Preparation method of alpha-chlorocarboxylic acid and derivatives thereof

Abstract

The invention provides a preparation method of alpha-chlorocarboxylic acid and derivatives thereof, and belongs to the technical field of organic synthesis.The synthesis method comprises the steps that an organic solution of inorganic salt chloride serving as a chlorine source and inorganic acid is placed in a photoreactor, then an iron / sulfur catalyst and alpha-H-containing carboxylic acid or derivatives thereof are added, the mixture is stirred and heated to 25-55 DEG C, a reaction is conducted for 1-2 h, and the alpha-chlorocarboxylic acid and derivatives thereof are obtained; and carrying out catalytic reaction for 4-12 hours under the illumination of sunlight or a 300W xenon lamp or an LED lamp, cooling the reaction liquid to room temperature, filtering, collecting filtrate, concentrating under reduced pressure, and recovering the reaction solvent. And adding water and methyl tert-butyl ether into the residues, extracting the water phase for three times by using the methyl tert-butyl ether, combining the organic phases, washing and drying the organic phases by using a saturated saline solution, separating the dried organic phases, concentrating under reduced pressure, and cooling to obtain the corresponding alpha-chlorocarboxylic acid or the derivative thereof. The method can effectively reduce environmental pollution and improve reaction selectivity, and is a feasible green way.

Description

Technical Field

[0001] The present invention relates to a method for preparing α-chlorocarboxylic acid and its derivatives, in particular to a method for preparing α-chlorocarboxylic acid using iron / sulfur as catalysts, belonging to the technical field of organic synthesis. Background Art

[0002] Carboxylic acids and nitrile compounds are important organic compounds closely related to pharmaceuticals and are common building blocks in the production of fine chemicals. However, the most classic method for acid chlorination is the Hell-Volhard-Zelinsky (HVZ) method, which uses chlorine gas as the chlorinating agent. Chlorine gas is produced in the chlor-alkali industry. The production, transportation, and use of chlorine gas are not only dangerous, but also release large amounts of hydrogen chloride gas as a byproduct, which is highly corrosive and has serious environmental impacts. Furthermore, this method requires high temperatures (>150°C), resulting in high energy consumption and often produces mixtures of mono- and polyhalogenated acids. Clearly, this traditional method does not conform to the principles of atom economy or the basic requirements of sustainable chemical processes. Therefore, developing a method for directly chlorinating the α-H of carboxylic acids using inorganic chloride salts as a chlorine source in the absence of strong oxidants could overcome the theoretical maximum chlorine utilization rate of 50% while ensuring green chemical production, and has significant technical and economic value.

[0003] Nano-precious metal / semiconductor photocatalysts and visible light synergistic catalysis can achieve chemical transformations at room temperature that are inaccessible to traditional methods, including photolysis of water to produce hydrogen, oxidation of alkanes, oxidation of alkenes, oxidation of alcohols, direct oxidative hydroxylation of aromatic rings, oxidation of fused rings, and halogenation of C-H bonds. However, due to the high loss of precious metal catalysts during use, they are not economically advantageous. The present invention uses readily available and inexpensive iron as a visible light catalyst and an inorganic salt chloride as a chlorine source under light radiation to achieve highly selective, highly safe, and nearly pollution-free α-chlorination of carboxylic acids or corresponding nitriles to synthesize the corresponding chlorinated products. This method has not been reported previously. Summary of the Invention

[0004] Based on current theory and practice, the present invention provides a method for preparing α-chlorocarboxylic acid and its derivatives, which solves the technical problems of existing chlorination methods such as safety, low selectivity, high cost, and serious environmental pollution.

