A method for synthesizing 2-methyl glutaronitrile

Abstract

This invention provides a method for synthesizing 2-methylglutaronitrile. The method uses 2-ethylbutadionitrile as a raw material and, under a nitrogen atmosphere and visible light irradiation, undergoes an isomerization reaction via a synergistic catalytic system of a photocatalyst and a hydrogen atom transfer catalyst to generate 2-methylglutaronitrile. The photocatalyst is an organic dye-based photocatalyst, and the hydrogen atom transfer catalyst is an aryl thiol compound with electron-donating substituents. This invention effectively achieves the high-value conversion of adiponitrile byproduct 2-ethylbutadionitrile and has promising application prospects.

Description

Technical Field

[0001] This invention belongs to the field of polymer synthesis technology, and in particular relates to a method for synthesizing 2-methylglutaronitrile. Background Technology

[0002] 2-Methylglutaronitrile is a common isomer in the butadiene-to-adiponitrile process and is an important chemical intermediate. Its core value lies in its ability to be further converted into various high-value chemicals. For example, 2-methylglutaronitrile can be converted into 2-methylpentanediamine through catalytic hydrogenation. In existing technologies, the synthesis of 2-methylglutaronitrile mainly relies on transition metal-catalyzed cyanidation reactions. These methods generally have significant drawbacks in terms of safety, selectivity, and environmental friendliness. Traditional synthetic routes involve the use of highly toxic cyanide feedstocks, such as nucleophilic substitution of sodium (potassium) cyanide with haloalkanes. This method not only has poor atom economy and generates large amounts of wastewater and waste residue containing highly toxic cyanide ions, resulting in high environmental remediation costs, but also involves lengthy and inefficient steps, contradicting the principles of green chemistry.

[0003] To avoid inorganic cyanide salts, subsequent methods have largely employed organic cyanide sources or hydrogen cyanide in the presence of a nickel catalyst to react with 3-pentenonitrile. Specifically, a representative method uses catalysts such as bis-(1,5-cyclooctadiene)nickel, reacting acetone cyanohydrin and 3-pentenonitrile as raw materials. However, acetone cyanohydrin is sensitive to heat and moisture, requiring stringent storage and handling conditions, posing safety risks. More importantly, this reaction exhibits low chemoselectivity, typically producing a mixture of isomers of 2-methylglutaronitrile and 2-ethylbutadionitrile, leading to difficulties in subsequent separation and purification, and consequently, reduced yield and economic benefits. Another similar route employs a nickel / phosphine ligand catalytic system, allowing hydrogen cyanide to directly hydrocyanate 3-pentenonitrile. While this method changes the cyanide source, it uses highly toxic and volatile hydrogen cyanide, posing extreme challenges to production equipment, operational safety, and environmental protection. It also fails to address the fundamental problem of poor regioselectivity and relies on expensive and complex phosphine ligands.

[0004] In summary, existing technologies for synthesizing 2-methylglutaronitrile share common drawbacks: First, they are highly dependent on highly hazardous and toxic raw materials such as acetone cyanohydrin and hydrogen cyanide, resulting in inherently poor safety. Second, the regioselectivity is not ideal, leading to a mixture of product isomers and high separation and purification costs. Third, the use of precious metal catalysts and complex ligands results in poor economic efficiency and may introduce metal residues. Fourth, low atom economy or significant waste treatment pressures make them environmentally unfriendly. These long-standing technical challenges have hindered the safe, green, and efficient production of 2-methylglutaronitrile. Summary of the Invention

[0005] In view of this, the present invention aims to propose a method for synthesizing 2-methylglutaronitrile, the core of which lies in the use of a novel photocatalytic isomerization reaction strategy, using stable and non-toxic 2-ethylbutanedionitrile as a single raw material, to directly achieve intramolecular skeleton rearrangement under mild visible light conditions, thus solving the above-mentioned problems.

