palladium pentanoate) (3.1 mg, 0.01 mmol), bisphosphine ligand L4 (11.7 mg, 0.02 mmol), methanesulfonic acid (10.4 μL, 0.16 mmol), methanol (10 mL) and a stirrer were added to a 300 mL Parr autoclave under nitrogen protection, and acetylene gas was replaced. Acetylene gas (100 mmol) was added through a flow meter under cooling, and then carbon monoxide was added until the pressure in the autoclave was 6 MPa. The temperature was quickly raised to 120°C and stirred for 5 hours. After the reaction was completed, the temperature was lowered, and the yield of methyl acrylate was 92% by nuclear magnetic resonance, and the selectivity was greater than 90%.

Example 6

Pd ₂ (dba) ₃ (tridibenzylideneacetone dipalladium) (4.6 mg, 0.005 mmol), bisphosphine ligand L5 (9.7 mg, 0.02 mmol), p-toluenesulfonic acid (17.2 mg, 0.10 mmol), methanol (10 mL) and a stirrer were added to a 300 mL Parr autoclave under nitrogen protection, and acetylene gas was replaced. Acetylene gas (100 mmol) was added through a flow meter under cooling, and then carbon monoxide was added until the pressure in the autoclave was 6 MPa. The temperature was quickly raised to 120°C and stirred for 5 hours. After the reaction was completed, the temperature was lowered, and the yield of methyl acrylate was 96% by nuclear magnetic resonance, and the selectivity was greater than 90%.

Example 7

Pd(OAc) ₂ (2.2 mg, 0.01 mmol), bisphosphine ligand L6 (19.6 mg, 0.04 mmol), methanesulfonic acid (6.5 μL, 0.10 mmol), methanol (20 mL) and a stirrer were added to a 300 mL Parr autoclave under nitrogen protection, and acetylene gas was replaced. Acetylene gas (62 mmol) was added through a flow meter under cooling, and then carbon monoxide was added until the pressure in the autoclave was 4 MPa. The temperature was quickly raised to 120°C and stirred for 5 hours. After the reaction was completed, the temperature was lowered, and the yield of methyl acrylate was 80% and the selectivity was greater than 90% by nuclear magnetic resonance.

Example 8

Pd(OAc) ₂ (2.2 mg, 0.01 mmol), bisphosphine ligand L7 (9.2 mg, 0.02 mmol), dodecylsulfonic acid (26.1 mg, 0.08 mmol), methanol (20 mL) and a stirrer were added to a 300 mL Parr autoclave under nitrogen protection, and acetylene gas was replaced. Acetylene gas (62 mmol) was added through a flow meter under cooling, and then carbon monoxide was added until the pressure in the autoclave was 4 MPa. The temperature was quickly raised to 120°C and stirred for 5 hours. After the reaction was completed, the temperature was lowered, and the yield of methyl acrylate was 57% by nuclear magnetic resonance, and the selectivity was greater than 90%.

Example 9

Pd(hfacac) ₂ (hexafluoroacetylacetonate palladium) (3.1 mg, 0.01 mmol), bisphosphine ligand L8 (19.7 mg, 0.04 mmol), methanesulfonic acid (10.4 μL, 0.16 mmol), octanol (10 mL), n-hexane (10 mL) and a stirrer were added to a 300 mL Parr autoclave under nitrogen protection, and acetylene gas was replaced. Acetylene gas (62 mmol) was added through a flow meter under cooling, and then carbon monoxide was added until the pressure in the autoclave was 4 MPa. The temperature was quickly raised to 120°C and stirred for 5 hours. After the reaction was completed, the temperature was lowered, and the yield of octyl acrylate was 87% by nuclear magnetic resonance, and the selectivity was greater than 90%.

