阅读说明：本技术 一种取代二苯并噻吩化合物的合成方法 (Synthesis method of substituted dibenzothiophene compound ) 是由 朱卫刚 于留建 杨芳 于 2020-12-24 设计创作，主要内容包括：本发明属于有机合成技术领域,具体公开了一种取代二苯并噻吩化合物的合成方法。本发明通过将卤代的取代联苯在低温下与有机强碱反应,然后再与乙二硫醇反应得到高纯度的关键中间体巯基联苯,然后在催化剂作用下发生偶联反应得到取代二苯并噻吩化合物。本发明方法具有原料成本低,反应条件温和,反应时间短,后处理简单,反应产物单一,副产物极少,无难除杂质,工艺操作简单,很容易地拿到高纯产品且适合工艺放大生产等优点。(The invention belongs to the technical field of organic synthesis, and particularly discloses a synthesis method of a substituted dibenzothiophene compound. The method comprises the steps of reacting halogenated substituted biphenyl with organic strong base at low temperature, then reacting with ethanedithiol to obtain high-purity key intermediate mercaptobiphenyl, and then performing coupling reaction under the action of a catalyst to obtain the substituted dibenzothiophene compound. The method has the advantages of low raw material cost, mild reaction conditions, short reaction time, simple post-treatment, single reaction product, few byproducts, no impurities difficult to remove, simple process operation, easy taking of high-purity products, suitability for process scale-up production and the like.)

1. A method for synthesizing a substituted dibenzothiophene compound is characterized in that the reaction equation is as follows:

wherein the content of the first and second substances,

x is halogen;

R₁and R₂Each independently selected from: any one of hydrogen, alkyl, haloalkyl, alkoxy, alkylamino, phenyl, halogen, hydroxyl, and nitro;

m and n are each independently selected from: 0.1, 2, 3 or 4;

the synthesis method comprises the following steps:

the first step is as follows: reacting the compound 1 with alkali, then adding ethanedithiol for reaction, and adding acid for quenching after the reaction is finished to obtain a compound 2;

the second step is that: the compound 2 is subjected to coupling reaction under the action of a catalyst to obtain a target compound 3;

the alkali in the first step is organic strong alkali; the solvent adopted in the first step is tetrahydrofuran, methyltetrahydrofuran, 1, 4-dioxane or methyl tert-butyl ether;

in the second step, the catalyst is any one or a mixture of more of palladium dichloride, cuprous chloride and ferrous chloride; the solvent adopted in the second step is dimethyl sulfoxide or N, N-dimethylformamide.

2. The synthesis method according to claim 1, wherein the ratio of the amount of the compound 1 to the amount of the organic strong base and the ethanedithiol is: compound 1: organic strong base: ethanedithiol ═ 1: (1.0-2.0): (1.2-1.5); the mass ratio of compound 2 to catalyst is: compound 2: catalyst 1: (0.01-0.15).

3. The synthesis method according to claim 1 or 2, characterized in that the organic strong base in the first step is selected from any one of n-butyl lithium, tert-butyl lithium, isopropyl magnesium chloride, isopropyl magnesium bromide, methyl magnesium chloride and ethyl magnesium chloride, and the solvent adopted in the first step is tetrahydrofuran, methyl tetrahydrofuran or methyl tert-butyl ether; in the second step, the catalyst is palladium dichloride, cuprous chloride or a mixture of palladium dichloride and cuprous chloride, and the solvent adopted in the second step is dimethyl sulfoxide.

4. The synthesis method according to claim 3, wherein the ratio of the amount of the compound 1 to the amount of the organic strong base and the ethanedithiol is: compound 1: organic strong base: ethanedithiol ═ 1: (1.5-2.0): (1.2-1.5), the mass ratio of the compound 2 to the catalyst is: compound 2: catalyst 1: (0.05-0.15); the reaction temperature of the first step is-78 ℃ to-70 ℃, and the reaction temperature of the second step is 140 ℃ to 160 ℃.

