Triaryl phosphine ligand as well as preparation method and application thereof

Abstract

The invention discloses a triaryl phosphine ligand as well as a preparation method and application thereof, belongs to the technical field of chemical engineering, and solves the problem that the action efficiency of a catalyst is not ideal enough in a reaction for generating 1-methoxy-2, 7-octadiene through telomerization of 1, 3-butadiene and methanol catalyzed by palladium in the prior art. The preparation method comprises the following steps: in a water-free and oxygen-free environment, dissolving brominated benzotrifluoride in diethyl ether, dropwise adding n-butyllithium at the temperature of-5 to 5 DEG C, and fully stirring to obtain a lithium reagent; the preparation method comprises the following steps: adding chlorodiaryl phosphorus into a lithium reagent, mixing and stirring, heating to 20-30 DEG C in stages, continuously stirring and reacting under an anaerobic condition, and recrystallizing to obtain the triarylphosphine ligand. The palladium catalytic system obtained by the preparation method is high in 1, 3-butadiene conversion rate, better in ligand selectivity and lower in catalyst concentration, and can be used for industrial production of 1-MOD.

Description

Technical Field

[0001] The present invention relates to the field of chemical engineering technology, and more specifically to a triarylphosphine ligand and its preparation method and application. Background Art

[0002] The telomerization reaction of 1,3-butadiene and methanol is a key step in the commercial route for producing 1-octene reported in relevant literature. Catalyst ligands are selected for the reaction of catalytic telomerization of 1,3-butadiene to form 1-methoxy-2,7-octadiene. According to the published literature, the catalyst ligands include the synthesized monoXantphos ligand, N-heterocyclic carbene ligand, and the monoSPANphos ligand and triarylphosphine ligand being synthesized. Among them, the triarylphosphine ligand has attracted extensive attention due to its simple synthesis method and stable structure.

[0003] In the palladium-catalyzed telomerization reaction of 1,3-butadiene and methanol to produce 1-methoxy-2,7-octadiene, the electron-donating group has a significant effect on the catalyst performance. The electron-donating phosphine ligand can increase the electron density of the palladium center and promote the key steps in the catalytic cycle (such as olefin coordination, insertion, and proton transfer). This electronic effect helps to stabilize the palladium hydride intermediate (Pd-H), thereby improving the catalytic activity; at the same time, a strong electron-donating group may enhance the regioselectivity through stronger metal-ligand interactions. For example, in the palladium / N-heterocyclic carbene (NHC) system developed by Matthias Beller, the NHC ligand, as a strong electron donor, further optimizes the selectivity. In the reported literature, the methoxy group is mostly used as the electron-donating group, and the electron-donating ability and steric hindrance ability of N,N-dimethyl depend on the methoxy group. Summary of the Invention

[0004] The present invention provides a triarylphosphine ligand and its preparation method and application to solve the problem that the catalytic efficiency of the catalyst is not ideal enough in the reaction of palladium-catalyzed telomerization of 1,3-butadiene and methanol to produce 1-methoxy-2,7-octadiene in the prior art.

[0005] In the first aspect, the present invention provides a preparation method of a triarylphosphine ligand, including the following steps: under an anhydrous and anaerobic environment, dissolve benzotrifluoride bromide in diethyl ether, and dropwise add n-butyllithium at -5 to 5 °C, stir well to obtain a lithium reagent; add chlorodiarylphosphine to the lithium reagent, mix and stir, gradually heat up to 20 to 30 °C in stages, continue to stir and react under anaerobic conditions, and recrystallize to obtain the triarylphosphine ligand; wherein, the benzotrifluoride bromide is 2-position or 4-position brominated benzotrifluoride; the triarylphosphine ligand is any one of formula (1), formula (2), formula (3), formula (4), formula (5), and formula (6),

[0006]

[0007] As a possible implementation, according to the preparation method described in claim 1, it is characterized in that the bromotrifluorotoluene is any one of 1-bromo-4-(trifluoromethyl)benzene and 1-bromo-2-(trifluoromethyl)benzene; and / or, the chlorodiarylphosphine is any one of bis(2-methoxyphenyl)phosphine chloride, bis(2-N,N-dimethyl)phenylphosphine chloride, and bis(2-tolyl)phosphine chloride; and / or, in terms of the amount of substance, the addition ratio of the bromotrifluorotoluene, the n-butyllithium, and the chlorodiarylphosphine is 1:1:1.

