Synthesis method of trifluoromethanesulfonic acid silicone ester
Technical Field
The invention belongs to the technical field of fine chemical engineering, relates to the technical field of organic synthesis, and particularly relates to a method for synthesizing trifluoromethanesulfonic acid silicone ester.
Background
The trifluoromethanesulfonic acid silyl ester is generally colorless liquid, is extremely easy to hydrolyze in air, is a commonly used silicon-based reagent, can be used for conversion and protection of functional groups such as alcohol, amine, ketone, aldehyde, carboxylic acid and the like, is commonly used as a catalyst for Dieckmann reaction and Morita-Baylis-Hillman reaction, is also a commonly used initiator for cationic polymerization reaction, and has wide application in the fields of medicines, pesticides, liquid crystals, silicon materials and the like.
The trifluoromethanesulfonic acid silicone ester mainly comprises trifluoromethanesulfonic acid trimethylsilyl ester, trifluoromethanesulfonic acid triethylsilicone ester, trifluoromethanesulfonic acid triisopropyl silicone ester, trifluoromethanesulfonic acid tert-butyl dimethylsilyl ester and the like, wherein the trifluoromethanesulfonic acid trimethylsilyl ester is most widely applied.
The earliest Synthesis of trimethylsilyl trifluoromethanesulfonate was carried out by reacting silver trifluoromethanesulfonate with trimethylchlorosilane (Chemische Berichte-Recueil 1970,103,868-879), followed by the development of a preparation method of trifluoromethanesulfonic anhydride by reacting it with trimethylsilylether (Synthesis-Stuttgart 1985,2,206-207), but the starting materials for this method are expensive and limit its industrial application. Patent CN103665017A reports a method for preparing trimethylsilyl trifluoromethanesulfonate by reacting trimethylsilanol with trifluoromethanesulfonic anhydride, trifluoromethanesulfonyl chloride or trifluoromethanesulfonyl fluoride, but trifluoromethanesulfonic anhydride and trifluoromethanesulfonyl chloride are expensive, trifluoromethanesulfonyl fluoride itself has low reactivity, and is difficult to react with trimethylsilanol, and trimethylsiloxane is easily polymerized into hexamethyldisiloxane under acidic conditions, so the method has little industrial application value. The most common method in industry is to prepare by reacting trifluoromethanesulfonic acid with tetramethylsilane or trimethylchlorosilane, but tetramethylsilane is used as a raw material, and reaction byproducts are more, and the purification of the product is difficult; when trimethylchlorosilane is used as a raw material, a large amount of hydrogen chloride gas is generated to seriously corrode equipment, the process operation is difficult, alkali absorption treatment is needed, and the three-waste treatment difficulty is high. Other triflates were synthesized in a similar manner as described above.
The trifluoromethanesulfonic acid is generally trifluoromethanesulfonic acid salt obtained by electrolyzing corresponding alkyl sulfonyl chloride or alkyl sulfonyl fluoride and hydrolyzing with alkali, and the trifluoromethanesulfonic acid is obtained by acidifying with concentrated sulfuric acid.
Disclosure of Invention
In order to solve the problems of the method, the invention provides a novel synthesis process which is low in cost, controllable in process and environment-friendly.
In order to realize the purpose, the invention combines the special reactivity of fluorine and silicon with the DMAP catalytic acylation reaction to realize the method for preparing the trifluoromethanesulfonic acid silicone ester by the reaction of the trifluoromethanesulfonyl fluoride and the siloxane. DMAP and trifluoromethanesulfonyl fluoride generate a stable acyl compound at low temperature, and release fluoride ions, the stable acyl compound reacts with siloxane to cut a siloxane bond in situ to generate silanol fluoride ions, and the silanol fluoride ions and activated acyl fluoride undergo an acylation reaction in situ to obtain trifluoromethanesulfonic acid silyl ester.
The invention is realized by the following technical scheme:
a method for synthesizing trifluoromethanesulfonic silicon ester comprises the steps of mixing siloxane with a catalyst Dimethylaminopyridine (DMAP), and introducing trifluoromethanesulfonyl fluoride at a low temperature of-40-0 ℃ for reaction under the protection of inert gas.
Wherein, the reaction rate can be improved by increasing the temperature of acyl fluoride, but after the temperature is higher than 0 ℃, the equilibrium reaction of the DMAP and the acyl compound generated by the acyl fluoride can move to the decomposition direction, and the concentration of the acyl compound is reduced.
In certain embodiments, the siloxane is represented by formula II:
wherein R is1、R2、R3Each independently selected from methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, tert-butyl.
In certain embodiments, the molar ratio of catalyst DMAP to siloxane is from 0.001 to 0.1: 1.
