A process for the preparation of 4-halo-2-methyl-2-butenoic acid hydrocarbyl esters

Abstract

The application discloses a method for preparing 4-halogen-2-methyl-2-butenoic acid alkyl ester, which is prepared by a Reformatsky reaction with halogenated acetaldehyde and 2-bromine zinc propionate as raw materials. The reaction has mild conditions, good economy, no toxicity and harm, and high safety factor, and is suitable for industrial large-scale production. The Reformatsky S reaction and the subsequent dehydration reaction generate mainly inorganic solid waste zinc halide as well as a small amount of organic by-products, and the reaction solvent can be recycled, so that the pollution is very small.

Description

Technical Field

[0001] This invention relates to the field of fine organic synthesis, and specifically to a method for preparing 4-halo-2-methyl-2-butenoic acid hydrocarbon esters. Background Technology

[0002] Carotenoids are a general term for an important class of natural pigments, widely found in the yellow, orange-red, or red pigments of animals, higher plants, fungi, and algae. Carotenoids are a major source of vitamin A in the body and also possess antioxidant, immunomodulatory, anti-cancer, and anti-aging effects. 4-Halo-2-methyl-2-butenoic acid hydrocarbon esters are important intermediates in the preparation of carotenoid carboxylic acid esters. Examples include crocinate diester, β-apo-8'-carotene ester, and β-apo-4'-carotene ester; they can also be used to prepare other compounds.

[0003] Currently, the main methods for synthesizing 4-chloro / bromo-2-methyl-2-butenoate are as follows:

[0004] (1) Addition-elimination method: Applicable to the preparation of chlorides and bromides. See the reaction formula below for details:

[0005]

[0006] (2) Alcohol halogenation method: suitable for the preparation of chlorides and bromides. See the reaction formula below for details:

[0007]

[0008] (3) Free radical substitution method: Applicable to the preparation of bromides. See the reaction formula below for details:

[0009]

[0010] (4) Wittig method: suitable for the preparation of chlorides and bromides. See the following reaction formula for details:

[0011]

[0012] However, each of the above methods has its own drawbacks. For example, in method (1), the main raw material is not readily available and needs to be prepared from more basic raw materials through several steps. Furthermore, halogens are used directly as reaction reagents, which is not only highly dangerous and polluting, but also has poor atom economy because the theoretical utilization rate of halogens is only half. In method (2), the situation is similar to method (1) except that the degree of danger is reduced. In method (3), the main raw material is also not easy to obtain, NBS is expensive, and a large amount of NHS is obtained after the reaction, which is difficult to handle. In addition, there are a large number of isomers (I') in the product, which is very uneconomical. Finally, in method (4), compared with the previous three methods, it is undoubtedly the best method in terms of raw material source, reaction effect and economy. However, in terms of the current production environment, it also has fatal drawbacks. The reaction involves organophosphorus reagents, and the large amount of oxidized organophosphorus generated in the product is difficult to recover and regenerate, pollutes a lot and costs a lot. Improper handling will cause great harm to the environment. Summary of the Invention

[0013] In order to overcome the shortcomings of the prior art, the present invention aims to provide a method for preparing 4-halo-2-methyl-2-butenoic acid hydrocarbon esters, which has the advantages of inexpensive and readily available raw materials, stable and reliable reaction, mild reaction conditions, and environmental friendliness, and is very suitable for industrial production.

[0014] The objective of this invention is achieved through the following technical solution:

[0015] A method for preparing 4-halo-2-methyl-2-butenoic acid hydrocarbon esters includes the following steps: reacting compound A with compound B via a Reformatsky reaction, followed by in-situ dehydration to obtain compound of general formula (I):

[0016] Where X is a halogen and R is a hydrocarbon group.

[0017] Furthermore, compound A reacts with compound B in the form of an anhydrous haloacetaldehyde solution. The preparation method of the anhydrous haloacetaldehyde solution includes the following steps: mixing an aqueous haloacetaldehyde solution with anhydrous calcium chloride, allowing it to stand to separate the oil phase and the aqueous phase; collecting the oil phase, adding a solvent to the aqueous phase for extraction, combining the oil phases, drying, and filtering to obtain the anhydrous haloacetaldehyde solution. Specifically, the drying step involves sequential drying with anhydrous calcium chloride and drying with 4A molecular sieves.