[0008] As a possible implementation, the duration of the sufficient stirring is 1 h; and / or, the duration of the continued stirring reaction is 4 h.

[0009] As a possible implementation, the recrystallization includes the following steps: after removing the volatile substances in the reaction system, dissolving it in benzene, filtering, and collecting the filtrate; after removing the volatile substances in the filtrate, dissolving it in acetonitrile, filtering, placing it at -10 °C overnight, and collecting the precipitated crystals, which are the triarylphosphine ligand.

[0010] In a second aspect, the present invention provides a triarylphosphine ligand prepared by the preparation method described in any one of the first aspects.

[0011] In a third aspect, the present invention provides an application of the triarylphosphine ligand described in the second aspect in the preparation of 1-methoxy-2,7-octadiene.

[0012] As a possible implementation, it includes the following steps: dissolving a palladium source and the triarylphosphine ligand in methanol, adding acetic acid to obtain a catalyst pre-prepared solution; adding methanol, sodium methoxide, and 1,3-butadiene to the catalyst pre-prepared solution in sequence, and performing a telomerization reaction under an anaerobic condition, reacting at a set temperature and an initial pressure condition, and after the reaction ends, adjusting the reaction system to normal temperature and pressure to obtain the 1-methoxy-2,7-octadiene; wherein, the set temperature is 50 - 90 °C, and the initial pressure ≥ 0.80 MPa.

[0013] As a possible implementation, the amount of the palladium source ligand is twice the equivalent of the palladium source; and / or, the acetic acid is one equivalent of the palladium source.

[0014] As a possible implementation, the palladium source is any one of palladium(II) acetylacetonate, palladium(II) chloride, tetrakis(triphenylphosphine)palladium(0), tris(dibenzylideneacetone)dipalladium(0), and bis(dibenzylideneacetone)palladium(0); and / or, the concentration of the palladium source is 0.00065 mol% - 0.0025 mol%; and / or, the water content of the methanol is 0 - 240 ppm.

[0015] Fourthly, the present invention provides an application of 1-methoxy-2,7-octadiene prepared by using the triarylphosphine ligand described in the second aspect in the preparation of 1-octene.

[0016] In the palladium-catalyzed telomerization reaction of 1,3-butadiene and methanol to produce 1-methoxy-2,7-octadiene, for ligands with relatively excellent performance, when the electron-donating group N,N-dimethyl replaces the methoxy group or this group is added to its parent body, both the conversion rate and selectivity of the p-methoxytriarylphosphine ligand are lower than those of N,N-dimethyltriarylphosphine. This proves that this group is suitable for this reaction and has a positive feedback. The present invention introduces N,N-dimethyl into the novel triarylphosphine to construct a series of novel phosphine ligands, which have relatively high catalytic performance and ideal catalytic effects.

[0017] The present invention aims to provide a high-efficiency catalyst system for the telomerization reaction of 1,3-butadiene and methanol. The triarylphosphine ligand obtained by the preparation method provided by the present invention has better selectivity, lower catalyst concentration and is easy to synthesize, and can be used for industrial production of 1-MOD. Moreover, the present invention further conducts a comparison of the catalytic performance of this series of ligands under the same conditions. This series of ligands has high butadiene conversion rates (60% - 95%) and high 1-MOD selectivities (89% - 95%) for this reaction at low concentrations (5 - 50 ppm).

[0018] The palladium-catalyzed system obtained by the preparation method of the present invention has a high 1,3-butadiene conversion rate, better selectivity of the ligand and lower catalyst concentration, and can be used for industrial production of 1-MOD. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0020] Figure 1 It is a nuclear magnetic resonance hydrogen spectrum schematic diagram of product I provided by an embodiment of the present invention.

