CN114409570A - Preparation method of chlorinated L-carnitine nitrile - Google Patents
Preparation method of chlorinated L-carnitine nitrile Download PDFInfo
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Abstract
本发明提供了一种氯化左旋肉碱腈的制备方法。所述制备方法包括如下步骤：左旋环氧氯丙烷与三甲胺盐酸盐在含有缓冲剂的水中进行反应，生成季铵化物；其中，所述缓冲剂包括甲醇、乙醇和乙酸乙酯中的一种或多种；将所述季铵化物与氰化物反应，生成氯化左旋肉碱腈。本发明提供的方法具有反应条件温和，反应速度快，转化率高，产品收率高的优点。The invention provides a preparation method of chlorinated L-carnitine nitrile. The preparation method includes the following steps: reacting L-epichlorohydrin and trimethylamine hydrochloride in water containing a buffer to generate a quaternary ammonium compound; wherein the buffer comprises one of methanol, ethanol and ethyl acetate. one or more; reacting the quaternary ammonium compound with cyanide to generate chlorinated L-carnitine nitrile. The method provided by the invention has the advantages of mild reaction conditions, fast reaction speed, high conversion rate and high product yield.
Description
Technical Field
The invention belongs to the technical field of chemical synthesis, and particularly relates to a preparation method of chlorinated L-carnitine nitrile.
Background
L-carnitine, also known as L-carnitine, L-carnitine and vitamin BT, has the chemical name of (R) -beta-hydroxy-gamma-trimethylammonium butyrate and the molecular formula of C7H15NO3The product has molecular weight of about 161.20, is white crystalline lens or white transparent fine powder, has special fishy smell, and is easy to absorb moisture. At present, the L-carnitine is widely applied to infant food, weight-losing food, sportsman food and nutritional supplements for middle-aged and elderly people, and has huge market demand.
The synthesis method of L-carnitine comprises an extraction method, a chemical synthesis method, a biological fermentation method and the like. The extraction method is to directly extract the L-carnitine from the biological material, and the method has the advantages of complex operation and small yield and is only suitable for experimental research. The biological fermentation method adopts enzyme or microorganism to produce L-carnitine by fermentation, and has low cost and little environmental pollution, but is limited by process conditions and has small production scale. At present, chemical synthesis is adopted for large-scale industrial production of L-carnitine.
The chemical synthesis method has more process routes, and currently, the most widely applied method is to use epoxy chloropropane as an initial raw material, synthesize L-carnitine chloride nitrile through trimethylamine ring-opening amination and cyanide substitution, and obtain L-carnitine hydrochloride through hydrochloric acid hydrolysis. Chlorinated L-carnitine nitrile is an important intermediate in the L-carnitine synthesis process, but the existing production process has the defects of low reaction conversion rate, more raw material residues, difficult waste liquid recovery and treatment, low product yield and poor quality, and needs to be further improved.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a preparation method of chlorinated L-carnitine nitrile. The method has the advantages of mild reaction conditions, high reaction speed, high conversion rate and high product yield.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention provides a preparation method of chlorinated L-carnitine nitrile, which comprises the following steps:
(1) reacting levo-epichlorohydrin with trimethylamine hydrochloride in water containing a buffering agent to generate a quaternary ammonium compound;
wherein the buffer comprises one or more of methanol, ethanol, and ethyl acetate;
(2) reacting the quaternary ammonium compound with cyanide to generate the chlorinated L-carnitine nitrile.
In the invention, the buffer can be used as a micro-reaction phase of the L-epichlorohydrin and the trimethylamine hydrochloride, so that the L-epichlorohydrin and the trimethylamine hydrochloride can react more fully, the reaction efficiency is improved, and the yield of the chlorinated L-carnitine nitrile is improved.
In some embodiments of the invention, the molar ratio of trimethylamine hydrochloride to levo-epichlorohydrin is (1.01-1.03): 1.
In some embodiments of the invention, the mass ratio of the buffer to the levo-epichlorohydrin is (0.1-0.2): 1; for example, it may be 0.1:1, 0.12:1, 0.13:1, 0.15:1, 0.16:1, 0.18:1, or 0.2: 1.
In some embodiments of the present invention, in step (1), the l-epichlorohydrin is added dropwise to an aqueous solution containing trimethylamine hydrochloride and a buffer to perform a reaction.
In some embodiments of the invention, the aqueous solution comprising trimethylamine hydrochloride and a buffer has a pH of 9 to 9.5; for example, it may be 9, 9.1, 9.2, 9.3, 9.4, or 9.5, etc.
In the invention, if the pH of the reaction system in the step (1) is too low, the reaction conversion rate is easily reduced; if the pH value is too high, side reactions are easily caused to increase, and the yield and the purity of the chlorinated L-carnitine nitrile are influenced.
