RU2311231C1 - Catalyst for production of acrylic acid esters according to metathesis reaction of dialkyl malates (variants) and a catalytic composition based thereof - Google Patents

Abstract

FIELD: organic synthesis catalysts.

SUBSTANCE: invention is dealing with preparation of homogenous catalyst for production of acrylic acid esters according to metathesis reaction of malates with ethylene. Two variants of preparing catalyst are developed. In particular, catalyst of general formula

, wherein A¹, A² represent chlorine, L dihydroimidazole ligand, R¹, R², R³, the same or different, are substituents selected from hydrogen, alkyl, trialkylsylyl, and alkoxy; and catalyst of formula

are proposed. Use of these catalysts allows number of cycles of metathesis reaction of dialkyl malates with ethylene to be increased both under moderate temperature (about 50°C) conditions when reaction is carried out without distillation of product and at temperatures about 120°C when acrylate produced is distilled out of reaction mixture. Catalytic composition is further developed allowing not only number of reaction cycles but also catalyst lifetime to be increased. Such composition contains indicated catalyst and 2-isopropoxystyrene or its derivative at molar ratio 1:(5-500), respectively.

EFFECT: increased catalyst activity and lifetime.

7 cl, 4 tbl, 28 ex

Description

FIELD OF THE INVENTION

The invention relates to the field of catalysis and can be used as catalysts for the production of acrylic acid esters by the reaction of the metathesis of maleates with ethylene.

State of the art

The highly active Hoveida-Blehert catalyst for the metathesis of electron-deficient olefins is known, containing a phenyl substituent in the ortho position to the isopropoxy group of the benzylidene fragment (US 2004/0176608 A1, 2004).

The known Hoveida-Grela catalyst containing electron acceptor groups in meta and para positions to the isopropoxy group of a benzylidene fragment, such as a nitro group (WO 2004/035596 A1, 2004). The high activity of this catalyst is associated with a high initiation rate due to a partial loss of electron density on the isopropoxy group and, as a result, weak retention of the chelating substituent by the ruthenium center.

The disadvantage of these catalysts is the insufficient period of effective operation caused by the low number of revolutions in the metathesis reactions of maleic acid esters (maleates) with ethylene.

Disclosure of invention

The problem solved by this invention is to develop a catalyst for the reaction of the metathesis of dialkyl maleates with ethylene, which retains its activity over a long period of work.

The technical result consists in increasing the number of revolutions of the catalyst for the metathesis reaction of dialkyl maleates with ethylene.

The technical result is achieved by the fact that the catalyst for producing acrylic acid esters by the reaction of metathesis of dialkyl maleates with ethylene has the formula:

where A ¹ , A ² is chlorine,

L is a dihydroimidazole ligand,

R ¹ , R ² , R ³ are the same or different, substituents selected from the group consisting of hydrogen, alkyl, trialkylsilyl or alkoxy groups.

The introduction of electron-donating substituents, such as alkyl, alkoxy, or trimethylsilyl, into the carbenoid fragment of the catalyst allows one to increase the number of revolutions by reducing the rate of catalyst initiation: the rate of decomposition of active particles by the bimolecular mechanism decreases due to a decrease in their concentration in the reaction mixture.

As the dihydroimidazole ligand L, a ligand (IMesH ₂ ) of the formula can be used:

In the particular case of the invention, R ¹ and R ³ are hydrogen, R ² is trimethylsilyl, and A ¹ and A ² are chlorine. Then the catalyst has the formula:

The use of chloride ions as anions and the introduction of a trimethylsilyl group at the para position of the benzylidene substituent contribute to an increase in the number of revolutions of the catalyst.

In another particular case of the invention, R ¹ and R ² are hydrogen, R ³ is trimethylsilyl, and A ¹ , A ² is chlorine. Then the catalyst has the formula:

As in the previous case, the introduction of the trimethylsilyl group in the meta position of the benzylidene substituent contributes to an increase in the number of revolutions of the catalyst.

