A process for the preparation of 2-substituted pyridines from diester succinates

Abstract

The present application relates to a method for preparing 2-substituted pyridine from succinic acid diester, which comprises: S1, substituting compound I with compound II to obtain compound III; S2, reducing and cyclizing compound III to obtain compound IV; S3, dehydrogenating and deoxidizing compound IV to obtain compound V. The present application also relates to a method for preparing 2-substituted pyridine from nylon acid diester and a method for preparing 2-substituted pyridine from nylon acid. According to the method of the present application, the yield of 2-substituted pyridine product is high, the quality is stable, and the production cost is low, which can effectively improve the processing level of nylon acid and the preparation level of 2-substituted pyridine compounds.

Description

Technical Field

[0001] This invention relates to the field of comprehensive utilization of nylonic acid, specifically to a method for preparing 2-substituted pyridine from succinate diester, and a method for preparing 2-substituted pyridine from nylonic acid diester including the above method and a method for preparing 2-substituted pyridine from nylonic acid. Background Technology

[0002] In the production process of adipic acid, the oxidation of a mixture of cyclohexanol and cyclohexanone with nitric acid produces not only the main product, adipic acid, but also dicarboxylic acids, primarily succinic acid and glutaric acid, as byproducts. After separating the main product, adipic acid, the resulting mixture of succinic acid and glutaric acid, containing small amounts of adipic acid, is called nylon acid. Currently, the common method is to esterify nylon acid and use it as a mixed organic solvent. However, this method has a low market price, which is not conducive to increasing the profits of adipic acid producers. More importantly, with the continuous increase in the production capacity of my country's adipic acid industry, the output of nylon acid is also rising, while the market for nylon ester mixed solvents is becoming increasingly saturated. Therefore, there is an urgent need to find a more efficient and high-value-added resource utilization method. Summary of the Invention

[0003] To address the shortcomings of nylon acid, such as its limited application scenarios and low added value, this invention proposes a method for producing 2-substituted pyridine compounds, key pharmaceutical and pesticide products, using nylon acid as a raw material. This method enables the resource utilization of nylon acid and enhances its utilization value.

[0004] 2-Substituted pyridines are an important class of pharmaceutical and pesticide intermediates, but their preparation methods are complex and costly. For example, 2-methylpyridine is mainly produced by reacting acrylonitrile with acetone or by separating it as a byproduct of pyridine production. Therefore, these preparation methods all have certain drawbacks, such as producing a large number of byproducts and high separation costs.

[0005] This invention develops a technique for preparing 2-substituted pyridine from succinate diester and realizes a method for the resource utilization of nylon acid, which has important practical significance.

[0006] According to the method of the present invention, the 2-substituted pyridine product has a high yield, stable quality, and low production cost, which not only effectively improves the processing level of nylon acid but also enhances the preparation level of 2-substituted pyridine compounds.

[0007] This invention provides a method for preparing 2-substituted pyridine from succinate diester, as shown in the following reaction formula, the method comprising the following steps:

[0008] S1, Compound I and Compound II undergo a substitution reaction to give Compound III;

[0009] S2, compound III is reduced and cyclized to compound IV;

[0010] S3, compound IV is dehydrogenated and deoxygenated to give compound V;

[0011]

[0012] in,

[0013] R is selected from alkyl, cycloalkyl, aryl, heteroaryl, heterocyclic, cycloalkylalkyl, arylalkyl, heteroarylalkyl, heterocyclic alkyl, etc., preferably selected from C1-C10 alkyl, C3-C10 cycloalkyl, C6-C12 aryl, 5-12-membered heteroaryl, 3-12-membered heterocyclic, C3-C10 cycloalkylC1-C4 alkyl, C6-C12 arylC1-C4 alkyl, 5-12-membered heteroarylC1-C4 alkyl, 3-12-membered heterocyclic C1-C4 alkyl, etc., more preferably selected from C1-C 8-alkyl, C3-C8 cycloalkyl, C6-C10 aryl, 5-10 heteroaryl, 3-10 heterocyclic, C3-C8 cycloalkylC1-C2 alkyl, C6-C10 arylC1-C2 alkyl, 5-10 heteroarylC1-C2 alkyl, 3-10 heterocyclicC1-C2 alkyl, etc., especially selected from methyl, ethyl, propyl, butyl, pentyl, hexyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, phenyl, tolyl, xylyl, benzyl, etc.; and even more particularly methyl and ethyl;

[0014] R1 and R2 are each independently selected from alkyl groups, preferably from C1-C10 alkyl groups, more preferably from C1-C8 alkyl groups, and particularly from methyl, ethyl, propyl, butyl, and even more particularly methyl or ethyl.