[0005] To achieve the above-mentioned object, the technical solution of a method for preparing α-chlorocarboxylic acid and its derivatives of the present invention comprises the following steps:

[0006] An inorganic salt chloride as a chlorine source and an inorganic acid or an organic acid are placed in a photoreactor containing an organic solvent, and an iron / sulfur catalyst and a substrate carboxylic acid containing α-H or its derivative are added. The mixture is stirred and heated to 25-55° C., and a catalytic reaction is carried out under sunlight or a 300W xenon lamp or LED light for 4-12 hours. The reaction solution is then cooled to room temperature, the filtrate is filtered and collected, and the filtrate is concentrated under reduced pressure to recover the solvent. Water and methyl tert-butyl ether are added to the residue, and the aqueous phase is extracted three times with methyl tert-butyl ether. The organic phases are combined and then washed with saturated brine. The organic phases are dried, and the dried organic phases are separated, concentrated under reduced pressure, and cooled to obtain the corresponding α-chlorocarboxylic acid or its derivative.

[0007] Furthermore, the inorganic salt chloride serving as a chlorine source is any one of magnesium chloride, sodium chloride, potassium chloride, calcium chloride, lithium chloride, ammonium chloride, ferric chloride, tetrabutylammonium chloride, aluminum chloride, and copper chloride.

[0008] Furthermore, the inorganic acid is hydrochloric acid, sulfuric acid, phosphoric acid or sulfonic acid, and the organic acid is benzoic acid, trichloroacetic acid or trifluoroacetic acid.

[0009] Furthermore, the sulfonic acid is selected from methanesulfonic acid, trifluoromethanesulfonic acid, chlorosulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, nitrobenzenesulfonic acid or benzene disulfonic acid.

[0010] Furthermore, the substrate carboxylic acid or its derivative containing α-H is an acid, a corresponding anhydride or ester, or a nitrile compound;

[0011] Wherein, the acid is an acid compound containing α-H, which is selected from fatty acids, alicyclic acids or aromatic substituted fatty acids;

[0012] The fatty acid comprises a C2-C18 straight-chain hydrocarbon group or a branched hydrocarbon acid selected from acetic acid, propionic acid, butyric acid, valeric acid, hexanoic acid, octanoic acid, dodecanoic acid, hexadecanoic acid, octadecanoic acid or isomers thereof; wherein the aromatic substituted fatty acid is a phenylacetic acid or phenylpropionic acid series compound;

[0013] Among them, fatty acid anhydrides include acetic anhydride, propionic anhydride, succinic anhydride, and mixed anhydrides formed by other fatty acids and formic acid or benzoic acid;

[0014] Wherein, the nitrile compound is aliphatic nitrile or aromatic aliphatic nitrile.

[0015] Furthermore, alicyclic acids include but are not limited to camphoric acid, anisic acid and macrocyclic acid; or their corresponding dicarboxylic acids, malonic acid, succinic acid, adipic acid; fatty nitriles include C2-C18 straight-chain alkyl groups or branched alkyl groups selected from acetonitrile, propionitrile, butyronitrile, valeronitrile, capronitrile, octanonitrile, dodecanitrile, hexadecanenitrile, octanonitrile or their isomers, or their corresponding dinitriles, malonic dinitrile, succinic dinitrile, adiponitrile; aromatic fatty nitriles are benzyl cyanide or benzyl propionitrile series compounds.

[0016] Furthermore, the iron in the iron / sulfur catalyst is selected from one of iron powder, ferric chloride, ferrous chloride, ferric sulfate, ferrous sulfate, ferric nitrate, ferrosoferric oxide, and ferric oxide.

[0017] Furthermore, the catalytic reaction solvent is selected from any one of tetrahydrofuran, chlorobenzene, fluorobenzene, dichloromethane, chloroform, and 1,2-dichloroethane.

[0018] Furthermore, the molar ratio of chloride ions in the added inorganic salt chloride to the α-H-containing substrate carboxylic acid or its derivative is between 0.25:1 and 28:1.

[0019] Furthermore, the molar ratio of the added organic acid or inorganic acid to the chloride ion in the inorganic chloride salt is between 0.1:1-1:25; the mass volume ratio of the amount of the iron / sulfur catalyst used to the α-H-containing substrate carboxylic acid or its derivative is between 0.5-30%.

[0020] The beneficial effects of the preparation method of an α-chlorocarboxylic acid and its derivatives of the present invention are:

[0021] The present invention provides a method for synthesizing α-chlorocarboxylic acid (nitrile), which has low cost, simple and easy-to-operate equipment, high product selectivity, easy separation, and large-scale production. It is a new, environmentally friendly, highly selective, low-energy, and feasible green approach for the chlorination of organic matter, and has very good industrial application prospects.