5. The synthesis method according to claim 3, wherein in the first step, the strong organic base is n-butyllithium or isopropyl magnesium chloride, and the solvent used is tetrahydrofuran; in the second step, the catalyst is palladium dichloride or a mixture of palladium dichloride and cuprous chloride.

6. The method of claim 1, wherein X is bromine or iodine and R is₁And R₂Each independently selected from any one of hydrogen, alkyl, halogenated alkyl, phenyl, halogen, hydroxyl and nitro, and m and n are each independently selected from 0, 1, 2 or 3.

7. The synthesis method according to claim 5, wherein in the first step, the strong organic base is n-butyllithium; in the second step, the catalyst is a mixture of palladium dichloride and cuprous chloride, and the mass ratio of the palladium dichloride to the cuprous chloride is as follows: palladium dichloride: cuprous chloride 1: 2.

8. The method of claim 6, wherein X is bromine and R is bromine₁Is a hydrogen atom, R₂Is selected from any one of methyl, ethyl, bromine atom, chlorine atom, nitro, phenyl, trifluoromethyl and hydroxyl, and n is 1.

Technical Field

The invention relates to the technical field of organic synthesis, in particular to a synthesis method of a substituted dibenzothiophene compound.

Background

Dibenzothiophene and its derivatives are important organic molecular frameworks, and widely exist in chemical raw materials, pharmaceutically active molecules and photoelectric materials.

The synthesis methods of the compounds mainly comprise the following steps:

(1) the method comprises the following steps of taking brominated biphenyl as a raw material, carrying out coupling reaction with sodium thiosulfate under the catalysis of palladium to obtain a sulfydryl intermediate, and carrying out coupling reaction on the intermediate under the action of a catalyst to generate substituted dibenzothiophene. The reaction formula is as follows (reference: Tetrahedron Letters,2011, vol.52,2, p.205-208):

(2) the method is characterized in that brominated biphenyl is used as a raw material and is subjected to coupling reaction with ethanedithiol under the catalysis of copper to obtain a sulfydryl intermediate, and then the intermediate is subjected to coupling reaction under the action of a catalyst to generate the substituted dibenzothiophene. The reaction formula is as follows (reference: Advanced Synthesis and Catalysis,2015, vol.357,10, p.2205-2212):

(3) the method comprises the following steps of taking brominated biphenyl as a raw material, carrying out substitution reaction with mercaptan under high pressure to obtain a sulfydryl intermediate, and carrying out coupling reaction on the intermediate under the action of a catalyst to generate substituted dibenzothiophene. The reaction formula is as follows (CN 106432013):

as can be seen from the analysis of the above three synthetic methods, the existing synthetic method has the problem of high cost, such as Pd used in the first method₂(dba)₃/Pd(OAc)₂The catalyst is expensive; the reaction conditions are harsh, for example, the second method needs high temperature (more than 150 ℃), and the reaction time is too long (more than 24 h); the third method requires high pressure and high temperature; the method I and the method II need strict inert gas protection, the method III needs high pressure, has higher requirements on reaction devices, has overlong reaction time, complex post-treatment and larger smell, is not easy to obtain high-purity products, is not suitable for being amplified into technological operation, and the like. In addition, the conventional method uses an expensive palladium catalyst in the second step, and it is also urgently required to develop a new catalyst in order to reduce the reaction cost.

Therefore, a new synthesis method of the substituted dibenzothiophene is developed to replace the existing synthesis process, and the method has important significance for realizing the industrial production of the substituted dibenzothiophene.

Disclosure of Invention

The invention solves the technical problem of providing a synthetic method for replacing a dibenzothiophene compound, and the method has the advantages of low raw material cost, mild reaction conditions, short reaction time, simple post-treatment, single reaction product, few byproducts, no impurities difficult to remove, simple process operation, easy taking of high-purity products, suitability for process amplification production and the like.

