Preparation method of 1-chloro-4-methylnaphthalene

Abstract

The invention belongs to the technical field of organic synthesis, and particularly relates to a preparation method of 1-chloro-4-methylnaphthalene. The preparation method comprises the following steps: reacting 1-methylnaphthalene serving as a reaction raw material in an organic solvent under the action of hypochlorous acid or salt and acid of hypochlorous acid to obtain 1-chloro-4-methylnaphthalene. The preparation method is mild in reaction condition, simple to operate, high in chlorination selectivity, high in product yield, low in cost and suitable for industrial production.

Description

Technical Field

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

[0002] 1,4-Dimethylnaphthalene is mainly used in the fields of plant growth inhibitors and fluorescent whitening agents, and is a high value-added fine chemical. Naturally derived 1,4-dimethylnaphthalene mainly exists in petroleum / coal tar, but the content is not high. Therefore, it is difficult and uneconomical to separate and extract single 1,4-dimethylnaphthalene from petroleum / coal tar. In order to meet market demand, 1,4-dimethylnaphthalene can only be obtained by chemical synthesis.

[0003] At present, there are two main strategies for synthesizing 1,4-dimethylnaphthalene (CAS: 571-58-4): one is to obtain 1,4-dimethylnaphthalene by alkylation of naphthalene or methylnaphthalene, and the other is mainly to obtain 1,4-dimethylnaphthalene by multi-step chemical reactions of benzene and its derivatives. The former is a Friedel-Crafts reaction with only one unit reaction. Because the reaction is relatively simple, it is widely used in industry. However, there are many reaction sites on naphthalene or methylnaphthalene, and the reaction activity of each site is not much different. There are many alkylated products generated after the reaction, and a complex separation process is required to obtain 1,4-dimethylnaphthalene with higher purity. Although the multi-step method in the latter is technically feasible, the reaction route is long, some steps require anhydrous conditions, and the specifications of the chemicals used are high. Some reaction products also require silica gel column chromatography during purification, which leads to excessively high production costs of 1,4-dimethylnaphthalene, so it has no industrial value.

[0004] 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-dihalonaphthalene as raw materials. The method has a short synthetic route, mild reaction conditions, low cost, and high industrial application prospects. As a key intermediate for synthesizing 1,4-dimethylnaphthalene, it is very urgent to develop an industrial synthetic route for 1-halogenated-4-methylnaphthalene (mainly including 1-chloro-4-methylnaphthalene and 1-bromo-4-methylnaphthalene).

[0005] At present, about the preparation method of 1-chloro-4-methylnaphthalene (CAS:17075-39-7), the content disclosed in the literature is as follows:

[0006] 1) M. Hasebe et al. (see Tetrahedron Letters (1981), 22 (51): 5149-5152) and M. Kodomari et al. (see Journal of Organic Chemistry (1988), 53: 2093-2094) respectively disclosed the chlorination of 1-methylnaphthalene (CAS: 90-12-0) using ferric chloride or cupric chloride as a chlorine source in the presence of aluminum oxide, with a yield of up to 100%, but the reaction requires a measured amount of heavy metal;

[0007] 2) S. Kajigaeshi et al. (see Bulletin of the Chemical Society of Japan (1989), 62(6): 2096-2098) disclosed the use of benzyltrimethylammonium tetrachloroiodate as a chlorine source in the presence of acetic acid to chlorinate 1-methylnaphthalene. In this reaction system, the yield of the target product can reach 73%. However, the chlorine source used in the reaction is expensive and the atom economy is poor.

[0008] 3) M. Bucos et al. (see Tetrahedron (2010), 66(11): 2061-2065) disclosed the use of N-chlorosuccinimide and barium chloride as chlorine sources to carry out chlorination of 1-methylnaphthalene in a microwave reactor. In this reaction system, the yield of the target product was only 45%, and the main by-product was benzyl chloride;

[0009] 4) WO 2019133770 A2 and WO 2020257487 A1 respectively disclose the chlorination of 1-methylnaphthalene using tin tetrachloride as a chlorine source and dichloromethane as a solvent in the presence of lead tetraacetate. The reaction needs to be carried out at room temperature overnight, but the reaction also requires the use of heavy metals.

