A method for preparing benzothiazole compounds using CO2

Abstract

The present invention relates to a method for synthesizing compounds, specifically a method for preparing benzothiazole compounds by using CO2. The preparation method of the present invention uses o-aminodisulfide as a substrate, carbon dioxide as a carbonylation reagent, and phenylsilane as a reducing agent, and synthesizes benzothiazole compounds in one pot in a polar aprotic solvent without a catalyst. The preparation method of the present invention does not require a catalyst, reducing the preparation cost; it can react under normal pressure and relatively low temperature conditions, and the required reaction time is relatively short; it can achieve a relatively high yield, and the yield of benzothiazole compounds can reach 85.9%.

Description

Technical Field

[0001] The present invention relates to a method for synthesizing compounds, and more particularly, to a method for preparing benzothiazole compounds using CO2. Background Art

[0002] Benzothiazole compounds are very important chemical raw materials and fine chemicals, and have extensive applications in the fields of medicine, pesticides, materials science, etc. For example, ethoxzolamide is a carbonic anhydrase inhibitor and is used as a diuretic and a glaucoma treatment drug; riluzole is a nervous system drug, which has the effects of inhibiting glutamate release and regulating calcium channels, and at the same time has potential efficacy for neurological diseases such as epilepsy. Therefore, exploring the synthesis method of benzothiazole compounds is of great significance.

[0003] Benzothiazole compounds without substituents at the 2-position are mainly synthesized by reacting reaction substrates and carbonylation reagents by adding different catalysts.

[0004] Currently, the disclosed reaction substrate is 2-aminobenzenethiol, and its structural formula is . 2-Aminobenzenethiol has an unpleasant pungent smell and is unstable in air and easily oxidized and deteriorated. In the selection of carbonylation reagents, using carbon dioxide as a carbonylation reagent to synthesize benzothiazole compounds can effectively reduce carbon dioxide emissions, thereby reducing the harm to the environment, and thus has become a research hotspot in recent years.

[0005] In the process of synthesizing benzothiazole compounds using carbon dioxide as a carbon source in the presence of a reducing agent; first, carbon dioxide needs to be activated, so high temperature and high pressure are required in the reaction; second, due to the thermodynamic stability and kinetic inertness of carbon dioxide, usually a highly efficient catalyst is required to activate carbon dioxide; in addition, o-aminobenzenethiol and carbon dioxide react in the presence of a reducing agent, and the key factor in the reaction lies in the activation of the reducing agent; therefore, different catalysts also need to be added to activate the reducing agent.

[0006] Currently, the latest synthesis route is: in the presence of various reducing agents and catalysts, under high temperature and high pressure, using 2-aminobenzenethiol as a substrate and carbon dioxide as a carbon source, 2-unsubstituted benzothiazole is synthesized. For example, using H2 as a reducing agent, under high temperature and high pressure conditions, CoF2 / PP3 / CsF catalyzes the reaction of carbon dioxide with 2-aminothiophenol to obtain 2-unsubstituted benzothiazole.

[0007] It can be seen that the existing synthesis methods of benzothiazole compounds need to face harsh reaction conditions such as high temperature and high pressure, expensive catalysts, etc.; at the same time, the use of catalysts also brings certain difficulties to the post-treatment of the reaction. Summary of the Invention

[0008] To solve the problem that the existing synthesis methods of benzothiazole compounds require catalysts and high-temperature and high-pressure reaction conditions, the present invention provides a method for preparing benzothiazole compounds by using CO2.

[0009] The new preparation method of benzothiazole compounds provided by the present invention uses o-aminodisulfide as a substrate, carbon dioxide as a carbonylating agent, and phenylsilane as a reducing agent, and synthesizes benzothiazole compounds by a one-pot method in a polar aprotic solvent without a catalyst.

[0010] One of the purposes of the present invention is to provide a method for preparing benzothiazole compounds by using CO2.

[0011] The preparation method includes: under the condition of isolating air, o-aminodisulfide, carbon dioxide, and phenylsilane react in a polar aprotic solvent. The preparation method does not require a catalyst and is carried out without a catalyst.