In some embodiments of the invention, the temperature of the reaction in step (1) is 30-35 ℃; for example, it may be 30 ℃, 31 ℃, 32 ℃, 33 ℃, 34 ℃ or 35 ℃.
In some embodiments of the invention, the reaction in step (1) is carried out for a time ranging from 1 to 3 hours; for example, it may be 1h, 1.2h, 1.5h, 1.8h, 2h, 2.2h, 2.5h, 2.8h, 3h, or the like.
In some embodiments of the invention, the mole ratio of cyanide to levo-epichlorohydrin is (1.01-1.03): 1.
In some embodiments of the invention, the cyanide is sodium cyanide.
In some embodiments of the present invention, in the step (2), the aqueous cyanide solution is added dropwise to the reaction solution obtained in the step (1) to perform a reaction.
In some embodiments of the invention, the aqueous cyanide solution has a pH of 7.2 to 7.5; for example, it may be 7.2, 7.3, 7.4, 7.5, etc.
In the present invention, if the pH of the aqueous cyanide solution is too low, the reaction conversion rate tends to decrease; if the pH value is too high, side reactions are easily caused to increase, and the yield and the purity of the chlorinated L-carnitine nitrile are influenced.
In some embodiments of the invention, the temperature of the reaction in step (2) is 35-40 ℃; for example, it may be 35 ℃, 36 ℃, 37 ℃, 38 ℃, 39 ℃ or 40 ℃.
In some embodiments of the invention, the reaction in step (2) is carried out for a time ranging from 1 to 3 hours; for example, it may be 1h, 1.2h, 1.5h, 1.8h, 2h, 2.2h, 2.5h, 2.8h, 3h, or the like.
In some embodiments of the invention, the preparation method further comprises the following steps:
and (3) concentrating the reaction solution obtained in the step (2), cooling and crystallizing to separate out salt, evaporating water to a liquid phase, re-dissolving solute components with methanol, adding activated carbon for decoloring, filtering, cooling and crystallizing, and drying to obtain the chlorinated L-carnitine nitrile.
Preferably, the concentration is to a water content of 35-45 wt%; for example, it may be 35 wt%, 36 wt%, 38 wt%, 40 wt%, 42 wt%, 43 wt%, or 45 wt%, etc.
Preferably, the temperature for reducing and crystallizing during salting-out is 1-5 ℃; for example, the temperature may be 1 ℃, 2 ℃, 3 ℃, 4 ℃ or 5 ℃.
Preferably, the temperature of the redissolution by the methanol is 60-65 ℃; for example, the temperature may be 60 ℃, 61 ℃, 62 ℃, 63 ℃, 64 ℃ or 65 ℃.
Preferably, the temperature of the cooling crystallization after adding activated carbon and filtering is 1-5 ℃; for example, the temperature may be 1 ℃, 2 ℃, 3 ℃, 4 ℃ or 5 ℃.
In some embodiments of the invention, the preparation method comprises the following steps:
(1) mixing trimethylamine hydrochloride, a buffering agent and water, adjusting the pH value to 9-9.5, dropwise adding levorotatory epoxy chloropropane at the temperature of 30-35 ℃, and preserving heat for reaction for 1-3 hours after dropwise adding is finished to generate a quaternary ammonium compound;
wherein the buffer is one or more of methanol, ethanol and ethyl acetate;
(2) dropwise adding sodium cyanide aqueous solution with the pH of 7.2-7.5 into the reaction solution obtained in the step (1), and after dropwise adding, carrying out heat preservation reaction at 35-40 ℃ for 1-3h to generate L-carnitine chloride nitrile;
(3) concentrating the reaction solution obtained in the step (2) until the water content is 35-45 wt%, cooling to 1-5 ℃ for crystallization to separate out sodium chloride, filtering, concentrating the filtrate in vacuum to remove dry water, re-dissolving solute components with methanol at 60-65 ℃, adding activated carbon for decolorization, filtering, cooling to 1-5 ℃ for crystallization, and drying to obtain the L-carnitine chloride.
Compared with the prior art, the invention has the following beneficial effects:
according to the method provided by the invention, the buffer is added to serve as a micro-reaction phase of the levorotatory epichlorohydrin and the trimethylamine hydrochloride, so that the levorotatory epichlorohydrin and the trimethylamine hydrochloride are reacted more fully, the reaction rate is increased, and the reaction conversion rate is increased. The purity of the L-carnitine chloride nitrile product obtained by the method reaches more than 98%, and the yield reaches more than 85%.
Detailed Description
The technical solution of the present invention is further explained by the following embodiments. It should be understood by those skilled in the art that the specific embodiments are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.