Another embodiment of the invention, which also achieves the above technical result, is proposed a catalyst of the formula:

When using the proposed catalysts in a catalytic composition containing 2-isopropoxystyrene or its derivative as a second component, an increase is achieved not only in the number of revolutions of the catalyst, but also in its lifetime. The ratio of catalyst to 2-isopropoxystyrene or its derivative is: per 1 mol of the proposed catalyst accounts for 5 to 100 molar equivalents of 2-isopropoxystyrene or its derivative. Such catalyst systems are most effective at 100-120 ° C in reactions with distillation of the resulting acrylate.

As a derivative of 2-isopropoxystyrene, 2-isopropoxy-5-trimethylsilyl styrene may be selected. Due to the presence of an electron-donating substituent in its structure (trimethylsilyl group), the lifetime of the catalytic system and its speed are significantly increased.

The implementation of the invention

The development of a catalyst with an increased number of revolutions for the metathesis of dialkyl maleates with ethylene was carried out on the basis of the second-generation Hoveida catalyst (1), which is the most effective in the reaction of ethenolysis of maleates. The tested modifications included the variation of substituents in the benzylidene fragment, the variation of the imidazole ligand and anions.

The introduction of electron-withdrawing substituents, such as a nitro group, into the benzylidene fragment led to the preparation of catalyst (3), which has the highest productivity among the tested complexes (about 2220 h ^-1 , table 2). However, the lifetime of this catalyst was only about 70 minutes, and the number of revolutions did not exceed 1500 (tables 1 and 2).

On the contrary, the introduction of electron-donating substituents, such as alkyl, alkoxy, or trialkylsilyl, into the ortho and (or) para position of the benzylidene fragment of the catalyst, leads to catalysts with productivity, lifetime and speed comparable to those for complex (1). It should be noted that such catalysts have a lower initiation rate compared to complexes (1) and (3), which is due to the increased electron density on the isopropoxy group and, as a consequence, a stronger Ru – O bond. The observed effect of increasing the number of revolutions of such catalysts is due to the lower concentration of active particles in the reaction mixture.

The highest number of revolutions have catalysts with trimethylsilyl groups, such as (4) and (5) (1760 and 1900, respectively, tables 1 and 2). Close values of productivity and speed were obtained for catalyst (6) containing a methyl group in the benzylidene moiety (2040 h ^-1 , 1750 revolutions, tables 1 and 2). The speed numbers for the catalysts (7) and (8) containing the isopropoxy group were slightly lower than even for complex (1) (1600 and 1670 revolutions for complexes 7 and 8, respectively, tables 1 and 2). The lifetime of the catalysts in all cases is about 100-120 minutes.

Variation in the heterocyclic ligand affects the lifetime and the number of revolutions of the catalyst to a greater extent. Thus, the use of an imidazole ligand (as in complex 9) instead of a dihydroimidazole ligand (complex 1) leads to a decrease in the catalyst lifetime to 50 minutes and its speed from 1740 to 600 (tables 1 and 2). An increase in steric barriers at the ruthenium center by substituents of the aromatic rings of the heterocyclic ligand contributes to an increase in the catalyst lifetime. For example, catalyst (10) containing isopropyl groups in a heterocyclic ligand has one of the longest lifetimes among the complexes tested (more than 5 hours, tables 1 and 2), although its productivity and speed are only 1080 h ^-1 and 1310, respectively ( tables 1 and 2). In contrast, catalyst (11), in which the ruthenium center is less blocked by the heterocyclic ligand, has a significantly shorter lifetime (about 50 minutes, tables 1 and 2). Productivity and speed are also low. The most optimal is the use of 2,5-N, N'-di (2,4,6-trimethylphenyl) -3,4-dihydroimidazolidene (IMesH ₂ ) as a heterocyclic ligand.