[0012] Under the condition of without a catalyst, the reaction route for synthesizing the benzothiazole compounds by one-pot reaction of o-aminodisulfide and phenylsilane with carbon dioxide is as follows:

[0013] ,

[0014] Among them, formula I is o-aminodisulfide, formula II is phenylsilane, and formula III is benzothiazole compounds.

[0015] The reaction mechanism of the preparation method is as follows:

[0016] .

[0017] In the above reaction mechanism, "Si" refers to phenylsilyl (PhSiH2-). Experimental studies have found that when using a polar aprotic solvent as the reaction solvent to prepare benzothiazole compounds, the polar aprotic solvent may have the effect of activating the Si-H bond in phenylsilane, thereby releasing hydride ions. On the one hand, the released hydride ions reduce carbon dioxide to obtain a two-electron reduction intermediate state of carbon dioxide; on the other hand, the released hydride ions can promote the cleavage of the S-S bond of the substrate o-aminodisulfide, breaking o-aminodisulfide into o-aminothiophenol and o-aminophenylsulfide anion. The two-electron reduction intermediate state of carbon dioxide combines with the phenylsilyl group after phenylsilane releases hydride ions, and then forms the target product benzothiazole through nucleophilic attack on o-aminothiophenol, elimination of phenylsilanol (PhSiH2OH), and dehydration cyclization. The o-aminophenylsulfide anion has nucleophilicity and can further promote the cleavage of the Si-H bond to release hydrogen ions, promoting the continuous progress of the whole reaction.

[0018] The chemical formula of the o-aminodisulfide compound is: , R is selected from an electron-donating group and an electron-withdrawing group. Specifically, R can be selected from hydrogen, methyl, and halogen. The halogen can specifically be bromine, chlorine, or fluorine.

[0019] The o-aminodisulfide compound can specifically be: diaminodisulfide ( ), p-methyl o-aminodisulfide ( ), p-bromo o-aminodisulfide ( ), p-chloro o-aminodisulfide ( ), o-methyl o-aminodisulfide ( ), m-chloro o-aminodisulfide ( ). Among them, diaminodisulfide, p-methyl o-aminodisulfide, p-bromo o-aminodisulfide, p-chloro o-aminodisulfide, and m-chloro o-aminodisulfide can be obtained through commercial channels; o-methyl o-aminodisulfide is prepared by oneself. The preparation method of o-methyl o-aminodisulfide is an existing method, and specific references can be made to Chem. Eur. J. 2012, 18, 4840–4843.

[0020] The chemical formula of the phenylsilane is: .

[0021] The organic solvent is selected from N , N -dimethylformamide (DMF), N-methylpyrrolidone (NMP), acetonitrile (MeCN), tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), at least one of them. DMF, NMP, MeCN, THF, and DMSO are all polar aprotic solvents. The electron-rich groups of these solvents can act as nucleophiles to promote the release of hydride ions from phenylsilane, thus playing a role in activating the Si-H bond in phenylsilane; in addition, these solvents also play a key role in carbon dioxide reduction. The basicity and polarity of different polar aprotic solvents are different. For different reaction properties (solubility in the substrate, oxidizing property of the product, boiling point of the solvent, viscosity, etc.), the effect of each solvent on the reaction (such as yield, etc.) is different. As a preferred scheme, the organic solvent is selected from N , N -dimethylformamide (DMF), N-methylpyrrolidone (NMP); more preferably N , N -dimethylformamide (DMF).

[0022] The molar ratio change of the phenylsilane to the o-aminodisulfide will affect the yield of the product (benzothiazole compounds). As a preferred option, the molar ratio of the phenylsilane to the o-aminodisulfide is greater than or equal to 1. As a more preferred option, the molar ratio of the phenylsilane to the o-aminodisulfide is 2 - 8:1. As a further preferred option, the molar ratio of the phenylsilane to the o-aminodisulfide is 4 - 6:1; at this time, the yield of the benzothiazole compounds is as high as over 77.5%. When the molar ratio of the phenylsilane to the o-aminodisulfide is 5:1; at this time, the yield of the benzothiazole compounds is as high as 85.9%.

