Preparation method of 1-bromo-4-methylnaphthalene

Abstract

The invention belongs to the technical field of organic synthesis, and particularly relates to a preparation method of 1-bromo-4-methylnaphthalene. The preparation method comprises the following steps: taking 1-methylnaphthalene as a reaction raw material, and reacting in an organic solvent under the action of hydrobromic acid and hydrogen peroxide to obtain 1-bromo-4-methylnaphthalene. The preparation method is simple in process route, easily available in raw materials, mild in reaction condition, convenient to operate, high in bromination selectivity and suitable for large-scale industrial production, and the byproduct is only water, and accords with atom economy, and the harm to the environment is small.

Description

Technical Field

[0001] The invention belongs to the technical field of organic synthesis, and specifically relates to a method for preparing 1-bromo-4-methylnaphthalene. Background Art

[0002] 1,4-Dimethylnaphthalene (CAS: 571-58-4) is a high value-added fine chemical, mainly used in the fields of plant growth inhibitors and fluorescent whitening agents.

[0003] CN 113004110 A and CN 107266282 A respectively disclose a method for preparing 1,4-dimethylnaphthalene by Grignard reaction using 1-bromo-4-methylnaphthalene (i.e. 4-bromomethylnaphthalene) or 1,4-dibromonaphthalene as a reaction raw material. The method has a short synthesis route, mild reaction conditions, low cost, and high industrial application prospects. As a key intermediate for the synthesis of 1,4-dimethylnaphthalene, it is very urgent to develop an industrial synthesis route for 1-bromo-4-methylnaphthalene.

[0004] At present, there are two main methods for synthesizing 1-bromo-4-methylnaphthalene (CAS: 6627-78-7) using 1-methylnaphthalene (CAS: 90-12-0) as a reaction raw material:

[0005] One type is composed of bromine (Br 2 ) as a bromine source, the contents disclosed in the literature are as follows:

[0006] 1) C.Ge et al. (see Carbon (2015), 95:780) disclosed that bromine was used as a bromine source under visible light irradiation to bromine 1-methylnaphthalene in the form of bromine free radicals;

[0007] 2) H. Maeda et al. (see Photochemical & Photobiological Sciences (2016), 15:1385 and Journal of Organic Chemistry (2016), 81:8544) disclosed that bromine was used as a bromine source and carbon tetrachloride was used as a solvent under the conditions of iron / iodine catalysis to carry out bromination of 1-methylnaphthalene with a yield of up to 94%;

[0008] 3) L. Pan et al. (see Organic Letters (2023), 25(1):53-57) disclosed the bromination of 1-methylnaphthalene using boron tribromide as a bromine source and dichloromethane as a solvent in the presence of iodophenyldiacetic acid. In this reaction system, the yield of the target product can reach 88%.

[0009] The other type uses N-bromosuccinimide (NBS) as a bromine source, and the contents disclosed in the literature are as follows:

[0010] 1) H. Togo et al. (see Synlett (2003), 5:702-704) disclosed that N-bromosuccinimide was used as a bromine source, and the bromination product of 1-methylnaphthalene was obtained by reaction at 90°C for 1 h under the catalysis of dibenzoyl peroxide, with a yield of 73%. 1-Butyl-3-methylimidazolium hexafluorophosphate played an important role as an ionic liquid solvent in the reaction, and the methyl bromide byproduct was 3%;

[0011] 2) GA Heropoulos et al. (see Tetrahedron Letters (2007), 48: 3247-3250) disclosed that N-bromosuccinimide was used as a bromine source, water was used as a solvent, and the reaction was carried out at 90°C for 40 minutes under ultrasound to obtain the brominated product of 1-methylnaphthalene with a yield of up to 94%;

[0012] 3) Ruan Libo et al. (see Acta Chimica Sinica (2010), 68(7):713-716) disclosed the preparation of 1-bromo-4-methylnaphthalene by refluxing with N-bromosuccinimide as bromine source and acetonitrile as solvent under the catalysis of phosphoric acid and zirconium hydroxide, with a yield of up to 95%;

[0013] 4) CN 105906530 A discloses that N-bromosuccinimide is used as a bromine source and dimethyl sulfoxide is used as a solvent, and the reaction is heated at 90° C. for 10 h to obtain a brominated product of 1-methylnaphthalene with a yield of up to 88%;

[0014] 5) R.-J. Tang et al. (see Journal of Organic Chemistry (2018), 83(2):930-938) disclosed that N-bromosuccinimide was used as a bromine source and hexafluoroisopropanol was used as a solvent to obtain the brominated product of 1-methylnaphthalene at room temperature for 8 hours with a yield of up to 94%;