[0010] In summary, the existing synthesis methods of 1-chloro-4-methylnaphthalene have the following disadvantages: they do not meet the atom economy, the chlorination reagents used are expensive, the reaction operation process is complicated, and it is difficult to meet the industrialization requirements. Therefore, it is urgent to find a low-cost, easy-to-operate, environmentally friendly, and environmentally friendly method for preparing 1-chloro-4-methylnaphthalene. Summary of the invention

[0011] Problem that the invention aims to solve

[0012] The purpose of the present invention is to provide an improved method for preparing 1-chloro-4-methylnaphthalene, so as to solve the technical problems existing in the prior art that the chlorination reagent is expensive, the reaction yield is low, the operation process is complicated and it is not suitable for industrial production.

[0013] Solutions for solving problems

[0014] The present invention provides a method for preparing 1-chloro-4-methylnaphthalene, which comprises the following steps:

[0015] Using 1-methylnaphthalene as a reaction raw material, reacting in an organic solvent under the action of hypochlorous acid or its salt and acid to obtain 1-chloro-4-methylnaphthalene;

[0016] Wherein, the acid is an inorganic acid and / or an organic acid containing not less than 2 carbon atoms.

[0017] Preferably, the hypochlorous acid or its salt is present in the form of an aqueous solution thereof.

[0018] Preferably, the hypochlorous acid or its salt is selected from hypochlorous acid, sodium hypochlorite and calcium hypochlorite, preferably calcium hypochlorite.

[0019] More preferably, the effective chlorine content of the calcium hypochlorite is 60% to 70%, preferably 60%.

[0020] Further preferably, the molar ratio of the effective chlorine to the 1-methylnaphthalene is 1:1 to 1.5:1, preferably 1:1 to 1.3:1, and more preferably 1:1 to 1.2:1, based on the effective chlorine calculated from the calcium hypochlorite based on its effective chlorine content.

[0021] Preferably, when the acid is an inorganic acid, the inorganic acid is hydrochloric acid or sulfuric acid.

[0022] Preferably, when the acid is an organic acid containing not less than 2 carbon atoms, the organic acid is a carboxylic acid, preferably the carboxylic acid is acetic acid; and / or, preferably the molar ratio of the carboxylic acid to the 1-methylnaphthalene is 1:1 to 10:1, preferably 2:1 to 10:1, more preferably 3:1 to 10:1.

[0023] Preferably, the organic solvent is selected from ethanol, acetonitrile, N,N-dimethylformamide, N-methylpyrrolidone, acetone, butanone, 2-pentanone and cyclohexanone, preferably ethanol, acetonitrile, acetone and butanone, more preferably acetone and butanone, most preferably butanone.

[0024] Preferably, the weight ratio of the organic solvent to the 1-methylnaphthalene is 8:1 to 20:1.

[0025] Preferably, the reaction temperature is -10 to 25°C, preferably -10 to 10°C, more preferably -5 to 10°C.

[0026] Preferably, the preparation method further comprises the following post-treatment steps: phase separation, desolventizing under reduced pressure and distillation.

[0027] More preferably, the distillation pressure is 80Pa-100Pa.

[0028] More preferably, the distillation temperature is 160-180°C.

[0029] Effects of the Invention

[0030] The method for preparing 1-chloro-4-methylnaphthalene provided by the invention is as follows: 1-methylnaphthalene is used as a reaction raw material, and under the action of calcium hypochlorite and acetic acid, the 1-chloro-4-methylnaphthalene is reacted in butanone / water to obtain the 1-chloro-4-methylnaphthalene, the product yield reaches 90%, the reaction conditions are mild, the operation is simple, the chlorination selectivity is high, the product yield is high, the cost is low, and the method is suitable for industrial production. DETAILED DESCRIPTION

[0031] The embodiments of the present invention are described in detail below in conjunction with the examples, but those skilled in the art will appreciate that the following examples are only used to illustrate the present invention and should not be considered to limit the scope of the present invention. Where specific conditions are not specified in the examples, they are carried out under conventional conditions or conditions recommended by the manufacturer. Calcium hypochlorite (Article No.: 05.001.2433) was purchased from Chengdu Cologne Chemicals Co., Ltd.