[0021] Figure 2 It is a nuclear magnetic resonance hydrogen spectrum schematic diagram of product II provided by an embodiment of the present invention.

[0022] Figure 3 It is a nuclear magnetic resonance hydrogen spectrum schematic diagram of 1-methoxy-2,7-octadiene provided by an embodiment of the present invention.

[0023] Figure 4 It is a gas chromatogram schematic diagram of the product of Experiment IX provided by an embodiment of the present invention.

[0024] Figure 5 This is the gas chromatogram of the product of Experiment X provided by the embodiments of the present invention.

[0025] Figure 6 This is the gas chromatogram of the product of Experiment XIII provided by the embodiments of the present invention. Detailed implementation manners

[0026] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0027] To solve the problem that the catalytic efficiency of the catalyst is not ideal enough in the reaction of palladium-catalyzed telomerization of 1,3-butadiene and methanol to produce 1-methoxy-2,7-octadiene in the prior art, this embodiment provides an experiment for the preparation of a triarylphosphine ligand and its application experiment. It can be seen that the palladium catalytic system obtained by the preparation method provided by the present invention has a high conversion rate of 1,3-butadiene, better selectivity of the ligand and a lower catalyst concentration, and can be used for the industrial production of 1-MOD. The present invention synthesized this series of ligands. In an anaerobic environment, trifluorotoluene brominated at the 2-position or 4-position was dissolved in diethyl ether, and n-butyllithium was added to obtain the corresponding lithium reagent; then dichloro(2-methoxyphenyl)phosphine was added and stirred to obtain the triarylphosphine ligand. The present invention provides a series of ligands, and this series of ligands have a high butadiene conversion rate (70% - 95%) and a high selectivity for 1-MOD (89% - 95%) at a low concentration (5 - 50 ppm) for this reaction.

[0028] Next, the technical solutions of the present invention will be further elaborated in conjunction with specific embodiments.

[0029] Example 1

[0030] This embodiment provides an experiment for the preparation of a triarylphosphine ligand.

[0031] Add bromotrifluorotoluene (2.63 mmol) to a 50 mL Schlenk tube and dissolve it in diethyl ether (30 mL) at 0 °C. Dropwise add n-butyllithium (n-BuLi, 2.63 mmol, 1.32 mL of a 2.0 M cyclohexane solution) to the reaction system and continue stirring for one hour to obtain the corresponding lithium reagent. Then add the corresponding phosphorus chloride (2.63 mmol), heat the temperature in segments to 25 °C (5 segments of temperature increase, staying for 5 minutes each segment), and let the reaction system continue stirring at room temperature for 4 hours. After the reaction is completed, remove the volatile substances, dissolve the reaction system in benzene and filter to remove salts. Remove the volatile substances from the filtrate to obtain a yellow residue. Dissolve the residue in the minimum amount of acetonitrile, filter, and place it in the glove box freezer (-10 °C) overnight. During this period, crystals precipitate out. Separate the crystals by pouring off the liquid and drying under vacuum. Repeat the recrystallization process three times to obtain the target product, which is a white microcrystalline solid.

[0032]

[0033]

[0034] When bromotrifluorotoluene is 1-bromo-4-(trifluoromethyl)benzene (0.593 g, 2.63 mmol) and the corresponding phosphorus chloride is bis(2-methoxyphenyl)phosphinous chloride (0.739 g, 2.63 mmol), product I is obtained. Perform nuclear magnetic resonance hydrogen spectrum analysis on the obtained product I, and the result is as shown in Figure 1 It can be seen that the chemical structure of product I is as shown in formula (1).

[0035] When bromotrifluorotoluene is 1-bromo-2-(trifluoromethyl)benzene (0.593 g, 2.63 mmol) and the corresponding phosphorus chloride is bis(2-methoxyphenyl)phosphinous chloride (0.739 g, 2.63 mmol), product II is obtained. Perform nuclear magnetic resonance hydrogen spectrum analysis on the obtained product II, and the result is as shown in Figure 2 It can be seen that the chemical structure of product II is as shown in formula (2).