An increase in the size of the anion at the ruthenium center also leads to an increase in the lifetime of the catalyst, although productivity and its speed are reduced. So, the lifetime of the catalyst (12) under the test conditions is more than 5 hours, and its number of revolutions is less than 100 (tables 1 and 2).

In the case of carrying out the reaction with distillation of the resulting product, the catalyst (1) has a speed of 930. The test results of other catalysts are presented in table 3. The maximum number of turns was shown by complex (13) containing a naphthylidene substituent.

Table 3
The number of revolutions of various catalysts in the reaction of the metathesis of dimethyl maleate with ethylene under conditions of distillation of the product from the reaction mixture. Example Catalyst The yield of methyl acrylate,% Catalyst speed one one 9.3 930 2 four 11.5 1150 3 13 11.9 1190

To obtain esters of acrylic acid by the reaction of ethenolysis of maleates under conditions of distillation of the resulting product at atmospheric pressure during the reaction, it was cheaper and more effective to carry out metathesis in the presence of a catalytic system consisting of the claimed catalyst and 2-isopropoxystyrene derivatives.

As the second component of the catalytic system, 2-isopropoxystyrene (14) and its derivatives (15) and (16) were tested, on the basis of which catalysts with the maximum number of revolutions were previously obtained. The results of these experiments are presented in table 4.

Table 4
Effect of the amount of 2-isopropoxystyrene derivative on the yield of methyl acrylate and the number of revolutions of the catalyst in the ethenolysis of dimethyl maleate under conditions of distillation of the product from the reaction mixture. Example Catalyst Additive Amount of additive, equiv. The yield of methyl acrylate,% Catalyst speed one one fourteen 5 12.7 1265 2 7.7 15.2 1515 3 fifteen 15.1 1505 four 25 14.8 1480 5 one hundred 10.3 1030 6 fifteen 10 15.3 1525 7 16 fifteen 7.5 745 8 four fifteen 10 14.3 1430 9 13 16 5 10.8 1080 Note: 1) reaction conditions — temperature 120 ° С, maleate: catalyst ratio = 10000: 1, ethylene flow rate 7.0 l / h, the amount of maleate used is 10.81 g (75 mmol); 2) the amount of additive is given in relation to the catalyst.

The most effective additives were styrenes (14) and (15) in an amount of 5 to 100 molar equivalents. When these compounds are used in an amount of 8 to 25 molar equivalents (relative to the catalyst), the number of catalyst revolutions increases by more than 1.6 times and reaches 1525 under the test conditions. In the presence of styrene (16), a decrease in the number of revolutions of the catalyst was observed in all cases (table 4), despite the fact that the catalyst (13) obtained from this olefin is most active in the reaction with distillation of acrylate.

The invention is illustrated by the following examples.

Example 1

The synthesis of catalysts, reactions using butyl lithium and Grignard reagents, and the reactions of maleates with ethylene are carried out according to standard methods under conditions that exclude moisture and air from entering the reaction system using Schlenk reactors connected to vacuum and ethylene lines. Catalysts (1), (2), (3), (6), (7), (8), (9), (10), (12), (IMesH ₂ ) (Cl) ₂ (C ₅ H ₅ N) ₂ RuC = CHPh (third generation Grubbs catalyst), (Cy ₃ P) ₂ (Cl) ₂ RuC = CHPh (first generation Grubbs catalyst) and 2-isopropoxystyrene (14) are prepared according to published procedures. Polymerization ethylene (GOST 25070-87) is dried before use, sequentially passing through columns filled with aluminum oxide and 13X zeolite, calcined at 400 ° C. Commercial diethyl maleate (97%, Aldrich), dimethyl maleate (96%, Acros) and dibutyl maleate (97%, Acros) were vacuum distilled and dried over molecular sieves. The reaction mixture is analyzed by GLC, taking 0.1 ml of the reaction mixture and treating it with 1 ml of vinyl ethyl ether in order to deactivate the active catalytic particles. When calculating the product yield, calibration coefficients are used, obtained from the analysis of artificial mixtures of the corresponding acrylates, maleates and fumarates, followed by recalculation of the area ratios in the chromatogram to the mass ratios of the component components.