[0006] To achieve the above objectives, the technical solution of the present invention is implemented as follows: A method for synthesizing 2-methylglutaronitrile, using 2-ethylbutadionitrile as a raw material, isomerizes the product under nitrogen atmosphere and visible light irradiation via a synergistic catalytic system of a photocatalyst and a hydrogen atom transfer catalyst; wherein the photocatalyst is an organic dye-based photocatalyst, and the hydrogen atom transfer catalyst is an aryl thiol compound with an electron-donating substituent.

[0007] Furthermore, the photocatalyst is selected from at least one of eosin Y, Bengal rose red, methylene blue, acridine salt, phenothiazine, 9-trimethyl-10-methylacidine perchlorate, and 4CzIPN (2,4,5,6-tetra(9-carbazolyl)-isophthalonitrile).

[0008] The photocatalysts described herein follow redox potential matching, are compatible with the triplet energy transfer mechanism, and have been experimentally verified to be effective through screening. These photocatalysts all possess sufficiently strong excited-state oxidation potentials (approximately +0.8 to +1.5 V) and sufficiently long triplet lifetimes under visible light excitation, enabling them to fully convert light energy into chemical energy. This drives the hydrogen atom transfer catalyst to generate sterically hindered sulfur radicals, which, based on their steric hindrance, can precisely extract the hydrogen atom at the α-position of 2-ethylbutadienenitrile and further precisely stereoguide the hydrogen atom, guiding the intramolecular carbon skeleton to undergo 1,4-cyano migration and rearrangement, thereby achieving highly regioselective isomerization. The photocatalysts of this invention exhibit a good synergistic effect with the hydrogen atom transfer catalysts, which is something many other common organic dyes cannot achieve due to insufficient oxidation potential or excessively short triplet lifetimes.

[0009] Preferably, the photocatalyst is one of eosin Y, phenothiazine, and 4CzIPN. These three have a better synergistic effect with hydrogen atom transfer catalysts, especially 2,4,6-triisopropylbenzylthiophenol.

[0010] Furthermore, the hydrogen atom transfer catalyst is selected from at least one of thiophene, 2,4,6-triisopropylthiophene, p-methylthiophene, p-tert-butylthiophene, and p-methoxythiophene.

[0011] Preferably, the hydrogen atom transfer catalyst is one of 2,4,6-triisopropylbenzylthiophenol, p-tert-butylbenzylthiophenol, and p-methoxybenzylthiophenol, with these substituents exhibiting the best electron-donating properties.

[0012] Furthermore, the molar percentage of the photocatalyst to 2-ethylbutadiene is 1-3%.

[0013] Furthermore, the molar ratio of the photocatalyst to the hydrogen atom transfer catalyst is 1:15-1:25.

[0014] Furthermore, the synthesis method specifically includes the following steps: S1. The photocatalyst and the hydrogen transfer catalyst are added sequentially to the reaction tube; S2. Replace the atmosphere inside the reaction tube with a nitrogen atmosphere; S3. Add the solvent and 2-ethylbutadiene nitrile sequentially to the reaction tube; S4. Place the reaction tube under visible light irradiation and heat and stir. S5. The obtained reaction solution is distilled to obtain purified 2-methylglutaronitrile.

[0015] Furthermore, the solvent in S3 is selected from at least one of toluene, fluorobenzene, acetonitrile, N,N-dimethylformamide, and dimethyl sulfoxide.

[0016] Preferably, the solvent is one of acetonitrile, toluene, and dimethyl sulfoxide.

[0017] Furthermore, in S4, the wavelength of visible light is 450nm-470nm, the heating temperature is 25-60℃, and the stirring time is 48-72h; preferably, the heating temperature is 40-60℃ and the stirring time is 50-72h.

[0018] Preferably, the heating temperature is 45-55℃.

