N-methyl-N-(trimethylsilyl) acetamide and preparation method thereof

Abstract

The invention discloses N-methyl-N-(trimethylsilyl) acetamide and a preparation method thereof.The preparation method comprises the steps that S100, raw materials including N-methyl acetamide and trimethylchlorosilane are adopted to react under a triethylamine system, and a first material is obtained; and S200, sequentially carrying out filter pressing, concentration and rectification on the first material to obtain the N-methyl-N-(trimethylsilyl) acetamide. The N-methyl-N-(trimethylsilyl) acetamide is prepared from the raw materials which are low in cost, safe and reliable through reaction under the conditions of normal pressure and low temperature, and the N-methyl-N-(trimethylsilyl) acetamide preparation method which is safe, environmentally friendly, low in cost, simple in process and suitable for industrial production is provided.

Description

Technical Field

[0001] The invention relates to the field of chemical materials, and in particular to the preparation of N-methyl-N-(trimethylsilyl)acetamide. Background Art

[0002] N-Methyl-N-(trimethylsilyl)acetamide is a compound with important uses in organic synthesis. N-Methyl-N-(trimethylsilyl)acetamide is mainly used as a protecting agent and silanizing agent to introduce trimethylsilyl groups into organic molecules, thereby protecting certain functional groups from the influence of other reagents. It can also be used as a trimethylsilylating agent for polar compounds to improve the detection sensitivity and selectivity of analytes in the derivatization process of gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS).

[0003] In the prior art, there are two ways to synthesize N-methyl-N-(trimethylsilyl)acetamide: TR Bailey et al. disclosed in Science of Synthesis (2005), 21, 811-31 that N-methylacetamide can be silylated with trimethylchlorosilane, triethylamine is used as a nitrogen-containing organic base in anhydrous benzene, and the reaction is carried out at a temperature of 0°C to 5°C to obtain the product N-methyl-N-(trimethylsilyl)acetamide; another method for synthesizing N-methyl-N-(trimethylsilyl)acetamide is to directly heat N-methylacetamide and N-trimethylsilyl imidazole to boiling at 13 mbar for reaction, the reaction temperature of the method is between 120°C and 170°C, and the reaction product is removed by continuous distillation within 8 hours. The synthesized crude product needs to be further purified by rectification to finally obtain the product N-methyl-N-(trimethylsilyl)acetamide.

[0004] The above prior art has the disadvantages that, if benzene is used as a solvent, its toxicity is high, which will endanger the health of production personnel and is not conducive to the environment. If N-trimethylsilyl imidazole is used, it is expensive. In production, it is necessary to recover the imidazole in the reaction process and then convert the imidazole into N-trimethylsilyl imidazole with the help of hexamethyldisilazane. Therefore, the method has high production cost, complex process and long reaction time. In addition, in industrial production, it is also very difficult to use such a low pressure to carry out the reaction.

[0005] In summary, how to provide a method for preparing N-methyl-N-(trimethylsilyl)acetamide that is safe, environmentally friendly, low-cost, simple in process, and suitable for industrial production is a technical problem that needs to be solved by those skilled in the art. Summary of the invention

[0006] The purpose of the present application is to provide N-methyl-N-(trimethylsilyl)acetamide and a preparation method thereof, which can solve the technical problems in the prior art that the production process of N-methyl-N-(trimethylsilyl)acetamide is not safe and environmentally friendly, has high cost and complex process.

[0007] In order to solve the above technical problems, this application is implemented as follows:

[0008] The present application provides a method for preparing N-methyl-N-(trimethylsilyl)acetamide, the method comprising:

[0009] S100, using raw materials including N-methylacetamide and trimethylchlorosilane to react in a triethylamine system to obtain a first material;

[0010] S200, sequentially filter-filtering, concentrating and distilling the first material to obtain the N-methyl-N-(trimethylsilyl)acetamide.

[0011] In the above technical solution, S100 specifically includes:

[0012] S110, under an inert gas protective atmosphere, feeding the N-methylacetamide and the triethylamine into a reaction kettle, and heating them to a reaction temperature;

[0013] S120, controlling the reactor to maintain the reaction temperature, and dropwise adding trimethylsilyl chloride into the reactor;

[0014] S130, after the trimethylsilyl chloride is completely added, continue the heat-insulating reaction to obtain the first material.

