Preparation method of carborane derivative

Abstract

The invention relates to a preparation method of a carborane derivative, which comprises the following steps: reacting carborane with n-butyllithium in an ether solvent in an inert gas atmosphere, adding an inorganic base and a copper catalyst after the reaction is completed, reacting for a period of time, adding pyridine, stirring for a period of time, filtering, washing, and drying to obtain the carborane derivative. And finally, adding a compound L-R1, and carrying out heating reaction to obtain a derivative in which H on one or two carbons on carborane is substituted by R1. According to the preparation method disclosed by the invention, the complete reaction can be carried out only by one solvent, the operation is obviously simpler, and the cost is lower. More importantly, the method provided by the invention significantly improves the yield of the carborane derivative, and has certain application prospects.

Description

Technical Field

[0001] The present invention belongs to the field of organic synthesis, and particularly relates to a preparation method of a carborane derivative. Background Art

[0002] With the rapid development of modern aviation and aerospace requirements, the flight speed of aircraft is required to be faster and faster, resulting in higher and higher temperatures faced by the aircraft. This puts higher and higher requirements on high-temperature resistant protective materials, such as excellent high-temperature resistance, oxidation resistance, and ablation resistance characteristics.

[0003] Phenolic resin is a polymer formed by the addition, condensation, and polycondensation reactions of phenols and formaldehyde under the catalysis of an acid or base catalyst. By changing the ratio of formaldehyde to phenol and the type of catalyst, thermosetting or thermoplastic phenolic resins can be obtained. Phenolic resin has become an advantageous resin matrix for carbon-based thermal protection materials due to its good mechanical, char-forming, and ablation-resistant properties. Ordinary phenolic resin begins to oxidize above 200°C and undergoes rapid thermal decomposition at 340 - 360°C, which greatly limits its application range. Therefore, when ordinary phenolic resin faces the harsh thermal environment of hypersonic aircraft, its high-temperature resistance and ablation resistance need to be further improved, especially in an oxygen-containing environment, to enhance its oxidation resistance and maintain a high char yield in an oxygen ablation environment, thereby achieving thermal protection of the aircraft surface.

[0004] Traditional methods for improving the ablation resistance characteristics of phenolic resin mainly involve blending ablation-resistant fillers in the phenolic resin, which often leads to an increase in the viscosity of the resin and a decrease in its processability. Introducing ablation-resistant inorganic components into the phenolic resin structure by copolymerization can effectively improve the ablation resistance characteristics of the resin without affecting its processability. This method of improving resin performance by organic-inorganic hybridization has become a hot topic in materials basic and applied research. How to construct an organic-inorganic hybrid structure has become the core key.

[0005] Carborane (C2B 10 H 12 ) refers to an icosahedral cage compound composed of carbon, boron, and hydrogen elements. Two carbons and ten borons are located at twelve vertices respectively, and each carbon and boron atom is connected to a hydrogen atom. According to the different positions of carbon atoms, there are three isomers of carborane, namely ortho (o) carborane (1,2-Carborane), meta (m) carborane (1,7-Carborane), and para (p) carborane (1,12-Carborane). Ortho carborane can be prepared by reacting decaborane with acetylene under the action of a Lewis acid. Meta carborane can be prepared by isomerizing ortho carborane at a high temperature of 475 - 600°C in an inert gas atmosphere. Meta carborane can be further isomerized to para carborane at 650 - 700°C.

[0006] Carboranes have characteristics such as high boron content, steric aromaticity, and stable cage structures. When carborane derivatives are introduced as structural units into the main chain of polymers, the high-temperature resistance of the polymers can be significantly improved. This is because the electron-deficiency of carboranes increases the degree of ionization of adjacent bonds and enhances stability. How to introduce the large-sized icosahedral carborane cage structure into phenolic resin to form an organic-inorganic hybrid structure with uniform molecular-level distribution has become a key technology in the synthesis and preparation of carborane-modified phenolic resin.

[0007] Qi Shicheng et al. "Synthesis and Property Study of Carborane Phenolic Resin" [J]. Journal of Aeronautical Materials, 2014, 34(01): 46-51 discloses a preparation method of carborane derivatives. This literature records that two solvents, THF and pyridine, are required in the preparation of 1,7-bis(4'-methoxyphenyl)carborane. During the operation, THF needs to be removed first, and then pyridine is added. The operation is complex. Moreover, this method has a long reaction time and the product yield needs to be improved. Summary of the Invention

[0008] To solve the above technical problems, the present invention provides a preparation method of carborane derivatives. This method is an one-pot operation, with simple steps, short reaction time, and the product yield is significantly improved compared with the existing methods.

