A process for the preparation of 2,6-di-tert-butylpyranium tetrafluoroborate

Abstract

The application discloses a preparation method of 2,6-di-tert-butylpyranylium tetrafluoroborate, and belongs to the technical field of organic synthesis. The method comprises the following steps: under acid catalysis, 3,3-dimethylbutan-2-one is added dropwise into excessive triethyl orthoformate to generate an intermediate, the intermediate is distilled and purified to obtain the intermediate with a high rate; then, the intermediate is reacted with 3,3-dimethylbutan-2-one under the action of an ethyl ether solution of tetrafluoroboric acid to generate the product 2,6-di-tert-butylpyranylium tetrafluoroborate, the product yield is remarkably improved, the route is simple and efficient, the product separation and purification are simple, and the method is suitable for industrial amplification.

Description

Technical Field

[0001] This invention relates to a method for preparing 2,6-di-tert-butylpyranocyanate, belonging to the field of organic synthesis technology. Background Technology

[0002] Pyranium salts are an important class of organic cationic compounds with unique conjugated structures and photoelectric properties, finding wide applications in photocatalysis, organic optoelectronic materials, and pharmaceutical intermediates. Among them, tetrafluoroborate pyranium salts have become a research hotspot due to their high anionic stability and good solubility. 2,6-Di-tert-butylpyranium tetrafluoroborate can be used to prepare organic molecules with various stable redox states, applicable to data storage and energy storage, as well as logic devices suitable for quantum information science. Furthermore, organic free radicals generated by external stimuli such as light and electric fields have great application potential in the fields of tunable conductive and magnetic functional materials.

[0003] A review of existing literature revealed that only one method for synthesizing 2,6-di-tert-butylpyranone tetrafluoroborate has been reported so far. This method uses 3,3-dimethylbut-2-one as a starting material and generates 2,6-di-tert-butylpyranone tetrafluoroborate in a one-step process with a low yield (approximately 20%) in tetrafluoroborate diethyl ether solution [Journal of the American Chemical Society, 2018, 140, 14823].

[0004] Currently, the lack of an efficient and simple synthetic method for 2,6-di-tert-butylpyranone tetrafluoroborate limits its application and promotion. Therefore, developing a synthetic method with readily available raw materials, simple operation, and high yield, and expanding its application scenarios, is of significant practical importance. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing 2,6-di-tert-butylpyranocyanate in high yield.

[0006] To achieve the above objectives, this invention employs a two-step process. Under acid catalysis, 3,3-dimethylbut-2-one is added dropwise to excess triethyl orthoformate to generate an intermediate, which is then purified by distillation to obtain a high-yield intermediate. Subsequently, the intermediate reacts with 3,3-dimethylbut-2-one in tetrafluoroborate ether solution to generate the product 2,6-di-tert-butylpyranocyanate. This significantly improves the product yield, provides a simple and efficient route, and simplifies product separation and purification, making it suitable for industrial-scale production.

[0007] The preparation method of 2,6-di-tert-butylpyranone tetrafluoroborate according to the present invention is shown in the following synthetic route:

[0008] Includes the following steps: A. Triethyl orthoformate and an acid catalyst were mixed, and 3,3-dimethylbut-2-one was added at room temperature. After the reaction was completed, the mixture was distilled under reduced pressure to obtain the intermediate. B. Mix the intermediate with 3,3-dimethylbut-2-one, and slowly add tetrafluoroborate diethyl ether solution under heating conditions. After the addition is complete, continue the reaction. Monitor the reaction by GC until it is complete. After post-treatment, 2,6-di-tert-butylpyranone tetrafluoroborate is obtained.

[0009] In a preferred embodiment, in the above technical solution, in step A, the acid is selected from tetrafluoroborate ether (50%), methanesulfonic acid, or p-toluenesulfonic acid.

[0010] In a preferred embodiment, in the above technical solution, in step A, the molar ratio of 3,3-dimethylbut-2-one, acid catalyst, and triethyl orthoformate is 1:0.05-0.15:2-3.

[0011] In a preferred embodiment, in the above technical solution, the heating reaction in step B is 40-80°C.

[0012] In a preferred embodiment of the above technical solution, in step B, the molar ratio of the intermediate, 3,3-dimethylbutan-2-one, and tetrafluoroborate diethyl ether solution is 1:1-1.5:1.2-1.5. After screening and optimization, it was found that the product 2,6-di-tert-butylpyranone tetrafluoroborate is liquid at high temperatures. Therefore, the final optimized step is to select a reaction that does not use additional solvents in the second step to reduce losses and recovery costs.

[0013] Beneficial effects of this invention: 1. This invention uses readily available 3,3-dimethylbut-2-one as raw material, obtains an intermediate through acid catalysis, and purifies it by distillation, which can greatly improve the yield of the first step, making the route simple and efficient.

[0014] 2. In this invention, the intermediate is reacted with 3,3-dimethylbut-2-one in tetrafluoroborate ether solution to generate 2,6-di-tert-butylpyranone tetrafluoroborate, which significantly improves the product yield, generates less waste, operates under mild and environmentally friendly conditions, has high selectivity, and simplifies product separation and purification.

[0015] 3. The reaction system of this invention has good process stability and is easy to implement industrially. Specific Implementation Although the present invention has been described in detail by way of preferred embodiments, the present invention is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the present invention by those skilled in the art without departing from the spirit and essence of the invention, and such modifications or substitutions should all be within the scope of the present invention. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should also be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the scope of the claims.