[0022] (1) The present invention provides a novel preparation method for α-chlorocarboxylic acid and its derivatives, which uses chloride ions in inorganic salt chloride as a chlorine source and Fe / sulfur as a photocatalyst. Under the irradiation of sunlight, visible light or LED light, valence electrons receive photons and undergo electron transitions, resulting in the formation of photogenerated electrons and holes. In this way, the electrons of the chloride ions are transferred to the holes to generate chloride free radicals, initiating free radical reactions. Subsequently, the chloride ions of the inorganic salts immediately replenish the chloride ions on the catalyst surface to maintain the composition of the catalyst. The driving force of the reaction comes from the generated photogenerated electrons reducing the oxygen molecules dissolved in the reaction system to form hydrogen peroxide, which then oxidizes the chloride ions in situ under acidic conditions to form chlorine gas molecules. Since the speed of photogenerated electron formation is relatively slow, the concentration of chlorine is ultimately very low. Therefore, the speed of chlorination can be effectively controlled by kinetics, so that the method provided by the present invention has extremely high selectivity. The reaction process avoids the generation of three wastes, thereby limiting the generation of pollutants from the source and solving the key technical problems existing in traditional processes.

[0023] (2) The novel preparation method of the present invention for α-chlorocarboxylic acid and its derivatives uses readily available chlorinating agents and catalysts, has low synthesis costs, and has good industrial prospects;

[0024] (3) A method for preparing α-chlorocarboxylic acid or its derivatives, wherein the gas phase purity of the synthesized chloroacetonitrile is 97%-99% and the selectivity is >98%. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] Figure 1 This is the GC-MS chart of acetic acid-chloroacetic acid.

[0027] Figure 2 This is the GC-MS chart of acetonitrile-chloroacetonitrile. DETAILED DESCRIPTION

[0028] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can also be implemented in other ways different from those described herein, and those skilled in the art can make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0029] A technical solution for a preparation method of α-chlorocarboxylic acid and its derivatives comprises the following steps:

[0030] An inorganic salt chloride as a chlorine source and an inorganic acid or an organic acid are placed in a photoreactor containing a solvent, and an iron / sulfur catalyst and a substrate carboxylic acid or a derivative thereof containing α-H are added. The mixture is stirred and heated to 25-55° C., and a catalytic reaction is carried out under sunlight or a 300W xenon lamp or LED light for 4-12 hours. The reaction solution is then cooled to room temperature, the filtrate is filtered and collected, and the reaction solvent is recovered by concentration under reduced pressure. Water and methyl tert-butyl ether are added to the residue, and the aqueous phase is extracted three times with methyl tert-butyl ether. The organic phases are combined and then washed with saturated brine. The organic phases are dried, and the dried organic phases are separated, concentrated under reduced pressure, and cooled to obtain the corresponding α-chlorocarboxylic acid or a derivative thereof.

[0031] Furthermore, the inorganic salt chloride serving as the chlorine source is any one of magnesium chloride, sodium chloride, potassium chloride, calcium chloride, lithium chloride, ammonium chloride, ferric chloride, tetrabutylammonium chloride, aluminum chloride, and copper chloride. The inorganic acid is hydrochloric acid, sulfuric acid, phosphoric acid, or sulfonic acid, and the organic acid is benzoic acid, trichloroacetic acid, or trifluoroacetic acid. The sulfonic acid is selected from methanesulfonic acid, trifluoromethanesulfonic acid, chlorosulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, nitrobenzenesulfonic acid, or benzenedisulfonic acid.

[0032] Furthermore, the substrate carboxylic acid containing α-H or its derivative is an acid, a corresponding acid anhydride or ester, or a nitrile compound; preferably, the acid is an acid compound containing α-H, selected from fatty acids, alicyclic acids, or aromatic substituted fatty acids; wherein the fatty acid includes a C1-C18 linear alkyl group or a branched alkyl group selected from acetic acid, propionic acid, butyric acid, valeric acid, hexanoic acid, octanoic acid, dodecanoic acid, hexadecanoic acid, octadecanoic acid, or isomers thereof; wherein the aromatic substituted fatty acid is a phenylacetic acid or phenylpropionic acid series compound; wherein the fatty acid anhydride includes acetic anhydride, propionic anhydride, succinic anhydride, or a mixed anhydride formed by other fatty acids and formic acid or benzoic acid; wherein the nitrile compound is a fatty nitrile or an aromatic fatty nitrile.