In certain embodiments, the molar ratio of catalyst DMAP to siloxane is from 0.01 to 0.05: 1.
Wherein, increasing the amount of catalyst DMAP in the reaction is beneficial to increase the reaction speed, but excessive DMAP can increase the production cost.
In certain embodiments, the reaction temperature is from-40 to 80 ℃.
In certain embodiments, the reaction temperature is from-20 to 40 ℃.
In some embodiments, after the reaction is completed, the temperature is reduced to separate out the excessive trifluoromethanesulfonyl fluoride, and the excessive trifluoromethanesulfonyl fluoride is separated by distillation to obtain the fluorosilane as a byproduct and the product trifluoromethanesulfonic silicon ester.
In certain embodiments, the distillation temperature is from 20 to 120 ℃.
Wherein the distillation temperature is determined according to the reaction raw materials, and the distillation temperature is properly increased along with the increase of the carbon number of the siloxane alkyl.
In certain embodiments, the distillation pressure is from-0.098 to 0 MPa.
Wherein the distillation pressure is determined according to the reaction raw material, and the vacuum degree of distillation is properly increased along with the increase of the carbon number of the siloxane alkyl group.
In some embodiments, the separated fluorosilane is added into a calcium hydroxide aqueous solution to react to generate siloxane and calcium fluoride shown in a general formula II, the calcium fluoride is separated by filtration, and the lower layer of water is separated from the filtrate, and then the filtrate is frozen and dried to obtain the raw material siloxane which can be recycled to participate in the reaction.
In certain embodiments, the molar ratio of calcium hydroxide to reaction charge siloxane is 1: 2.
Wherein, the siloxane is the original feeding amount for participating in the reaction, the increase of the dosage of the calcium hydroxide can increase the generation amount of the calcium fluoride, and the decrease of the dosage of the calcium hydroxide can cause incomplete reaction.
In some embodiments, the reaction temperature of the fluorosilane and the calcium hydroxide is 0-120 ℃.
In some embodiments, the reaction temperature of the fluorosilane and the calcium hydroxide is 20-80 ℃.
Wherein, increasing the temperature is beneficial to increase the reaction rate, but the solubility of calcium hydroxide decreases with increasing temperature.
In certain embodiments, the freeze-drying temperature is from-5 to-30 ℃.
Wherein the freezing temperature is determined according to the characteristics of the siloxane, and the larger the molecular weight of the siloxane is, the higher the freezing temperature is, and the solidification of the siloxane or the increase of the viscosity is prevented.
The synthetic method of the trifluoromethanesulfonic acid silicone ester has the following advantages:
(1) the synthesis method provided by the invention adopts the trifluoromethyl sulfonyl fluoride as the raw material, and compared with the industrial existing method which adopts the triflic acid process as the raw material, the method has the advantages that the raw material is cheaper and is easy to obtain, and the reaction steps are simple to operate, so the production cost is lower.
(2) The synthesis method of the trifluoromethanesulfonic acid silicon ester provided by the invention has the advantages that the product purity is easy to control, particularly, acid is not used as a raw material, the acid content of the product is easier to control, the quality requirement can be met only by simple distillation, the product purity is more than 99%, and the acid content is less than 0.05%.
(3) The synthetic method realizes the self-circulation of the process, does not use a solvent, only needs simple treatment to generate fluorosilane which can be used as the raw material siloxane for application, has the only byproduct of calcium fluoride with the purity of more than 95 percent, belongs to common waste, is the main raw material for hydrogen fluoride production, and can realize the resource utilization of the waste.
(4) The whole production process does not use and generate strong acid and strong base, the reaction safety is greatly improved, the equipment condition is easy to meet, and the industrial production is facilitated.
Drawings
FIG. 1 is a diagram of the process for producing fluoromethanesulfonic acid silicone ester according to the present invention.
Detailed Description
The following examples are provided to further illustrate the embodiments of the present invention.
Example 1
486g (3mol) of hexamethyldisiloxane and 11.2g (0.1mol) of DMAP are added into a 2L stainless steel reaction kettle, the temperature is reduced to minus 30 ℃ under the protection of nitrogen, and the reaction kettle is evacuated to minus 0.09 MPa. 532g (3.5mol) of trifluoromethanesulfonyl fluoride is slowly introduced, the reaction kettle is closed after the introduction is finished, and the temperature is raised to 20 ℃ for reaction for 8 hours. After the reaction is finished, slowly opening an air outlet valve of the reaction kettle, controlling the temperature of the condenser to be-20 ℃, and collecting the unreacted trifluoromethanesulfonyl fluoride at the temperature of-30 ℃ in the receiving tank. Then controlling the temperature of the condenser to be 16 ℃, and collecting the byproduct trimethyl fluorosilane at the temperature of the receiving tank to be 0 ℃. And (3) increasing the vacuum degree of the reaction kettle to-0.08 MPa, heating to 60 ℃ for distillation, and collecting fractions at 42-44 ℃ to obtain 642g of trimethylsilyl trifluoromethanesulfonate with the yield of 96.4%, the purity of 99.1% and the acid content of 0.03%.