[0018] Furthermore, the solvent used for extraction is one or more of toluene, xylene, dichloromethane, and 2-methyltetrahydrofuran, preferably 2-methyltetrahydrofuran; the anhydrous haloacetaldehyde solution has a mass percentage of 4-25%.

[0019] Furthermore, the halogen is chlorine or bromine; the compound of formula A is chloroacetaldehyde or bromoacetaldehyde.

[0020] Furthermore, the hydrocarbon group is one or more of methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl or vinyl, preferably methyl or ethyl.

[0021] Furthermore, the compound of formula B is prepared by an in-situ reaction of zinc powder and 2-bromopropionate, wherein the molar ratio of zinc powder to 2-bromopropionate is (2:1) to (1:1), preferably 1.1:1. Since compound B is not suitable for isolated use, the molar ratio of compound A to 2-bromopropionate is used to represent this ratio. The molar ratio of compound A to 2-bromopropionate is (2:1) to (0.5:1), preferably 1:1.

[0022] Furthermore, the temperature of the in-situ reaction is 0–100°C, preferably 70°C; the reaction time is 20 min–10 h, preferably 0.5 h.

[0023] Furthermore, during the reaction of compound A with compound B, titanium dichlorophenoxyacetate can be added as a catalyst, with the molar amount of catalyst being 0.5% to 2% of the molar amount of 2-bromopropionate, preferably 0.8%. It should be noted that the reaction of compound A with compound B may also be carried out without the addition of titanium dichlorophenoxyacetate as a catalyst.

[0024] Furthermore, after the compound of formula A and the compound of formula B are mixed and reacted to obtain a mixed solution, an aqueous solution of H2SO4 is added for hydrolysis, the filtrate and the solid are separated, and the filtrate is distilled to obtain the compound of general formula (I).

[0025] Furthermore, the reaction temperature is 0–100°C, preferably 70–76°C, more preferably 70°C; the reaction time is 20 min–10 h, preferably 0.5 h.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] (1) The preparation method of this invention uses haloacetaldehyde and 2-zinc bromide propionate as raw materials to prepare 4-halo-2-methyl-2-butenoic acid hydrocarbon ester through the Reformatsky reaction. The conditions are mild, economical, and the product is essentially non-toxic and harmless with a high safety factor, making it suitable for large-scale industrial production. The Reformatsky reaction itself and the subsequent dehydration reaction produce, apart from the main product and a small amount of organic byproducts, primarily solid waste inorganic salt zinc halide, which can be easily recovered. Furthermore, the reaction solvent can be recycled, resulting in very low pollution.

[0028] (2) The compound of formula B of the present invention is prepared by in-situ reaction of zinc powder and 2-bromopropionate, and the raw materials used are inexpensive and readily available.

[0029] (3) In the process of preparing compound of general formula (I), a catalyst may be added or not. The difference is that the catalyst can make the reaction milder and easier to carry out and can improve the reaction effect. Detailed Implementation

[0030] The present invention will now be further described in conjunction with specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0031] The following are supplementary explanations regarding some of the raw materials or reagents involved in the following examples:

[0032] A 40% chloroacetaldehyde aqueous solution is of industrial grade. Chloroacetaldehyde drying solution is prepared in-house using the following method:

[0033] In a separatory funnel, 500 ml of a 40% (w / w) aqueous solution of chloroacetaldehyde was added to 300 ml of 2-methyltetrahydrofuran solvent. Then, 140 g of anhydrous calcium chloride was added and dissolved thoroughly to induce precipitation of the aqueous phase. After standing, the aqueous phase was separated. Another 60 g of anhydrous calcium chloride was added to the oil phase and dissolved thoroughly to induce precipitation of the aqueous phase. After standing, the aqueous phase was separated. The aqueous phases were combined and extracted twice with 2 x 100 ml of 2-methyltetrahydrofuran solvent. The combined oil phases were then thoroughly dried using 100 g of anhydrous calcium chloride and 100 g of molecular sieve (4A). After filtration, a dried chloroacetaldehyde-2-methyltetrahydrofuran solution was obtained, with a GC normalization content of 21.4% and a moisture content of <0.06%.