[0033] Further preferably, the fatty acids include but are not limited to camphoric acid, anisic acid and macrocyclic acid; or their corresponding dicarboxylic acids, malonic acid, succinic acid, adipic acid; the fatty nitrile includes a C1-C18 straight-chain alkyl group or a branched alkyl group selected from acetonitrile, propionitrile, butyronitrile, valeronitrile, capronitrile, octanonitrile, dodecanitrile, hexadecanitrile, octanonitrile or their isomers, or their corresponding dinitriles, malonic acid, succinic acid, adiponitrile; the aromatic fatty nitrile is phenylacetonitrile or a phenylpropionitrile series compound.

[0034] Furthermore, the iron in the iron / sulfur catalyst is selected from one of iron powder, ferric chloride, ferrous chloride, ferric sulfate, ferrous sulfate, ferric nitrate, ferrosoferric oxide, and ferric oxide. The catalytic reaction is carried out in an organic solvent selected from any one of tetrahydrofuran, chlorobenzene, fluorobenzene, dichloromethane, chloroform, and 1,2-dichloroethane.

[0035] Furthermore, the molar ratio of chloride ions in the added inorganic chloride salt to the α-H-containing substrate carboxylic acid or its derivative is between 0.25:1 and 28:1. The molar ratio of the added organic acid or inorganic acid to the chloride ions in the inorganic chloride salt is between 0.1:1 and 1:25. The mass volume ratio of the iron / sulfur catalyst used to the α-H-containing substrate carboxylic acid or its derivative is between 0.5% and 30%.

[0036] Example 1 Chlorination of acetic acid

[0037] Take 57.1g (0.6mol) of magnesium chloride, 69.0mL (1.2mol) of acetic acid, and 0.3mol of chlorosulfonic acid, and add them to the photoreactor in sequence; under stirring, add 1.5g of ferric chloride / sulfur catalyst, turn on the 300W xenon lamp light source, and react at room temperature for 8h; track the reaction with gas chromatography; after the reaction is completed, filter and collect the filtrate, concentrate under reduced pressure, and recover the excess acetic acid. Add water and methyl tert-butyl ether to the residue, and extract the aqueous phase with methyl tert-butyl ether 3 times, combine the organic phases, and wash with saturated brine, dry the organic phase, and concentrate under reduced pressure to recover methyl tert-butyl ether. Cool the residue to obtain the corresponding α-chloroacetic acid, and obtain 32.7g. The sample was analyzed by GS, and the purity of the gas phase detection was 92.2%, and no polychlorinated products were detected. Figure 1 Shown is a GC-MS graph of the reaction mixture.

[0038] Example 2 Chlorination of acetic acid

[0039] The same synthesis method as in Example 1 was adopted, except that the system was heated to 30° C. to obtain 33.5 g of chloroacetic acid, with a purity of 91% as determined by gas phase analysis.

[0040] Example 3 Chlorination of acetic acid

[0041] The same synthesis method as in Example 1 was adopted, except that the system was heated to 50° C. to obtain 30.5 g of chloroacetic acid, with a purity of 90.5% as determined by gas phase analysis.

[0042] Example 4 Chlorination of acetic acid

[0043] The same synthesis method as in Example 1 was used, except that the chlorine source was changed to sodium chloride, to obtain 25.5 g of chloroacetic acid with a purity of 88.6% as determined by gas phase analysis.

[0044] Example 5 Chlorination of acetic acid

[0045] The same synthesis method as in Example 1 was used, except that the chlorine source was changed to lithium chloride, to obtain 26.5 g of chloroacetic acid with a purity of 91.5% as determined by gas phase analysis.