In order to solve the technical problems, the invention adopts the following technical scheme:

a method for synthesizing a substituted dibenzothiophene compound has the following reaction equation:

wherein the content of the first and second substances,

x is halogen;

R₁and R₂Each independently selected from: any one of hydrogen, alkyl, haloalkyl, alkoxy, alkylamino, phenyl, halogen, hydroxyl, and nitro;

m and n are each independently selected from: 0.1, 2, 3 or 4;

the synthesis method comprises the following steps:

the first step is as follows: reacting the compound 1 with alkali, then adding ethanedithiol for reaction, and adding acid for quenching after the reaction is finished to obtain a compound 2;

the second step is that: the compound 2 is subjected to coupling reaction under the action of a catalyst to obtain a target compound 3;

the alkali in the first step is organic strong alkali; the solvent adopted in the first step is tetrahydrofuran, methyltetrahydrofuran, 1, 4-dioxane or methyl tert-butyl ether;

in the second step, the catalyst is any one or a mixture of more of palladium dichloride, cuprous chloride and ferrous chloride; the solvent adopted in the second step is dimethyl sulfoxide or N, N-dimethylformamide.

As a preferred embodiment of the invention, the ratio of the amounts of the compound 1 to the substances of strong organic base and ethanedithiol is: compound 1: organic strong base: ethanedithiol ═ 1: (1.0-2.0): (1.2-1.5); the mass ratio of compound 2 to catalyst is: compound 2: catalyst 1: (0.01-0.15).

As a preferred embodiment of the present invention, the organic strong base in the first step is selected from any one of n-butyllithium, tert-butyllithium, isopropyl magnesium chloride, isopropyl magnesium bromide, methyl magnesium chloride, and ethyl magnesium chloride, and the solvent used in the first step is tetrahydrofuran, methyl tetrahydrofuran, or methyl tert-butyl ether; in the second step, the catalyst is palladium dichloride, cuprous chloride or a mixture of palladium dichloride and cuprous chloride, and the solvent adopted in the second step is dimethyl sulfoxide.

As a preferred embodiment of the invention, the ratio of the amounts of the compound 1 to the substances of strong organic base and ethanedithiol is: compound 1: organic strong base: ethanedithiol ═ 1: (1.5-2.0): (1.2-1.5), the mass ratio of the compound 2 to the catalyst is: compound 2: catalyst 1: (0.05-0.15); the reaction temperature of the first step is-78 ℃ to-70 ℃, and the reaction temperature of the second step is 140 ℃ to 160 ℃.

In a preferred embodiment of the present invention, in the first step, the strong organic base is n-butyllithium or isopropylmagnesium chloride, and the solvent used is tetrahydrofuran; in the second step, the catalyst is palladium dichloride or a mixture of palladium dichloride and cuprous chloride.

As a preferred embodiment of the invention, X is bromine or iodine, R₁And R₂Each independently selected from any one of hydrogen, alkyl, halogenated alkyl, phenyl, halogen, hydroxyl and nitro, and m and n are each independently selected from 0, 1, 2 or 3.

As a preferred embodiment of the present invention, the strong organic base in the first step is n-butyllithium; in the second step, the catalyst is a mixture of palladium dichloride and cuprous chloride, and the mass ratio of the palladium dichloride to the cuprous chloride is as follows: palladium dichloride: cuprous chloride 1: 2.

As a preferred embodiment of the invention, X is bromine and R is₁Is a hydrogen atom, R₂Selected from methyl, ethyl, bromine atom, chlorineAny one of atom, nitryl, phenyl, trifluoromethyl and hydroxyl, and n is 1.

The invention has the beneficial effects that: the invention provides a novel synthesis method of a substituted dibenzothiophene compound, which comprises the steps of reacting halogenated substituted biphenyl with organic strong base at low temperature, reacting with ethanedithiol to obtain high-purity key intermediate mercaptobiphenyl, and carrying out coupling reaction under the catalysis of a catalyst to obtain the substituted dibenzothiophene compound.

