CN107011254B - Synthesis and purification method of 2-amino-4-methylpyridine - Google Patents
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- C07D213/02—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members
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Abstract
The invention relates to the field of chemical synthesis, in particular to a synthesis method and a purification method of 2-amino-4-methylpyridine, wherein 2- (4-methylfuran) ethyl formate is used as a raw material for synthesizing the 2-amino-4-methylpyridine, and a crude product of the 2-amino-4-methylpyridine is prepared through the steps of ring expansion, hydroxyl chlorination, dechlorination and the like, and a post-treatment method of each step of reaction is easy for industrial operation, and a 2, 6-diamino-4-methylpyridine byproduct which is difficult to separate is not generated; the 2-amino-4-methylpyridine crude product and acid are salified and dissolved in water, an organic reagent is used for extraction, the pH value is adjusted until the solution is alkaline, the purity of the finally obtained product reaches more than 98%, the purification method is simple and easy to operate, the used organic reagent has low irritation, and the method is suitable for industrial production.
Description
Technical Field
The invention relates to the field of chemical synthesis, in particular to a synthesis method and a purification method of 2-amino-4-methylpyridine.
Background
In the culture process of producing lycopene by utilizing Blakeslea trispora fermentation, an aminomethyl pyridine compound is added to inhibit the activity of lycopene cyclase, block or weaken metabolic flow flowing to β -carotene, continuously stimulate de novo synthesis of dehydrogenase in lycopene biosynthesis, stimulate formation of lycopene and achieve the aim of accumulating lycopene.
The raw materials for synthesizing the aminomethyl pyridine compounds on the market are expensive, and some of the aminomethyl pyridine compounds even use expensive catalysts, so that the synthesis cost is increased; in the reaction, nitric acid is usually used as a reaction reagent to introduce nitro on a pyridine ring, and then the nitro is reduced into amino, so that a dibit substituted nitro byproduct is easily obtained, a target product and the byproduct are difficult to separate while the yield is influenced, the purity of the product is reduced, and a purified product is obtained by column chromatography purification and reduced pressure concentration.
The furoate compounds are a kind of perfume with special fragrance, and are naturally present in plants such as peanut, cocoa, coffee and the like. China is a large country for producing furfural, and in the deep processing of furfural, furoate ester compounds are a class of main products.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a synthesis method and a purification method of 2-amino-4-methylpyridine, wherein a furoate compound 2- (4-methylfuran) ethyl formate is used as a raw material, a dibit substituted amino byproduct cannot be generated in the reaction, and a simple and easy-to-operate method is adopted to purify a final product and improve the product purity.
In order to achieve the purpose, the invention is realized by the following technical scheme:
the synthesis of 2-amino-4-methylpyridine comprises the following steps:
(1) dissolving ethyl 2- (4-methylfuran) formate in Dimethylformamide (DMF), adding a water removing agent and formamide, introducing ammonia gas, carrying out reflux reaction for 24 hours, adding dilute hydrochloric acid to adjust the pH to 2, extracting with ethyl acetate to leave a water phase, adding a sodium hydroxide solution to the water phase to adjust the pH to be neutral, extracting with diethyl ether to leave an organic phase, concentrating and drying to obtain 2-amino-3-hydroxy-4-methylpyridine;
(2) adding 2-amino-3-hydroxy-4-methylpyridine, phosphorus trichloride and an acid-binding agent into dichloroethane, carrying out reflux reaction for 6 hours, adding a concentrated mixture into ice water, adding a decolorizing agent, adjusting the pH value of the filtered solution to be neutral, extracting an organic phase by using ethyl acetate, concentrating and drying to obtain 2-amino-3-chloro-4-methylpyridine;
(3) mixing 2-amino-3-chloro-4-methylpyridine and benzoic acid (BzOH), adding copper powder, reacting for 1h at 150 ℃, adding the reaction solution into water, adding a decolorizing agent, adjusting the pH value of the filtered solution to 9, filtering, and drying the filter cake to obtain a crude product of 2-amino-4-methylpyridine.