[0023] The molar ratio change of the carbon dioxide to the o-aminodisulfide will affect the yield of the product (benzothiazole compounds). As a preferred option, the molar ratio of the carbon dioxide to the o-aminodisulfide is greater than or equal to 1. As a more preferred option, the molar ratio of the carbon dioxide to the o-aminodisulfide is 2 - 40:1. As a further preferred option, the molar ratio of the carbon dioxide to the o-aminodisulfide is 14 - 28:1; at this time, the yield of the benzothiazole compounds is as high as over 83.2%.

[0024] Because the reaction is carried out under airtight conditions with air isolation. Therefore, the higher the molar ratio of the carbon dioxide to the o-aminodisulfide, the higher the reaction pressure.

[0025] The change of the reaction temperature will affect the yield of the product (benzothiazole compounds). As a preferred option, the reaction temperature is 20 - 140 °C. As a more preferred option, the reaction temperature is 60 - 120 °C. As a further preferred option, the reaction temperature is 80 - 100 °C; at this time, the yield of the benzothiazole compounds is as high as over 84.2%. When the reaction temperature is 60 °C, the yield of the benzothiazole compounds is already as high as 70.7%; when the reaction temperature is 80 °C, the yield of the benzothiazole compounds can be as high as 85.9%. It can be seen that compared with the existing preparation methods of benzothiazole compounds, the preparation method of the present invention requires a lower reaction temperature.

[0026] The change of the reaction time will affect the yield of the product (benzothiazole compounds). As a preferred option, the reaction time is 1 h or more. As a more preferred option, the reaction time is 2 h or more. As a further preferred option, the reaction time is 2 - 4 h. When the reaction time is 1 h, the yield of the benzothiazole compounds is already as high as 65.5%; when the reaction time is 2 h, the yield of the benzothiazole compounds is already as high as 80.3%. It can be seen that compared with the existing preparation methods of benzothiazole compounds, the preparation method of the present invention requires a shorter reaction time.

[0027] For the described preparation method, a reaction kettle can be used as the reaction device.

[0028] For the described preparation method, the way to isolate air can be: introducing N2 or other protective gases into a closed container to remove the air in the closed container.

[0029] In one specific embodiment of the described preparation method, it includes: adding o-aminodisulfide, phenylsilane, and an organic solvent into a reaction kettle, blowing N2 into the reaction kettle to remove the air in the reaction kettle, filling with carbon dioxide, and stirring for reaction.

[0030] After the reaction is completed in the described preparation method, it further includes a separation and purification step. Separation and purification can be carried out by conventional methods. For example: after the reaction is completed, the reaction mixture is extracted, dried, concentrated, and then purified by silica gel column chromatography.

[0031] In one specific embodiment of the separation and purification step, it includes: after the reaction is completed, adding a saturated sodium chloride solution to the reaction mixture solution, then extracting three times with ethyl acetate, combining the organic layers, drying with anhydrous MgSO4, filtering, and concentrating under reduced pressure to obtain a crude mixture; the crude mixture is collected by gradient elution through silica gel column chromatography and the eluent is distilled under reduced pressure to obtain the benzothiazole compound.

[0032] The second object of the present invention is to provide a benzothiazole compound prepared by the preparation method described in the first object of the invention.

[0033] The chemical formula of the described benzothiazole compound is: 。

[0034] In [[ ]], R comes from the reaction substrate o-aminodisulfide compound Specifically, R is selected from an electron-donating group, an electron-withdrawing group, and a heterocycle. Specifically, R is selected from hydrogen, methyl, methoxy, halogen, pyridine ring, and naphthalene ring. R can be located at any position of 2, 3, 4, 5 on the benzene ring.