[0015] In the above technical solution, in S110, for every 100L of the triethylamine added, 15kg to 20kg of the N-methylacetamide is added accordingly, and 20kg to 30kg of the trimethylsilyl chloride is added dropwise accordingly.

[0016] In the above technical solution, in S110, for every 100L of the triethylamine added, 16kg to 16.5kg of the N-methylacetamide is added accordingly, and 24kg to 24.5kg of the trimethylsilyl chloride is added dropwise accordingly.

[0017] In the above technical solution, in S110, the reaction temperature is 30°C to 38°C.

[0018] In the above technical solution, in S120, the trimethylchlorosilane is controlled to be added dropwise within 4 hours.

[0019] In the above technical solution, in S130, the time for continuing the heat preservation reaction is 1 hour.

[0020] In the above technical solution, S200 specifically includes:

[0021] S210, under an inert gas protective atmosphere, pressing the first material into a filter press, after the filter cake is pressed dry, adding triethylamine to wash once, and continuing to press dry to obtain a filtrate;

[0022] S220, pumping the filtrate into a concentration kettle, removing the triethylamine under negative pressure, stopping concentration and recovering the triethylamine under target temperature conditions to obtain a concentrated material;

[0023] S230, transferring the concentrated material to a distillation tower for distillation to obtain the N-methyl-N-(trimethylsilyl)acetamide.

[0024] In the above technical solution, the target temperature condition is 60°C.

[0025] The present invention also provides N-methyl-N-(trimethylsilyl)acetamide, and the N-methyl-N-(trimethylsilyl)acetamide is obtained by the preparation method described in any of the above technical solutions.

[0026] Beneficial Effects

[0027] The present invention provides a method for preparing N-methyl-N-(trimethylsilyl)acetamide. The method first uses raw materials including N-methylacetamide and trimethylchlorosilane to react under a triethylamine system to obtain a first material; and then the first material is subjected to filter pressing, concentration and rectification in sequence to obtain the N-methyl-N-(trimethylsilyl)acetamide. In the above method, the hydrogen atom on the nitrogen atom of N-methylacetamide is replaced by the trimethylsilyl group in trimethylchlorosilane, thereby generating N-methyl-N-(trimethylsilyl)acetamide. The raw material triethylamine is used as both an acid binding agent and a solvent in the reaction. Triethylamine is a colorless oily liquid that is slightly soluble in water, but soluble in most organic solvents such as ethanol, ether, and acetone. This solubility enables triethylamine to be used as a solvent to dilute organic reactants and active substances, so that the reactants are fully mixed in the reaction, thereby improving the reaction efficiency and the quality of the polymer. In the reaction of the present invention, the generation of acidic substances will reduce the efficiency and quality of the reaction. Triethylamine, as a weak base, can be used as an acid binding agent to maintain the balance of the reaction, thereby improving the reaction quality. In addition, when triethylamine is used as a solvent, due to its relatively stable physical and chemical properties, it is easy to be recovered and processed by methods such as distillation. This helps to reduce production costs and reduce environmental pollution. In summary, the present invention adopts low-cost, safe and reliable raw materials, and reacts and prepares N-methyl-N-(trimethylsilyl) acetamide under normal pressure and relatively low temperature conditions, providing a kind of safe and environmentally friendly, low-cost, simple process, suitable for industrialized production of N-methyl-N-(trimethylsilyl) acetamide preparation method. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The process flow chart of the preparation method of N-methyl-N-(trimethylsilyl)acetamide according to the embodiment of the present invention is shown. DETAILED DESCRIPTION

[0029] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the following is a detailed description of the specific embodiments of the present invention.

[0030] Unless otherwise specified, the reagents and raw materials used in the present invention can be purchased through commercial channels. The experimental methods in the following examples without specifying specific conditions are selected according to conventional methods and conditions, or according to the product specifications.