Further, the water removal agent is selected from ammonium chloride or sodium sulfate.
Further, the acid scavenger is Dimethylformamide (DMF).
Further, the decolorant is selected from activated carbon, diatomite or acid clay.
A purification method of 2-amino-4-methylpyridine comprises the steps of dissolving a crude product of 2-amino-4-methylpyridine in a dilute acid solution until the crude product is completely dissolved to obtain a salt solution, adding an organic solvent into the salt solution to extract a residual water phase, slowly adding an alkaline solution into the water phase until the pH value is 8-9, completely separating out solids, filtering, washing a filter cake with distilled water, and drying in vacuum to obtain the 2-amino-4-methylpyridine.
Further, the dilute acid solution is selected from one of dilute hydrochloric acid, dilute acetic acid and dilute sulfuric acid, and is preferably dilute hydrochloric acid.
Further, the pH value of the dilute acid solution is 2-3.
Further, the organic reagent is selected from one of ethyl acetate, dichloromethane and diethyl ether, and ethyl acetate is preferred.
Further, the alkaline solution is selected from one of sodium hydroxide solution, sodium carbonate solution, sodium bicarbonate solution, ammonia water and triethylamine, and is preferably sodium bicarbonate solution.
Due to the adoption of the technical scheme, the invention has the following advantages:
the invention provides a novel high-purity new way for industrially producing 2-amino-4-methylpyridine. The method comprises the steps of taking furoate ester compound ethyl 2- (4-methylfuran) formate as a raw material, carrying out ring expansion, hydroxychlorination, dechlorination and the like to obtain the 2-amino-4-methylpyridine, wherein the reaction does not generate the 2, 6-diamino-4-methylpyridine which is difficult to separate, the conversion rate of the reaction is improved, and a water removal agent is added to remove water generated in the ring expansion reaction in time and improve the reaction speed.
In the purification method, amino of 2-amino-4-methylpyridine reacts with dilute acid solution to generate salt and the salt is dissolved in water, organic solvent extracts organic impurities insoluble in water, 2-amino-4-methylpyridine is dissociated and separated out through alkaline solution, and by-products are continuously left in the water phase by controlling the pH value.
Drawings
FIG. 1 is a schematic diagram of the reaction scheme of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1:
the synthesis of 2-amino-4-methylpyridine comprises the following steps:
(1) dissolving 1.54g (0.01mol) of ethyl 2- (4-methylfuran) formate in 15ml of dimethylformamide, adding 0.80g (0.015mol) of ammonium chloride and 0.45g (0.01mol) of formamide, introducing ammonia gas, carrying out reflux reaction for 24 hours, adding dilute hydrochloric acid to adjust the pH value to 2, extracting the remaining aqueous phase by ethyl acetate, adding a sodium hydroxide solution to the aqueous phase to adjust the pH value to be neutral, extracting the remaining organic phase by diethyl ether, concentrating and drying to obtain 0.89g of 2-amino-3-hydroxy-4-methylpyridine, wherein the yield is 71.8%;
(2) adding 0.89g (0.0072mol) of 2-amino-3-hydroxy-4-methylpyridine, 1.92g (0.014mol) of phosphorus trichloride and 0.73g (0.01mol) of dimethylformamide into 12ml of dichloroethane, carrying out reflux reaction for 6h, adding the concentrated mixture into ice water, adding a decolorizing agent, adjusting the pH of the filtered solution to be neutral, extracting with ethyl acetate to leave an organic phase, concentrating and drying to obtain 0.96g of 2-amino-3-chloro-4-methylpyridine, wherein the yield is 93.9%;
(3) mixing 0.96g (0.0067mol) of 2-amino-3-chloro-4-methylpyridine and 1.83g (0.015mol) of benzoic acid, adding copper powder, reacting at 150 ℃ for 1h, adding a decolorizing agent into the reaction solution, adjusting the pH value of the filtered solution to 9, filtering, and drying a filter cake to obtain 0.65g of a yellow solid crude product of 2-amino-4-methylpyridine, wherein the yield is 89.3%.