[0035] The described benzothiazole compound can specifically be selected from at least one of the following: 5-methylbenzothiazole, 5-bromobenzothiazole, 5-chlorobenzothiazole, 3-methylbenzothiazole, 3-fluorobenzothiazole, etc.

[0036] Compared with the prior art, the beneficial effects of the present invention:

[0037] The present invention provides a preparation method for synthesizing benzothiazole compounds using carbon dioxide as a carbonylation reagent, which can enable o-aminodisulfide and phenylsilane to react efficiently with carbon dioxide at normal pressure to synthesize benzothiazole compounds, and has strong industrial application value. Specifically:

[0038] 1. This method selects o-aminodisulfide as the substrate, carbon dioxide as the carbonylation reagent, and phenylsilane as the reducing agent, providing a new synthetic route for the synthesis of benzothiazole compounds.

[0039] 2. This method does not require a catalyst, reducing the preparation cost.

[0040] 3. This method can react under atmospheric pressure. Under atmospheric pressure, the yield of benzothiazole compounds can reach 41.3%.

[0041] 4. This method can carry out the reaction at a relatively low temperature. The reaction temperature required for the yield of benzothiazole compounds to reach over 70% is only 60 °C, and the required reaction temperature is low.

[0042] 5. This method requires a relatively short reaction time. The reaction time required for the yield of benzothiazole compounds to reach over 80% is only 2 h, and the required reaction time is short.

[0043] 6. This method can achieve a high yield. The yield of benzothiazole compounds can reach 85.9%. Specific Embodiments

[0044] The present invention will be specifically described below in conjunction with specific embodiments. It is necessary to point out here that the following embodiments are only for further illustration of the present invention and cannot be construed as limiting the protection scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention still fall within the protection scope of the present invention.

[0045] Unless otherwise specified, the reagents used in the following embodiments are all commercially available products.

[0046] Examples 1 - 28

[0047] Diaminodisulfide ( ), phenylsilane ( ) react with carbon dioxide to synthesize benzothiazole compounds. The synthetic route is as follows:

[0048] .

[0049] The preparation method is as follows:

[0050] 0.5 mmol of diamino disulfide, phenylsilane, and a solvent were charged into a 15 mL stainless-steel autoclave equipped with a magnetic stirrer; wherein, the molar ratio of phenylsilane to diamino disulfide was M. N2 was blown into the stainless-steel autoclave to remove the air in the autoclave. Subsequently, carbon dioxide was introduced into the stainless-steel autoclave so that the pressure of carbon dioxide in the autoclave was P. The stainless-steel autoclave was placed in a constant-temperature sand bath at T °C, and the reaction mixture solution was reacted for t hours under stirring conditions. After the reaction was completed, saturated brine solution was added to the reaction mixture solution, and then extracted three times with ethyl acetate. The organic layers were combined, dried over anhydrous MgSO4, filtered, and concentrated under reduced pressure to obtain a crude mixture. The crude mixture was eluted by silica gel column chromatography (PE / EA = 10 / 1, v / v) and the eluent at a ratio of 6 / 1 was collected and distilled under reduced pressure to obtain a pale yellow oily liquid.

[0051] The prepared pale yellow oily liquid, its 1 H NMR (500 MHz, DMSO-d6) δ 9.39 (s, 1H), 8.14 (d, J = 8.0 Hz, 1H), 8.10 (d, J = 8.2 Hz, 1H), 7.53 (t, J = 7.6 Hz, 1H), 7.46 (t, J = 7.5 Hz, 1H; 13C NMR (125 MHz, DMSO-d6) δ 156.42, 153.48, 134.01, 126.58, 125.88, 123.49, 122.90 ppm.

[0052] The prepared pale yellow oily liquid is 2-H benzothiazole (2-H benzothiazole), and its structural formula is: .