In a 25 ml Schlenk flask equipped with a magnetic stirrer and reflux condenser, 212 mg (0.25 mmol) of second-generation Grubbs catalyst (2) and 37 mg (0.375 mmol) of copper (I) chloride are placed. The flask was filled with argon and a solution of 117 mg (0.500 mmol) of 2-isopropoxy-5-trimethylsilyl styrene (15) in dry dichloromethane (4 ml) was added. The reaction mixture is boiled for 1 hour, after which it is cooled to room temperature. Further, all operations are performed in air. The solvent was evaporated in vacuo, the product was isolated by preparative chromatography on silica gel, eluting with a mixture of cyclohexane: ethyl acetate = 4: 1. 130 mg (yield 74%) of complex (4) are obtained in the form of green crystals.

¹ H NMR spectrum (500 MHz, in CD ₂ Cl ₂ ): 0.25 (9H, s), 1.23 (6H, d, J 6.0 Hz), 2.42 (6H, s), 2.44 (12H, s), 4.18 (4H , s), 4.89 (1Н, septet, J 6.0 Hz), 6.85 (1Н, d, J 8.8 Hz), 7.08 (5Н, m), 7.70 (1Н, dd, J 8.8, 1.9 Hz), 16.40 (1Н, from).

Example 2

In a 25 ml Schlenk flask equipped with a magnetic stirrer and reflux condenser, 212 mg (0.25 mmol) of second-generation Grubbs catalyst (2) and 37 mg (0.375 mmol) of copper (I) chloride are placed. The flask was filled with argon and a solution of 117 mg (0.500 mmol) of 2-isopropoxy-5-trimethylsilyl styrene in dry dichloromethane (4 ml) was added. The reaction mixture is boiled for 1 hour, after which it is cooled to room temperature. Further, all operations are performed in air. The solvent was evaporated in vacuo, the product was isolated by preparative chromatography on silica gel, eluting with a mixture of cyclohexane: ethyl acetate = 4: 1. 100 mg (yield 57%) of complex (5) are obtained in the form of green crystals.

¹ H NMR spectrum (500 MHz, in CD ₂ Cl ₂ ): 0.23 (9H, s), 1.23 (6H, d, J 5.6 Hz), 2.41 (6H, s), 2.44 (12H, s), 4.15 (4H , s), 4.94 (1Н, septet, J 5.6 Hz), 6.93 (1Н, d, J 7.7 Hz), 6.95 (1Н, s), 7.07 (1Н, d, J 7.7 Hz), 7.07 (4Н, s) 16.51 (1H, s).

Example 3

300 mg (0.752 mmol) of EN, N'-bis- (2,4-dimethylphenyl) -4,5-diisopropyl-4,5-dihydro- are placed in a 50 ml argon filled Schlenk flask equipped with a magnetic stirrer and reflux condenser. 1,3-imidazole chloride, 0.44 ml (0.752 mmol, 1.7 M in toluene) potassium tert-amylate, 44 ml of dry hexane and 309 mg (0.376 mmol) of the first generation Grubbs catalyst. The reaction mixture was heated at 50 ° C. for 17 hours, cooled to room temperature and the solvent was evaporated in vacuo. The dry residue was dissolved in dichloromethane (10 ml), 60 mg (0.60 mmol) of copper (I) chloride and 150 mg (0.925 mmol) of 2-isopropoxystyrene (14) were added and the mixture was stirred at 40 ° C for 1 hour, then cooled to room temperature temperature. Further, all operations are performed in air. The solvent was evaporated in vacuo, the product was isolated by preparative chromatography on silica gel, eluting with a mixture of cyclohexane: ethyl acetate = 6: 1. Obtain 85 mg (yield 25%) of complex (11) in the form of green crystals. Judging by the ¹ H NMR spectra, the complex is a mixture of two isomers in a ratio of 1: 3.4.