[0019] Compared with existing technologies, the method for synthesizing 2-methylglutaronitrile described in this invention has the following advantages: (1) The method for synthesizing 2-methylglutaronitrile described in this invention constructs a synergistic catalytic system composed of an organic dye photocatalyst and a hydrogen atom transfer catalyst with a specific structure. The core mechanism of this system lies in a light-driven, sterically hindered, and precise hydrogen atom transfer process. Under visible light excitation, the organic dye efficiently captures light energy to drive the hydrogen atom transfer catalyst to generate a sulfur radical with specific steric hindrance, thereby precisely extracting the hydrogen atom at the α-position of 2-ethylbutanedione. Aryl thiols, as hydrogen atom transfer catalysts, participate in the catalytic cycle through a reversible hydrogen atom transfer process. In particular, aryl thiols with electron-donating substituents and bulky substituents, with the synergistic effect of the hydrogen atom donor activity of the thiol group and the steric hindrance effect, precisely guide the radical intermediate to undergo 1,4-cyano migration along a single reaction pathway, thereby generating the target 2-methylglutaronitrile with high selectivity and high yield. In particular, 2,4,6-triisopropylbenzylthiophenol possesses both electron-rich properties and significant steric hindrance. Its sulfhydryl bonds act as a hydrogen atom transfer medium, not only efficiently transferring hydrogen atoms but also, through the stereoshiking effect of its three isopropyl groups, forcing the reaction along the path of least steric resistance, thereby precisely guiding the 1,4-cyano group migration and rearrangement of the intramolecular carbon skeleton. The uniqueness of this combination lies in the perfect match between structure and function: inexpensive organic dyes ensure mild visible light driving, while the specially designed thiophenol acts as a molecular-level "directing group," fundamentally determining the selectivity of the reaction.

[0020] (2) The method of the present invention directly synthesizes the target 2-methylglutaronitrile with near-specific selectivity, which effectively solves the pain points of mixed product isomers and difficult separation and purification in traditional methods. At the same time, the present invention fundamentally solves the selectivity problem by abandoning highly toxic raw materials, avoiding precious metals, using light energy to drive the reaction, and optimizing the catalyst system design and ratio. Thus, it systematically surpasses the existing technology in terms of safety, selectivity and economy, and provides a safe, precise and green innovative way for the industrial production of 2-methylglutaronitrile. Detailed Implementation

[0021] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0022] In this document, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0023] In this document, when values ​​are described as ranges, it should be understood that such disclosure includes disclosure of all possible subranges within that range, as well as the specific numerical values ​​falling within that range, regardless of whether the specific numerical value or specific subrange is explicitly specified.

[0024] In this article, the terms "multiple" or "more than" are used unless otherwise specified, referring to a quantity greater than or equal to 2. For example, "one or more" means one or more types.

[0025] In this document, the terms "preferred" and "more preferred" are used only to describe implementation methods or embodiments with better effects, and should be understood as not constituting a limitation on the scope of protection of this invention.

[0026] In this document, terms such as "further" are used for descriptive purposes to indicate differences in content, but should not be construed as limiting the scope of protection of this invention.

[0027] In this article, the term "and / or" describes an association between objects, indicating that three relationships can exist. For example, A and / or B means: A or B, or A and B.

[0028] In this document, the term "about" means a specified value of + / - 10%, preferably + / - 5%, and more preferably + / - 1%.

[0029] In this article, the terms “include,” “including,” “have,” “contain,” etc., are all open-ended terms, meaning that they include but are not limited to.

[0030] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar to or equivalent to those described herein may be used in the implementation or testing of this invention.

[0031] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0032] The synthesis method of 2-methylglutaronitrile according to the present invention specifically includes the following steps: A photocatalyst and a hydrogen atom transfer catalyst are added sequentially to a 10 mL Shrek tube, and the tube is sealed with a flap stopper. The reaction tube is purged with nitrogen using a double-row tube system. Subsequently, the reaction solvent is added using a syringe, and 2-ethylbutadionitrile is added using a microsyringe. The Shrek tube is placed in a photoreactor, and the reaction is carried out under stirring. After the reaction is complete, the crude product is analyzed by 1H NMR spectroscopy (using deuterated chloroform as solvent and 2-methoxynaphthalene as internal standard) to determine the reaction yield, and gas chromatography analysis is used to determine the regioselectivity of the reaction.