[0034] By successively replacing the above extraction solvents with dichloromethane and xylene, chloroacetaldehyde-dichloromethane dried solution and chloroacetaldehyde-xylene dried solution can be prepared, respectively. The chloroacetaldehyde-dichloromethane dried solution has a GC normalization content of 8.7% and a moisture content of <0.03%; the chloroacetaldehyde-xylene dried solution has a GC normalization content of 4.6% and a moisture content of <0.03%.

[0035] The 10% bromoacetaldehyde-dichloromethane dry solution was a reagent purchased directly.

[0036] The solvents, raw materials methyl 2-bromopropionate and ethyl 2-bromopropionate, and the titanium dichlorocerocene (Cp2TiCl2) used as catalyst were all industrial grade.

[0037] Example 1

[0038] The preparation method of ethyl 4-chloro-2-methyl-2-butenoate includes the following steps:

[0039] Under nitrogen protection, 8.1 g (90%) of zinc powder was dispersed in 100 ml of 2-methyltetrahydrofuran solvent. Then, 18.5 g (99%) of ethyl 2-bromopropionate was added and thoroughly mixed. The mixture was stirred and heated to 70°C to initiate the reaction. Due to the exothermic reaction, the internal temperature rose to 75°C. The reaction was continued for 0.5 h, after which the internal temperature returned to 70°C. 37.0 g (21.4%) of chloroacetaldehyde-2-methyltetrahydrofuran dry solution was added dropwise over 10 min. After the addition was complete, the reaction was continued for 0.5 h, and then allowed to cool naturally to room temperature. With stirring, 20 ml of 10% (w / w) H₂SO₄ aqueous solution was added for complete hydrolysis. The turbid reaction solution precipitated a muddy solid and then became clear and transparent. At this point, the solid formed a firm clump at the bottom of the flask. The filtrate was directly decanted to separate the solid, and the surface of the solid was washed with a small amount of the reaction solvent and combined with the filtrate. The solvent was recovered by vacuum distillation, and further distillation yielded 16.7 g of crude product, providing ethyl 4-chloro-2-methyl-2-butenoate. The GC-normalized purity was 68.3%. The main impurities in the crude product were residual solvent and low-boiling substances. Redistillation increased the GC-normalized purity to 87.2%. The sample was purified by silica gel column chromatography (ethyl acetate / petroleum ether = 1:50). The NMR and mass spectrometry data of the product are as follows:

[0040] UV(MeOH) absorption: λmax = 218 nm;

[0041] IR (KBr) absorption: 2984, 1717, 1651, 1273, 756 (cm²) -1 );

[0042] MS (EI): m / z 162 (M+, 6%), 134 (45%), 117 (73%), 113 (72%), 99 (58%), 89 (64%), 82 (17%), 69 (14%), 53 (100%), 39 (23%);

[0043] 1 H-NMR (CDCl3, 600MHz): δ6.79 (qt, J=1.54, 7.79Hz, =CH-), 4.19 (q, J=7.17Hz, -OCH2- ), 4.13 (d, J = 7.79Hz, -CH2Cl), 1.88 (d, J = 1.71, -CH3), 1.27 (t, J = 7.2Hz, -OCH2-CH3).

[0044] Example 2

[0045] The preparation method of methyl 4-chloro-2-methyl-2-butenoic acid includes the following steps:

[0046] Under nitrogen protection, 8.1 g (90%) of zinc powder was dispersed in 100 ml of 2-methyltetrahydrofuran solvent. Then, 17.1 g (99%) of methyl 2-bromopropionate was added and thoroughly mixed. The mixture was stirred and heated to 68°C to initiate the reaction. Due to the exothermic reaction, the internal temperature rose to 74°C. The reaction was continued for 0.5 h, after which the internal temperature returned to 70°C. 37.0 g (21.4%) of a dry solution of chloroacetaldehyde-2-methyltetrahydrofuran was added dropwise over 10 min. After the addition was complete, the reaction was continued for 0.5 h, and then allowed to cool naturally to room temperature. With stirring, 20 ml of a 10% (w / w) aqueous solution of H₂SO₄ was added for complete hydrolysis. The turbid reaction solution precipitated a muddy solid and then became clear and transparent. The filtrate was directly decanted to separate the solids. The surface of the solids was washed with a small amount of the reaction solvent and combined with the filtrate. The solvent was recovered by vacuum distillation, and further distillation yielded 14.6 g of crude product, giving methyl 4-chloro-2-methyl-2-butenoic acid. The GC normalization purity was 70.7%. After redistillation, the GC normalization purity was 83.4%. The sample was purified by silica gel column chromatography (ethyl acetate / petroleum ether = 1:50). The NMR and mass spectrometry data of the product are as follows:

[0047] UV(MeOH) absorption: λmax = 218 nm;

[0048] IR (KBr) absorption: 2987, 1716, 1652, 1280, 757 (cm²) -1 );

[0049] MS (EI): m / z 148 (M+, 12%), 117 (69%), 113 (57%), 99 (64%), 89 (71%), 82 (23%), 69 (17%), 53 (100%), 39 (24%);

[0050] 1 H-NMR (CDCl3, 600MHz): δ6.80 (qt, J=1.55, 7.99Hz, =CH-), 4.14 (d, J=7.97Hz, -CH2Cl), 3.74 (s, -OCH3), 1.90 (d, J=1.71Hz, -CH3).

[0051] Example 3

[0052] The preparation method of ethyl 4-chloro-2-methyl-2-butenoate includes the following steps:

[0053] Under nitrogen protection, 8.1 g (90%) of zinc powder was dispersed in 100 ml of 2-methyltetrahydrofuran solvent. Then, 18.5 g (99%) of ethyl 2-bromopropionate was added and thoroughly mixed. The mixture was stirred and heated to 72°C to initiate the reaction. Due to the exothermic reaction, the internal temperature rose to 76°C. The reaction continued for 0.5 h, after which the internal temperature returned to 70°C. The temperature was then lowered to 60°C, and 91.0 g (8.7%) of a chloroacetaldehyde-dichloromethane dry solution was added dropwise while simultaneously recovering some of the dichloromethane by atmospheric distillation over 30 min. After the addition was complete, the reaction continued for 0.5 h, followed by natural cooling to room temperature. With stirring, 20 ml of a 10% (w / w) H₂SO₄ aqueous solution was added for complete hydrolysis. The turbid reaction solution precipitated a muddy solid and then became clear and transparent. The filtrate was directly decanted to separate the solids, and the solid surface was washed with a small amount of the reaction solvent, which was then combined with the filtrate. The solvent was recovered by vacuum distillation, and further distillation yielded 13.2 g of crude product, providing ethyl 4-chloro-2-methyl-2-butenoate. The purity was 53.4% ​​by GC normalization.

[0054] Example 4

[0055] The preparation method of ethyl 4-chloro-2-methyl-2-butenoate includes the following steps:

[0056] Under nitrogen protection, 8.1 g (90%) of zinc powder was dispersed in 100 ml of 2-methyltetrahydrofuran solvent, followed by the addition of 18.5 g (99%) of ethyl 2-bromopropionate, which was thoroughly mixed. The mixture was stirred and heated to 69 °C to initiate the reaction. Due to the exothermic reaction, the internal temperature rose to 75 °C, and the reaction was continued for 0.5 h until the internal temperature returned to 70 °C. 173.0 g (4.6%) of a chloroacetaldehyde-xylene drying solution was added dropwise over 15 min. After the addition was complete, the reaction was continued for 0.5 h, followed by natural cooling to room temperature. While stirring, 20 ml of a 10% (w / w) H₂SO₄ aqueous solution was added for complete hydrolysis. The turbid reaction solution precipitated a muddy solid and then became clear and transparent. The filtrate was directly decanted to separate the solids, and the solid surface was washed with a small amount of the reaction solvent and combined with the filtrate. The solvent was recovered by vacuum distillation, and further distillation yielded 7.9 g of crude product, giving ethyl 4-chloro-2-methyl-2-butenoate. The GC normalization method yielded a content of 84.1%.