[0053] In Examples 1-28, the pressure P of carbon dioxide corresponded to the amount of carbon dioxide used. Among them, P = 0.1 MPa corresponded to the amount of carbon dioxide used of 1.4 - 1.6 mmol, and the molar ratio of carbon dioxide to o-aminodisulfide was 2.8 - 3.2:1; P = 0.25 MPa corresponded to the amount of carbon dioxide used of 3.5 - 4 mmol, and the molar ratio of carbon dioxide to o-aminodisulfide was 7 - 8:1; P = 0.5 MPa corresponded to the amount of carbon dioxide used of 7 - 8 mmol; P = 1 MPa corresponded to the amount of carbon dioxide used of 14 - 16 mmol; P = 1.25 MPa corresponded to the amount of carbon dioxide used of 17.5 - 20 mmol; P = 1.5 MPa corresponded to the amount of carbon dioxide used of 21 - 24 mmol.

[0054] The solvents and the conditions of M, T, P, and t used in Examples 1-28 are shown in Table 1; the yields of benzothiazole prepared in Examples 1-28 are shown in Table 1. 2-H The yields of benzothiazole are shown in Table 1.

[0055] Table 1

[0056]

[0057] Example 29

[0058] Raw materials: 0.5 mmol of p-methyl-o-aminodisulfide ( ), 2.5 mmol of phenylsilane, carbon dioxide. The crude mixture was obtained by using the preparation method of Example 1; among them, the solvent was DMF, M = 5, T = 80 °C, P = 0.25 Mpa, t = 2 h.

[0059] The crude mixture was separated by wet-column chromatography (200-300 mesh silica gel) with wet sample loading: Petroleum ether: Ethyl acetate (V / V) = 10 / 1 - 8 / 1 was used as the eluent to purify the crude residue, and a yellow oily liquid (121 mg, yield 81.1%) was obtained.

[0060] For the yellow oily liquid 1 1H NMR (500 MHz, DMSO- d 6) δ 9.29 (s, 1H), 7.96 (d, J = 8.3 Hz, 1H), 7.90 - 7.81 (s, 1H), 7.33 - 7.31 (d, J = 8.3 Hz, 1H), 2.42 (s, 1H); 13 13C NMR (126 MHz, DMSO- d 6) δ 155.18, 151.67, 135.57, 134.16, 128.08, 122.96, 122.29, 21.40.

[0061] The prepared yellow liquid product is 5-methyl-benzothiazole, and its structural formula is: .

[0062] Example 30

[0063] Raw materials: 0.5 mmol of p-bromo-o-aminodisulfide ( ), 2.5 mmol of phenylsilane, carbon dioxide. The crude mixture was obtained by using the preparation method of Example 1; among them, the solvent was DMF, M = 5, T = 80 °C, P = 0.25 Mpa, t = 2 h.

[0064] The crude mixture was separated by column chromatography with wet packing and wet sample loading (200 - 300 mesh silica gel): Petroleum ether: Ethyl acetate (V / V) = 10 / 1 - 1 / 1 was used as the developing solvent to purify the crude residue, and a yellow solid product (147.7 mg, 69%) was obtained.

[0065] The m.p. of the prepared yellow solid product = 53 - 55 °C; 1 H NMR (500 MHz, DMSO - d 6) δ9.40 (s, 1H), 8.43 (s, 1H), 8.02 - 8.00 (dd, J = 8.8,1.4 Hz 1H), 7.67 - 7.65 (dd, J = 8.7,2.0 Hz 1H); 13 C NMR (126 MHz, DMSO - d 6) δ 157.69, 152.53, 136.18, 129.76,125.47, 124.96, 118.71, 127.35, 126.86, 126.64, 125.11.

[0066] The prepared yellow solid product is 5 - Bromo - benzaothiazole, and its structural formula is: .

[0067] Example 31

[0068] Raw materials: 0.5 mmol of p - chloro - o - aminodisulfide ( ), 2.5 mmol of phenylsilane, carbon dioxide. The crude mixture was obtained by the preparation method of Example 1; among them, the solvent was DMF, M = 5, T = 80 °C, P = 0.25 Mpa, t = 2 h.