The method has the advantages of low raw material cost, mild reaction conditions, short reaction time, simple post-treatment, single reaction product, few byproducts, no impurities difficult to remove, simple process operation, easy taking of high-purity products, suitability for process scale-up production and the like, and the mixed catalyst is creatively used in the second step, so that the cost of the second step and the whole synthesis method is greatly reduced under the condition of keeping the yield, and the method is very suitable for industrial production.

Detailed Description

The technical solution of the present invention will be described in detail by examples.

Example 1: synthesis of 3-methyl dibenzothiophene

The synthesis steps are as follows:

the first step is as follows: synthesis of 4' -methyl-biphenyl-2-thiol

Weighing 10g of 2-bromo-4' -methylbiphenyl in 100mL of THF, cooling to-78 ℃, slowly dropwise adding n-butyllithium (2.5M, 25.9mL), controlling the internal temperature to be less than-70 ℃, and stirring for 1h after dropwise adding; slowly dripping ethanedithiol (4.6g), controlling the internal temperature to be less than-70 ℃, stopping cooling after dripping, and stirring for 5 hours. Then cooling to 0 ℃, dropwise adding 4M HCl aqueous solution for quenching, adjusting the pH value of the system to be about 6, stirring for 10min, standing to separate out an aqueous phase, and washing an organic phase by saturated sodium chloride aqueous solution; drying with anhydrous sodium sulfate, concentrating the organic phase under reduced pressure, adding PE (petroleum ether) 60mL, stirring at 60 deg.C for 0.5h, cooling, filtering, pulping with MTBE (methyl tert-butyl ether) 30mL at 50 deg.C for 0.5h, filtering, and drying to obtain 7.3g of the target compound.

The second step is that: synthesis of 3-methyl dibenzothiophene

Mixing 7g of 4' -methylPhenyl-biphenyl-2-thiol and 0.6g palladium dichloride were added to 70ml DMSO, N₂Protecting, carrying out oil bath at 140 ℃ for 8h, pouring into ice water after the reaction is finished, filtering, dissolving DCM (dichloromethane), drying with anhydrous sodium sulfate, decolorizing with silica gel, concentrating, adding acetonitrile 60mL, stirring at 60 ℃ for 0.5h, cooling, filtering to obtain solid 5.9g, and detecting by thin layer chromatography to obtain the target compound.

Example 2: synthesis of 3-bromodibenzothiophene

The synthesis steps are as follows:

the first step is as follows: synthesis of 4' -bromo-biphenyl-2-thiol

Weighing 10g of 2-bromo-4' -bromobiphenyl in 100mL of THF, cooling to about-78 ℃, slowly dropwise adding n-butyllithium (2.5M, 20mL), controlling the internal temperature to be less than-70 ℃, and stirring for 1h after dropwise adding; slowly dripping ethanedithiol (4.5g), controlling the internal temperature to be less than-70 ℃, stopping cooling after dripping, and stirring for 5 hours. Cooling to 0 ℃, dropwise adding 4M HCl aqueous solution for quenching, adjusting the pH value of the system to be about 6, stirring for 10min, standing to separate out an aqueous phase, and washing an organic phase by using saturated sodium chloride aqueous solution; drying with anhydrous sodium sulfate, concentrating the organic phase under reduced pressure, adding PE 60mL, stirring at 60 deg.C for 0.5h, cooling, filtering, pulping with MTBE 30mL, pulping at 50 deg.C for 0.5h, filtering, and drying to obtain 7.8g of the target compound.

2) Synthesis of 3-bromodibenzothiophene

Adding 7g of 4' -bromo-biphenyl-2-thiol and 0.47g of palladium dichloride into 70mL of DMSO (dimethylsulfoxide), carrying out protection by N2, carrying out oil bath at 140 ℃ for reaction for 8h, pouring into ice water after the reaction is finished, filtering, dissolving DCM, drying by using anhydrous sodium sulfate, decoloring by using silica gel, concentrating, adding 60mL of acetonitrile, stirring at 60 ℃ for 0.5h, cooling, filtering to obtain 4.6g of solid, and detecting by using thin layer chromatography to obtain the target compound.