¹ H NMR spectrum (300 MHz, in CD ₂ Cl ₂ ): 0.87 (6H, m), 1.17 (6H, m), 1.25 (6H, d J 5.6 Hz, minor isomer), 1.35 (6H, d J 5.6 Hz , main isomer), 1.87 (1Н, m), 2.03 (1Н, m), 1.39 (6Н, d J 2.8 Hz), 1.49 (6Н, d J 4.8 Hz), 4.05 (2Н, m), 4.88 (1Н, Septet, J 5.7 Hz), 6.83-6.94 (3Н, m), 7.17-7.30 (4Н, m), 7.38 (1Н, d, J 7.6 Hz), 7.54 (1Н, m), 8.50 (1Н, d, J 8.6 Hz, main isomer), 8.59 (1H, d, J 8.6 Hz, minor isomer), 16.54 (1H, s, main isomer), 17.18 (1H, s, minor isomer).

Example 4

150 mg (0.18 mmol) of second-generation Grubbs catalyst (2) and 23 mg (0.23 mmol) of copper (I) chloride are placed in a 25 ml Schlenk flask equipped with a magnetic stirrer and reflux condenser. The flask was filled with argon and a solution of 50 mg (0.23 mmol) of 1-vinyl-2-isopropoxynaphthalene (16) in dry dichloromethane (6 ml) was added. The reaction mixture is boiled for 30 minutes, after which it is cooled to room temperature. Further, all operations are performed in air. The solvent was evaporated in vacuo, the product was isolated by preparative chromatography on silica gel, eluting with a mixture of cyclohexane: ethyl acetate = 6: 1. 55 mg (49% yield) of complex (13) are obtained in the form of green crystals.

¹ H NMR spectrum (500 MHz, in CD ₂ Cl ₂ ): 1.33 (6H, d, J 5.6 Hz), 2.53 (18H, br.s), 4.21 (4H, s), 5.14 (1H, septet, J 5.6 Hz), 7.09-7.29 (5H, m), 7.36 (1H, d, J 8.8 Hz), 7.39 (1H, d, J 8.8 Hz), 7.62 (1H, t, J 6.8 Hz), 7.85 (1H, d , J 8.8 Hz), 8.27 (1H, d, J 9.8 Hz), 18.17 (1H, s).

Example 5

In a 25 ml Schlenk flask equipped with a magnetic stirrer, 11.91 g (69.2 mmol) of diethyl maleate are placed and frozen with liquid nitrogen, after which they are evacuated to 0.1 Pa. The degassing operation is repeated two times. The vacuum is closed, the reaction mixture is allowed to warm to room temperature and ethylene is introduced into the reaction flask, creating a pressure of 101325 Pa, after which the mixture is heated to 50 ° C. The ethylene pressure is kept constant throughout the experiment. Then, a suspension of 4.70 mg of catalyst (1) in 1.00 g (5.8 mmol) of diethyl maleate is introduced into the reaction mixture. Monitoring the progress of the reaction is carried out by GLC 10, 20, 30, 45, 60 minutes after the start of the experiment and then every 30 minutes until the completion of the reaction (table 1, example 1).

Example 6

Etenolysis of diethyl maleate is carried out according to example 5, but using 6.37 mg of catalyst (2) (tables 1 and 2, examples 2).

Example 7

Etenolysis of diethyl maleate is carried out according to example 5, but instead of catalyst (1), 5.04 mg of catalyst (3) is used (tables 1 and 2, examples 3).

Example 8

Etenolysis of diethyl maleate is carried out according to example 5, but instead of catalyst (1), 5.24 mg of catalyst (4) is used (tables 1 and 2, examples 4).