Example 10

Pd(CH ₃ CN) ₄ (BF ₄ ) ₂ (tetraacetonitrile palladium tetrafluoroborate) (4.4 mg, 0.01 mmol), bisphosphine ligand L9 (18.3 mg, 0.04 mmol), methanesulfonic acid (10.4 μL, 0.16 mmol), methanol (10 mL), 1,4-dioxane (10 mL) and a stirrer were added to a 300 mL Parr autoclave under nitrogen protection, and acetylene gas was replaced. Acetylene gas (62 mmol) was added through a flow meter under cooling, and then carbon monoxide was added until the pressure in the autoclave was 4 MPa. The temperature was quickly raised to 120°C and stirred for 5 hours. After the reaction was completed, the temperature was lowered, and the yield of methyl acrylate was 86% and the selectivity was greater than 90% by nuclear magnetic resonance.

Embodiment 11

Pd(OAc) ₂ (0.2 mg, 0.001 mmol), bisphosphine ligand L10 (1.3 mg, 0.002 mmol), methanesulfonic acid (10.4 μL, 0.16 mmol), butanol (10 mL), tetrahydrofuran (10 mL) and a stirrer were added to a 300 mL Parr autoclave under nitrogen protection, and acetylene gas was replaced. Acetylene gas (62 mmol) was added through a flow meter under cooling, and then carbon monoxide was added until the pressure in the autoclave was 4 MPa. The temperature was quickly raised to 120°C and stirred for 7 hours. After the reaction was completed, the temperature was lowered, and the yield of butyl acrylate was 81% and the selectivity was greater than 90% by nuclear magnetic resonance.

Example 12

Pd(OAc) ₂ (2.2 mg, 0.01 mmol), bisphosphine ligand L11 (13.5 mg, 0.02 mmol), p-toluenesulfonic acid (17.5 mg, 0.10 mmol), methanol (10 mL), tetrahydrofuran (10 mL) and a stirrer were added to a 300 mL Parr autoclave under nitrogen protection, and acetylene gas was replaced. Acetylene gas (100 mmol) was added through a flow meter under cooling, and then carbon monoxide was added until the pressure in the autoclave reached 6 MPa. The temperature was quickly raised to 120°C and stirred for 5 hours. After the reaction was completed, the temperature was lowered, and the yield of methyl acrylate was 68% and the selectivity was greater than 90% by nuclear magnetic resonance.

Example 13

Pd(OAc) ₂ (2.2 mg, 0.01 mmol), bisphosphine ligand L12 (14.6 mg, 0.02 mmol), methanesulfonic acid (10.4 μL, 0.16 mmol), methanol (10 mL) and a stirrer were added to a 300 mL Parr autoclave under nitrogen protection, and acetylene gas was replaced. Acetylene gas (100 mmol) was added through a flow meter under cooling, and then carbon monoxide was added until the pressure in the autoclave reached 6 MPa. The temperature was quickly raised to 120°C and stirred for 5 hours. After the reaction was completed, the temperature was lowered, and the yield of methyl acrylate was 92% by nuclear magnetic resonance, and the selectivity was greater than 90%.

Embodiment 14

Pd(OAc) ₂ (2.24 mg, 0.01 mmol), bisphosphine ligand L14 (15.7 mg, 0.02 mmol), trifluoroacetic acid (12 μL, 0.16 mmol), methanol (20 mL), tetrahydrofuran (10 mL) and a stirrer were added to a 300 mL Parr autoclave under nitrogen protection, and acetylene gas was replaced. Acetylene gas (100 mmol) was added through a flow meter under cooling, and then carbon monoxide was added until the pressure in the autoclave reached 6 MPa. The temperature was quickly raised to 120°C and stirred for 5 hours. After the reaction, the yield of methyl acrylate was 75% and the selectivity was greater than 90% by nuclear magnetic resonance.

Embodiment 15

Pd(OAc) ₂ (2.2 mg, 0.01 mmol), bisphosphine ligand L15 (15.1 mg, 0.02 mmol), methanesulfonic acid (10.4 μL, 0.16 mmol), methanol (20 mL), tetrahydrofuran (10 mL) and a stirrer were added to a 300 mL Parr autoclave under nitrogen protection, and acetylene gas was replaced. Acetylene gas (100 mmol) was added through a flow meter under cooling, and then carbon monoxide was added until the pressure in the autoclave reached 6 MPa. The temperature was quickly raised to 120°C and stirred for 5 hours. After the reaction, the yield of methyl acrylate was 82% and the selectivity was greater than 90% by nuclear magnetic resonance.