[0057] Example 5

[0058] The preparation method of ethyl 4-bromo-2-methyl-2-butenoate includes the following steps:

[0059] Under nitrogen protection, 8.1 g (90%) of zinc powder was dispersed in 100 ml of 2-methyltetrahydrofuran solvent. Then, 18.5 g (99%) of ethyl 2-bromopropionate was added and thoroughly mixed. The mixture was stirred and heated to 71°C to initiate the reaction. Due to the exothermic reaction, the internal temperature rose to 74°C. The reaction continued for 0.5 h, after which the internal temperature returned to 70°C. The temperature was then lowered to 60°C, and 125.0 g (10%) of a bromoacetaldehyde-dichloromethane dry solution was added dropwise while simultaneously recovering some of the dichloromethane by atmospheric distillation over 30 min. After the addition was complete, the reaction continued for another 0.5 h, followed by natural cooling to room temperature. With stirring, 20 ml of a 10% (w / w) H₂SO₄ aqueous solution was added for complete hydrolysis. The turbid reaction solution precipitated a muddy solid and then became clear and transparent. At this point, the solid formed a firm clump at the bottom of the flask. The filtrate was directly decanted to separate the solid, and the surface of the solid was washed with a small amount of the reaction solvent and combined with the filtrate. The solvent was recovered by vacuum distillation, followed by further distillation to obtain 21.7 g of crude product, yielding ethyl 4-bromo-2-methyl-2-butenoate. The GC-normalized purity was 55.5%. Redistillation increased the GC-normalized purity to 76.2%. The sample was purified by silica gel column chromatography (ethyl acetate / petroleum ether = 1:30). The NMR and mass spectrometry data of the product are as follows:

[0060] UV(MeOH) absorption: λmax = 225nm;

[0061] IR (KBr) absorption: 2991, 1713, 1646, 1276, 757 (cm⁻¹);

[0062] MS (EI): m / z 206 (M+, 3%), 161 (9%), 133 (2%), 127 (18%), 117 (73%), 113 (1%), 99 (100%), 82 (10%), 71 (19%), 53 (32%), 39 (12%);

[0063] 1 H-NMR (CDCl3, 600MHz): δ6.92 (qt, J=1.21, 8.38Hz, =CH-), 4.21 (q, J=7.19Hz, -OCH2-) ,4.03(d,J=8.39Hz,-CH2Br), 1.92(d,J=1.22,-CH3), 1.31(t,J=7.20Hz,-OCH2-CH3).

[0064] Example 6

[0065] The preparation method of methyl 4-bromo-2-methyl-2-butenoic acid includes the following steps:

[0066] Under nitrogen protection, 8.1 g (90%) of zinc powder was dispersed in 100 ml of 2-methyltetrahydrofuran solvent. Then, 17.1 g (99%) of methyl 2-bromopropionate was added and thoroughly mixed. The mixture was stirred and heated to 68°C to initiate the reaction. Due to the exothermic reaction, the internal temperature rose to 73°C. The reaction continued for 0.5 h, after which the internal temperature returned to 70°C. The temperature was then lowered to 60°C, and 125.0 g (10%) of a bromoacetaldehyde-dichloromethane dry solution was added dropwise while simultaneously recovering some of the dichloromethane by atmospheric distillation over 30 min. After the addition was complete, the reaction continued for 0.5 h, followed by natural cooling to room temperature. With stirring, 20 ml of a 10% (w / w) H₂SO₄ aqueous solution was added for complete hydrolysis. The turbid reaction solution precipitated a muddy solid, which then became clear and transparent. The filtrate was directly decanted to separate the solids, and the solid surface was washed with a small amount of the reaction solvent, which was then combined with the filtrate. The solvent was recovered by vacuum distillation, followed by further distillation to obtain 19.6 g of crude product, yielding methyl 4-bromo-2-methyl-2-butenoic acid. The purity was 60.7% by GC normalization. After redistillation, the purity was 78.4% by GC normalization. The sample was purified by silica gel column chromatography (ethyl acetate / petroleum ether = 1:30). The NMR and mass spectrometry data of the product are as follows:

[0067] UV(MeOH) absorption: λmax = 225nm;

[0068] IR (KBr) absorption: 2990, 1714, 1647, 1279, 760 (cm⁻¹);

[0069] MS (EI): m / z 192 (M+, 7%), 161 (7%), 133 (3%), 113 (4%), 99 (100%), 82 (11%), 59 (2%), 53 (100%), 39 (22%);

[0070] 1 H-NMR (CDCl3, 600MHz): δ6.83 (qt, J=1.72, 8.29Hz, =CH-), 4.02 (d, J=8.30Hz, -CH2Br), 3.73 (s, -OCH3), 1.89 (d, J=1.70Hz, -CH3).