[0009] A preparation method of carborane derivatives, comprising:

[0010] First, react carborane with n-butyllithium in an ether solvent under an inert gas atmosphere. After the reaction is completed, add an inorganic base and a copper catalyst and react for a period of time, then add pyridine and stir for a period of time, and finally add compound L-R1 and heat to react to obtain a derivative in which one or two hydrogens on the carbon of carborane are replaced by R1;

[0011] In L-R1, L is a halogen, and R1 is a phenyl or 5-12 membered heteroaryl substituted by one, two or more Rs; 6-12 Rs is selected from C 1-12 alkoxy, C 1-12 alkyl, C 3-12 cycloalkyl, 3-12 membered heterocyclic group, C 6-12 aryl or 5-12 membered heteroaryl, provided that at least one Rs is selected from C 1-12 alkoxy.

[0012] According to an embodiment of the present invention, in L-R1, L is I;

[0013] R1 is a phenyl or pyridyl substituted by one, two or more Rs;

[0014] Rs is selected from C 1-6 alkoxy, C1-6 alkyl, C 3-6 cycloalkyl, 3- to 6-membered heterocyclic group, phenyl or pyridyl, provided that at least one of Rs is selected from C 1-6 alkoxy group.

[0015] In a preferred embodiment of the present invention, in L-R1, L is I;

[0016] R1 is phenyl or pyridyl substituted by one or two Rs;

[0017] Rs are selected from C 1-3 alkoxy group, C 1-3 alkyl, wherein the number of C 1-3 alkoxy groups is 1 or 2. For example, L-R1 is selected from the following compounds:

[0018]

[0019] In an embodiment of the present invention, the carborane is ortho (o) carborane (1,2-Carborane), meta (m) carborane (1,7-Carborane) or para (p) carborane (1,12-Carborane).

[0020] In an embodiment of the present invention, the inorganic base is an alkali metal carbonate or an alkali metal phosphate.

[0021] In an embodiment of the present invention, the alkali metal carbonate is selected from at least one of cesium carbonate, sodium carbonate and potassium carbonate.

[0022] In an embodiment of the present invention, the alkali metal phosphate is selected from potassium phosphate or sodium phosphate.

[0023] In an embodiment of the present invention, the inert gas is nitrogen or argon.

[0024] In an embodiment of the present invention, the carborane reacts with n-butyllithium at a temperature below 30 °C, for example, at a temperature of -10 °C to 30 °C.

[0025] In an embodiment of the present invention, the molar ratio of carborane to n-butyllithium is 1:(1 to 10), for example, 1:(2 to 5).

[0026] In an embodiment of the present invention, the ether solvent is selected from at least one of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, diethyl ether, 1,4-dioxane or tetrahydrofuran.

[0027] In an embodiment of the present invention, the reaction time of carborane with n-butyllithium is more than 1 hour, for example, 2-24 hours, such as 3-8 hours.

[0028] According to an embodiment of the present invention, the copper catalyst is selected from nano copper powder, copper chloride, cuprous iodide, cuprous chloride or cuprous bromide.

[0029] According to an embodiment of the present invention, the molar ratio of carborane, inorganic base and copper catalyst is 1:(0.01 - 1):(1 - 10), for example 1:(0.1 - 0.8):(2 - 5).

[0030] According to an embodiment of the present invention, the inorganic base and copper catalyst are added and reacted for more than 10 minutes, for example, reacted for 20 minutes to 120 minutes, such as 30 minutes to 60 minutes.

[0031] According to an embodiment of the present invention, the inorganic base and copper catalyst are added and reacted at 0 - 30°C.

[0032] According to an embodiment of the present invention, after adding pyridine, the reaction is carried out for more than 10 minutes, for example, reacted for 20 minutes to 120 minutes, such as 30 minutes to 60 minutes.

[0033] According to an embodiment of the present invention, after adding pyridine, the reaction is carried out at 0 - 30°C.

[0034] According to an embodiment of the present invention, the solvent used in the whole reaction process for preparing the carborane derivative as described above is the ether solvent used for carborane and n-butyllithium. Before adding the compound L-R1, or before adding the inorganic base and copper catalyst, or before adding pyridine until the carborane derivative is prepared after the reaction is completed, there is no need to remove the solvent. That is, the method of this application is a one-pot method for preparation.