[0046] Example 6 Chlorination of acetic acid

[0047] 38g (0.4mol) of magnesium chloride, 0.2g (2.0mmol) of phosphoric acid, and 46.0mL (0.8mol) of acetic acid were added sequentially to a photoreactor. With stirring, 3.0g of iron powder and 0.9g of sulfur were added. The reaction was conducted at 40°C under a 420nm LED light source for 6 hours. The reaction was monitored by gas chromatography. After completion, the filtrate was filtered, collected, and concentrated under reduced pressure to recover excess acetic acid. Water and methyl tert-butyl ether were added to the residue, and the aqueous phase was extracted three times with methyl tert-butyl ether. The organic phases were combined and washed with saturated brine. The organic phases were dried and concentrated under reduced pressure to recover methyl tert-butyl ether. The residue was cooled to yield 0.033g of the corresponding α-chloroacetic acid. A sample was taken and analyzed by GC, and the purity was 95.2% as determined by gas chromatography.

[0048] Example 7 Chlorination of acetic acid

[0049] The same synthesis method as in Example 6 was used, except that the catalyst was changed to ferrous chloride / sulfur, to obtain 0.031 g of chloroacetic acid with a purity of 93.4% as determined by gas phase analysis.

[0050] Example 8 Chlorination of acetic acid

[0051] The same synthesis method as in Example 6 was used, except that the catalyst was changed to ferric sulfate / sulfur, the light source was 400 nm, and the reaction was carried out for 12 h to obtain 0.035 g of chloroacetic acid with a purity of 95.2% as determined by gas phase analysis.

[0052] Example 9 Chlorination of butyric acid

[0053] The same method as in Example 1 was used, butyric acid was used instead of acetic acid. The residue obtained after concentration of methyl tert-butyl ether was subjected to vacuum fractional distillation, and the 122-124°C / 34 mmHg fraction was collected to obtain 35.8 g of α-chlorobutyric acid product.

[0054] Example 10 Chlorination of hexanoic acid

[0055] The same method as in Example 1 was used, except that hexanoic acid was used instead of acetic acid. The residue obtained after concentration of methyl tert-butyl ether was slowly cooled to obtain 33.5 g of a solid product, α-chlorohexanoic acid.

[0056] Example 11 Chlorination of acetic anhydride

[0057] 0.6 mol of magnesium chloride, 1.2 mol of acetic anhydride, and 0.1 mol of chlorosulfonic acid were added sequentially to a photoreactor. While stirring, 0.8 g of an iron sulfate / sulfur catalyst was added, and a 300 W xenon lamp was used as the light source. The reaction was allowed to proceed at room temperature for 6 hours. The reaction was monitored by gas chromatography. After completion, the filtrate was filtered, collected, and concentrated under reduced pressure to recover the acetic anhydride and acetic acid. Water and methyl tert-butyl ether were added to the residue, and the aqueous phase was extracted three times with methyl tert-butyl ether. The organic phases were combined and washed with saturated brine. The organic phases were dried and concentrated under reduced pressure to recover the methyl tert-butyl ether. The residue was cooled to yield 35.5 g of the corresponding α-chloroacetic acid. A sample was taken and analyzed by GC analysis, and the purity was 95.5% with no polychlorinated products detected.

[0058] Example 12 Chlorination of Succinic Anhydride

[0059] 0.2 mol of calcium chloride, 0.2 mol of succinic anhydride, and 0.04 mol of chlorosulfonic acid were added sequentially to a 50 mL photoreactor of fluorobenzene. With stirring, 1.8 g of an iron powder / sulfur catalyst was added, and a 300 W xenon lamp was used as the light source. The reaction was allowed to react at room temperature for 6 hours. The reaction was monitored by gas chromatography. After completion, the filtrate was filtered, collected, and concentrated under reduced pressure to recover the fluorobenzene. Water and methyl tert-butyl ether were added to the residue, and the aqueous phase was extracted three times with methyl tert-butyl ether. The organic phases were combined and washed with saturated brine. The organic phases were dried and concentrated under reduced pressure to recover the methyl tert-butyl ether. The residue was cooled to yield 4.3 g of the corresponding α-chlorosuccinic anhydride. A sample was taken and analyzed by GC, and the purity was 97.5% with no polychlorinated products detected.