Example 1
The embodiment provides a preparation method of chlorinated L-carnitine nitrile, which comprises the following steps:
(1) adding 19.5g of trimethylamine hydrochloride, 2g of methanol and 30g of water into a 500mL four-mouth bottle, keeping the temperature of a water bath at 35 ℃, adjusting the pH to 9.2, dropwise adding 18.6g (the mass fraction is 99%) of levorotatory epoxy chloropropane, finishing the adding within 1 hour, and after the dropwise adding is finished, carrying out heat preservation reaction for 3 hours to generate a quaternary ammonium compound;
(2) adding 10.0g of sodium cyanide into 6g of water, uniformly stirring, dropwise adding hydrochloric acid to adjust the pH value to 7.3, dropwise adding the sodium cyanide aqueous solution into the reaction solution obtained in the step (1), finishing the addition within 1 hour, heating to 40 ℃ after the dropwise addition is finished, and carrying out heat preservation reaction for 2 hours to generate the chlorinated L-carnitine nitrile;
(3) concentrating the reaction solution obtained in the step (2) until the water content is 36 wt%, cooling to 3 ℃, stirring and crystallizing for 1h, filtering and recovering precipitated sodium chloride, vacuum concentrating the filtrate at 90 ℃ until no condensed water drips, adding 100g of methanol into solute components, heating to 65 ℃, stirring and dissolving, adding activated carbon for decolorization, filtering while hot, cooling the filtrate to 3 ℃, keeping the temperature, standing for 2h for crystallization, filtering to obtain a wet product of L-carnitine chloride, and vacuum drying at 60 ℃ to obtain 32g of L-carnitine chloride finished product.
Example 2
The embodiment provides a preparation method of chlorinated L-carnitine nitrile, which comprises the following steps:
(1) adding 19.3g of trimethylamine hydrochloride, 1.85g of ethanol and 30g of water into a 500mL four-mouth bottle, keeping the temperature of a water bath at 30 ℃, adjusting the pH to 9.0, dropwise adding 18.6g (the mass fraction is 99%) of levorotatory epoxy chloropropane within 1 hour, and keeping the temperature for reacting for 2 hours after the dropwise adding is finished to generate a quaternary ammonium compound;
(2) adding 9.85g of sodium cyanide into 6g of water, uniformly stirring, dropwise adding hydrochloric acid to adjust the pH value to 7.2, dropwise adding the sodium cyanide aqueous solution into the reaction solution obtained in the step (1), completing the addition within 1 hour, heating to 35 ℃ after the dropwise addition is completed, and carrying out heat preservation reaction for 3 hours to generate L-carnitine chloride nitrile;
(3) concentrating the reaction solution obtained in the step (2) until the water content is 38 wt%, cooling to 3 ℃, stirring for crystallization for 1h, filtering and recovering precipitated sodium chloride, vacuum concentrating the filtrate at 90 ℃ until no condensed water drips, adding 100g of methanol into solute components, stirring and dissolving at 65 ℃, adding activated carbon for decolorization, filtering while hot, cooling the filtrate to 3 ℃, preserving heat, standing for 2h for crystallization, filtering to obtain a wet L-carnitine chloride product, and vacuum drying at 60 ℃ to obtain 30.6g of L-carnitine chloride finished product.
Example 3
The embodiment provides a preparation method of chlorinated L-carnitine nitrile, which comprises the following steps:
(1) adding 19.4g of trimethylamine hydrochloride, 3.5g of ethyl acetate and 30g of water into a 500mL four-mouth bottle, keeping the temperature of a water bath at 33 ℃, adjusting the pH to 9.5, dropwise adding 18.6g (the mass fraction is 99%) of levorotatory epoxy chloropropane within 1 hour, and carrying out heat preservation reaction for 1 hour after the dropwise adding is finished to generate a quaternary ammonium compound;
(2) adding 9.9g of sodium cyanide into 6g of water, uniformly stirring, dropwise adding hydrochloric acid to adjust the pH value to 7.5, dropwise adding the sodium cyanide aqueous solution into the reaction solution obtained in the step (1), completing the addition within 1 hour, heating to 37 ℃ after the dropwise addition is completed, and carrying out heat preservation reaction for 1 hour to generate L-carnitine chloride nitrile;
(3) concentrating the reaction solution obtained in the step (2) until the water content is 39 wt%, cooling to 3 ℃, stirring and crystallizing for 1h, filtering and recovering precipitated sodium chloride, vacuum concentrating the filtrate at 90 ℃ until no condensed water drips off, adding 100g of methanol into solute components, stirring and dissolving at 65 ℃, adding activated carbon for decoloring, filtering while hot, cooling the filtrate to 3 ℃, keeping the temperature and standing for 2h for crystallization, filtering to obtain a wet L-carnitine chloride product, and vacuum drying at 60 ℃ to obtain 31.7g of L-carnitine chloride finished product.