[0035] According to an embodiment of the present invention, the molar ratio of carborane to the compound L-R1 is 1:(1 - 10), for example 1:(2 - 5). When the molar ratio is 1:1, a structure in which the carborane is mono-substituted by R1 can be obtained; when the molar ratio is 1:2 or more, a mainly double-substituted structure is obtained.

[0036] According to an embodiment of the present invention, the reaction of adding the compound L-R1 is carried out at 80°C to 120°C.

[0037] According to an embodiment of the present invention, the method further includes a reduction step, including hydrolyzing and reducing the substituent of Rs of the carborane derivative being an alkoxy group of C 1-12 to a hydroxyl group.

[0038] According to an embodiment of the present invention, the reduction step is carried out in the presence of boron tribromide or pyridinium hydrochloride.

[0039] As an example, the following method is used to prepare carborane derivatives: First, carborane is lithiated with n-butyllithium and reacted in an ethereal solvent under a nitrogen atmosphere to obtain dilithium carborane salt. After the reaction is completed, an alkali metal carbonate and a copper catalyst are added and reacted for a period of time, then pyridine is added and stirred for a period of time, and finally, carborane anisole is obtained through an Ullmann coupling reaction with haloanisole, and finally, carborane phenol is obtained by hydrolyzing and reducing anisole. Taking the synthesis of meta-carborane phenol as an example, the reaction equation is as follows (ortho- and para-carborane diols can also be synthesized by this method):

[0040]

[0041] Among them, the used haloanisole I-R-OCH3 is any one of the following:

[0042]

[0043] Advantages of the present invention

[0044] 1. The present invention improves the existing synthesis method of carborane derivatives and increases the yield. Taking the synthesis of 1,7-bis(4'-methoxyphenyl)carborane as an example, compared with the route proposed by Qi Shicheng et al., the yield of the synthesis route of the present discovery is 63%, while that of Qi Shicheng is 46%.

[0045] 2. The method of the present invention is an one-pot operation, and there is no need to change the solvent during the reaction process. Therefore, compared with the methods disclosed in the existing literature, the operation is simpler..

[0046] In summary, the preparation method of the present invention only requires one solvent to carry out the whole reaction, the operation is significantly simpler, and the cost is lower. More importantly, the method of the present invention significantly improves the yield of carborane derivatives and has certain application prospects. Brief description of the drawings

[0047] Figure 1 It is the gas chromatogram of the product HCB-1 obtained in Example 1 of the present invention.

[0048] Figure 2 It is the 1H nuclear magnetic resonance spectrum of the product HCB-1 obtained in Example 1 of the present invention.

[0049] Figure 3 It is the Fourier transform infrared spectrum of the products obtained in Comparative Example 1 (without adding modifier) and Example 5 (adding modifier) of the present invention.

[0050] Figure 4 It is the thermogravimetric curve of the phenolic resins prepared in Examples 5-9 and Comparative Example 1 of the present invention in a nitrogen atmosphere.

[0051] Figure 5It is the thermogravimetric curve of the phenolic resins prepared in Examples 5-9 and Comparative Example 1 of the present invention in an air atmosphere. Detailed implementation manners

[0052] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are only illustrative explanations of the present invention and should not be construed as limiting the protection scope of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0053] Unless otherwise specified, the raw materials and reagents used in the following examples are all commercially available products or can be prepared by known methods.

[0054] The test method for thermogravimetric (mass retention rate) is as follows:

[0055] The TGA test was performed using TGA 2 of Mettler Toledo. The sample mass was about 5 mg. The test conditions were a nitrogen atmosphere, 50-800 °C or an air atmosphere, 50-1000 °C. The gas flow rate was 50 mL / min for both, and the heating rate was 10 °C / min for both.

[0056] Example 1

[0057] Add 1.44 g of meta-carborane (10 mmol) into a dry 100 mL three-necked flask equipped with a reflux condenser, a constant pressure dropping funnel, and a mechanical stirrer paddle, and then add 16 mL of ethylene glycol dimethyl ether and stir to dissolve. Under nitrogen protection, take 9.2 mL of a n-butyllithium (22 mmol) hexane solution (2.4 M) and add it to the constant pressure dropping funnel. Place the flask in an ice-water bath and slowly dropwise add the n-butyllithium solution. After the addition, react at room temperature for 4 hours. Immerse the above flask in an ice-water bath, weigh 1 g of cesium carbonate (3 mmol) and 4.18 g of copper iodide (22 mmol) and add them to the flask, and react for half an hour. Then take 6 ml of pyridine and add it to the above flask, and react at room temperature for half an hour. Finally, add 5.15 g of 4-iodoanisole (22 mmol) and heat and react at 100 °C for 24 hours. After the reaction is completed and cooled to room temperature, add an appropriate amount of dichloromethane to precipitate impurities, filter by suction, and rotary evaporate to obtain a brown solid. Separate by column chromatography to obtain 2.25 g of white powder 1,7-bis(4'-methoxyphenyl)carborane. The yield is 63%, and the purity is 99%.