[0069] The crude mixture was separated by column chromatography with wet packing and wet sample loading (200 - 300 mesh silica gel): Petroleum ether: Ethyl acetate (V / V) = 9 / 1 - 7 / 1 was used as the developing solvent to purify the crude residue, and a brown solid product (87.8 mg, yield 50.2%) was obtained.

[0070] The m.p. of the prepared brown solid product = 41 - 43 °C; 1H NMR (500 MHz, DMSO - d6) δ9.42 (s, 1H),8.29 (d, J =2.1 Hz 1H), 8.07 (d, J =8.6 Hz 1H), 7.55 - 7.53 (dd, J = 8.7,2.2 Hz 1H); 1313C NMR (126 MHz, DMSO-d6) δ 157.68, 152.26, 135.69, 130.56, 127.09, 124.59, 122.56.

[0071] The prepared brown solid product is 5-Chloro-benzaothiazole, and its structural formula is: 。

[0072] Example 32

[0073] The o-iodoaniline with substituents (1 mmol), sulfur (3 mmol), 1,10-phenanthroline (0.1 mmol), copper(I) iodide (0.1 mmol), and potassium carbonate (2 mmol) were charged into a 25 mL round-bottom flask and a magnetic stirrer was added. Using 5 mL N , N N,N-Dimethylformamide (DMF) as the solvent, the round-bottom flask was placed in a 100 °C constant-temperature sand bath, and the reaction mixture solution was reacted for 24 hours under stirring conditions. After the reaction was completed, saturated brine solution was added to the reaction mixture solution, and then it was extracted three times with ethyl acetate. The organic layers were combined, dried over anhydrous MgSO4, filtered, and concentrated under reduced pressure to obtain a crude mixture. The crude mixture was collected by gradient elution of silica gel column chromatography (PE / EA = 15 / 1, v / v) at a ratio of 8 / 1 and the eluent was distilled under reduced pressure to obtain the target product o-methyl-o-aminodisulfide.

[0074] Raw materials: 0.5 mmol of o-methyl-o-aminodisulfide ( ), 2.5 mmol of phenylsilane, and carbon dioxide. The crude mixture was obtained by the preparation method of Example 1; among them, the solvent was DMF, M = 5, T = 80 °C, P = 0.25 Mpa, t = 2 h.

[0075] The crude mixture was separated by wet column packing and wet sample loading column chromatography (200 - 300 mesh silica gel): Petroleum ether: Ethyl acetate (V / V) = 12 / 1 - 8 / 1 was used as the eluent to purify the crude residue, and a yellow liquid product (115.5 mg, yield 77.4%) was obtained.

[0076] The prepared yellow liquid product's 1 1H NMR (500 MHz, DMSO- d 6) δ 9.35 (s, 1H), 7.94 - 7.93 (dd, J = 8.0, 15 Hz 1H), 7.36 - 7.3 (m, 2H), 2.69 (s, 3H); 1313C NMR (126 MHz, DMSO- d 6) δ 155.18, 152.76, 133.82, 132.97, 126.87, 125.76, 120.18, 18.43.

[0077] The prepared yellow liquid product is 3-Methyl-benzaothiazole, and its structural formula is: .

[0078] Example 33

[0079] Raw materials: 0.5 mmol of m-chloro-o-aminodisulfide ( ), 2.5 mmol of phenylsilane, carbon dioxide. The crude mixture was obtained by the preparation method of Example 1; among them, the solvent was DMF, M = 5, T = 80 °C, P = 0.25 Mpa, t = 2 h.

[0080] The crude mixture was separated by wet-column chromatography (200 - 300 mesh silica gel): The crude residue was purified with petroleum ether: ethyl acetate (V / V) = 10 / 1 - 1 / 1 as the eluent to obtain a brown solid product (137.7 mg, yield 81.4%).

[0081] The m.p. of the prepared brown solid product = 104 - 106 °C; 1 1H NMR (500 MHz, DMSO- d 6) δ9.47 (s, 1H),8.22 - 8.20 (d, J = 8.6 Hz 1H), 8.17 (d, J = 2.0 Hz 1H), 7.55 - 7.53(dd, J = 8.6,2.1 Hz 1H); 13C NMR (126 MHz, DMSO-d6) δ 159.08, 154.44, 132.90,131.47, 126.09, 124.45, 122.94.