[0032] The abbreviations in this invention have the following meanings:

[0033] abbreviation meaning DMF N,N-Dimethylformamide NMP N-Methylpyrrolidone GC Gas chromatography

[0034] Embodiment 1:

[0035]

[0036] Take 12.0g of calcium hypochlorite (142.98g / mol, 60% effective chlorine, calculated as 1eq based on effective chlorine), 125g of water, and 30.0g of acetic acid (60.05g / mol, 10eq) and add them to a 500mL three-necked flask, and stir at 25°C until the solution is slightly yellow and clear. Take another 7.1g of 1-methylnaphthalene (142.20g / mol, 1eq) and add it to 125g of organic solvent acetone to form a solution, and slowly drip it into the above calcium hypochlorite solution, drip it for 1h, continue the reaction at 25°C for 1h to monitor the reaction completion, then stop stirring, separate the phases, detect the product GC relative content in the organic phase to 79.9%, and after the organic phase is decompressed and desolventized, distill out the product 1-chloro-4-methylnaphthalene at 80Pa-100 Pa, 160-180°C, and detect the product GC absolute content to 93.1%, with a yield of 70%.

[0037] Embodiment 2-4:

[0038] According to the method in Example 1, the reaction was continued for 1 hour after the raw materials were added dropwise. The type of acid was changed. The reaction conditions and results are listed in the following Table 1: wherein the concentration of hydrochloric acid was 30%, the concentration of sulfuric acid was 98%, and the rt was 25°C.

[0039] Table 1

[0040]

[0041] The results in Table 1 show that when the acid used in the reaction system is acetic acid, the GC relative content of the target product 1-chloro-4-methylnaphthalene is relatively high (about 80%); when the acid used in the reaction system is formic acid, the target product 1-chloro-4-methylnaphthalene cannot be detected; when the acid used in the reaction system is hydrochloric acid and sulfuric acid, the GC relative content of the target product 1-chloro-4-methylnaphthalene is relatively low (between 20% and 40%); therefore, specific types of inorganic acids and organic acids can be used as acids in the reaction system, and acetic acid is preferred.

[0042] Embodiment 5-11:

[0043] According to the method in Example 1, the reaction was continued for 1 hour after the raw materials were added dropwise. The type of organic solvent was changed. The reaction conditions and results are listed in Table 2 below.

[0044] Table 2

[0045]

[0046] The results of Table 2 show that, except for Example 9 and Example 10, which use cyclohexanone and 2-pentanone as organic solvents, the GC relative content of 1-chloro-4-methylnaphthalene in each example using other solvents is above 60%; among them, the GC relative content of 1-chloro-4-methylnaphthalene in Example 1, Example 5, Example 6 and Example 11, which use acetone, acetonitrile, ethanol and butanone as organic solvents, is above 75%, and the result is relatively ideal; and when acetone and butanone are used as organic solvents, the GC relative content of the obtained target product 1-chloro-4-methylnaphthalene can even reach about 80% and above. Therefore, butanone is preferably used as the organic solvent in the reaction system.

[0047] Embodiment 12-14:

[0048] According to the method in Example 11, after the raw materials were added dropwise, the reaction was continued for 1 hour, and the amount of acid was changed. The reaction conditions and results are listed in Table 3 below.

[0049] Table 3

[0050]

[0051] The results of Table 3 show that when acetic acid is used as the acid in the reaction system, when the amount of acetic acid is less, the reaction rate is significantly slower, and under the same reaction time, the GC relative content of the obtained target product 1-chloro-4-methylnaphthalene is lower (less than 30%). With the increase of the amount of acetic acid (e.g., doubling), the GC relative content of the target product 1-chloro-4-methylnaphthalene is significantly increased (reaching more than 70%), but when the amount of acetic acid is 3eq-10eq, the GC relative content of the target product 1-chloro-4-methylnaphthalene has no significant change, therefore, from the perspective of saving material cost, the amount of acetic acid in the chlorination reaction system is preferably 3eq.

[0052] Embodiment 15-18:

[0053] According to the method in Example 12, after the raw materials were added dropwise, the reaction was continued for 1 hour, and the reaction temperature was changed. The reaction conditions and results are listed in Table 4 below.

[0054] Table 4

[0055]

[0056] The result of Table 4 shows that, as the reaction temperature is reduced from 25 ℃ to -5 ℃, the GC relative content of the obtained target product 1-chloro-4-methylnaphthalene presents a trend of gradually increasing, but further reducing the reaction temperature, the GC relative content decreases instead; within the temperature range of -10 to 10 ℃ (especially -5 to 10 ℃), the GC relative content of the target product 1-chloro-4-methylnaphthalene can reach 90% and above: wherein, when the reaction temperature is -5 ℃, the GC relative content of the target product 1-chloro-4-methylnaphthalene is the highest (can reach more than 95%), therefore, preferably -5 ℃ is carried out chlorination reaction.