[0058] Take 1.78 g of 1,7-bis(4′-methoxyphenyl)carborane (5 mmol) in a 100 mL flask equipped with a constant pressure dropping funnel, add 30 mL of dichloromethane to dissolve it. Then take 11 mL of a dichloromethane solution (1 M) of boron tribromide (11 mmol) in the constant pressure dropping funnel. Place the flask in an ice-water bath and slowly add the boron tribromide solution dropwise. After the addition is complete, react at room temperature for 8 hours. Pour the liquid in the above flask into ice cubes, let it stand for 10 minutes, then extract with 3×20 mL of ethyl acetate. Let it stand for liquid separation, combine the organic layers, dry with anhydrous sodium sulfate, rotary evaporate and separate by column chromatography to obtain 1.38 g of white powder 1,7-bis(4′-hydroxyphenyl)carborane (HCB-1) with a yield of 84% and a purity of 99%. Calculated based on carborane, the total yield of the two-step reaction is 52.9%.

[0059] The NMR characterization of HCB-1 is as follows:

[0060]

[0061] 130.11, 126.59, 116.41, 79.85. 11 B NMR (128 MHz, DCON(CD3)2-d7) δ (ppm): -5.78, -10.53, -11.73, -13.10 HRMS(ESI-TOF): m / z calcd for C 14 H 20 B 10 O2[M + H] + 328.4154, found 328.4107.

[0062] Example 2

[0063] Add 1.44 g of m-carborane (10 mmol) into a dry 100 mL three-necked flask equipped with a reflux condenser, a constant pressure dropping funnel, and a mechanical stirring paddle, and then add 16 mL of ethylene glycol dimethyl ether and stir to dissolve. Under nitrogen protection, take 9.2 mL of a n-hexane solution (2.4 M) of n-butyllithium (22 mmol) and add it into the constant pressure dropping funnel. Place the flask in an ice-water bath and slowly add the n-butyllithium solution dropwise. After the addition is complete, react at room temperature for 4 hours. Immerse the above flask in an ice-water bath, weigh 1 g of cesium carbonate (3 mmol) and 4.18 g of copper(I) iodide (22 mmol) and add them into the flask, and react for half an hour. Then take 6 ml of pyridine and add it into the above flask, and react at room temperature for half an hour. Finally, add 5.46 g of 4-iodo-3-methylanisole (22 mmol), and heat and react at 100 °C for 24 hours. After the reaction is completed and cooled to room temperature, add an appropriate amount of dichloromethane to precipitate impurities, filter by suction, and rotary evaporate to obtain a brown solid. Separate by column chromatography to obtain 2.08 g of white powder 1,7-bis(2'-methyl-4'-methoxyphenyl)carborane. The yield is 54%, and the purity is 99%.

[0064] Take 1.92 g of 1,7-bis(2'-methyl-4'-methoxyphenyl)carborane (5 mmol) in a 100 mL flask equipped with a constant pressure dropping funnel, add 30 mL of dichloromethane to dissolve, and then take 11 mL of a dichloromethane solution (1 M) of boron tribromide (11 mmol) in the constant pressure dropping funnel. Place the flask in an ice-water bath and slowly add the boron tribromide solution dropwise. After the addition is complete, react at room temperature for 8 hours. Pour the liquid in the above flask into ice cubes, let it stand for 10 minutes, then take 3×20 mL of ethyl acetate for extraction, let it stand for liquid separation, combine the organic layers, dry with anhydrous sodium sulfate, rotary evaporate and separate by column chromatography to obtain 1.46 g of white powder 1,7-bis(2'-methyl-4'-hydroxyphenyl)carborane (HCB-2). The yield is 82%, and the purity is 99%. Calculated based on carborane, the total yield of the two-step reaction is 44.3%.