[0015] The above steps are described in detail below.

[0016] Step S1

[0017] In step S1, compound I and compound II undergo a substitution reaction to obtain compound III.

[0018] Compound I is a succinate diester. The succinate diester can be derived from succinate esterification or purified from nylon esters. Preferably, for cost reasons, a succinate diester isolated from nylon esters is used. In some specific embodiments, for product availability and cost reasons, the succinate diester is preferably selected from dimethyl succinate and diethyl succinate.

[0019] Compound II is a nitro compound. There are no particular limitations on the nitro compound; it may be a commercially available product or a product synthesized by any suitable method.

[0020] In some embodiments, compound II is prepared as shown in the reaction formula below:

[0021]

[0022] S0, aldehyde compound II-1 undergoes a nitration reaction with NH3 and H2O2 to transform into nitro compound II.

[0023] The definition of R is the same as described above.

[0024] Step S0 can be carried out in the presence of any suitable catalyst; therefore, there are no particular limitations on the catalyst, as long as the reaction can proceed. Suitable catalysts can be found, for example, in descriptions of the reaction in the prior art. In some embodiments, the catalyst may be the modified titanium-silicon catalyst described in CN115845915A, but the invention is not limited thereto.

[0025] In some embodiments, step S1 is carried out in the presence of a base. The base can be an inorganic or organic base, such as sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, potassium tert-butoxide, calcium carbonate, calcium hydroxide, DBU, etc., preferably sodium hydroxide or potassium hydroxide. The amount of base added is 0.1% to 10% of the mass of compound II, preferably 0.5% to 1.0%, for example 0.6%, 0.7%, 0.8%, 0.9%, etc., but not limited thereto.

[0026] In some embodiments, in step S1, the molar ratio of compound II to compound I can be 1:0.5 to 2, preferably 1:0.8 to 1.5, such as 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, etc., but is not limited thereto.

[0027] In some embodiments, the reaction temperature of step S1 can be 20-90°C, preferably 30-80°C, more preferably 40-70°C, for example, 45-65°C, 50-60°C, 50-55°C, but is not limited thereto.

[0028] In some embodiments, the reaction time of step S1 can be 1 to 24 hours, preferably 1 to 12 hours, such as 2 to 10 hours, 3 to 8 hours, 4 to 7 hours, 5 to 6 hours, etc., but is not limited thereto.

[0029] In some embodiments, step S1 is carried out in a solvent selected from methanol, ethanol, isopropanol, glycerol, diethyl ether, methyl tert-butyl ether, tetrahydrofuran, methyltetrahydrofuran, etc., preferably methanol. The amount of solvent added is 0.5 to 5 times the mass of compound II, preferably 1 to 3 times, 1 to 2 times, or 1.1 to 1.5 times, for example 1.2, 1.3, or 1.4 times, but not limited thereto.

[0030] Step S2

[0031] In step S2, compound III is hydrogenated and cyclized to form compound IV.

[0032] In some embodiments, step S2 is carried out in the presence of a hydrogenation catalyst, hydrogen, and a base.

[0033] The hydrogenation catalyst can be a common solid hydrogenation catalyst, such as Raney-Ni, Rh / C, Rh / Al, Pd / C, etc., but is not limited thereto. Preferably, the hydrogenation catalyst is a Pd / C with a Pd loading ratio of 5-10%, and the amount added is 0.1-10% of the mass of compound III, preferably 0.2-3.0%, 0.3-2.0%, 0.4-1.5% or 0.5-1.0%, for example 0.6%, 0.7%, 0.8%, 0.9%, etc., but is not limited thereto.