[0036] When bromotrifluorotoluene is 1-bromo-4-(trifluoromethyl)benzene (0.593 g, 2.63 mmol) and the corresponding phosphorus chloride is bis(2-N,N-dimethyl)phenylphosphinous chloride (0.788 g, 2.63 mmol), product III is obtained, and its structural formula is as shown in formula (3).

[0037] When bromotrifluorotoluene is 1-bromo-2-(trifluoromethyl)benzene (0.593 g, 2.63 mmol) and the corresponding phosphorus chloride is bis(2-N,N-dimethyl)phenylphosphinous chloride (0.788 g, 2.63 mmol), product IV is obtained, and its structural formula is as shown in formula (4).

[0038] When the trifluoromethylbenzene bromide is 1-bromo-4-(trifluoromethyl)benzene (0.593 g, 2.63 mmol) and the corresponding phosphorus chloride is bis(2-tolyl)phosphorus chloride (0.678 g, 2.63 mmol), product V is obtained, and its structural formula is as shown in formula (5).

[0039] When the trifluoromethylbenzene bromide is 1-bromo-2-(trifluoromethyl)benzene (0.593 g, 2.63 mmol) and the corresponding phosphorus chloride is bis(2-tolyl)phosphorus chloride (0.678 g, 2.63 mmol), product VI is obtained, and its structural formula is as shown in formula (6).

[0040] Example 2

[0041] This example provides an experiment for the preparation of 1-methoxy-2,7-octadiene.

[0042] After two gas exchanges with low-pressure high-purity nitrogen, the autoclave is evacuated to a negative pressure (-0.09 MPa); sodium methoxide (0.01 mol% - 0.5 mol%) is dissolved in methanol (1 - 10 wt) (sodium methoxide serves as a promoter to provide an alkaline environment for the reaction, and methanol serves as both a solvent and a reactant), and is introduced into the autoclave through negative pressure. In this example, methanol is dried by 3A molecular sieve, and the water content is 10 - 200 ppm; the reaction kettle is cooled to -20 - 0 °C, 1,3-butadiene (30 - 300 g) is frozen into a liquid in a -40 °C cold bath, and is introduced into the autoclave through negative pressure; a catalyst pre-prepared solution is added through negative pressure [the preparation method includes the steps: dissolving a palladium source (0.0001 mol% - 0.01 mol%) and its two equivalents of ligand in about 50 g of methanol, and adding one equivalent of acetic acid as a stabilizer and stirring at room temperature for half an hour]; the temperature is gradually increased, and after reaching the predetermined temperature, the reaction pressure is increased to the predetermined pressure through nitrogen; after the predetermined reaction time, the temperature is decreased and the pressure is released to atmospheric pressure to end the reaction. The obtained product is analyzed by nuclear magnetic resonance hydrogen spectrum, and the result as shown in Figure 3 is obtained, and it can be seen that the product is 1-methoxy-2,7-octadiene.

[0043] Experiment VII: The palladium source is Pd(acac)2 (0.0025 mol%, 20 mg), the ligand is product I prepared in Example 1 (0.005 mol%, 52 mg), the predetermined temperature is 90 °C, the predetermined pressure is 1.13 Mpa, and the predetermined reaction time is 2.5 h.

[0044] Experiment VIII: The palladium source is Pd(acac)2 (0.0025 mol%, 20 mg), the ligand is product II prepared in Example 1 (0.005 mol%), the predetermined temperature is 80 °C, the predetermined pressure is 1.03 Mpa, the predetermined reaction time is 2.5 h, and the pressure decreases to 0.75 Mpa with time during the reaction.

[0045] Experiment IX: The palladium source is Pd(acac)2 (0.0025 mol%, 20 mg), the ligand is Product III prepared in Example 1 (0.005 mol%, 67 mg), the predetermined temperature is 70 °C, the predetermined pressure is 1.01 Mpa, and the predetermined duration is 2.5 h. During the reaction, the pressure decreases to 0.71 Mpa over time.