Dissolving 0.65g of crude 2-amino-4-methylpyridine in a dilute hydrochloric acid solution until the crude product is completely dissolved to obtain a salt solution, adding ethyl acetate into the salt solution to extract a residual water phase, slowly adding a sodium bicarbonate solution into the water phase until the pH value is 9, completely separating out the solid, filtering, washing a filter cake with distilled water, and drying in vacuum to obtain 0.53g of light yellow solid 2-amino-4-methylpyridine, wherein the yield is 81.5 percent and the purity is 99.2 percent; m.p.95-96 deg.c;1H NMR(300MHz，CDCl3)δ：8.07(d，1H，J＝5.7Hz)；6.38(d，1H，J＝2.3Hz)；6.34(dd，1H，J＝5.7Hz，2.3Hz)；3.46(s，2H)；2.39(s，3H)；ESI-MS m/z(％)：109.1([M+1]+)
example 2:
the synthesis of 2-amino-4-methylpyridine comprises the following steps:
(1) dissolving 1.54g (0.01mol) of ethyl 2- (4-methylfuran) formate in 15ml of dimethylformamide, adding 1.07g (0.02mol) of ammonium chloride and 0.68g (0.015mol) of formamide, introducing ammonia gas, carrying out reflux reaction for 24 hours, adding dilute hydrochloric acid to adjust the pH value to 2, extracting ethyl acetate to leave a water phase, adding a sodium hydroxide solution to the water phase to adjust the pH value to be neutral, extracting diethyl ether to leave an organic phase, concentrating and drying to obtain 0.90g of 2-amino-3-hydroxy-4-methylpyridine, wherein the yield is 72.6%;
(2) adding 0.90g (0.0073mol) of 2-amino-3-hydroxy-4-methylpyridine, 1.92g (0.014mol) of phosphorus trichloride and 0.73g (0.01mol) of dimethylformamide into 12ml of dichloroethane, carrying out reflux reaction for 6h, adding the concentrated mixture into ice water, adding a decolorizing agent, adjusting the pH of the filtered solution to be neutral, extracting with ethyl acetate to leave an organic phase, concentrating and drying to obtain 0.95g of 2-amino-3-chloro-4-methylpyridine, wherein the yield is 91.9%;
(3) mixing 0.95g (0.0067mol) of 2-amino-3-chloro-4-methylpyridine and 1.83g (0.015mol) of benzoic acid, adding copper powder, reacting at 150 ℃ for 1h, adding a decolorizing agent into the reaction solution, adjusting the pH value of the filtered solution to 9, filtering, and drying a filter cake to obtain 0.65g of a yellow solid crude product of 2-amino-4-methylpyridine, wherein the yield is 90.3%.
Dissolving 0.65g of crude 2-amino-4-methylpyridine in a dilute hydrochloric acid solution until the crude product is completely dissolved to obtain a salt solution, adding ethyl acetate into the salt solution to extract a residual water phase, slowly adding a sodium hydroxide solution into the water phase until the pH value is 8, completely separating out the solid, filtering, washing a filter cake with distilled water, and drying in vacuum to obtain 0.52g of light yellow solid 2-amino-4-methylpyridine, wherein the yield is 80.0 percent and the purity is 99.4 percent; m.p.95-96 deg.c;1H NMR(300MHz，CDCl3)δ：8.07(d，1H，J＝5.7Hz)；6.38(d，1H，J＝2.3Hz)；6.34(dd，1H，J＝5.7Hz，2.3Hz)；3.46(s，2H)；2.39(s，3H)；ESI-MS m/z(％)：109.1([M+1]+)
example 3:
the synthesis of 2-amino-4-methylpyridine comprises the following steps:
(1) dissolving 3.08g (0.02mol) of ethyl 2- (4-methylfuran) formate in 25ml of dimethylformamide, adding 1.60g (0.03mol) of ammonium chloride and 0.90g (0.02mol) of formamide, introducing ammonia gas, carrying out reflux reaction for 24 hours, adding dilute hydrochloric acid to adjust the pH value to 2, extracting the remaining aqueous phase by ethyl acetate, adding a sodium hydroxide solution to the aqueous phase to adjust the pH value to be neutral, extracting the remaining organic phase by diethyl ether, concentrating and drying to obtain 1.81g of 2-amino-3-hydroxy-4-methylpyridine, wherein the yield is 73.0%;