[0065] The NMR characterization of HCB-2 is as follows:

[0066]

[0067] (ppm): 159.95, 133.09, 128.01, 126.59, 118.41, 115.31, 76.15, 22.34. 11 B NMR (128 MHz, DCON(CD3)2-d7) δ (ppm): -5.58, -9.97, -11.3, -12.91 HRMS (ESI-TOF): m / z calcd for C 16 H 24 B 10 O2[M + H] +356.4726, found 356.4653.

[0068] Example 3

[0069] Add 1.44 g of m-carborane (10 mmol) into a dry 100 mL three-necked flask equipped with a reflux condenser, a constant pressure dropping funnel, and a mechanical stirring paddle, and then add 16 mL of ethylene glycol dimethyl ether and stir to dissolve. Under nitrogen protection, take 9.2 mL of a n-hexane solution (2.4 M) of n-butyllithium (22 mmol) and add it into the constant pressure dropping funnel. Place the flask in an ice-water bath and slowly add the n-butyllithium dropwise. After the addition is complete, react at room temperature for 4 hours. Immerse the above flask in an ice-water bath, weigh 1 g of cesium carbonate (3 mmol) and 4.18 g of copper(I) iodide (22 mmol) and add them into the flask, and react for half an hour. Then take 6 ml of pyridine and add it into the above flask, and react at room temperature for half an hour. Finally, add 5.46 g of 3-iodo-4-methylanisole (22 mmol), and heat and react at 100 °C for 24 hours. After the reaction is completed and cooled to room temperature, add an appropriate amount of dichloromethane to precipitate impurities, filter by suction, and rotary evaporate to obtain a brown solid. Separate by column chromatography to obtain 1.88 g of white powder 1,7-bis(2'-methyl-5'-methoxyphenyl)carborane. The yield is 49%, and the purity is 99%.

[0070] Take 1.54 g of 1,7-bis(2'-methyl-5'-methoxyphenyl)carborane (4 mmol) in a 100 mL flask equipped with a constant pressure dropping funnel, add 24 mL of dichloromethane to dissolve it, and then take 8.8 mL of a dichloromethane solution (1 M) of boron tribromide (8.8 mmol) in the constant pressure dropping funnel. Place the flask in an ice-water bath and slowly add the boron tribromide solution dropwise. After the addition is complete, react at room temperature for 8 hours. Pour the liquid in the above flask into ice cubes, let it stand for 10 minutes, then extract with 3 × 20 mL of ethyl acetate, let it stand for liquid separation, combine the organic layers, dry over anhydrous sodium sulfate, rotary evaporate and separate by column chromatography to obtain 1.2 g of white powder 1,7-bis(2'-methyl-5'-hydroxyphenyl)carborane (HCB-3). The yield is 84%, and the purity is 99%. Calculated based on carborane, the total yield of the two-step reaction is 41.2%.

[0071] The NMR characterization of HCB-3 is as follows:

[0072]

[0073] MHz, DCON(CD3)2-d7) δ (ppm):, 156.80, 135.17, 131.81, 129.34, 118.55, 110.34, 77.51. 1111B NMR (128 MHz, DCON(CD3)2-d7) δ (ppm): -5.81, -10.27 - 11.45, -13.21. HRMS (ESI-TOF): m / z calcd for C 16 H 24 B 10 O2[M + H] + 356.4726, found 356.4689.

[0074] Example 4

[0075] Add 1.44 g of m-carborane (10 mmol) into a dry 100 mL three-necked flask equipped with a reflux condenser, a constant-pressure dropping funnel, and a mechanical stirrer paddle, and then add 16 mL of ethylene glycol dimethyl ether and stir to dissolve. Under nitrogen protection, take 9.2 mL of a hexane solution (2.4 M) of n-butyllithium (22 mmol) and add it into the constant-pressure dropping funnel. Place the flask in an ice-water bath, slowly add the n-butyllithium dropwise, and react at room temperature for 4 hours after the addition is complete. Immerse the above flask in an ice-water bath, weigh 1 g of cesium carbonate (3 mmol) and 4.18 g of copper(I) iodide (22 mmol) and add them into the flask, and react for half an hour. Then take 6 ml of pyridine and add it into the above flask, and react at room temperature for half an hour. Finally, add 5.81 g of 3,5-dimethoxyphenyl iodide (22 mmol), and heat and react at 100 °C for 24 hours. After the reaction is completed and cooled to room temperature, add an appropriate amount of dichloromethane to precipitate impurities, filter by suction, and rotary evaporate to obtain a brown solid. Separate by column chromatography to obtain 2.5 g of white powder 1,7-bis(3′,5′-dimethoxyphenyl)carborane. The yield is 60%, and the purity is 99%.