[0033] Example 1 In a 10 mL Shrek tube, 4CzIPN (0.02 mmol, 15.78 mg, 0.02 equiv.) and 2,4,6-triisopropylbenzylthiophenol (0.4 mmol, 94.57 mg, 0.4 equiv.) were added sequentially, and the tube was sealed with a stopper. The reaction tube was purged with nitrogen using a double-row tube system. Subsequently, acetonitrile (1 mL) was added using a syringe, and 2-ethylbutadione (1 mmol, 108.14 mg, 1 equiv.) was added using a microsyringe. The Shrek tube was placed in a photoreactor and irradiated at 460 nm wavelength at 50 °C with stirring for 72 h. After the reaction was completed, the crude product was analyzed by 1H NMR (using deuterated chloroform as solvent and 2-methoxynaphthalene as internal standard), confirming a reaction yield of 97%. Gas chromatography analysis was also performed to confirm that the regioselectivity of the reaction was greater than 20:1.

[0034] The chemical reaction equation of this invention is as follows: Example 2 In a 10 mL Shrek tube, eosin Y (0.02 mmol, 13.84 mg, 0.02 equiv.) and 2,4,6-triisopropylbenzylthiophenol (0.3 mmol, 70.93 mg, 0.3 equiv.) were added, and the tube was sealed with a stopper. The reaction tube was purged with nitrogen using a double-row tube system. Then, acetonitrile (1 mL) was added using a syringe, and 2-ethylbutadione (1 mmol, 108.14 mg, 1 equiv.) was added using a microsyringe. The Shrek tube was placed in a photoreactor and irradiated at 450 nm wavelength at 55 °C with stirring for 68 h. After the reaction was complete, the crude product was analyzed by 1H NMR (using deuterated chloroform as solvent and 2-methoxynaphthalene as internal standard), confirming a yield of 92%; gas chromatography was also performed to confirm a regioselectivity greater than 20:1.

[0035] Example 3 In a 10 mL Shrek tube, phenothiazine (0.02 mmol, 3.99 mg, 0.02 equiv.) and 2,4,6-triisopropylbenzylthiophenol (0.4 mmol, 94.57 mg, 0.4 equiv.) were added, and the tube was sealed with a stopper. The reaction tube was purged with nitrogen using a double-row tube system. Acetonitrile (1 mL) was then added using a syringe, followed by 2-ethylbutadione (1 mmol, 108.14 mg, 1 equiv.) using a microsyringe. The Shrek tube was placed in a photoreactor and irradiated at 460 nm wavelength at 50 °C with stirring for 72 h. After the reaction was complete, the crude product was analyzed by 1H NMR (using deuterated chloroform as solvent and 2-methoxynaphthalene as internal standard), confirming a yield of 90%; gas chromatography was also performed to confirm a regioselectivity greater than 20:1.

[0036] Example 4 In a 10 mL Shrek tube, 4CzIPN (0.02 mmol, 15.78 mg, 0.02 equiv.) and p-tert-butylthiophenol (0.4 mmol, 94.57 mg, 0.4 equiv.) were added, and the tube was sealed with a stopper. The reaction tube was purged with nitrogen using a double-row tube system. Subsequently, toluene (1 mL) was added using a syringe, and 2-ethylbutanedionitrile (1 mmol, 108.14 mg, 1 equiv.) was added using a microsyringe. The Shrek tube was placed in a photoreactor and irradiated at 470 nm wavelength at 45 °C with stirring for 72 h. After the reaction was completed, the crude product was analyzed by 1H NMR (using deuterated chloroform as solvent and 2-methoxynaphthalene as internal standard), confirming a reaction yield of 93%; gas chromatography was also performed to confirm a regioselectivity greater than 20:1.