Example 9

Etenolysis of diethyl maleate is carried out according to example 5, but instead of catalyst (1), 5.24 mg of catalyst (5) is used (tables 1 and 2, examples 5).

Example 10

Etenolysis of diethyl maleate is carried out according to example 5, but instead of catalyst (1), 4.80 mg of catalyst (6) is used (tables 1 and 2, examples 6).

Example 11

Etenolysis of diethyl maleate is carried out according to example 5, but instead of catalyst (1), 5.14 mg of catalyst (7) is used (tables 1 and 2, examples 7).

Example 12

Etenolysis of diethyl maleate is carried out according to example 5, but instead of catalyst (1), 5.14 mg of catalyst (8) is used (tables 1 and 2, examples 8).

Example 13

Etenolysis of diethyl maleate is carried out according to example 5, but instead of catalyst (1), 4.68 mg of catalyst (9) is used (tables 1 and 2, examples 9).

Example 14

Etenolysis of diethyl maleate is carried out according to example 5, but instead of catalyst (1), 5.33 mg of catalyst (10) is used (tables 1 and 2, examples 10).

Example 15

Etenolysis of diethyl maleate is carried out according to example 5, but instead of catalyst (1), 5.12 mg of catalyst (11) is used (tables 1 and 2, examples 11).

Example 16

Etenolysis of diethyl maleate is carried out according to example 5, but instead of catalyst (1), 5.86 mg of catalyst (12) is used (tables 1 and 2, examples 12).

Example 17

The production of methyl acrylate by the reaction of metathesis of dimethyl maleate with ethylene under conditions of distillation of the resulting product at atmospheric pressure is carried out in a plant with a volume of a distillation flask of 15 ml, which does not contain a reflux condenser and includes a trap connected to the outlet of the allonge instead of a vacuum pump. 9.81 g (68.1 mmol) of dimethyl maleate are placed in the described setup. The section through which the capillary is connected to introduce ethylene is closed with a septum. The distillation flask with the maleate placed in it is frozen with liquid nitrogen and vacuumized to 0.1 Pa. The vacuum is then closed and the reaction mixture is allowed to warm to room temperature. The degassing operation is repeated two times, after which a metal capillary is introduced through the septum to the bottom of the distillation flask and the installation is filled with ethylene purified in Example 1. The ethylene flow rate is set to 7.0 l / h. The reaction mixture is heated with an oil bath to 120 ° C, after which a suspension of 4.70 mg of catalyst (1) in 1.00 g (6.9 mmol) of dimethyl maleate is introduced into the unit using a syringe. The reaction is carried out for 30 minutes. The receiver and the trap are cooled to -30 ° C using a mixture of alcohol - liquid nitrogen. The product yield and the number of revolutions of the catalyst are presented in table 3, example 1. The purity of the product, judging by GLC, more than 99.5%.

Example 18

Etenolysis of dimethyl maleate is carried out as in Example 17, but instead of catalyst (1), 5.24 mg of catalyst (4) is used. The product yield and the number of revolutions of the catalyst are presented in table 3, example 2. The purity of the product, judging by the data of GLC, more than 99.5%.

Example 19

Etenolysis of dimethyl maleate is carried out as in Example 17, but instead of catalyst (1), 5.08 mg of catalyst (13) is used. The product yield and the number of revolutions of the catalyst are presented in table 3, example 3. The purity of the product, judging by the data of GLC, more than 99.5%.

Example 20

Etenolysis of dimethyl maleate is carried out according to example 17, but in addition to dimethyl maleate, 6.08 mg of 2-isopropoxystyrene is also placed in the installation (14). The product yield and the number of revolutions of the catalyst are presented in table 4, example 1. The purity of the product, judging by the data of GLC, more than 99.5%.

Example 21

Etenolysis of dimethyl maleate is carried out according to example 20, but using 9.37 mg of 2-isopropoxystyrene (14). The product yield and the number of revolutions of the catalyst are presented in table 4, example 2. The purity of the product, judging by the data of GLC, more than 99.5%.