[0076] Take 2.08 g of 1,7-bis(3′,5′-dimethoxyphenyl)carborane (5 mmol) in a 100 mL flask equipped with a constant-pressure dropping funnel, add 30 mL of dichloromethane to dissolve it, and then take 22 mL of a dichloromethane solution (1 M) of boron tribromide (22 mmol) in the constant-pressure dropping funnel. Place the flask in an ice-water bath, slowly add the boron tribromide solution dropwise, and react at room temperature for 8 hours after the addition is complete. Pour the liquid in the above flask into ice cubes, let it stand for 10 minutes, then extract with 3 × 20 mL of ethyl acetate, let it stand for liquid separation, combine the organic layers, dry with anhydrous sodium sulfate, rotary evaporate and separate by column chromatography to obtain 1.46 g of white powder 1,7-bis(3′,5′-hydroxyphenyl)carborane (HCB-4) with a yield of 81%. Calculated based on carborane, the total yield of the two-step reaction is 48.6%.

[0077] The NMR characterization of HCB-4 is as follows:

[0078] 135.52, 109.61, 102.48, 76.38. 1111B NMR (128 MHz, DCON(CD3)2-d7) δ (ppm): -5.51, -10.17, -11.25, -13.27. HRMS (ESI-TOF): m / z calcd for C 14 H 20 B 10 O4[M + H] + 360.4124, found 360.4101.

[0079] Example 5

[0080] Add 4 g of 2402# thermoplastic phenolic resin and 200 mg of HCB-1 into a 20 ml beaker. Add 5 ml of absolute ethanol and stir to dissolve to obtain a light yellow viscous liquid. Then add 1 g of curing agent hexamethylenetetramine and stir to dissolve. Heat and stir at 80 °C to evaporate the solvent completely. Place the sample in an oven and cure it according to the following heating program: 135 °C / 2 h + 150 °C / 2 h + 170 °C / 2 h + 215 °C / 2 h + 240 °C / 10 min + 260 °C / 5 min. A transparent dark brown flaky solid is obtained.

[0081] The infrared spectrum of the cured product is as Figure 3 shown in Curve B. The stretching vibration of the C-H bond on the benzene ring is at 3012.32, the stretching vibration absorption peak of the B-H bond on the carborane cage is at 2598.59, the absorption peaks of the benzene ring skeleton vibration are at 1593.31 - 1440.14, the stretching vibration absorption peaks of the C-O bond are at 1235.92 and 1096.83, and the out-of-plane vibration absorption peaks of the C-H bond on the benzene ring are at 813.38 and 753.52.

[0082] The mass retention rate of the cured product under a nitrogen atmosphere at 800 °C is 61.92% ( Figure 4 Curve D1 in). The mass retention rate under an air atmosphere at 1000 °C is 15.52% ( Figure 5 Curve D2 in). It shows that introducing a small amount (5 parts) of HCB-1 can significantly improve the high-temperature resistance of the resin under an air atmosphere. The residue weight of the blank sample reduces to zero at 780 °C under an air atmosphere.

[0083] Example 6

[0084] Add 4 g of 2402# thermoplastic phenolic resin and 400 mg of HCB-1 into a 20-ml beaker. Add 5 ml of absolute ethanol and stir to dissolve, obtaining a light yellow viscous liquid. Then add 1 g of curing agent hexamethylenetetramine and stir to dissolve. After that, heat and stir at 80 °C to volatilize the solvent completely. Place the sample in an oven and cure it according to the following temperature-rising program: 135 °C / 2 h + 150 °C / 2 h + 170 °C / 2 h + 215 °C / 2 h + 240 °C / 10 min + 260 °C / 5 min. A transparent dark brown flaky solid is obtained.

[0085] The mass retention rate of this cured product is 64.90% at 800 °C under a nitrogen atmosphere ( Figure 4 curve E1 in). The mass retention rate is 42.57% at 1000 °C under an air atmosphere ( Figure 5 curve E2 in). It shows that introducing 10 parts of HCB-1 can further improve the high-temperature resistance of the resin. Compared with Example 5, although only 5 more parts are introduced, the residual weight increases by 30%.