[0015] 6) S. Ni et al. (see Advanced Synthesis & Catalysis (2018), 360(21): 4197-4204) disclosed that N-bromosuccinimide was used as a bromine source, acetonitrile was used as a solvent, and trityl tetrafluoroborate was used as a catalyst. The reaction was carried out at room temperature for 2 hours to obtain the brominated product of 1-methylnaphthalene with a yield of up to 92%;

[0016] 7) W. Cai et al. (see Molecules (2018), 23(2): 252), CN 106366018 B, CN 113861178A, CN 110128359B and WO 2019149090A1 respectively disclosed the use of N-bromosuccinimide as a bromine source and acetonitrile as a solvent at 30-40° C. to prepare 1-bromo-4-methylnaphthalene with a yield of up to 99%.

[0017] In addition, M. Kodomari et al. (see Journal of Organic Chemistry (1988), 53(9): 2093-2094) and X. Liang et al. (see Asian Journal of Organic Chemistry (2017), 6(8): 1063) respectively disclosed the use of aluminum-based copper bromide as a bromine source, carbon tetrachloride as a solvent, and a reaction at 50° C. for 2 h to obtain a brominated product of 1-methylnaphthalene with a yield of up to 100%; S. Kajigaeshi et al. (see Bulletin of the Chemical Society of Japan (1989), 62(2): 439-443) disclosed the use of benzyltrimethylammonium tribromide as a bromine source, zinc chloride as a catalyst, and a reaction in the presence of acetic acid to obtain a brominated product of 1-methylnaphthalene with a yield of up to 99%.

[0018] In summary, although some existing 1-bromo-4-methylnaphthalene synthesis methods have high yields, they also have problems that are difficult to process for production: for example, the harm of bromine is relatively large, it is not suitable for large-scale industrial production, the bromination reagent is expensive, the reaction atom economy is poor, the reaction equipment requirements are high, the reaction conditions are not mild enough, and the amount of reaction reagents used is large. Therefore, it is particularly important to develop a low-cost, easy-to-operate, environmentally friendly, and industrializable 1-bromo-4-methylnaphthalene synthesis route. Summary of the invention

[0019] Problem that the invention aims to solve

[0020] The purpose of the present invention is to provide an improved method for preparing 1-bromo-4-methylnaphthalene, so as to solve the technical problems existing in the prior art that the bromination reagent is expensive, the reaction atom economy is poor, the operation process is complicated, and it is not suitable for industrial production.

[0021] Solutions for solving problems

[0022] The present invention provides a method for preparing 1-bromo-4-methylnaphthalene, which comprises the following steps:

[0023]

[0024] 1-Methylnaphthalene is used as a reaction raw material, and reacts in an organic solvent under the action of hydrobromic acid and hydrogen peroxide to obtain 1-bromo-4-methylnaphthalene.

[0025] Preferably, the organic solvent is a polar solvent or a non-polar solvent, preferably a non-polar solvent.

[0026] Preferably, the polar solvent is selected from ethanol, acetonitrile, ethyl acetate and tetrahydrofuran, preferably tetrahydrofuran and acetonitrile, more preferably acetonitrile.

[0027] Preferably, the non-polar solvent is selected from dichloromethane and 1,2-dichloroethane, preferably 1,2-dichloroethane.

[0028] Preferably, the usage ratio of the organic solvent to the 1-methylnaphthalene is 1-10 mL:1 g, preferably 3-7 mL:1 g, more preferably 5 mL:1 g.

[0029] Preferably, the concentration of hydrogen bromide in the hydrobromic acid is 48 wt %.

[0030] Preferably, the molar ratio of hydrogen bromide in the hydrobromic acid to the 1-methylnaphthalene is 0.95:1 to 1.25:1, preferably 1.05:1 to 1.25:1, and more preferably 1.05:1 to 1.15:1.

[0031] Preferably, the concentration of hydrogen peroxide in the hydrogen peroxide is 30 wt %.

[0032] Preferably, the molar ratio of hydrogen peroxide to 1-methylnaphthalene in the hydrogen peroxide is 0.9:1 to 3:1, preferably 1.1:1 to 3:1, and more preferably 1.3:1 to 3:1.

[0033] Preferably, the reaction temperature is -20 to 25°C, preferably -10 to 25°C, more preferably 0 to 10°C.

[0034] Preferably, the preparation method further comprises the following post-treatment steps: quenching reaction, phase separation, desolventizing under reduced pressure and distillation.