[0017] Example 1

[0018] Under nitrogen protection, triethyl orthoformate (0.25 mol, 37.1 g) and tetrafluoroborate ether (0.01 mol, 1.6 g) were mixed, and 3,3-dimethylbut-2-one (0.1 mol, 10.0 g) was added at room temperature. The reaction was continued for 3 hours. The reaction was monitored by GC until it was complete. Excess triethyl orthoformate was recovered by vacuum distillation, followed by fractional distillation to obtain 17.2 g of intermediate, with a yield of 85% and a GC content of 98.5%. 1 HNMR (400 MHz, CDCl3): 4.83 (t, 1H), 358-3.42 (t, 4H), 2.62 (m, 2H), 1.14 (t, 6H), 1.1 (s, 9H).

[0019] Example 2

[0020] Under nitrogen protection, triethyl orthoformate (0.25 mol, 37.1 g) and p-toluenesulfonic acid (0.01 mol, 1.7 g) were mixed, and 3,3-dimethylbut-2-one (0.1 mol, 10.0 g) was added at room temperature. The reaction was continued for 6 hours. The reaction was monitored by GC until it was completed. Excess triethyl orthoformate was recovered by vacuum distillation, followed by fractional distillation to obtain 16.4 g of intermediate, with a yield of 81% and a GC content of 98.1%.

[0021] Example 3

[0022] Under nitrogen protection, triethyl orthoformate (0.25 mol, 37.1 g) and methanesulfonic acid (0.01 mol, 0.96 g) were mixed, and 3,3-dimethylbut-2-one (0.1 mol, 10.0 g) was added at room temperature. The reaction was continued for 3 hours. The reaction was monitored by GC until it was completed. Excess triethyl orthoformate was recovered by vacuum distillation, followed by fractional distillation to obtain 18.4 g of intermediate, with a yield of 91% and a GC content of 98.6%.

[0023] Example 4

[0024] Under nitrogen protection, the intermediate (0.1 mol, 20.2 g), 3,3-dimethylbut-2-one (0.13 mol, 13.0 g), and tetrafluoroborate ether solution (0.13 mol, 21.1 g) were mixed and heated to 60 °C for 3 hours. The reaction was monitored by GC until completion. The mixture was then cooled to room temperature and concentrated under reduced pressure. The remaining reaction solution was poured into 350 mL of ether solution, filtered, and the filter cake was washed twice with 100 mL of ether. After drying, 17.1 g of 2,6-di-tert-butylpyranone tetrafluoroborate was obtained, with a yield of 61% and an HPLC purity of 98.2%.

[0025] Example 5

[0026] Under nitrogen protection, the intermediate (0.1 mol, 20.2 g) and 3,3-dimethylbut-2-one (0.13 mol, 13.0 g) were mixed in 100 mL of chloroform. The mixture was heated to 60 °C, and tetrafluoroborate ether solution (0.13 mol, 21.1 g) was slowly added dropwise. After the addition was complete, the reaction was continued for 5 hours. The reaction was monitored by GC until it was complete. The mixture was then cooled to room temperature and concentrated under reduced pressure. The remaining reaction solution was poured into 350 mL of ether solution, filtered, and the filter cake was washed twice with 100 mL of ether. After drying, 22.1 g of 2,6-di-tert-butylpyranone tetrafluoroborate was obtained, with a yield of 79% and an HPLC purity of 98.8%.

[0027] Example 6

[0028] Under nitrogen protection, the intermediate (0.1 mol, 20.2 g) and 3,3-dimethylbutan-2-one (0.13 mol, 13.0 g) were mixed and heated to 60 °C. Then, a tetrafluoroborate ether solution (0.13 mol, 21.1 g) was slowly added dropwise. After the addition was complete, the reaction continued for 2 hours. The reaction was monitored by GC until completion. The mixture was then cooled to room temperature and concentrated under reduced pressure. The remaining reaction solution was poured into 350 mL of ether solution, filtered, and the filter cake was washed twice with 100 mL of ether. After drying, 23.8 g of 2,6-di-tert-butylpyranone tetrafluoroborate was obtained, with a yield of 85% and an HPLC purity of 99.1%. 1 HNMR (400MHz, CD3CN): 8.83 (t, 1H), 8.00 (d, 2H), 1.52 (s, 18H).

[0029] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing 2,6-di-tert-butylpyranocyanate, characterized in that, Includes the following steps: ； A. Triethyl orthoformate and an acid catalyst were mixed, and 3,3-dimethylbut-2-one was added at room temperature. After the reaction was completed, the mixture was distilled under reduced pressure to obtain the intermediate. B. Mix the intermediate with 3,3-dimethylbut-2-one, and slowly add tetrafluoroborate diethyl ether solution under heating conditions. After the addition is complete, continue the reaction. Monitor the reaction by GC until it is complete. After post-treatment, 2,6-di-tert-butylpyranone tetrafluoroborate is obtained.

2. The method for preparing 2,6-di-tert-butylpyranone tetrafluoroborate according to claim 1, characterized in that: In step A, the acid is selected from tetrafluoroborate ether (50%), methanesulfonic acid, or p-toluenesulfonic acid.

3. The method for preparing 2,6-di-tert-butylpyranone tetrafluoroborate according to claim 1, characterized in that: In step A, the molar ratio of 3,3-dimethylbut-2-one, acid catalyst, and triethyl orthoformate is 1:0.05-0.15:2-3.

4. The method for preparing 2,6-di-tert-butylpyranone tetrafluoroborate according to claim 1, characterized in that: In step B, the heating reaction is carried out at 40-80°C.

5. The method for preparing 2,6-di-tert-butylpyranone tetrafluoroborate according to claim 1, characterized in that: In step B, the molar ratio of the intermediate, 3,3-dimethylbut-2-one, and tetrafluoroborate ether solution is 1:1-1.5:1.2-1.5.

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