[0034] The hydrogen pressure is 0.1–10 MPa, preferably 0.5–5 MPa, 0.6–4 MPa, 0.7–3 MPa, 0.8–2.5 MPa or 1–2 MPa, such as 1.2 MPa, 1.4 MPa, 1.5 MPa, 1.6 MPa, 1.8 MPa, etc., but is not limited thereto.

[0035] The alkali can be an inorganic or organic alkali, such as sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, potassium tert-butoxide, calcium carbonate, calcium hydroxide, triethylamine, ammonia, diethylisopropylamine, DBU, etc., preferably ammonia or triethylamine. The amount of alkali added is 0.5-5% of the mass of compound III, preferably 0.8-3% or 1.0-2.0%, for example 1.2%, 1.4%, 1.5%, 1.6%, 1.8%, etc., but not limited thereto.

[0036] In some embodiments, step S2 is carried out in a solvent selected from methanol, ethanol, isopropanol, glycerol, diethyl ether, methyl tert-butyl ether, tetrahydrofuran, methyltetrahydrofuran, etc., preferably methanol. The amount of solvent added is 0.5 to 5 times the mass of compound III, preferably 1 to 3 times, 1 to 2 times, or 1 to 1.5 times, for example 1.2, 1.3, or 1.4 times, but not limited thereto.

[0037] In some embodiments, the reaction temperature of step S2 can be 20-100°C, preferably 30-90°C, more preferably 40-80°C, for example, 50-70°C, 55-65°C, 60-65°C, etc., but is not limited thereto.

[0038] In some embodiments, the reaction time of step S2 can be 1 to 24 hours, preferably 1 to 12 hours, such as 2 to 11 hours, 3 to 10 hours, 4 to 9 hours, 5 to 8 hours, 6 to 8 hours, etc., but is not limited thereto.

[0039] After the reaction is complete, the product is filtered and desolventized. It can be used directly in the next step without further purification, or it can be purified before use in the next step.

[0040] Step S3

[0041] In step S3, compound IV is dehydrogenated and dehydroxylated to obtain compound V.

[0042] In some embodiments, step S3 is performed in the presence of a catalyst.

[0043] The catalyst is a noble metal catalyst, preferably a supported noble metal catalyst. The noble metal can be selected from gold, platinum, palladium, rhodium, ruthenium, etc., with platinum being preferred. The support is selected from silica gel, alumina, etc., with alumina being preferred. The loading amount of the noble metal on the support can be 0.1–5 wt%, preferably 0.1–3 wt%, 0.2–2 wt%, or 0.3–1 wt%, for example, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, etc.

[0044] In some embodiments, step S3 is carried out in a fixed-bed reactor. There is no particular limitation on the sample flow rate, which can be determined according to the inner diameter of the fixed-bed reactor, for example, 10-300 mL / min, 20-250 mL / min, 30-200 mL / min, 40-150 mL / min, etc., such as 50, 60, 70, 80, 90, 100, 110, 120, 130, 140 mL / min, etc., but is not limited to these.

[0045] In some embodiments, the reaction temperature of step S3 can be 200–400°C, preferably 210–350°C, 220–300°C, or 230–280°C, especially 240–260°C.

[0046] In some embodiments, step S3 is carried out in a solvent selected from benzene, toluene, xylene, etc., preferably xylene.

[0047] The method according to the invention may further include: S4, a purification step to prepare the finished product 2-substituted pyridine, i.e., compound V. The purification method is not particularly limited, as long as it yields compound V with higher purity. In some embodiments, the purification step is carried out by distillation.

[0048] Another aspect of the present invention provides a method for preparing 2-substituted pyridine from nylon diester, comprising the following steps:

[0049] S11, succinate diester is separated from nylon diester;

[0050] S12, succinate diester is prepared into 2-substituted pyridine according to the method of the present invention.

[0051] The nylon acid diester can be commercially available or obtained by esterification of nylon, for example, it can be dimethyl nylonate, such as dimethyl nylonate produced by Shandong Dongming Xuyang Chemical Co., Ltd.