(2) adding 1.81g (0.0146mol) of 2-amino-3-hydroxy-4-methylpyridine, 4.10g (0.03mol) of phosphorus trichloride and 0.15g (0.02mol) of dimethylformamide into 20ml of dichloroethane, carrying out reflux reaction for 6h, adding the concentrated mixture into ice water, adding a decolorizing agent, adjusting the pH of the filtered solution to be neutral, extracting the residual organic phase by ethyl acetate, concentrating and drying to obtain 2.00g of 2-amino-3-chloro-4-methylpyridine, wherein the yield is 96.2%;
(3) mixing 2.00g (0.014mol) of 2-amino-3-chloro-4-methylpyridine with 3.06g (0.03mol) of benzoic acid, adding copper powder, reacting at 150 ℃ for 1h, adding a decolorizing agent into the reaction solution, adjusting the pH value of the filtered solution to 9, filtering, and drying a filter cake to obtain 1.38g of a yellow solid crude product of 2-amino-4-methylpyridine, wherein the yield is 91.0%.
Dissolving 1.38g of crude 2-amino-4-methylpyridine in a dilute hydrochloric acid solution until the crude product is completely dissolved to obtain a salt solution, adding ethyl acetate into the salt solution to extract a residual water phase, slowly adding a sodium carbonate solution into the water phase until the pH value is 9, completely separating out the solid, filtering, washing a filter cake with distilled water, and drying in vacuum to obtain 1.13g of light yellow solid 2-amino-4-methylpyridine, wherein the yield is 81.9 percent and the purity is 99.2 percent; m.p.95-96 deg.c;1H NMR(300MHz，CDCl3)δ：8.07(d，1H，J＝5.7Hz)；6.38(d，1H，J＝2.3Hz)；6.34(dd，1H，J＝5.7Hz，2.3Hz)；3.46(s，2H)；2.39(s，3H)；ESI-MS m/z(％)：109.2([M+1]+)
example 4:
the synthesis of 2-amino-4-methylpyridine comprises the following steps:
(1) dissolving 15.40g (0.1mol) of ethyl 2- (4-methylfuran) formate in 100ml of dimethylformamide, adding 8.03g (0.15mol) of ammonium chloride and 4.50g (0.1mol) of formamide, introducing ammonia gas, carrying out reflux reaction for 24 hours, adding dilute hydrochloric acid to adjust the pH value to 2, extracting the remaining aqueous phase by ethyl acetate, adding a sodium hydroxide solution to the aqueous phase to adjust the pH value to be neutral, extracting the remaining organic phase by diethyl ether, concentrating and drying to obtain 9.20g of 2-amino-3-hydroxy-4-methylpyridine, wherein the yield is 74.2%;
(2) adding 9.20g (0.074mol) of 2-amino-3-hydroxy-4-methylpyridine, 19.20g (0.14mol) of phosphorus trichloride and 7.33g (0.1mol) of dimethylformamide into 100ml of dichloroethane, carrying out reflux reaction for 6h, adding a concentrated mixture into ice water, adding a decolorizing agent, adjusting the pH of the filtered solution to be neutral, extracting the remaining organic phase by ethyl acetate, concentrating and drying to obtain 9.92g of 2-amino-3-chloro-4-methylpyridine, wherein the yield is 93.8%;
(3) mixing 9.92g (0.07mol) of 2-amino-3-chloro-4-methylpyridine with 18.30g (0.15mol) of benzoic acid, adding copper powder, reacting at 150 ℃ for 1h, adding a decolorizing agent into water, adjusting the pH value of the filtered solution to 9, filtering, and drying a filter cake to obtain 6.86g of a yellow solid crude 2-amino-4-methylpyridine product with the yield of 91.2%.