[0057] Examples 19-22:

[0058] According to the method in Example 17, the reaction was continued for 1 hour after the raw materials were added dropwise. The amount of calcium hypochlorite was changed. The reaction conditions and results are listed in Table 5 below.

[0059] Table 5

[0060]

[0061] The results in Table 5 show that when the amount of calcium hypochlorite (calculated as available chlorine) is 1eq-1.5eq, the GC relative content of the target product 1-chloro-4-methylnaphthalene can reach about 90% or more; when it is 1eq-1.3eq, the GC relative content of 1-chloro-4-methylnaphthalene can reach more than 90%; when it is 1eq-1.2eq, the GC relative content of 1-chloro-4-methylnaphthalene can even reach more than 95%: Among them, when the amount of calcium hypochlorite (calculated as available chlorine) is 1.2eq, the GC relative content of 1-chloro-4-methylnaphthalene is the highest (can reach more than 97%), therefore, the amount of calcium hypochlorite (calculated as available chlorine) in the chlorination reaction system is preferably 1.2eq.

[0062] Embodiment 23 (amplification experiment):

[0063] This is an enlarged experiment of Example 19, and the dosage is 4 times that of Example 19.

[0064] A 2000mL three-necked flask equipped with a thermometer was placed in an alcohol cold bath, 57.2g of calcium hypochlorite (60% effective chlorine, calculated as 1.2eq based on effective chlorine), 500g of water, and 36.0g of acetic acid (3.0eq) were added to the three-necked flask, and stirred at -5°C until the solution was slightly yellow and clear. Another 28.4g of 1-methylnaphthalene (1eq) was added to 500g of organic solvent butanone to prepare a solution, which was slowly dripped into the above calcium hypochlorite solution, and the dripping was completed for 1h. The reaction was continued at -5°C for 1h to monitor the reaction completion, and then the stirring was stopped, the phases were separated, and the GC relative content of the product in the organic phase was detected to be 91.2%. After the organic phase was desolventized, the product 1-chloro-4-methylnaphthalene was distilled out at 80Pa-100 Pa and 160-180°C. The GC absolute content of the product was detected to be 93.5%, and the yield was 90%.

[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-chloro-4-methylnaphthalene, comprising the following steps: using 1-methylnaphthalene as a reaction raw material, reacting in an organic solvent under the action of hypochlorous acid or its salt and an acid to obtain 1-chloro-4-methylnaphthalene; in, The acid is an inorganic acid and / or an organic acid containing not less than 2 carbon atoms.

2. The preparation method according to claim 1, characterized in that: The hypochlorous acid or its salt is present in the form of an aqueous solution thereof; and / or, The hypochlorous acid or its salt is selected from hypochlorous acid, sodium hypochlorite and calcium hypochlorite, preferably calcium hypochlorite.

3. The preparation method according to claim 2, characterized in that: The effective chlorine content of the calcium hypochlorite is 60% to 70%, preferably 60%; Preferably, based on the available chlorine calculated based on the available chlorine content of the calcium hypochlorite, the molar ratio of the available chlorine to the 1-methylnaphthalene is 1:1 to 1.5:1, preferably 1:1 to 1.3:1, and more preferably 1:1 to 1.2:

1.

4. The preparation method according to any one of claims 1 to 3, characterized in that The inorganic acid is hydrochloric acid or sulfuric acid.

5. The preparation method according to any one of claims 1 to 3, characterized in that: The organic acid is a carboxylic acid, preferably the carboxylic acid is acetic acid; and / or, preferably the molar ratio of the carboxylic acid to the 1-methylnaphthalene is 1:1 to 10:1, preferably 2:1 to 10:1, more preferably 3:1 to 10:

1.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The organic solvent is selected from ethanol, acetonitrile, N,N-dimethylformamide, N-methylpyrrolidone, acetone, butanone, 2-pentanone and cyclohexanone, preferably ethanol, acetonitrile, acetone and butanone, more preferably acetone and butanone, most preferably butanone.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The reaction temperature is -10 to 25°C, preferably -10 to 10°C, more preferably -5 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: phase separation, desolventizing under reduced pressure and distillation.

9. The preparation method according to claim 8, characterized in that: The distillation pressure is 80Pa-100Pa; and / or, The distillation temperature is 160-180°C.

Images