[0060] Example 13 Chlorination of acetonitrile

[0061] Take 24g of magnesium chloride, 0.263g (2.0mmol) of trichloroacetic acid, and 25mL (0.5mol) of acetonitrile, and add them to the photoreactor in sequence; under stirring, add 0.3g of ferric chloride catalyst, turn on the LED 450nm light source, the temperature is 35℃, react for 6h, and track the reaction with gas chromatography; after the reaction is completed, filter and collect the filtrate, concentrate under reduced pressure, and recover the excess acetonitrile. Add water and methyl tert-butyl ether to the residue, and extract the aqueous phase with methyl tert-butyl ether 3 times, combine the organic phases, wash with saturated brine, dry, and concentrate under reduced pressure to recover methyl tert-butyl ether, distill, collect the 123-124℃ fraction, and obtain 2.2g of chloroacetonitrile. Analyzed by GS, the purity was 98.1%, and no polychlorinated products were detected. Figure 2 Shown is a GC-MS graph of the reaction mixture.

[0062] Example 14 Chlorination of acetonitrile

[0063] 29g of inorganic salt, magnesium chloride, 2.70mL of sulfuric acid, and 35mL of acetonitrile were added to a photoreactor in this order. Under stirring, 1.5g of ferric chloride catalyst was added, and a 300W xenon lamp was used as a light source. The reaction was allowed to react at room temperature for 4 hours, and the reaction was monitored by gas chromatography. After completion, the filtrate was filtered, collected, and concentrated under reduced pressure to recover the excess acetonitrile. Water and methyl tert-butyl ether were added to the residue, and the aqueous phase was extracted three times with methyl tert-butyl ether. The organic phases were combined, washed with saturated brine, dried, and concentrated under reduced pressure to recover the methyl tert-butyl ether. The fraction at 123-124°C was then rectified to yield 1.5g of chloroacetonitrile. Glycerol analysis revealed a purity of 97.8%, with no polychlorinated products detected.

[0064] Example 15 Chlorination of Butyronitrile

[0065] By replacing the acetonitrile in Example 11 with butyronitrile, α-chlorobutyronitrile can be obtained using the same conditions and the same operation. After distillation under reduced pressure, 1.8 g of product was obtained with a purity of 97.3%. No polychlorinated products were detected.

[0066] Example 16 Chlorination of Succinonitrile

[0067] 29g of magnesium chloride, 0.263g (2.0mmol) of trichloroacetic acid, and 25mL (0.5mol) of succinonitrile were added sequentially to a photoreactor. With stirring, 0.5g of ferric chloride catalyst was added, and a 450nm LED light source was used. The reaction was allowed to react at 55°C for 6 hours, monitored by gas chromatography. After completion of the reaction, the filtrate was collected by filtration and concentrated under reduced pressure. Water and methyl tert-butyl ether were added to the residue, and the aqueous phase was extracted three times with methyl tert-butyl ether. The organic phases were combined, washed with saturated brine, dried, and concentrated under reduced pressure to recover the methyl tert-butyl ether. The mixture was slowly cooled to yield 2.8g of chlorosuccinonitrile as a solid. Glycerol analysis revealed a purity of 97.5%, with no polychlorinated products detected.

[0068] Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

Claims

1. A method for preparing α-chlorocarboxylic acid and its derivatives, characterized in that: The method comprises the following steps: placing an inorganic salt chloride as a chlorine source and an inorganic acid or an organic acid in a photoreactor containing a solvent, then adding an iron / sulfur catalyst and a substrate carboxylic acid containing α-H or a derivative thereof, stirring and heating to 25-55°C, and carrying out a catalytic reaction for 4-12 hours under sunlight or a 300W xenon lamp or LED light, then cooling the reaction liquid to room temperature, filtering and collecting the filtrate, and concentrating under reduced pressure to recover the solvent; adding water and methyl tert-butyl ether to the residue, extracting the aqueous phase with methyl tert-butyl ether three times, combining the organic phases, washing with saturated brine, drying the organic phases, separating and concentrating the dried organic phase under reduced pressure, and cooling to obtain the corresponding α-chlorocarboxylic acid or a derivative thereof.