[0086] Example 7

[0087] Add 4 g of 2402# thermoplastic phenolic resin and 600 mg of HCB-1 into a 20-ml beaker. Add 5 ml of absolute ethanol and stir to dissolve, obtaining a light yellow viscous liquid. Then add 1 g of curing agent hexamethylenetetramine and stir to dissolve. After that, heat and stir at 80 °C to volatilize the solvent completely. Place the sample in an oven and cure it according to the following temperature-rising program: 135 °C / 2 h + 150 °C / 2 h + 170 °C / 2 h + 215 °C / 2 h + 240 °C / 10 min + 260 °C / 5 min. A transparent dark brown flaky solid is obtained.

[0088] The mass retention rate of this cured product is 68.38% at 800 °C under a nitrogen atmosphere ( Figure 4 curve F1 in). The mass retention rate is 50.82% at 1000 °C under an air atmosphere ( Figure 5 curve F2 in). It shows that although the residual weight still increases (about 8%) when introducing 15 parts of HCB-1, the effect is not obvious.

[0089] Example 8

[0090] Add 4 g of 2402# thermoplastic phenolic resin and 800 mg of HCB-1 into a 20-ml beaker. Add 5 ml of absolute ethanol and stir to dissolve, obtaining a light yellow viscous liquid. Then add 1 g of curing agent hexamethylenetetramine and stir to dissolve. After that, heat and stir at 80 °C to volatilize the solvent completely. Place the sample in an oven and cure it according to the following temperature-rising program: 135 °C / 2 h + 150 °C / 2 h + 170 °C / 2 h + 215 °C / 2 h + 240 °C / 10 min + 260 °C / 5 min. A transparent dark brown flaky solid is obtained.

[0091] The mass retention rate of this cured product is 69.73% at 800 °C under a nitrogen atmosphere ( Figure 4 curve G1 in Figure 5 ). The mass retention rate is 64.31% at 1000 °C under an air atmosphere (

[0092] Example 9

[0093] Add 4 g of 2402# thermoplastic phenolic resin and 1000 mg of HCB-1 into a 20 ml beaker, add 5 ml of absolute ethanol and stir to dissolve to obtain a light yellow viscous liquid. Then add 1 g of curing agent hexamethylenetetramine, stir to dissolve, heat and stir at 80 °C to evaporate the solvent completely. Place the sample in an oven and cure it according to the following temperature rising program: 135 °C / 2 h + 150 °C / 2 h + 170 °C / 2 h + 215 °C / 2 h + 240 °C / 10 min + 260 °C / 5 min. A transparent dark brown flaky solid is obtained.

[0094] The mass retention rate of this cured product is 78.13% at 800 °C under a nitrogen atmosphere ( Figure 4 curve H1 in Figure 5 ). The mass retention rate becomes 64.65% at 1000 °C under an air atmosphere (

[0095] Comparative Example 1

[0096] Add 4 g of 2402# thermoplastic phenolic resin into a 20 ml beaker, add 5 ml of absolute ethanol and stir to dissolve to obtain a light yellow viscous liquid. Then add 1 g of curing agent hexamethylenetetramine, stir to dissolve, heat and stir at 80 °C to evaporate the solvent completely. Place the sample in an oven and cure it according to the following temperature rising program: 135 °C / 2 h + 150 °C / 2 h + 170 °C / 2 h + 215 °C / 2 h + 240 °C / 10 min + 260 °C / 5 min. A transparent dark brown flaky solid is obtained.

[0097] The infrared spectrum of this cured product is as Figure 3 shown in curve A. The stretching vibration of the C-H bond on the benzene ring is at 3012.32, the absorption peaks of the benzene ring skeleton vibration are at 1593.31 - 1440.14, the stretching vibration absorption peaks of the C-O bond are at 1235.92 and 1096.83, and the out-of-plane vibration absorption peaks of the C-H bond on the benzene ring are at 813.38 and 753.52.

[0098] The mass retention rate of this cured product is 54.61% at 800 °C under a nitrogen atmosphere ( Figure 4 curve C1 in Figure 5Therefore, compared with the cured product prepared without using HCB-1 in Comparative Example 1, the cured product prepared using HCB-1 in this application significantly improves the heat resistance of 2402# phenolic resin.

[0099] Comparative Example 2

[0100] Referring to the synthesis method of 1,7-bis(4-methoxyphenyl)-m-carborane (2) in Section 1.3 of Qi Shicheng et al., "Synthesis and Properties of Carborane Phenolic Resins" [J]. Journal of Aeronautical Materials, 2014, 34(01): 46-51, the difference is that the reaction time is adjusted to 24 hours. The purity of the obtained product is 99%, and the yield is 46%.