Comparative example 1
There is provided a process for the preparation of chlorinated L-carnitine nitrile, which differs from example 1 only in that no methanol is added in step (1).
Comparative example 2
There is provided a process for the preparation of chlorinated L-carnitine nitrile, differing from example 1 only in that the pH is adjusted to 8.5 in step (1).
Comparative example 3
There is provided a process for the preparation of chlorinated L-carnitine nitrile, differing from example 1 only in that the pH is adjusted to 10.0 in step (1).
Comparative example 4
There is provided a process for the preparation of L-carnitine nitrile chloride, differing from example 1 only in that the pH of the aqueous sodium cyanide solution in step (2) is 6.7.
Comparative example 5
There is provided a process for the preparation of L-carnitine nitrile chloride, differing from example 1 only in that the pH of the aqueous sodium cyanide solution in step (2) is 8.0.
The purity of the final product, L-carnitine chloride, obtained in the above examples and comparative examples was checked by liquid chromatography and the yield was calculated, and the results are shown in Table 1 below:
TABLE 1
| Sample (I) | Purity (%) | Yield (%) |
| Example 1 | 98.6 | 89.2 |
| Example 2 | 98.3 | 85.1 |
| Example 3 | 98.9 | 88.7 |
| Comparative example 1 | 83.2 | 71.1 |
| Comparative example 2 | 71.3 | 58.2 |
| Comparative example 3 | 81.3 | 69.8 |
| Comparative example 4 | 63.1 | 50.2 |
| Comparative example 5 | 85.1 | 73.2 |
As can be seen from the experimental data in Table 1, the purity of the L-carnitine chloride prepared by the method provided by the invention reaches more than 98%, the yield reaches more than 85%, and the L-carnitine chloride has high purity and yield.
Compared with the example 1, the method has the advantages that the buffer methanol is not added in the comparative example 1, the reaction of the L-epichlorohydrin and the trimethylamine hydrochloride is insufficient, the conversion rate is low, and the purity and the yield of the obtained chlorinated L-carnitine nitrile are obviously reduced. Comparative example 2 the purity and yield of L-carnitine chloride nitrile were significantly reduced due to the low pH of the reaction system of step (1) and comparative example 4 due to the low pH of the aqueous sodium cyanide solution, resulting in insufficient reaction; comparative example 3 the purity and yield of L-carnitine chloride nitrile were also decreased due to the increase of side reactions caused by the higher pH of the reaction system of step (1) and comparative example 5 due to the higher pH of the aqueous solution of sodium cyanide.
Although the invention has been described in detail hereinabove by way of general description, specific embodiments and experiments, it will be apparent to those skilled in the art that many modifications and improvements can be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.
Claims (10)
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN115636771A (en) * | 2022-11-01 | 2023-01-24 | 宁夏坤正生物科技有限公司 | Optimized synthesis method for cyanidation reaction in L-carnitine production process |
| CN115650868A (en) * | 2022-10-20 | 2023-01-31 | 安徽泰格生物科技有限公司 | Preparation method of L-carnitine |
| CN115850113A (en) * | 2022-12-16 | 2023-03-28 | 山东阳谷华泰化工股份有限公司 | Synthetic method of L-Carlactonitrile |
| WO2024145205A1 (en) * | 2022-12-28 | 2024-07-04 | Carnitech Llc | An improved process for producing l-carnitine |
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115650868A (en) * | 2022-10-20 | 2023-01-31 | 安徽泰格生物科技有限公司 | Preparation method of L-carnitine |
| CN115650868B (en) * | 2022-10-20 | 2024-01-26 | 安徽泰格生物科技有限公司 | A kind of preparation method of L-carnitine |
| CN115636771A (en) * | 2022-11-01 | 2023-01-24 | 宁夏坤正生物科技有限公司 | Optimized synthesis method for cyanidation reaction in L-carnitine production process |
| CN115850113A (en) * | 2022-12-16 | 2023-03-28 | 山东阳谷华泰化工股份有限公司 | Synthetic method of L-Carlactonitrile |
| CN115850113B (en) * | 2022-12-16 | 2024-10-01 | 山东阳谷华泰化工股份有限公司 | Synthesis method of L-caprolaconitrile |
| WO2024145205A1 (en) * | 2022-12-28 | 2024-07-04 | Carnitech Llc | An improved process for producing l-carnitine |
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Application publication date: 20220429 Assignee: Anhui Yukang New Materials Co.,Ltd. Assignor: Anhui tiger Biotechnology Co.,Ltd. Contract record no.: X2025980044562 Denomination of invention: A method for preparing levocarnitine nitrile chloride Granted publication date: 20240426 License type: Common License Record date: 20251215 |