[0037] Example 5 In a 10 mL Shrek tube, 4CzIPN (0.02 mmol, 15.78 mg, 0.02 equiv.) and p-methoxythiophenol (0.4 mmol, 94.57 mg, 0.4 equiv.) were added, and the tube was sealed with a stopper. The reaction tube was purged with nitrogen using a double-row tube system. Subsequently, dimethyl sulfoxide (1 mL) was added using a syringe, and 2-ethylbutanedionitrile (1 mmol, 108.14 mg, 1 equiv.) was added using a microsyringe. The Shrek tube was placed in a photoreactor and irradiated at 460 nm wavelength at 60 °C with stirring for 72 h. After the reaction was completed, the crude product was analyzed by 1H NMR (using deuterated chloroform as solvent and 2-methoxynaphthalene as internal standard), confirming a reaction yield of 90%; gas chromatography was also performed to confirm a regioselectivity greater than 20:1.

[0038] Example 6 In a 250 mL three-necked flask, 4CzIPN (2 mmol, 1.58 g, 0.02 equiv.) and 2,4,6-triisopropylbenzylthiophenol (40 mmol, 9.46 g, 0.4 equiv.) were added, and the flask was sealed with a flap stopper. The reaction tube was purged with nitrogen using a double-row tube system. Then, acetonitrile (100 mL) was added using a syringe, and 2-ethylbutadione (100 mmol, 10.8 g, 1 equiv.) was added using a microsyringe. The three-necked flask was placed in a photoreactor and irradiated at 470 nm wavelength at 50 °C with stirring for 70 h. After the reaction was complete, the crude product was analyzed by 1H NMR (using deuterated chloroform as solvent and 2-methoxynaphthalene as internal standard), confirming a yield of 93%; gas chromatography was also performed to confirm a regioselectivity greater than 20:1.

[0039] Example 7 In a 10 mL Shrek tube, 4CzIPN (0.02 mmol, 15.78 mg, 0.02 equiv.) and 2,4,6-triisopropylbenzylthiophenol (0.4 mmol, 94.57 mg, 0.4 equiv.) were added, and the tube was sealed with a stopper. The reaction tube was purged with nitrogen using a double-row tube system. Then, acetonitrile (1 mL) was added using a syringe, and 2-ethylbutadione (1 mmol, 108.14 mg, 1 equiv.) was added using a microsyringe. The Shrek tube was placed in a photoreactor and irradiated at 460 nm wavelength at 50 °C with stirring for 48 h. After the reaction was complete, the crude product was analyzed by 1H NMR (using deuterated chloroform as solvent and 2-methoxynaphthalene as internal standard), confirming a yield of 72%; gas chromatography was also performed to confirm a regioselectivity greater than 20:1.

[0040] Example 8 In a 10 mL Shrek tube, 4CzIPN (0.01 mmol, 7.89 mg, 0.01 equiv.) and 2,4,6-triisopropylbenzylthiophenol (0.2 mmol, 47.29 mg, 0.2 equiv.) were added, and the tube was sealed with a stopper. The reaction tube was purged with nitrogen using a double-row tube system. Then, acetonitrile (1 mL) was added using a syringe, and 2-ethylbutanedione (1 mmol, 108.14 mg, 1 equiv.) was added using a microsyringe. The Shrek tube was placed in a photoreactor and irradiated at 460 nm wavelength at 50 °C with stirring for 72 h. After the reaction was complete, the crude product was analyzed by 1H NMR (using deuterated chloroform as solvent and 2-methoxynaphthalene as internal standard), confirming a yield of 68%. Gas chromatography analysis confirmed a regioselectivity greater than 20:1.

[0041] Comparative Example 1: No hydrogen atom transfer catalyst added In a 10 mL Shrek tube, 4CzIPN (0.02 mmol, 15.78 mg, 0.02 equiv.) was added, and the tube was sealed with a flap stopper. The reaction tube was purged with nitrogen using a double-row tube system. Then, acetonitrile (1 mL) was added using a syringe, followed by 2-ethylbutadionitrile (1 mmol, 108.14 mg, 1 equiv.) using a microsyringe. The Shrek tube was placed in a photoreactor and irradiated at 460 nm wavelength at 50 °C with stirring for 72 h. After the reaction was complete, the crude product was analyzed by 1H NMR (using deuterated chloroform as solvent and 2-methoxynaphthalene as internal standard), and the target product 2-methylglutaronitrile was not detected.