Preparing 120g of calcium hydroxide (with the purity of 95%) in a suspension of 1500mL of water in a 2L reaction bottle, heating to 60 ℃, dripping collected trimethyl fluorosilane into the suspension for 3 hours, continuing to react for 30 minutes, and filtering to obtain a filter cake, namely calcium fluoride (with the purity of 96.1%) containing a small amount of calcium hydroxide; separating the filtrate, placing the upper organic phase into a reaction bottle, keeping the temperature at-20 ℃ for 30 minutes, attaching ice crystals to the reaction bottle, pouring out the liquid in the reaction bottle, and recovering 231g of hexamethyldisiloxane with the recovery rate of 95.1 percent.
Example 2
493g (2mol) of hexaethyldisiloxane and 11.2g (0.1mol) of DMAP are added into a 2L stainless steel reaction kettle, the temperature is reduced to-10 ℃ under the protection of nitrogen, and the reaction kettle is evacuated to-0.09 MPa. 380g (3.5mol) of trifluoromethanesulfonyl fluoride are slowly introduced, and after the introduction, the reaction vessel is closed and reacted at this temperature for 12 hours. After the reaction is finished, slowly opening an air outlet valve of the reaction kettle, controlling the temperature of the condenser to be-20 ℃, and collecting the unreacted trifluoromethanesulfonyl fluoride at the temperature of-30 ℃ in the receiving tank. Improving the vacuum degree of the reaction kettle to-0.085 MPa, and collecting fractions at the temperature of 55-58 ℃ to obtain triethyl fluorosilane; heating to 90 ℃, and collecting 85-87 ℃ fractions to obtain 501g of trifluoromethanesulfonic acid triethyl silyl ester, wherein the yield is 94.9%, the purity is 99.2%, and the acid content is 0.02%.
Preparing 80g of calcium hydroxide (with the purity of 95%) in a suspension of 1000mL of water in a 2L reaction bottle, heating to 60 ℃, dripping collected triethylfluorosilane into the suspension for 3 hours, continuing to react for 30 minutes, and filtering to obtain a filter cake, namely calcium fluoride (with the purity of 95.0%) containing a small amount of calcium hydroxide; separating the filtrate, placing the upper organic phase into a reaction flask, keeping the temperature at-30 ℃ for 10 minutes, attaching ice crystals to the reaction flask, pouring out the liquid in the reaction flask, and recovering 231g of hexaethyldisiloxane with the recovery rate of 93.7 percent.
Example 3
A1L four-necked flask was charged with 162g (1mol) of hexamethyldisiloxane and 5.6g (0.05mol) of DMAP, and purged with nitrogen. Reducing the temperature to-30 ℃ under the protection of nitrogen, and evacuating the reaction flask to-0.09 MPa. 182.4g (1.2mol) of trifluoromethanesulfonyl fluoride was slowly introduced, a white solid was gradually precipitated from the reaction flask, and the reaction was stopped after reacting at this temperature for 24 hours. Building a distillation device, slowly heating the reaction bottle to 0 ℃, controlling the temperature of a condenser pipe to be-20 to-15 ℃, and collecting unreacted trifluoromethanesulfonyl fluoride at the temperature of a receiving tank to be-35 to-30 ℃. And then heating the reaction bottle to 25 ℃, controlling the temperature of the condensation pipe to be 16-20 ℃, and collecting the byproduct trimethyl fluorosilane at the temperature of the receiving tank of 0 ℃. The vacuum degree of the reaction bottle is improved to-0.08 MPa, the temperature is increased to 60 ℃ for distillation, and fractions at 42-44 ℃ are collected to obtain 206.4g of trimethylsilyl trifluoromethanesulfonate with the yield of 93.0%, the purity of 99.3% and the acid content of 0.04%.
Preparing 40g of calcium hydroxide (with the purity of 95%) in a suspension of 500mL of water in a 1L reaction bottle, heating to 60 ℃, dripping collected trimethyl fluorosilane into the suspension for 3 hours, continuing to react for 30 minutes, and filtering to obtain a filter cake, namely calcium fluoride (with the purity of 95.8%) containing a small amount of calcium hydroxide; separating the filtrate, placing the upper organic phase into a reaction bottle, keeping the temperature at-20 ℃ for 30 minutes, attaching ice crystals to the reaction bottle, pouring out the liquid in the reaction bottle, and recovering 68g of hexamethyldisiloxane with the recovery rate of 84.0 percent.