Example 16

Pd(OAc) ₂ (2.2 mg, 0.01 mmol), bisphosphine ligand L1 (19.4 mg, 0.04 mmol), methanesulfonic acid (10.4 μL, 0.16 mmol), methanol (20 mL) and a stirrer were added to a 300 mL Parr autoclave under nitrogen protection, and acetylene gas was replaced. Acetylene gas (100 mmol) was added through a flow meter under cooling, and then carbon monoxide was added until the pressure in the autoclave reached 6 MPa. The temperature was quickly raised to 100 ° C and stirred for 5 hours. After the reaction was completed, the temperature was lowered, and the yield of methyl acrylate was 90% by nuclear magnetic resonance, and the selectivity was greater than 90%.

Embodiment 17

Pd(OAc) ₂ (2.2 mg, 0.01 mmol), bisphosphine ligand L1 (19.4 mg, 0.04 mmol), methanesulfonic acid (10.4 μL, 0.16 mmol), methanol (20 mL) and a stirrer were added to a 300 mL Parr autoclave under nitrogen protection, and acetylene gas was replaced. Acetylene gas (100 mmol) was added through a flow meter under cooling, and then carbon monoxide was added until the pressure in the autoclave reached 6 MPa. The temperature was quickly raised to 80°C and stirred for 5 hours. After the reaction was completed, the temperature was lowered, and the yield of methyl acrylate was 85% and the selectivity was greater than 90% by nuclear magnetic resonance.

Embodiment 18

Pd(OAc) ₂ (2.2 mg, 0.01 mmol), bisphosphine ligand L1 (19.4 mg, 0.04 mmol), methanesulfonic acid (10.4 μL, 0.16 mmol), methanol (20 mL) and a stirrer were added to a 300 mL Parr autoclave under nitrogen protection, and acetylene gas was replaced. Acetylene gas (100 mmol) was added through a flow meter under cooling, and then carbon monoxide was added until the pressure in the autoclave reached 6 MPa. The temperature was quickly raised to 40°C and stirred for 8 hours. After the reaction was completed, the temperature was lowered, and the yield of methyl acrylate was 84% by nuclear magnetic resonance, and the selectivity was greater than 90%.

When the phosphine ligand of the present invention is used for catalytic preparation of acrylic ester, the acrylic ester product can be obtained with a relatively high yield (>55%, the best embodiment>80%) and good selectivity, and therefore has potential industrial application.

In addition, the phosphine ligand of the present invention has a good catalytic conversion rate, and thus the catalytic reaction can be completed at a low dosage (<10 ^-4 equivalent, preferably <10 ^-5 equivalent, and more preferably <10 ^-6 equivalent).

All documents mentioned in the present invention are cited as references in this application, just as each document is cited as reference individually. In addition, it should be understood that after reading the above teachings of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

Claims (10)

1. A phosphine ligand, said ligand having a structure selected from the group consisting of formula I:

Wherein,

R ¹ and R ⁴ are each independently selected from the group consisting of: an alkyl group of substituted or unsubstituted C _1-10, a cycloalkyl group of substituted or unsubstituted C _3-10, a C _6-30 aryl group of substituted or unsubstituted;

R ² and R ³ are each independently selected from the group consisting of: a substituted or unsubstituted 5-20 membered heteroaryl;

Each R ⁵、R⁶ is independently one or more substituents on the corresponding ring selected from the group consisting of: H. c _1-10 alkyl, C _1-10 alkoxy, C _2-10 ester, cyano, COOH, benzenesulfonyl, trialkylsilyl (wherein said alkyl is C _1-4 alkyl), nitro, C _6-30 aryl, 5-to 30-membered heteroaryl; or two R ⁵、R⁶ located on adjacent ring atoms together with the ring atoms to which they are attached form a 5-7 membered carbocyclic or heterocyclic ring which may have 1-3 heteroatoms selected from the group consisting of: n, O or S;

Unless otherwise specified, the substituents refer to the substitution of one or more hydrogen atoms on a group with a substituent selected from the group consisting of: c _1-10 alkyl, C _1-10 alkoxy, C _2-10 ester group, cyano, COOH, benzenesulfonyl, trialkylsilyl (wherein the alkyl is C _1-4 alkyl), nitro, C _6-30 aryl, 5-30 membered heteroaryl.