[0042] Comparative Example 2: No photocatalyst added In a 10 mL Shrek tube, 2,4,6-triisopropylbenzylthiophenol (0.4 mmol, 94.57 mg, 0.4 equiv.) was added, and the tube was sealed with a flap stopper. The reaction tube was purged with nitrogen using a double-row tube system. Then, acetonitrile (1 mL) was added using a syringe, followed by 2-ethylbutadionitrile (1 mmol, 108.14 mg, 1 equiv.) using a microsyringe. The Shrek tube was placed in a photoreactor and irradiated at 460 nm wavelength at 50 °C with stirring for 72 h. After the reaction was complete, the crude product was analyzed by 1H NMR (using deuterated chloroform as solvent and 2-methoxynaphthalene as internal standard), and the target product 2-methylglutaronitrile was not detected.

[0043] Comparative Example 3: No light In a 10 mL Shrek tube, 4CzIPN (0.02 mmol, 15.78 mg, 0.02 equiv.) and 2,4,6-triisopropylbenzylthiophenol (0.4 mmol, 94.57 mg, 0.4 equiv.) were added, and the tube was sealed with a stopper. The reaction tube was purged with nitrogen using a double-row tube system. Acetonitrile (1 mL) was then added using a syringe, followed by 2-ethylbutadionitrile (1 mmol, 108.14 mg, 1 equiv.) using a microsyringe. The mixture was stirred for 72 h in the dark at 50 °C. After the reaction was complete, the crude product was analyzed by 1H NMR (using deuterated chloroform as solvent and 2-methoxynaphthalene as internal standard), and the target product 2-methylglutaronitrile was not detected.

[0044] Comparative Example 4: Short wavelength of light In a 10 mL Shrek tube, 4CzIPN (0.02 mmol, 15.78 mg, 0.02 equiv.) and 2,4,6-triisopropylbenzylthiophenol (0.4 mmol, 94.57 mg, 0.4 equiv.) were added, and the tube was sealed with a stopper. The reaction tube was purged with nitrogen using a double-row tube system. Acetonitrile (1 mL) was then added using a syringe, followed by 2-ethylbutadione (1 mmol, 108.14 mg, 1 equiv.) using a microsyringe. The Shrek tube was placed in a photoreactor and irradiated at 365 nm wavelength at 50 °C with stirring for 72 h. After the reaction was complete, the crude product was analyzed by 1H NMR (using deuterated chloroform as solvent and 2-methoxynaphthalene as internal standard), confirming a yield of 7%; gas chromatography was also performed to determine that the regioselectivity of the reaction was greater than 20:1.

[0045] Comparative Example 5: Different ratios of photocatalyst and hydrogen atom transfer catalyst. In a 10 mL Shrek tube, 4CzIPN (0.02 mmol, 15.78 mg, 0.02 equiv.) and 2,4,6-triisopropylbenzylthiophenol (0.2 mmol, 47.29 mg, 0.2 equiv.) were added, and the tube was sealed with a stopper. The reaction tube was purged with nitrogen using a double-row tube system. Then, acetonitrile (1 mL) was added using a syringe, and 2-ethylbutadione (1 mmol, 108.14 mg, 1 equiv.) was added using a microsyringe. The Shrek tube was placed in a photoreactor and irradiated at 460 nm wavelength at 50 °C with stirring for 72 h. After the reaction was complete, the crude product was analyzed by 1H NMR (using deuterated chloroform as solvent and 2-methoxynaphthalene as internal standard), confirming a yield of 96%. Gas chromatography analysis confirmed a regioselectivity of 9:1.