[0031] The present invention provides a method for preparing N-methyl-N-(trimethylsilyl)acetamide, the preparation method comprising:

[0032] S100, using raw materials including N-methylacetamide and trimethylchlorosilane to react in a triethylamine system to obtain a first material;

[0033] S200, sequentially subjecting the first material to filter pressing, concentration and distillation to obtain the N-methyl-N-(trimethylsilyl)acetamide.

[0034] In the above steps, N-methylacetamide and trimethylchlorosilane are used as reaction raw materials.

[0035] N-methylacetamide is also known as N-acetylmethylamine or methylacetamide, and its chemical formula is C3H7NO. N-methylacetamide usually appears as white needle-shaped crystals at room temperature. The N-methylacetamide of the present invention can be purchased through commercial channels, or it can be prepared by reacting ethyl acetate with methylamine. By mixing ethyl acetate and 65% methylamine, heating to about 60°C, reacting for 4 days and nights until there is no more stratification, that is, the reaction is completed, and ethanol is recovered by vacuum distillation. The fraction of 95 to 110°C is collected to obtain N-methylacetamide. Trimethylchlorosilane is an active compound that can react with many compounds. Trimethylchlorosilane is an important raw material for preparing silicon compounds such as silicone rubber, silicone oil, silicone resin, etc. It can also be used to prepare silane coupling agents, silanization agents, etc. The trimethylchlorosilane of the present invention can be purchased through commercial channels, or can be prepared by using methyl chloride and silicon powder as raw materials, using cuprous chloride as a catalyst to react to obtain a crude product, and then obtaining a finished product through processes such as distillation and purification. It can also be prepared by using tetramethylsilane and acetyl chloride as raw materials, adding aluminum chloride as a catalyst to react. Through the embodiments of the present invention, the hydrogen atom on the nitrogen atom of N-methylacetamide is replaced by the trimethylsilyl group in trimethylchlorosilane, thereby generating N-methyl-N-(trimethylsilyl)acetamide.

[0036] It should be noted that in the present invention, triethylamine is used as both an acid binding agent and a solvent in the reaction. Triethylamine is a colorless oily liquid, slightly soluble in water, but soluble in most organic solvents such as ethanol, ether, acetone. This solubility enables triethylamine to be used as a solvent for diluting organic reactants and active substances, so that reactants are fully mixed in the reaction, thereby improving the quality of reaction efficiency and polymer. In the reaction of the present invention, the generation of acidic substances can reduce the efficiency and quality of the reaction. As a weak base, triethylamine can be used as an acid binding agent to maintain the balance of the reaction, thereby improving the quality of the reaction.

[0037] In addition, when triethylamine is used as a solvent, it is easy to recover and process by distillation and other methods due to its relatively stable physical and chemical properties. This helps to reduce production costs and reduce environmental pollution.

[0038] The invention adopts low-cost, safe and reliable raw materials to react and prepare N-methyl-N-(trimethylsilyl)acetamide under normal pressure and relatively low temperature conditions, thereby providing a method for preparing N-methyl-N-(trimethylsilyl)acetamide which is safe, environmentally friendly, low-cost, simple in process and suitable for industrial production.

[0039] In some implementations of the present invention, S100 specifically includes:

[0040] S110, under an inert gas protective atmosphere, feeding the N-methylacetamide and the triethylamine into a reaction kettle, and heating them to a reaction temperature;

[0041] S120, controlling the reactor to maintain the reaction temperature, and dropwise adding trimethylsilyl chloride into the reactor;

[0042] S130, after the trimethylsilyl chloride is completely added, continue the heat-insulating reaction to obtain the first material.

[0043] In the above embodiments, the inert gas can be helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), radon (Rn, radioactive) etc. Preferably, the present invention adopts nitrogen as the inert gas. Under the inert gas protection atmosphere, the N-methylacetamide and the triethylamine are sent into the reactor, and the purpose of heating the temperature-raising reaction is to avoid the decomposition of the raw materials or reactants.

[0044] It is understood that the reaction temperature has an important influence on the quality and efficiency of the reaction of the present invention. The present invention carries out the reaction at a relatively low temperature. Preferably, the reaction temperature is 30°C to 38°C.