[0071] Example 7

[0072] The preparation method of ethyl 4-chloro-2-methyl-2-butenoate includes the following steps:

[0073] Under nitrogen protection, 8.1 g (90%) of zinc powder was dispersed in 100 ml of 2-methyltetrahydrofuran solvent. Then, 18.5 g (99%) of ethyl 2-bromopropionate and 0.2 g (97%) of dichlorodicyclopentadiene (Cp₂TiCl₂) were added sequentially and mixed thoroughly. The mixture was stirred and heated until the internal temperature exceeded 50 °C, at which point the reaction began to initiate steadily without significant exothermic reaction. The temperature was eventually raised to 70 °C and the reaction continued for 0.5 h. 37.0 g (21.4%) of a chloroacetaldehyde-2-methyltetrahydrofuran dry solution was added dropwise over 10 min. After the addition was complete, the reaction continued for another 0.5 h, followed by natural cooling to room temperature. With stirring, 20 ml of a 10% (w / w) H₂SO₄ aqueous solution was added for complete hydrolysis. The turbid reaction solution precipitated a muddy solid and then became clear and transparent. The filtrate was directly decanted to separate the solids, and the solid surface was washed with a small amount of the reaction solvent, which was then combined with the filtrate. The solvent was recovered by vacuum distillation, and further distillation yielded 15.1 g of crude product, providing ethyl 4-chloro-2-methyl-2-butenoate. The GC-normalized purity was 86.5%. Redistillation increased the GC-normalized purity to 92.0%.

[0074] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing 4-halo-2-methyl-2-butenoic acid hydrocarbon ester, characterized in that, Includes the following steps: Compound A and compound B undergo a Reformatsky reaction, followed by in-situ dehydration, to yield compound of general formula (I): ； Where X is a halogen and R is a hydrocarbon group; The compound of formula A reacts with the compound of formula B in the form of an anhydrous haloacetaldehyde solution; the method for preparing the anhydrous haloacetaldehyde solution includes the following steps: mixing an aqueous haloacetaldehyde solution with anhydrous calcium chloride, allowing it to stand to separate the oil phase and the aqueous phase; collecting the oil phase, adding a solvent to the aqueous phase for extraction, combining the oil phases, drying, and filtering to obtain the anhydrous haloacetaldehyde solution. The solvent used for extraction is one or more of toluene, xylene, dichloromethane, and 2-methyltetrahydrofuran; Titanium dichlorophenoxide is added as a catalyst during the reaction of compound A and compound B. The molar amount of catalyst is 0.5% to 2% of the molar amount of 2-bromopropionate; The reaction temperature is 70–76℃, and the reaction time is 20 min–10 h; After the compound of formula A and the compound of formula B are mixed and reacted, a mixed solution is obtained. Then, an aqueous solution of H2SO4 is added for hydrolysis, the filtrate and the solid are separated, and the filtrate is distilled to obtain the compound of general formula (I).

2. The method for preparing 4-halo-2-methyl-2-butenoic acid hydrocarbon ester according to claim 1, characterized in that, The solvent used for extraction was 2-methyltetrahydrofuran.

3. The method for preparing 4-halo-2-methyl-2-butenoic acid hydrocarbon ester as described in claim 1, characterized in that, The anhydrous haloacetaldehyde solution has a mass percentage of 4-25%.

4. The method for preparing 4-halo-2-methyl-2-butenoic acid hydrocarbon ester as described in claim 1, characterized in that, The halogen is chlorine or bromine; the compound of formula A is chloroacetaldehyde or bromoacetaldehyde.

5. The method for preparing 4-halo-2-methyl-2-butenoic acid hydrocarbon ester as described in claim 1, characterized in that, The hydrocarbon group is one or more of methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, or vinyl.

6. The method for preparing 4-halo-2-methyl-2-butenoic acid hydrocarbon ester according to claim 1, characterized in that, The compound of formula B is prepared by in-situ reaction of zinc powder and 2-bromopropionate; the molar ratio of compound of formula A to 2-bromopropionate is (2:1) to (0.5:1); the molar ratio of zinc powder to 2-bromopropionate is (2:1) to (1:1).

7. The method for preparing 4-halo-2-methyl-2-butenoic acid hydrocarbon ester as described in claim 6, characterized in that, The in-situ reaction temperature is 0–100℃, and the reaction time is 20 min–10 h.

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