[0052] There are no particular limitations on the method for separating succinate diester from nylonic acid diester; any suitable method in the relevant art can be used. In some embodiments, succinate diester can be separated from nylonic acid diester by distillation.

[0053] Another aspect of the present invention provides a method for preparing 2-substituted pyridine from nylonic acid, comprising the following steps:

[0054] S21, nylon is esterified to obtain nylon diester;

[0055] S22, succinate diester was isolated from nylon diester;

[0056] S23, succinate diester is prepared into 2-substituted pyridine according to the method of the present invention.

[0057] The method for esterifying nylon can be any conventional method used in the art and is not particularly limited. The other steps are the same as described above.

[0058] The present invention has been described in detail above; however, the above embodiments are merely illustrative in nature and are not intended to limit the invention. Furthermore, this document is not limited to the foregoing prior art or the invention itself, or to any theory described in the following embodiments.

[0059] In this document, all features or conditions defined in the form of numerical ranges or percentage ranges are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible secondary ranges and individual values ​​within those ranges, particularly integer values. For example, a range description of "1 to 8" should be considered as specifically disclosing all secondary ranges such as 1 to 7, 2 to 8, 2 to 6, 3 to 6, 4 to 8, 3 to 8, etc., particularly secondary ranges defined by all integer values, and should be considered as specifically disclosing individual values ​​within those ranges such as 1, 2, 3, 4, 5, 6, 7, 8, etc. Unless otherwise specified, the foregoing interpretation applies to all content throughout this invention, regardless of its scope.

[0060] If a quantity or other numerical value or parameter is expressed as a range, preferred range, or a series of upper and lower limits, it should be understood that this document has specifically disclosed all ranges consisting of any upper or preferred value of that range and the lower or preferred value of that range, regardless of whether such ranges are disclosed separately. Furthermore, when a range of numerical values ​​is mentioned herein, unless otherwise stated, the range shall include its endpoints and all integers and fractions within the range.

[0061] In this document, numerical values ​​are to be understood as having a precision with significant digits, provided that the purpose of the invention can be achieved. For example, the number 40.0 should be understood to cover the range from 39.50 to 40.49.

[0062] Beneficial effects

[0063] This invention designs a novel method for the resource utilization of nylonic acid and is also beneficial to the preparation method of 2-substituted pyridine.

[0064] It has the following advantages:

[0065] 1. Solved the problem of value-added processing of nylon acid, a byproduct of adipic acid production, which had been a problem for adipic acid companies;

[0066] 2. Compared with existing esterification methods, this invention significantly increases the value of nylon esters. For example, the market price of nylon esters is 5,000-7,000 yuan / ton, while the market price of 2-methylpyridine is 27,000-30,000 yuan / ton, thus greatly increasing the value of the product.

[0067] 3. By adopting the solution of the present invention, in addition to obtaining 2-substituted pyridine, other diacids in nylon acid, such as glutaric acid and adipic acid, do not affect their downstream applications or yield, thus realizing the refined utilization of nylon acid.

[0068] The present invention has been described in detail above; however, the above embodiments are merely illustrative in nature and are not intended to limit the invention. Furthermore, this document is not limited to the foregoing prior art or the invention itself, or to any theory described in the following embodiments. Attached Figure Description

[0069] Figure 1 Chromatogram of 2-methylpyridine obtained by reaction according to Example 1 of the present invention. Detailed Implementation

[0070] The present invention will be further described below with reference to embodiments. It should be noted that the following embodiments are provided for illustrative purposes only and do not constitute a limitation on the scope of protection of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0071] Unless otherwise specified, the raw materials, reagents, and methods used in the examples are all conventional in the art and are commercially available unless otherwise specified.

[0072] The process is specifically described in the following embodiments:

[0073] Material:

[0074] Dimethyl nylonate is produced by Shandong Dongming Xuyang. Dimethyl succinate and dimethyl glutarate are separated from dimethyl nylonate through distillation. The remaining mixed acid dimethyl ester is sold as a solvent oil.

[0075] Methanol, ammonia, ammonia water, hydrogen, and 50 wt% hydrogen peroxide came from Hebei Xuyang and Cangzhou Xuyang Chemical Company.