[0045] It can be understood that the reaction temperature of the present invention is an interval value. After the N-methylacetamide and the triethylamine are fed into the reactor, the reactor can be heated to the first reaction temperature. When the trimethylchlorosilane is added dropwise, the reactor can be heated from the first reaction temperature to the second reaction temperature. The first reaction temperature and the second reaction temperature can be within the temperature range of 30°C to 38°C. Preferably, the trimethylchlorosilane can be added dropwise at a temperature of 30°C, and the reaction temperature can be controlled to be within the temperature range of 30°C to 38°C.

[0046] It is understood that the rate of dripping the trimethylsilyl chloride will have an important impact on the quality and efficiency of the reaction of the present invention. The present invention needs to control the dripping of the trimethylsilyl chloride to be completed within 4 hours.

[0047] It should be noted that after the trimethylsilyl chloride is added dropwise, the heat preservation reaction should be continued, and after the heat preservation reaction is completed, the first material can be obtained. Preferably, in S130, the heat preservation reaction is continued for 1 hour.

[0048] It is understood that the amount and proportion of each raw material added will also have an important impact on the quality and efficiency of the reaction of the present invention. Preferably, in S110, for every 100L of triethylamine, 15kg to 20kg of N-methylacetamide is added accordingly, and 20kg to 30kg of trimethylchlorosilane is added dropwise accordingly. Further preferably, in S110, for every 100L of triethylamine, 16kg to 16.5kg of N-methylacetamide is added accordingly, and 24kg to 24.5kg of trimethylchlorosilane is added dropwise accordingly.

[0049] After the reaction is completed, the first material needs to be further subjected to filter pressing, concentration and rectification. S200 specifically includes:

[0050] S210, under an inert gas protective atmosphere, pressing the first material into a filter press, after the filter cake is pressed dry, adding triethylamine to wash once, and continuing to press dry to obtain a filtrate;

[0051] S220, pumping the filtrate into a concentration kettle, removing the triethylamine under negative pressure, stopping concentration and recovering the triethylamine under target temperature conditions to obtain a concentrated material;

[0052] S230, transferring the concentrated material to a distillation tower for distillation to obtain the N-methyl-N-(trimethylsilyl)acetamide.

[0053] Preferably, the target temperature condition is 60°C.

[0054] It should be noted that in the preparation stage of the filter press, it is necessary to ensure that the N-methyl-N-(trimethylsilyl)acetamide reaction mixture in the reactor has been fully reacted and the expected conversion rate has been achieved. Preferably, after the reaction is completed, the reaction medium can be cooled to an appropriate temperature (such as 0-5°C), and then an appropriate amount of solvent (such as hexane) is added for mixing to dilute the reaction mixture and promote the formation of a precipitate. By using a filter press to filter the mixture, solid impurities (such as triethylamine hydrochloride precipitate) can be removed. In this process, it is necessary to ensure that the pressure and flow control of the filter press are within an appropriate range to avoid damage to the product. Finally, the filter cake is washed with an appropriate amount of triethylamine to remove residual impurities. The filtrate and washing liquid after washing should be combined for recovery treatment to remove the low boiling point solvent therein. This can be achieved by methods such as distillation or stripping. After removing the solvent, the remaining mixture is concentrated to increase the concentration of N-methyl-N-(trimethylsilyl)acetamide. This can be achieved by methods such as reduced pressure distillation or heating evaporation. In the process of reactant being sent into a rectifying tower for rectification, by controlling the tower top temperature and the tower bottom temperature, as well as parameters such as the reflux ratio, the effective separation and purification of N-methyl-N-(trimethylsilyl)acetamide can be achieved. The fraction collected at the top of the tower is the purified N-methyl-N-(trimethylsilyl)acetamide. After being cooled, crystallized and dried, the final product can be obtained. It is understood that in the above whole process, those skilled in the art can control parameters such as temperature, pressure and flow according to actual needs to ensure the quality and yield of the product. By the above steps, the effective filter press, concentration and rectification of N-methyl-N-(trimethylsilyl)acetamide can be achieved, thereby obtaining high-quality products.