2. The method for preparing an α-chlorocarboxylic acid and its derivatives according to claim 1, characterized in that: The inorganic salt chloride serving as a chlorine source is any one of magnesium chloride, sodium chloride, potassium chloride, calcium chloride, lithium chloride, ammonium chloride, ferric chloride, tetrabutylammonium chloride, aluminum chloride, and copper chloride.

3. The method for preparing an α-chlorocarboxylic acid and its derivatives according to claim 1, characterized in that: The inorganic acid is one of hydrochloric acid, sulfuric acid, phosphoric acid or sulfonic acid, and the organic acid is one of benzoic acid, trichloroacetic acid or trifluoroacetic acid.

4. The method for preparing an α-chlorocarboxylic acid and its derivatives according to claim 3, characterized in that: The sulfonic acid is selected from methanesulfonic acid, trifluoromethanesulfonic acid, chlorosulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, nitrobenzenesulfonic acid or benzene disulfonic acid.

5. The method for preparing an α-chlorocarboxylic acid and its derivatives according to claim 1, characterized in that: The substrate carboxylic acid containing α-H or its derivative is an acid, a corresponding acid anhydride or ester, or a nitrile compound; wherein the acid is a carboxylic acid compound containing α-H, which is selected from fatty acids, alicyclic acids, or aromatic substituted fatty acids; Wherein, the fatty acid includes a C2-C18 straight chain or branched saturated or unsaturated acid selected from acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, octanoic acid, dodecanoic acid, hexadecanoic acid, oleic acid, linoleic acid, octadecanoic acid or their isomers; Wherein, the aromatic substituted fatty acid is a phenylacetic acid or phenylpropionic acid series compound; Among them, fatty acid anhydrides include acetic anhydride, propionic anhydride, succinic anhydride, and mixed anhydrides formed by other fatty acids and formic acid or benzoic acid; Wherein, the nitrile compound is aliphatic nitrile or aromatic aliphatic nitrile.

6. The method for preparing an α-chlorocarboxylic acid and its derivatives according to claim 5, characterized in that: Alicyclic acids include but are not limited to camphoric acid, anisic acid and macrocyclic acids; or their corresponding dicarboxylic acids, malonic acid, succinic acid, adipic acid; fatty nitriles include C2-C18 straight-chain alkyl groups or branched alkyl groups selected from acetonitrile, propionitrile, butyronitrile, valeronitrile, capronitrile, octanonitrile, dodecanitrile, hexadecanitrile, octanonitrile or their isomers, or their corresponding dinitriles, malonic dinitrile, succinic dinitrile, adiponitrile; aromatic fatty nitriles are benzyl cyanide or benzyl propionitrile series compounds.

7. The method for preparing an α-chlorocarboxylic acid and its derivatives according to claim 1, characterized in that: The iron in the iron / sulfur catalyst is selected from one of iron powder, ferric chloride, ferrous chloride, ferric sulfate, ferrous sulfate, ferric nitrate, ferrosoferric oxide and ferric oxide.

8. The method for preparing an α-chlorocarboxylic acid and its derivatives according to claim 1, characterized in that: An organic solvent is added during the catalytic reaction, and the organic solvent is selected from any one of tetrahydrofuran, chlorobenzene, fluorobenzene, dichloromethane, chloroform, and 1,2-dichloroethane.

9. The method for preparing an α-chlorocarboxylic acid and its derivatives according to claim 1, characterized in that: The molar ratio of chloride ions in the added inorganic salt chloride to the substrate carboxylic acid containing α-H or its derivative is between 0.25:1 and 28:

1.

10. The method for preparing an α-chlorocarboxylic acid and its derivatives according to claim 1, characterized in that: The molar ratio of the added organic acid or inorganic acid to the chloride ion in the inorganic salt chloride is between 0.1:1 and 1:25; the mass volume ratio of the amount of the iron / sulfur catalyst used to the substrate carboxylic acid or its derivative containing α-H is between 0.5 and 30%.

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