[0082] The prepared brown solid product is 4-Chloro-benzaothiazole., and its structural formula is: .

[0083] Comparative Examples 1 - 4

[0084] Raw materials: 0.5 mmol of diamino disulfide ( ), 2.5 mmol of reducing agent, and carbon dioxide. The preparation method of Example 1 was adopted; wherein, the solvent was DMF, M = 5, T = 80 °C, P = 0.25 Mpa, t = 2 h.

[0085] The reducing agents used in Comparative Examples 1-4 are shown in Table 2; the 2-H Yields of benzothiazole are shown in Table 2.

[0086] Table 2

[0087]

[0088] The yields of Comparative Examples 1, 3, and 4 were 0, indicating that PMHS, Ph3SiH, and (EtO)3SiH could not be used to prepare 2-H benzothiazole as reducing agents. It can be seen that although PMHS, Ph3SiH, and (EtO)3SiH also belong to hydrosilane compounds, in the preparation method using o-aminodisulfide as the substrate and carbon dioxide as the carbonylation reagent, using PMHS, Ph3SiH, and (EtO)3SiH as reducing agents cannot synthesize benzothiazole compounds.

[0089] Compared with Comparative Examples 1-4, the preparation process conditions of Example 20 were the same, except that the reducing agents were different. The yield of Example 20 was as high as 85.9%, while the yields of Comparative Examples 1-4 were only 0-3.6%. It can be seen that compared with other hydrosilane compounds, using phenylsilane as the reducing agent can not only synthesize benzothiazole compounds, but also significantly improve the yield.

[0090] In the present invention, the yield refers to the nuclear magnetic yield calculated based on pyrazine as the internal standard (yield = actual yield / theoretical yield × %).

Claims

1. A preparation method for preparing benzothiazole compounds using CO2, characterized in that, The preparation method comprises: under the condition of isolating from air, o-amino disulfide, carbon dioxide and phenylsilane react in a polar aprotic solvent; The structural formula of the benzothiazole compound is ; The structural formula of the o-aminodisulfide is as follows: ; R in the benzothiazole compound and the o-aminodisulfide is selected from hydrogen, methyl, methoxy, halogen, pyridine ring, and naphthalene ring; The structural formula of the phenylsilane is as follows: ; The polar aprotic solvent is selected from N , N -dimethylformamide or N-methylpyrrolidone; The reaction temperature is 60-140°C.

2. The preparation method according to claim 1, characterized in that The molar ratio of the phenylsilane to the o-aminodisulfide is greater than or equal to 1; or / and, The molar ratio of the carbon dioxide to the o-aminodisulfide is greater than or equal to 1; or / and, The reaction time is more than 1h.

3. The preparation method according to claim 1, characterized in that: The molar ratio of the phenylsilane to the o-aminodisulfide is 2-8:1; or / and, The molar ratio of the carbon dioxide to the o-aminodisulfide is 2-40:1; or / and, The reaction temperature is 60-120°C; or / and, The reaction time is more than 2 hours.

4. The preparation method according to claim 1, characterized in that: The molar ratio of the phenylsilane to the o-aminodisulfide is 4-6:1; or / and, The molar ratio of the carbon dioxide to the o-aminodisulfide is 14-28:1; or / and, The reaction temperature is 80-100°C; or / and, The reaction time is 2-4h.

5. The preparation method according to claim 1, characterized in that, o-Aminodisulfide, phenylsilane and polar aprotic solvent are added to a reaction kettle, N2 is blown into the reaction kettle to remove the air in the reaction kettle, carbon dioxide is filled in, and the reaction is stirred.

6. The preparation method according to claim 1, characterized in that, After the reaction is completed, the reaction mixture is extracted, dried, concentrated and purified by silica gel column chromatography.

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