[0055] Example 1

[0056] Figure 1 FIG. 5 is a process flow chart of the preparation method of N-methyl-N-(trimethylsilyl)acetamide according to an embodiment of the present invention. Figure 1 As shown, this embodiment provides an industrial production method of N-methyl-N-(trimethylsilyl)acetamide, which uses N-methylacetamide and trimethylchlorosilane as raw materials to react in a triethylamine system to prepare N-methyl-N-(trimethylsilyl)acetamide.

[0057] The specific steps of this method are:

[0058] 1. Raw material preparation: Under nitrogen protection, add 1400L triethylamine and 225kg N-methylacetamide into a 2000L reactor, stir and heat to 30 degrees. Add 340kg trimethylchlorosilane into the high-level tank;

[0059] 2. Addition: After the temperature of the reactor rises to 30 degrees, start to add trimethylchlorosilane, control the reaction temperature at 30-38 degrees, and complete the addition in about 4 hours. After the addition is completed, keep the temperature for one hour;

[0060] 3. Filter pressing: After the heat preservation reaction is completed, open the nitrogen to press the material into the filter press. After the filter cake is pressed dry, add 400 liters of triethylamine to wash it once, and continue to press dry;

[0061] 4. Concentration: Pump the filtrate from the previous step into the concentration kettle, remove triethylamine under negative pressure, and stop concentrating when the kettle temperature reaches 60 degrees. The recovered triethylamine is used for the next batch of production;

[0062] 5. Distillation: The concentrated material is transferred to a distillation tower and distilled to obtain the product.

[0063] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the claims.

Claims

1. A method for preparing N-methyl-N-(trimethylsilyl)acetamide, characterized in that: The preparation method comprises: S100, using raw materials including N-methylacetamide and trimethylchlorosilane to react in a triethylamine system to obtain a first material; S200, sequentially subjecting the first material to filter pressing, concentration and distillation to obtain the N-methyl-N-(trimethylsilyl)acetamide.

2. The preparation method according to claim 1, characterized in that: S100 specifically includes: S110, under an inert gas protective atmosphere, feeding the N-methylacetamide and the triethylamine into a reaction kettle, and heating them to a reaction temperature; S120, controlling the reactor to maintain the reaction temperature, and dropwise adding trimethylsilyl chloride into the reactor; S130, after the trimethylsilyl chloride is completely added, continue the heat preservation reaction to obtain the first material.

3. The preparation method according to claim 2, characterized in that: In S110, for every 100 L of the triethylamine added, 15 kg to 20 kg of the N-methylacetamide is added accordingly, and 20 kg to 30 kg of the trimethylsilyl chloride is added dropwise accordingly.

4. The preparation method according to claim 3, characterized in that: In S110, for every 100 L of the triethylamine added, 16 kg to 16.5 kg of the N-methylacetamide is added accordingly, and 24 kg to 24.5 kg of the trimethylsilyl chloride is added dropwise accordingly.

5. The preparation method according to claim 2, characterized in that: In S110, the reaction temperature is 30°C to 38°C.

6. The preparation method according to claim 2, characterized in that: In S120, the trimethylsilyl chloride is controlled to be added dropwise within 4 hours.

7. The preparation method according to claim 2, characterized in that: In S130, the time for continuing the heat preservation reaction is 1 hour.

8. The preparation method according to any one of claims 1 to 7, characterized in that S200 specifically includes: S210, under an inert gas protective atmosphere, pressing the first material into a filter press, after the filter cake is pressed dry, adding triethylamine to wash once, and continuing to press dry to obtain a filtrate; S220, pumping the filtrate into a concentration kettle, removing the triethylamine under negative pressure, stopping concentration and recovering the triethylamine under target temperature conditions to obtain a concentrated material; S230, transferring the concentrated material to a distillation tower for distillation to obtain the N-methyl-N-(trimethylsilyl)acetamide.

9. The preparation method according to claim 8, characterized in that: The target temperature condition is 60°C.

10. N-methyl-N-(trimethylsilyl)acetamide, characterized in that The N-methyl-N-(trimethylsilyl)acetamide is obtained by the preparation method according to any one of claims 1 to 9.

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