[0035] More preferably, the reagent for quenching the reaction is a 10 wt % sodium sulfite aqueous solution.

[0036] More preferably, the distillation pressure is 80Pa-90Pa.

[0037] More preferably, the distillation temperature is 95-100°C.

[0038] Effects of the Invention

[0039] The invention improves the bromination method of 1-methylnaphthalene. The selected hydrogen peroxide and hydrobromic acid are easy to obtain raw materials, and the reaction conditions are mild, thereby avoiding the harm caused by the use of bromine in industrial production and reducing the production cost. The obtained product has high purity and the yield reaches 96%.

[0040] The invention provides a method for preparing 1-bromo-4-methylnaphthalene. The method has a simple process route, is easy to operate, has high bromination selectivity, has only water as a byproduct, conforms to atom economy, has little harm to the environment, and is suitable for industrial production. DETAILED DESCRIPTION

[0041] The embodiments of the present invention are described in detail below in conjunction with the examples, but it will be appreciated by those skilled in the art that the following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. Where specific conditions are not specified in the examples, they are carried out according to conventional conditions or conditions recommended by the manufacturer.

[0042] The abbreviations and symbols used in this invention have the following meanings:

[0043] abbreviation meaning THF Tetrahydrofuran DCM Dichloromethane DCE 1,2-Dichloroethane HBr Hydrogen bromide <![CDATA[H 2 THE 2 ]]> Hydrogen Peroxide GC Gas chromatography

[0044] Embodiment 1:

[0045] Take a 500mL three-necked flask, add 30.0g 1-methylnaphthalene (142.20g / mol, 1eq), 150mL acetonitrile and 37.3g 48wt% HBr aqueous solution (in terms of HBr, 80.91g / mol, 1.05eq) in sequence under stirring, wait for the system to cool to 0℃, use a separatory funnel to slowly add 71.8g 30wt% H 2 O 2 Aqueous solution (H 2 O 2 After 1.5 hours of dropwise addition, the mixture was reacted at 0°C for 2 hours, and the reaction was detected to be complete. After the reaction was completed, the GC relative content of the product was detected to be 90.6%. 100g of 10wt% sodium sulfite aqueous solution was used to quench the reaction, and the phases were separated. The organic phase was decompressed and desolventized to obtain a crude 1-bromo-4-methylnaphthalene product. 43.4g of the product was distilled out at 80Pa-90Pa, 95-100°C, with a GC absolute content of 96.7% and a yield of 90%.

[0046] Embodiment 2-6:

[0047] According to the method in Example 1, the reaction was carried out for 2 hours after the dropwise addition was completed. The ratio of 1-methylnaphthalene to the solvent was 1 g:5 mL. The type of solvent was changed. The reaction conditions and results are listed in Table 1 below.

[0048] Table 1

[0049]

[0050] The results in Table 1 show that for 6 different organic solvents, the GC relative content of the target product 1-bromo-4-methylnaphthalene can reach more than 45%, which meets the most basic requirements; when acetonitrile, tetrahydrofuran, dichloromethane and 1,2-dichloroethane are used as solvents, the GC relative content of the target product 1-bromo-4-methylnaphthalene is relatively high (up to more than 85%), and the result is relatively ideal; and compared with polar solvents (acetonitrile and tetrahydrofuran), the GC relative content of 1-bromo-4-methylnaphthalene corresponding to non-polar solvents (dichloromethane and 1,2-dichloroethane) is higher: Among them, when 1,2-dichloroethane is used as the solvent in the reaction system, the GC relative content of the target product 1-bromo-4-methylnaphthalene is the highest. Therefore, 1,2-dichloroethane is preferably used as the solvent in the reaction system.

[0051] Embodiment 7-13:

[0052] According to the method in Example 6, after the addition was completed, the reaction was continued for 2 h, and the HBr and H 2 O 2 The dosage, reaction conditions and results are listed in Table 2 below.

[0053] Table 2

[0054]

[0055] The results in Table 2 show that, by comparing Examples 6 to 10, it is found that when the H 2 O 2 When the dosage is less than 1 eq, the GC relative content of the target product 1-bromo-4-methylnaphthalene is low (less than 90%). 2 O 2 The GC relative content of the target product 1-bromo-4-methylnaphthalene gradually increased with the increase of H 2 O 2 When the dosage is 1.3eq-3eq, the GC relative content of the target product 1-bromo-4-methylnaphthalene has no obvious change. Therefore, from the perspective of saving materials, the H 2 O 2 The preferred amount is 1.3 eq.