2. The ligand of claim 1, wherein, in the ligand,

R ¹ and R ⁴ are each independently selected from the group consisting of: a substituted or unsubstituted C _1-4 alkyl group, a substituted or unsubstituted C _3-6 cycloalkyl group, a substituted or unsubstituted C _6-14 aryl group;

R ² and R ³ are each independently selected from the group consisting of: a substituted or unsubstituted 5-20 membered heteroaryl;

Wherein each of R ¹、R²、R³ and R ⁴ is independently unsubstituted or substituted with 1-2 substituents selected from the group consisting of: methyl, methoxy, cyano, COOH, benzenesulfonyl, trimethylsilyl.

3. The ligand of claim 1, wherein, in the ligand,

R ¹ and R ⁴ are each independently selected from the group consisting of: methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl, isobutyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, phenyl or adamantyl;

R ² and R ³ are each independently selected from the group consisting of: pyridyl, pyrazinyl, pyrimidinyl, pyridazinyl, pyrrolyl, imidazolyl, pyrazolyl, thienyl, furyl, thiazolyl, and triazolyl;

r ⁵、R⁶ are each independently selected from the group consisting of: H. c _1-10 alkyl, C _1-10 alkoxy, C _2-10 ester, cyano, COOH, benzenesulfonyl, trialkylsilyl (wherein said alkyl is C _1-4 alkyl), nitro, C _6-30 aryl, 5-to 30-membered heteroaryl; or two R ⁵、R⁶ located on adjacent ring atoms together with the ring atoms to which they are attached form a 5-7 membered carbocyclic or heterocyclic ring.

4. The ligand of claim 1, wherein said ligand is selected from the group consisting of:

5. a method for synthesizing acrylic ester by palladium-catalyzed acetylene carbonyl, which is characterized by comprising the steps of:

a) Dissolving a palladium catalyst, a phosphine ligand and an acid in an alcohol and optionally a solvent in a reaction kettle; wherein the phosphine ligand is a phosphine ligand of formula I as defined in claim 1;

b) Acetylene is introduced into the kettle, and then carbon monoxide is introduced for reaction;

c) Ending the reaction and separating to obtain the product.

6. The process of claim 5 wherein said phosphine ligand is present in an amount of from 0.0001 to 80 mole percent of said acetylene.

7. The method of claim 5, wherein the alcohol is a C _1-12 alkyl alcohol; preferably, the alcohol is selected from the group consisting of: methanol, ethanol, propanol, butanol, octanol, or combinations thereof.

8. The method of claim 5, wherein the palladium catalyst is selected from the group consisting of: palladium acetate, palladium trifluoroacetate, palladium quaternary valerate, palladium tetra acetonitrile tetrafluoroborate, palladium hexafluoroacetylacetonate, palladium bis (acetylacetonate), palladium tetra acetonitrile trifluoromethane sulfonate, palladium pivalate, palladium bis (dibenzylideneacetone), palladium tris (dibenzylideneacetone) dipalladium, palladium chloride, palladium diacetonitrile dichloride, palladium dibenzonitrile dichloride, or a combination thereof.

9. The method of claim 5, wherein the acid is selected from the group consisting of: perchloric acid, sulfuric acid, phosphoric acid, sulfonic acid, alkylphosphonic acid, alkylsulfonic acid, alkylcarboxylic acid, perfluoroalkylsulfonic acid, perfluoroalkylcarboxylic acid, arylsulfonic acid, wherein the alkyl is a C _1-12 alkyl group and the aryl is a C ₆-C₁₀ aryl group.

10. The method of claim 5, wherein the solvent is selected from the group consisting of: an alkane solvent, a substituted aromatic hydrocarbon solvent, an ether solvent, a ketone solvent, a nitrile solvent, an ester solvent, or a combination thereof.