Dissolving 6.86g of crude 2-amino-4-methylpyridine in a dilute hydrochloric acid solution until the crude product is completely dissolved to obtain a salt solution, adding ethyl acetate into the salt solution to extract a residual water phase, slowly adding a sodium bicarbonate solution into the water phase until the pH value is 9, completely separating out the solid, filtering, washing a filter cake with distilled water, and drying in vacuum to obtain 5.98g of light yellow solid 2-amino-4-methylpyridine with the yield of 87.2% and the purity of 98.9%; m.p.95-96 deg.c;1H NMR(300MHz，CDCl3)δ：8.07(d，1H，J＝5.7Hz)；6.38(d，1H，J＝2.3Hz)；6.34(dd，1H，J＝5.7Hz，2.3Hz)；3.46(s，2H)；2.39(s，3H)；ESI-MS m/z(％)：109.1([M+1]+)
the purity of the 2-amino-4-methylpyridine obtained by the purification method is over 98.5 percent.
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (8)
1. The synthesis of 2-amino-4-methylpyridine is characterized by comprising the following steps:
(1) dissolving ethyl 2- (4-methylfuran) formate in dimethylformamide, adding a water removing agent and formamide, introducing ammonia gas, performing reflux reaction for 24 hours, adding dilute hydrochloric acid to adjust the pH to 2, extracting with ethyl acetate to leave a water phase, adding a sodium hydroxide solution to the water phase to adjust the pH to be neutral, extracting with diethyl ether to leave an organic phase, concentrating and drying to obtain 2-amino-3-hydroxy-4-methylpyridine;
(2) adding 2-amino-3-hydroxy-4-methylpyridine, phosphorus trichloride and an acid-binding agent into dichloroethane, carrying out reflux reaction for 6 hours, adding a concentrated mixture into ice water, adding a decolorizing agent, adjusting the pH value of the filtered solution to be neutral, extracting an organic phase by using ethyl acetate, concentrating and drying to obtain 2-amino-3-chloro-4-methylpyridine;
(3) mixing 2-amino-3-chloro-4-methylpyridine and benzoic acid, adding copper powder, reacting for 1h at 150 ℃, adding the reaction solution into water, adding a decolorizing agent, adjusting the pH value of the filtered solution to 9, filtering, and drying a filter cake to obtain a crude product of 2-amino-4-methylpyridine;
the purification method comprises the steps of dissolving the 2-amino-4-methylpyridine crude product in a dilute acid solution until the crude product is completely dissolved to obtain a salt solution, adding an organic solvent into the salt solution to extract a residual water phase, slowly adding an alkaline solution into the water phase until the pH value is 8-9, completely separating out solids, filtering, washing a filter cake with distilled water, and drying in vacuum to obtain the 2-amino-4-methylpyridine.
2. The synthesis of 2-amino-4-methylpyridine according to claim 1, wherein the water scavenger is selected from ammonium chloride or sodium sulfate.
3. The synthesis of 2-amino-4-methylpyridine according to claim 1, wherein the acid scavenger is dimethylformamide.
4. The synthesis of 2-amino-4-methylpyridine according to claim 1, wherein the decolorizing agent is selected from activated carbon, diatomaceous earth or acid clay.
5. The synthesis of 2-amino-4-methylpyridine according to claim 1, wherein the dilute acid solution in the purification process is selected from one of dilute hydrochloric acid, dilute acetic acid and dilute sulfuric acid.
6. The synthesis of 2-amino-4-methylpyridine according to claim 1, wherein the pH of the dilute acid solution in the purification process is 2-3.
7. The synthesis of 2-amino-4-methylpyridine according to claim 1, wherein the organic solvent is selected from one of ethyl acetate, dichloromethane and diethyl ether.
8. The synthesis of 2-amino-4-methylpyridine according to claim 1, wherein the basic solution in the purification process is selected from one of sodium hydroxide solution, sodium carbonate solution, sodium bicarbonate solution, ammonia water and triethylamine.
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