[0056] In addition, by comparing Example 9 with Examples 11 to 13, it was found that when the amount of HBr in the reaction system was less than 1 eq, the GC relative content of the target product 1-bromo-4-methylnaphthalene was low (less than 85%). As the amount of HBr increased to 1.05 eq, the GC relative content of the target product 1-bromo-4-methylnaphthalene increased significantly. However, when the amount of HBr further increased from 1.15 eq to 1.25 eq, the GC relative content of the target product 1-bromo-4-methylnaphthalene decreased. Therefore, the amount of HBr in the bromination reaction system is preferably 1.05 eq.

[0057] Embodiment 14-17:

[0058] According to the method in Example 9, the reaction was carried out for 2 hours after the dropwise addition was completed, and the reaction temperature was changed. The reaction conditions and results are listed in Table 3 below.

[0059] Table 3

[0060]

[0061] The result of Table 3 shows that when the reaction temperature is 0 ℃, the GC relative content of the target product 1-bromo-4-methylnaphthalene is the highest (can reach more than 95%). Taking 0 ℃ as a benchmark, no matter along with the rising or reducing of the reaction temperature, the GC relative content of the obtained target product 1-bromo-4-methylnaphthalene all has various degrees of decline; In the temperature range of -10~25 ℃, the GC relative content of 1-bromo-4-methylnaphthalene can reach more than 85%, and in the temperature range of 0~10 ℃, the GC relative content of 1-bromo-4-methylnaphthalene can reach more than 90%, and the result is relatively ideal. Therefore, preferably carry out bromination reaction at 0 ℃.

[0062] Embodiment 18:

[0063] This is an enlarged experiment of Example 9, and the amount used is 10 times that of Example 9.

[0064] Take a 5000mL three-necked flask, add 300.0g 1-methylnaphthalene, 1500mL 1,2-dichloroethane and 373.4g 48wt% HBr in sequence under stirring, wait for the system to cool to 0℃, and use a separatory funnel to slowly add 310.9g 30wt% HBr. 2 O 2 . After 1.5h of dropwise addition, the mixture was reacted at 0℃ for 2h, and the reaction was detected to be complete. After the reaction was completed, the GC relative content of the product was detected to be 96.8%. 1000g of 10wt% sodium sulfite aqueous solution was used to quench the reaction, and the phases were separated. The organic phase was decompressed and desolventized to obtain a crude 1-bromo-4-methylnaphthalene product. 459.8g of the product was distilled out at 80Pa-90 Pa and 95-100℃, with a GC absolute content of 98% and a yield of 96.6%.

[0065] The yield is calculated according to the following formula:

[0066]

[0067] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or technical improvements in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A method for preparing 1-bromo-4-methylnaphthalene, comprising the following steps: using 1-methylnaphthalene as a reaction raw material, reacting in an organic solvent under the action of hydrobromic acid and hydrogen peroxide to obtain 1-bromo-4-methylnaphthalene.

2. The preparation method according to claim 1, characterized in that: The organic solvent is a polar solvent or a non-polar solvent, preferably a non-polar solvent.

3. The preparation method according to claim 2, characterized in that: The polar solvent is selected from ethanol, acetonitrile, ethyl acetate and tetrahydrofuran, preferably tetrahydrofuran and acetonitrile, more preferably acetonitrile.

4. The preparation method according to claim 2, characterized in that: The non-polar solvent is selected from dichloromethane and 1,2-dichloroethane, preferably 1,2-dichloroethane.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The molar ratio of hydrogen bromide in the hydrobromic acid to the 1-methylnaphthalene is 0.95:1 to 1.25:1, preferably 1.05:1 to 1.25:1, and more preferably 1.05:1 to 1.15:

1.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The molar ratio of hydrogen peroxide to 1-methylnaphthalene in the hydrogen peroxide is 0.9:1 to 3:1, preferably 1.1:1 to 3:1, and more preferably 1.3:1 to 3:

1.

7. The preparation method according to any one of claims 1 to 6, characterized in that The reaction temperature is -20 to 25°C, preferably -10 to 25°C, more preferably 0 to 10°C.

8. The preparation method according to any one of claims 1 to 7, characterized in that: The preparation method further comprises the following post-processing steps: quenching reaction, phase separation, desolventizing under reduced pressure and distilling.

9. The preparation method according to claim 8, characterized in that: The reagent for quenching the reaction is a 10 wt % sodium sulfite aqueous solution.

10. The preparation method according to claim 8 or 9, characterized in that: The distillation pressure is 80Pa-90Pa; and / or, The distillation temperature is 95-100°C.

Images