[0076] Chloroplatinic acid was purchased from Aladdin Reagent Co., Ltd.

[0077] The 5% Pd / C and 10% Pd / C catalysts were sourced from Xi'an Kaili Catalyst Co., Ltd.

[0078] The active alumina supports for the noble metal catalysts were obtained from CNOOC Tianjin Chemical Research and Design Institute Co., Ltd., and were models TC-107 and TC-108. The main component of both was Al2O3, and the morphology was spherical with a diameter of Ф1.2~Ф3.5. The phase was γ, and the bulk density was (g / cm³). 3 The strength (N / P, N / cm) is 0.4-0.5 and 0.35-0.4 respectively; the strength (N / P, N / cm) is 50-80 and 30-50 respectively. Alternatively, products from other manufacturers with similar parameters can be selected.

[0079] Example 1: Process for preparing 2-methylpyridine using dimethyl nylonate

[0080] (1) Synthesis of methyl 4-hydroxy-5-nitrohexanoate

[0081]

[0082] At room temperature, 1000 g of nitrobenzene, 1947 g of dimethyl succinate, 1500 g of methanol, and 5 g of potassium hydroxide were added sequentially to a 10 L jacketed reactor. The mixture was reacted at 50–55 °C for 6 hours. After the reaction, the methanol was removed by concentration, and the potassium hydroxide was removed by filtration. The crude methyl 4-hydroxy-5-nitrohexanoate product obtained could be used directly for the next reaction without further purification. ESI-MS: 190.07 ([M+H) + ),212.11([M+Na] + )

[0083] (2) Synthesis of 6-methylpiperidine-2,5-dione

[0084]

[0085] In a 1000 mL high-pressure reactor, 200 g of crude methyl 4-hydroxy-5-nitrohexanoate obtained in step 1 was added, along with 300 g of methanol, 2 g of triethylamine, and 1 g of 5% Pd / C. The reactor was sealed, purged with nitrogen three times, and hydrogen was introduced to maintain the reaction pressure at 2.0 MPa. The temperature was raised to 60 °C, and the reaction was carried out for 6-8 hours. After the reaction was completed, nitrogen was purged, the pressure was released, and the reaction solution was cooled to room temperature. The catalyst was removed by filtration, and the reaction solution was concentrated. The crude 6-methylpiperidine-2,5-dione obtained was directly used for the next reaction step. 1 H-NMR (400MHz, CDCl3, 298K) δ (ppm): 6.80 (s, 1H), 4.32 (m, 1H), 2.40-2.70 (m, 4H), 1.25 (d, 3H).

[0086] (3) Synthesis of 2-methylpyridine

[0087]

[0088] A fixed-bed reactor was packed with a platinum-supported alumina catalyst (platinum loading 0.5% wt). A xylene solution (25% wt) of crude 6-methylpiperidine-2,5-dione was passed through the fixed bed at 240 °C. The fixed bed reactor tube had an inner diameter of 1 cm, a bed height of 10 cm, and a space velocity of 10 mL / min, yielding the dehydrogenation product 2-methylpyridine. The single-pass conversion and selectivity of 6-methylpiperidine-2,5-dione are shown in Table 1.

[0089] 2-Methylpyridine and xylene were separated sequentially by distillation, with 2-methylpyridine being the product and xylene being recycled. After purification, the 2-methylpyridine product was analyzed by LC and NMR.

[0090] 1 H-NMR (400MHz, CDCl3, 298K) δ (ppm): 8.60 (d, 1H), 7.55 (t, 1H), 7.17 (t, 1H), 7.02 (d, H), 2.45 (s, 3H).

[0091] Figure 1 The chromatogram of 2-methylpyridine obtained by the reaction according to Example 1 of the present invention is shown.

[0092] Examples 2-4

[0093] The operation method is the same as in Example 1, except that the loading of platinum metal in the dehydrogenation catalyst or the space velocity in the fixed bed is changed. Specific data are shown in Table 1 below.