[0046] Experiment X: The palladium source is Pd(acac)2 (0.0025 mol%, 20 mg), the ligand is Product IV prepared in Example 1 (0.005 mol%, 67 mg), the predetermined temperature is 60 °C, the predetermined pressure is 1.09 Mpa, and the predetermined duration is 2.5 h. During the reaction, the pressure decreases to 0.78 Mpa over time. Gas chromatography analysis was performed on the product of this experiment, and the results are as Figure 5 shown.

[0047] Experiment XI: The palladium source is Pd(acac)2 (0.0025 mol%, 20 mg), the ligand is Product V prepared in Example 1 (0.0025 mol%), the predetermined temperature is 90 °C, the predetermined pressure is 1.20 Mpa, and the predetermined duration is 2.5 h. During the reaction, the pressure decreases to 0.97 Mpa over time.

[0048] Experiment XII: The palladium source is Pd(acac)2 (0.0025 mol%, 20 mg), the ligand is Product VI prepared in Example 1 (0.0025 mol%), the predetermined temperature is 90 °C, the predetermined pressure is 1.36 Mpa, and the predetermined duration is 2.5 h. During the reaction, the pressure decreases to 1.22 Mpa over time.

[0049] Experiment XIII: The palladium source is Pd(acac)2 (0.000625 mol%, 10 mg), the ligand is Product I prepared in Example 1 (0.00125 mol%), and butadiene (5.32 mol, 288 g) is used; the predetermined temperature is 70 °C, the predetermined pressure is 1.13 Mpa, and the predetermined duration is 16 h. During the reaction, the pressure decreases to 0.85 Mpa over time.

[0050] Experiment XIV: The palladium source is Pd(acac)2 (0.000625 mol%, 10 mg), the ligand is Product II prepared in Example 1 (0.00125 mol%), and butadiene (5.32 mol, 288 g) is used; the predetermined temperature is 70 °C, the predetermined pressure is 1.06 Mpa, and the predetermined duration is 16 h. During the reaction, the pressure decreases to 0.69 Mpa over time. Gas chromatography analysis was performed on the product of this experiment, and the results are as Figure 4 shown.

[0051] Experiment XV: The palladium source was Pd(acac)2 (0.000625 mol%, 10 mg), the ligand was Product III prepared in Example 1 (0.00125 mol%), and butadiene (5.32 mol, 288 g) was used; the predetermined temperature was 70 °C, the predetermined pressure was 1.23 Mpa, and the predetermined duration was 16 h. During the reaction, the pressure decreased to 0.71 Mpa over time. The product of this experiment was analyzed by gas chromatography, and the result was as shown in Figure 5 the following.

[0052] Experiment XVI: The palladium source was Pd(acac)2 (0.000625 mol%, 10 mg), the ligand was Product IV prepared in Example 1 (0.00125 mol%), and butadiene (5.32 mol, 288 g) was used; the predetermined temperature was 70 °C, the predetermined pressure was 1.30 Mpa, and the predetermined duration was 16 h. During the reaction, the pressure decreased to 1.15 Mpa over time. The product of this experiment was analyzed by gas chromatography, and the result was as shown in Figure 6 the following.

[0053] The peak of the target product was determined by the fitting of GC-MS, the selectivity was obtained by comparing the integrated areas of the GC peaks, and the conversion rate of butadiene was calculated by the weight gain of the reaction solution. The experiments of this example were calculated respectively, and the results shown in Table 1 were obtained.

[0054] Table 1 Statistical parameters and results of each group of experiments

[0055]

[0056] It can be seen from the comparison of Experiments VII to XII in Table 1 that within a certain range, the conversion rate of butadiene is related to the selection of the ligand. When there are electron-donating groups such as methoxy and N,N-dimethyl on the ligand, both the reaction conversion rate and selectivity will increase. It can be seen from the comparison of Experiments VII to X and Experiments XIII to XVI in Table 1 that within a certain range, the conversion rate of butadiene is related to the concentration of the palladium source; when the concentration of the palladium source decreases, the conversion rate of butadiene decreases significantly. At a low palladium source concentration (0.000625 mol%), the ligands with the structural formula shown in Formula (3) and the ligands with the structural formula shown in Formula (4) still have excellent performance in terms of conversion rate and selectivity.