Example 22

Etenolysis of dimethyl maleate is carried out according to example 20, but using 18.25 mg of 2-isopropoxystyrene (14). The product yield and the number of revolutions of the catalyst are presented in table 4, example 3. The purity of the product, judging by the data of GLC, more than 99.5%.

Example 23

Etenolysis of dimethyl maleate is carried out according to example 20, but using 30.42 mg of 2-isopropoxystyrene (14). The product yield and the number of revolutions of the catalyst are presented in table 4, example 4. The purity of the product, judging by the data of GLC, more than 99.5%.

Example 24

Etenolysis of dimethyl maleate is carried out according to example 20, but using 121.7 mg of 2-isopropoxystyrene (14). The product yield and the number of revolutions of the catalyst are presented in table 4, example 5. The purity of the product, judging by the data of GLC, more than 99.5%.

Example 25

Etenolysis of dimethyl maleate is carried out according to example 20, but instead of 2-isopropoxystyrene (14), 17.58 mg of styrene (15) is used. The product yield and the number of revolutions of the catalyst are presented in table 4, example 6. The purity of the product, judging by the data of GLC, more than 99.5%.

Example 26

Etenolysis of dimethyl maleate is carried out according to example 20, but instead of 2-isopropoxystyrene (14), 23.9 mg of styrene (16) is used. The product yield and the number of revolutions of the catalyst are presented in table 4, example 7. The purity of the product, judging by the data of GLC, more than 99.5%.

Example 27

Etenolysis of dimethyl maleate is carried out as in Example 25, but instead of catalyst (1), 5.24 mg of catalyst (4) is used. The product yield and the number of revolutions of the catalyst are presented in table 4, example 8. The purity of the product, judging by the data of GLC, more than 99.5%.

Example 28

Etenolysis of dimethyl maleate is carried out as in Example 26, but instead of catalyst (1) and 2-isopropoxystyrene (16), 8.0 mg of styrene (16) and 5.08 mg of catalyst (13) are used. The product yield and the number of revolutions of the catalyst are presented in table 4, example 8. The purity of the product, judging by the data of GLC, more than 99.5%.

Industrial applicability

The production of acrylates by the metathesis reaction of olefins from maleates and ethylene is of interest to industry due to the low cost and availability of the starting compounds, as well as the mild conditions and high selectivity of the reaction. The catalysts and catalyst systems proposed in the invention for this reaction have a longer lifetime and have a higher number of revolutions compared to existing catalysts, which can significantly reduce the cost of production of acrylates.

Claims (7)

1. The catalyst for the production of esters of acrylic acid by the reaction of metathesis of dialkyl maleates with ethylene of the formula

where A ¹ , A ² is chlorine, L is a dihydroimidazole ligand, R ¹ , R ² , R ³ are the same or different substituents selected from the group, containing hydrogen, alkyl, trialkylsilyl or alkoxy groups. 2. The catalyst according to claim 1, characterized in that the dihydroimidazole ligand L has the formula

3. The catalyst according to claim 1 or 2, characterized in that R ¹ and R ³ are hydrogen, R ² is trimethylsilyl, and A ¹ and A ² are chlorine. 4. The catalyst according to claim 1 or 2, characterized in that R ¹ and R ² are hydrogen, R is trimethylsilyl, and A ¹ and A ² are chlorine. 5. The catalyst for the production of esters of acrylic acid by the reaction of metathesis of dialkyl maleates with ethylene of the formula

6. The catalyst composition containing the catalyst according to claim 1 or 5 and 2-isopropoxystyrene or its derivative in the ratio of 1 molar equivalent of catalyst to 5-100 molar equivalents of 2-isopropoxystyrene or its derivative. 7. The composition according to claim 6, characterized in that 2-isopropoxy-5-trimethylsilyl styrene is selected as the 2-isopropoxystyrene derivative.