[0046] Table 1 Comparison of results from various embodiments and comparative examples As can be seen from the table above, the regioselectivity of the embodiments using the technical solution of this invention is greater than 20:1. In particular, the yield of 2-methylglutaronitrile prepared in Examples 1-6 all reached over 90%, indicating that the photocatalyst and hydrogen atom transfer catalyst synergistic catalytic system described in this invention can achieve the isomerization conversion of 2-ethylbutadionitrile to 2-methylglutaronitrile with high efficiency and high selectivity under mild conditions. The byproduct obtained by this invention is adiponitrile.

[0047] Comparative Examples 1-3 lacked hydrogen atom transfer catalyst, photocatalyst, and visible light irradiation, respectively, and the target product 2-methylglutaronitrile was not detected in any of them. This indicates that the synergistic effect of the photocatalyst, hydrogen atom transfer catalyst, and visible light irradiation in this invention is a necessary condition for realizing this isomerization reaction, and none of them can be omitted.

[0048] In Comparative Example 4, when the light wavelength was changed to 365nm, the yield dropped sharply to 7%, indicating that the 450-470nm visible light wavelength selected in this invention matches the absorption characteristics of the photocatalyst. Deviating from this wavelength range will lead to a significant reduction in catalytic efficiency.

[0049] Comparative Example 5 adjusted the molar ratio of photocatalyst to hydrogen atom transfer catalyst to 1:10. Although the yield was still 96%, the regioselectivity decreased significantly to 9:1. This shows that the specific catalyst ratio range defined in this invention is crucial for achieving a highly selective reaction. Deviating from this range will lead to a significant decrease in isomer selectivity.

[0050] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for the synthesis of 2-methylglutaronitrile, characterized in that: Using 2-ethylbutadionitrile as a raw material, under a nitrogen atmosphere and visible light irradiation, an isomerization reaction is carried out through a synergistic catalytic system of a photocatalyst and a hydrogen atom transfer catalyst to generate 2-methylglutaronitrile; wherein, the photocatalyst is an organic dye photocatalyst, and the hydrogen atom transfer catalyst is an aryl thiol compound with an electron-donating substituent.

2. The method for synthesizing 2-methylglutaronitrile according to claim 1, characterized in that: The photocatalyst is selected from at least one of eosin Y, Bengal rose red, methylene blue, acridine salt, phenothiazine, 9-trimethyl-10-methylacidine perchlorate, and 4CzIPN.

3. The method for synthesizing 2-methylglutaronitrile according to claim 1, characterized in that: The hydrogen atom transfer catalyst is selected from at least one of thiophenol, 2,4,6-triisopropylthiophenol, p-methylthiophenol, p-tert-butylthiophenol, and p-methoxythiophenol.

4. The method for synthesizing 2-methylglutaronitrile according to claim 1, characterized in that: The photocatalyst has a molar percentage of 1-3% with 2-ethylbutadiene.

5. The method for synthesizing 2-methylglutaronitrile according to claim 1, characterized in that: The molar ratio of the photocatalyst to the hydrogen atom transfer catalyst is 1:15 to 1:

25.

6. The method for synthesizing 2-methylglutaronitrile according to any one of claims 1 to 5, characterized in that: The synthesis method specifically includes the following steps: S1. The photocatalyst and the hydrogen atom transfer catalyst are added to the reaction tube in sequence; S2. Replace the atmosphere inside the reaction tube with a nitrogen atmosphere; S3. Add the solvent and 2-ethylbutadiene nitrogen to the reaction tube in sequence; S4. Place the reaction tube under visible light irradiation and heat and stir. S5. The obtained reaction solution is distilled to obtain purified 2-methylglutaronitrile.

7. The method for synthesizing 2-methylglutaronitrile according to claim 6, characterized in that: The solvent in S3 is selected from at least one of toluene, fluorobenzene, acetonitrile, N,N-dimethylformamide, and dimethyl sulfoxide.

8. The method for synthesizing 2-methylglutaronitrile according to claim 6, characterized in that: In S4, the wavelength of visible light is 450nm-470nm, the heating temperature is 25-60℃, and the stirring time is 48-72h; preferably, the heating temperature is 40-60℃ and the stirring time is 50-72h.

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