[0057] Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications once they learn the basic creative concepts. Therefore, the appended claims are intended to be construed to include the preferred embodiments and all changes and modifications falling within the scope of the present invention.

[0058] Obviously, those skilled in the art can make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and variations.

Claims

1. A method for preparing a triarylphosphine ligand, characterized in that, It includes the following steps: Under an anhydrous and anaerobic environment, dissolve benzotrifluoride bromide in diethyl ether, and dropwise add n-butyllithium at -5 to 5 °C, and stir well to obtain a lithium reagent. Add dichloroarylphosphine to the lithium reagent, mix and stir, raise the temperature in stages to 20 to 30 °C, and continue to stir and react under anaerobic conditions, and recrystallize to obtain the triarylphosphine ligand. Among them, the benzotrifluoride bromide is 2-position or 4-position brominated benzotrifluoride; the triarylphosphine ligand is any one of formula (1), formula (2), formula (3), formula (4), formula (5) and formula (6).

2. The preparation method according to claim 1, characterized in that, The benzotrifluoride bromide is any one of 1-bromo-4-(trifluoromethyl)benzene and 1-bromo-2-(trifluoromethyl)benzene. And / or, the dichloroarylphosphine is any one of bis(2-methoxyphenyl)phosphine chloride, bis(2-N,N-dimethyl)phosphine chloride and bis(2-tolyl)phosphine chloride. And / or, in terms of amount of substance, the addition ratio of the benzotrifluoride bromide, the n-butyllithium and the dichloroarylphosphine is 1:1:

1.

3. The preparation method according to claim 1, characterized in that, The duration of the sufficient stirring is 1 h. And / or, the duration of the continued stirring reaction is 4 h.

4. The preparation method according to claim 1, characterized in that The recrystallization includes the following steps: After removing the volatile substances in the reaction system, dissolve it in benzene, filter, and collect the filtrate. After removing the volatile substances in the filtrate, dissolve it in acetonitrile, filter, and place it overnight at -10 °C, and collect the precipitated crystals, that is, the triarylphosphine ligand.

5. The triarylphosphine ligand prepared by the preparation method according to any one of claims 1 to 4.

6. Use of the triarylphosphine ligand according to claim 5 in the preparation of 1-methoxy-2,7-octadiene.

7. The application according to claim 6, wherein It includes the following steps: Dissolve the palladium source and the triarylphosphine ligand in methanol, add acetic acid to obtain a catalyst pre-prepared solution. Add methanol, sodium methoxide and 1,3-butadiene to the catalyst pre-prepared solution in sequence, and carry out a telomerization reaction under anaerobic conditions, and react at a set temperature and an initial pressure condition, and after the reaction is completed, adjust the reaction system to normal temperature and pressure to obtain the 1-methoxy-2,7-octadiene. Among them, the set temperature is 50 to 90 °C, and the initial pressure ≥ 0.80 MPa.

8. The application according to claim 7, wherein The amount of the palladium source ligand is twice the equivalent of the palladium source. And / or, the acetic acid is one equivalent of the palladium source.

9. The application according to claim 7, wherein The palladium source is any one of palladium di(acetylacetonate), palladium chloride, tetrakis(triphenylphosphine)palladium, tris(dibenzylideneacetone)dipalladium and bis(dibenzylideneacetone)palladium. And / or, the concentration of the palladium source is 0.00065 mol% to 0.0025 mol%. And / or, the water content of the methanol is 0 to 240 ppm.

10. Use of 1-methoxy-2,7-octadiene prepared by participating in the triarylphosphine ligand according to claim 5 in the preparation of 1-octene.

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