[0101] Comparative Example 3

[0102] Referring to the preparation method of Example 1, the difference is that THF is used as the solvent. The purity of the obtained product is 99%, and the yield is 21%.

[0103] Comparative Example 4

[0104] Referring to the preparation method of Example 1, the difference is that cesium carbonate is not used. The purity of the obtained product is 99%, and the yield is 46%.

[0105] The above describes the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of a carborane derivative, characterized in that, Comprising: First, react carborane with n-butyllithium in an ethereal solvent under an inert gas atmosphere. After the reaction is completed, add an inorganic base and a copper catalyst and react for a period of time, then add pyridine and stir for a period of time, and finally add compound L-R1 and heat to react to obtain a derivative in which one or two hydrogens on the carbon of carborane are replaced by R1; In L-R1, L is a halogen and R1 is a C substituted by one, two or more Rs 6-12 aryl or 5- to 12-membered heteroaryl; Rs are selected from C 1-12 alkoxy, C 1-12 alkyl, C 3-12 cycloalkyl, 3- to 12-membered heterocyclic group, C 6-12 aryl or 5- to 12-membered heteroaryl, provided that at least one of the Rs is selected from C 1-12 alkoxy.

2. The preparation method according to claim 1, wherein In L-R1, L is I; R1 is a phenyl or pyridyl group substituted by one, two or more Rs; Rs is selected from C 1-6 alkoxy, C 1-6 alkyl, C 3-6 cycloalkyl, 3- to 6-membered heterocyclic group, phenyl or pyridyl, provided that at least one Rs is selected from C 1-6 alkoxy.

3. The preparation method according to claim 1 or 2, characterized in that In L-R1, L is I; R1 is a phenyl or pyridyl group substituted by one or two Rs; Rs is selected from C 1-3 alkoxy, C 1-3 alkyl, wherein the number of C 1-3 alkoxy is 1 or 2.

4. The preparation method according to claim 3, characterized in that, L-R1 is selected from the following compounds: Preferably, the carborane is ortho (o) -carborane (1,2-Carborane), meta (m) -carborane (1,7-Carborane) or para (p) -carborane (1,12-Carborane).

5. The preparation method according to any one of claims 1-4, characterized in that, The inorganic base is an alkali metal carbonate or an alkali metal phosphate; Preferably, the alkali metal carbonate is selected from at least one of cesium carbonate, sodium carbonate, and potassium carbonate; Preferably, the alkali metal phosphate is selected from potassium phosphate or sodium phosphate.

6. The preparation method according to any one of claims 1-5, characterized in that, The inert gas is nitrogen or argon; Preferably, the reaction of carborane with n-butyllithium is carried out below 30 °C; Preferably, the molar ratio of carborane to n-butyllithium is 1:(1-10); Preferably, the ethereal solvent is selected from at least one of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, diethyl ether, 1,4-dioxane or tetrahydrofuran; Preferably, the reaction time of carborane with n-butyllithium is more than 1 hour; Preferably, the copper catalyst is selected from nano copper powder, copper chloride, cuprous iodide, cuprous chloride or cuprous bromide; Preferably, the molar ratio of carborane, inorganic base and copper catalyst is 1:(0.01-1):(1-10); Preferably, the reaction of adding the inorganic base and the copper catalyst is carried out for more than 10 minutes; Preferably, the reaction of adding the inorganic base and the copper catalyst is carried out at 0-30 °C; Preferably, the reaction after adding pyridine is carried out for more than 10 minutes; Preferably, the reaction of adding pyridine is carried out at 0-30 °C.

7. The preparation method according to any one of claims 1-6, characterized in that, The solvent used in the whole reaction process for preparing the carborane derivative is the ethereal solvent used for carborane and n-butyllithium. Before adding compound L-R1, or before adding the inorganic base and the copper catalyst, or before adding pyridine until the reaction is completed to prepare the carborane derivative, there is no need to remove the solvent.

8. The preparation method according to any one of claims 1 to 7, characterized in that, The molar ratio of carborane to compound L-R1 is 1:(1-10).

9. The preparation method according to any one of claims 1-8, characterized in that, The reaction of adding compound L-R1 is carried out at 80 °C to 120 °C.

10. The preparation method according to any one of claims 1-9, characterized in that, The method further includes a reduction step, including hydrolyzing and reducing the substituent of Rs being C 1-12 alkoxy of the carborane derivative to a hydroxyl group; Preferably, the reduction step is carried out in the presence of boron tribromide or pyridinium hydrochloride.

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