[0094] Comparative Example 1

[0095] To verify that succinic acid in nylonic acid has the same effect as commercially available pure succinic acid, a comparative experiment was conducted. The procedure was the same as in Example 1. Analytical pure succinic acid was purchased from Aladdin Reagent Company. Specific data are shown in Table 1.

[0096] Table 1

[0097]

[0098] The above embodiments are merely exemplary embodiments of the present invention and are not intended to limit the present invention. The scope of protection of the present invention is defined by the claims. Those skilled in the art can make various modifications or equivalent substitutions to the present invention within its substance and scope of protection, and such modifications or equivalent substitutions should also be considered to fall within the scope of protection of the present invention.

Claims

1. A method for preparing 2-substituted pyridine from succinate diester, as shown in the following reaction formula, the method comprising the following steps: S1, Compound I and Compound II undergo a substitution reaction to give Compound III; S2, compound III is reduced and cyclized to compound IV; wherein step S2 is carried out in the presence of a hydrogenation catalyst, hydrogen and a base; S3, compound IV is dehydrogenated and deoxygenated to obtain compound V; wherein step S3 is carried out in the presence of a noble metal catalyst; in, R is selected from alkyl, cycloalkyl, aryl, heteroaryl, heterocyclic, cycloalkylalkyl, arylalkyl, heteroarylalkyl, heterocyclicalkyl, tolyl, and xylyl. R1 and R2 are each independently selected from alkyl groups.

2. The method of claim 1, wherein, R is selected from C1-C10 alkyl, C3-C10 cycloalkyl, C6-C12 aryl, 5-12 heteroaryl, 3-12 heterocyclic, C3-C10 cycloalkylC1-C4 alkyl, C6-C12 arylC1-C4 alkyl, 5-12 heteroarylC1-C4 alkyl, 3-12 heterocyclicC1-C4 alkyl, tolyl, and xylyl. R1 and R2 are each independently selected from C1-C10 alkyl groups.

3. The method of claim 1, wherein, R is selected from C1-C8 alkyl, C3-C8 cycloalkyl, C6-C10 aryl, 5-10 heteroaryl, 3-10 heterocyclic, C3-C8 cycloalkylC1-C2 alkyl, C6-C10 arylC1-C2 alkyl, 5-10 heteroarylC1-C2 alkyl, 3-10 heterocyclicC1-C2 alkyl, tolyl, and xylyl. R1 and R2 are each independently selected from C1-C8 alkyl groups.

4. The method of claim 1, wherein, R is selected from methyl, ethyl, propyl, butyl, pentyl, hexyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, phenyl, tolyl, xylyl, and benzyl. R1 and R2 are each independently selected from methyl, ethyl, propyl, and butyl.

5. The method of claim 1, wherein, R is methyl or ethyl; R1 and R2 are each independently either methyl or ethyl.

6. The method of claim 1, wherein, In step S1, The succinic acid diester is a succinic acid diester isolated from nylon ester; and / or Step S1 is carried out in the presence of an alkali, wherein the alkali is an inorganic or organic alkali; and / or The amount of alkali added is 0.1 to 10% of the mass of compound II; and / or The molar ratio of compound II to compound I is 1:0.5 ~ 2; and / or The reaction temperature in step S1 is 20 ~ 90℃; and / or The reaction time for step S1 is 1 to 24 hours; and / or Step S1 is carried out in a solvent selected from methanol, ethanol, isopropanol, glycerol, diethyl ether, methyl tert-butyl ether, tetrahydrofuran, and methyltetrahydrofuran. The amount of solvent added is 0.5 to 5 times the mass of compound II.

7. The method of claim 6, wherein, Disuccinate is selected from dimethyl succinate, diethyl succinate; and / or The alkali is sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, potassium tert-butoxide, calcium carbonate, calcium hydroxide, or DBU; and / or The amount of alkali added is 0.5 to 1.0% of the mass of compound II; and / or The molar ratio of compound II to compound I is 1:0.8 ~ 1.5; and / or The reaction temperature in step S1 is 30 ~ 80℃; and / or The reaction time for step S1 is 1 to 12 hours; and / or The solvent is methanol; and / or The amount of solvent added is 1 to 3 times the mass of compound II.