Example 4
660g (2mol) of hexa-isopropyl disiloxane and 2.24g (0.02mol) of DMAP are added into a 2L stainless steel reaction kettle, the temperature is reduced to-30 ℃ under the protection of nitrogen, and the reaction kettle is evacuated to-0.09 MPa. 380g (2.5mol) of trifluoromethanesulfonyl fluoride is slowly introduced, the reaction kettle is closed after the introduction is finished, and the temperature is raised to-20 ℃ for reaction for 18 hours. After the reaction is finished, slowly opening an air outlet valve of the reaction kettle, controlling the temperature of the condenser to be-20 ℃, and collecting the unreacted trifluoromethanesulfonyl fluoride at the temperature of-30 ℃ in the receiving tank. Improving the vacuum degree of the reaction kettle to-0.085 MPa, and collecting fractions at 65-67 ℃ to obtain triisopropyl fluorosilane; and (3) increasing the vacuum degree of the reaction kettle to-0.08 MPa, heating to 100 ℃ for distillation, and collecting the fraction at 78-80 ℃ to obtain 582g of trimethylsilyl trifluoromethanesulfonate with the yield of 95.1%, the purity of 99.3% and the acid content of 0.03%.
Preparing 80g of calcium hydroxide (with the purity of 95%) in a suspension of 1500mL of water in a 2L reaction bottle, controlling the reaction temperature to be 20 ℃, dripping the collected trimethyl fluorosilane into the suspension for 3h, continuing to react for 5h, and filtering to obtain a filter cake, namely calcium fluoride (with the purity of 95.6%) containing a small amount of calcium hydroxide; separating the filtrate, placing the upper organic phase into a reaction flask, keeping the temperature at-20 ℃ for 30 minutes, attaching ice crystals to the reaction flask, pouring out the liquid in the reaction flask, and recovering 318g of hexaisopropyl disiloxane with a recovery rate of 96.3%.
Example 5
493g (2mol) of 1, 3-bis (tert-butyl) -1,1,3, 3-tetramethyldisiloxane and 22.4g (0.2mol) of DMAP are added into a 2L stainless steel reaction kettle, the temperature is reduced to-30 ℃ under the protection of nitrogen, and the reaction kettle is evacuated to-0.09 MPa. 380g (2.5mol) of trifluoromethanesulfonyl fluoride is slowly introduced, the reaction kettle is closed after the introduction is finished, and the temperature is raised to 40 ℃ for reaction for 3 hours. After the reaction is finished, slowly opening an air outlet valve of the reaction kettle, controlling the temperature of the condenser to be-20 ℃, and collecting the unreacted trifluoromethanesulfonyl fluoride at the temperature of-30 ℃ in the receiving tank. Improving the vacuum degree of the reaction kettle to-0.085 MPa, and collecting fractions at 70-73 ℃ to obtain tert-butyl dimethyl fluorosilane; and (3) increasing the vacuum degree of the reaction kettle to-0.08 MPa, heating to 100 ℃ for distillation, and collecting 83-85 ℃ fractions to obtain 508g of trimethylsilyl trifluoromethanesulfonate with the yield of 96.2%, the purity of 99.0% and the acid content of 0.02%.
Preparing 80g of calcium hydroxide (with the purity of 95%) in a suspension of 1500mL of water in a 2L reaction bottle, heating to the temperature of 80 ℃, dripping collected trimethyl fluorosilane into the suspension for 3h, continuing to react for 1h, and filtering to obtain a filter cake, namely calcium fluoride (with the purity of 95.8%) containing a small amount of calcium hydroxide; separating the filtrate, placing the upper organic phase into a reaction flask, keeping the temperature at-20 ℃ for 30 minutes, attaching ice crystals to the reaction flask, pouring out the liquid in the reaction flask, and recovering 236g of 1, 3-bis (tert-butyl) -1,1,3, 3-tetramethyldisiloxane with the recovery rate of 95.7 percent.
The synthetic method of the trifluoromethanesulfonic acid silicon ester provided by the invention is characterized in that siloxane and trifluoromethanesulfonyl fluoride react under the action of a catalyst dimethylaminopyridine DMAP. The product purity of the synthesis method is easy to control, the product quality requirement can be met only by simple distillation, the product purity is more than 99%, the acid content is less than 0.05%, the self-circulation of the process is realized, no solvent is used, the generated fluorosilane can be used as raw material siloxane for reuse only by simple treatment, and the only byproduct is calcium fluoride with the purity of more than 95%, so that the waste can be recycled.
The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various changes and modifications can be made without departing from the inventive concept of the present invention, and these should be considered as within the scope of the present invention.