8. The method of claim 6 or 7, wherein, The alkali is sodium hydroxide or potassium hydroxide; and / or The reaction temperature in step S1 is 40 ~ 70℃.

9. The method of claim 1, wherein, In step S2, The hydrogenation catalyst is a Pd / C supported on Pd at a mass ratio of 5-10%, and is added at an amount of 0.1-10% of the mass of compound III; and / or Hydrogen pressure is 0.1 ~ 10 MPa; and / or The base is an inorganic base or an organic base; and / or The amount of alkali added is 0.5 to 5% of the mass of compound III; and / or Step S2 is carried out in a solvent selected from methanol, ethanol, isopropanol, glycerol, diethyl ether, methyl tert-butyl ether, tetrahydrofuran, and methyltetrahydrofuran, wherein the amount of solvent added is 0.5 to 5 times the mass of compound III; and / or The reaction temperature in step S2 is 20 ~ 100℃; and / or The reaction time for step S2 is 1 to 24 hours.

10. The method of claim 9, wherein, The amount of hydrogenation catalyst added is 0.2 to 3.0% of the mass of compound III; and / or Hydrogen pressure is 0.5~5 MPa; and / or The alkali is selected from sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, potassium tert-butoxide, calcium carbonate, calcium hydroxide, triethylamine, ammonia, diethylisopropylamine, DBU; and / or The amount of alkali added is 0.8 to 3% of the mass of compound III; and / or The solvent is methanol; and / or The amount of solvent added is 1 to 3 times the mass of compound III; and / or The reaction temperature in step S2 is 30 ~ 90℃; and / or The reaction time for step S2 is 1 to 12 hours.

11. The method of claim 9 or 10, wherein, The amount of hydrogenation catalyst added is 0.3 to 2.0% of the mass of compound III; and / or Hydrogen pressure is 0.6~4 MPa; and / or The alkali is ammonia or triethylamine; and / or The amount of alkali added is 1.0 to 2.0% of the mass of compound III; and / or The solvent is methanol, and the amount of solvent added is 1 to 2 times the mass of compound III; and / or The reaction temperature in step S2 is 40 ~ 80℃; and / or The reaction time for step S2 is 2 to 11 hours.

12. The method of claim 1, wherein, In step S3, The noble metal catalyst is a supported noble metal catalyst; and / or The precious metals are selected from gold, platinum, palladium, rhodium, and ruthenium.

13. The method of claim 12, wherein, The precious metal is platinum; and / or The carrier is selected from silica gel, alumina; and / or The loading of precious metals on the carrier is 0.1 ~ 5 wt%; and / or Step S3 is carried out in a fixed-bed reactor; and / or The reaction temperature in step S3 is 200 ~ 400℃; and / or Step S3 is carried out in a solvent, which is selected from benzene, toluene, and xylene.

14. The method of claim 13, wherein, The carrier is alumina; The loading of precious metals on the carrier is 0.1 ~ 3 wt%; The reaction temperature in step S3 is 210 ~ 350℃; The solvent is xylene.

15. The method of claim 13 or 14, wherein, The loading of precious metals on the carrier is 0.2 ~ 2 wt%; The reaction temperature in step S3 is 220 ~ 300℃.

16. The method of claim 1, further comprising: S4, purification step, to prepare the finished product 2-substituted pyridine.

17. The method of claim 16, wherein, The purification step is performed by distillation.

18. A method for preparing 2-substituted pyridine from nylon diester, comprising the following steps: S11, succinate diester is separated from nylon diester; S12, succinate diester is prepared into 2-substituted pyridine according to the method of any one of claims 1-17.

19. The method of claim 18, wherein, The nylon acid diester is obtained by esterification of nylon.

20. The method of claim 18 or 19, wherein, The nylon acid diester is dimethyl nylon acid.

21. The method of claim 18, wherein, Dibutyl succinate was separated from nylon ester by distillation.

22. A method for preparing 2-substituted pyridine from nylonic acid, comprising the following steps: S21, nylon is esterified to obtain nylon diester; S22, succinate diester was isolated from nylon diester; S23, succinate diester is prepared into 2-substituted pyridine according to the method of any one of claims 1-17.

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