Example 3: synthesis of 3-nitrodibenzothiophene

The synthesis steps are as follows:

the first step is as follows: synthesis of 4' -nitro-biphenyl-2-thiol

Weighing 10g of 2-bromo-4' -nitrobiphenyl in 100mL of THF, cooling to about-78 ℃, slowly dropwise adding n-butyllithium (2.5M, 26mL), controlling the internal temperature to be less than-70 ℃, and stirring for 1h after dropwise adding; slowly dripping ethanedithiol (4.5g), controlling the internal temperature to be less than-70 ℃, stopping cooling after dripping, and stirring for 5 hours. Cooling to 0 ℃, dropwise adding 4M HCl aqueous solution for quenching, adjusting the pH value of the system to be about 6, stirring for 10min, standing to separate out an aqueous phase, and washing an organic phase by using saturated sodium chloride aqueous solution; drying with anhydrous sodium sulfate, concentrating the organic phase under reduced pressure, adding PE 60mL, stirring at 60 deg.C for 0.5h, cooling, filtering, pulping with MTBE 30mL, pulping at 50 deg.C for 0.5h, filtering, and drying to obtain 7.4g of the target compound.

The second step is that: synthesis of 3-nitrodibenzothiophene

Adding 7g of 4' -nitro-biphenyl-2-thiol and 0.47g of palladium dichloride into 70mL of DMSO (dimethylsulfoxide), carrying out protection by N2, carrying out oil bath at 140 ℃ for reaction for 8h, pouring into ice water after the reaction is finished, filtering, dissolving DCM, drying by using anhydrous sodium sulfate, decoloring by using silica gel, concentrating, adding 60mL of acetonitrile, stirring at 60 ℃ for 0.5h, cooling, filtering to obtain 5.4g of solid, and detecting by using thin layer chromatography to obtain the target compound.

Example 4: synthesis of 3-phenyldibenzothiophene

The synthesis steps are as follows:

the first step is as follows: synthesis of p-terphenyl-2-thiol

Weighing 10g of 2-bromo-p-terphenyl in 100mL of THF, cooling to about-78 ℃, slowly dropwise adding n-butyl lithium (2.5M, 23mL), controlling the internal temperature to be less than-70 ℃, and stirring for 1h after dropwise adding; slowly dripping ethanedithiol (4.6g), controlling the internal temperature to be less than-70 ℃, stopping cooling after dripping, and stirring for 5 hours. Cooling to 0 ℃, dropwise adding 4M HCl aqueous solution for quenching, adjusting the pH value of the system to be about 6, stirring for 10min, standing to separate out an aqueous phase, and washing an organic phase by using saturated sodium chloride aqueous solution; drying with anhydrous sodium sulfate, concentrating the organic phase under reduced pressure, adding PE 60mL, stirring at 60 deg.C for 0.5h, cooling, filtering, pulping with MTBE 30mL, pulping at 50 deg.C for 0.5h, filtering, and drying to obtain 7.3g of the target compound.

The second step is that: synthesis of 3-phenyldibenzothiophene

Adding 7g of terphenyl-2-thiol, 0.14g of palladium dichloride and 0.16g of cuprous chloride into 70mL of DMSO (dimethylsulfoxide), protecting by N2, carrying out oil bath at 150 ℃ for reacting for 8h, pouring into ice water after the reaction is finished, filtering, dissolving DCM, drying by anhydrous sodium sulfate, decoloring by silica gel, concentrating, adding 60mL of acetonitrile, stirring at 60 ℃ for 0.5h, cooling, filtering to obtain 5.7g of solid, and detecting by thin layer chromatography to obtain the target compound.

Example 5: synthesis of 3-trifluoromethyl dibenzothiophene

The synthesis steps are as follows:

the first step is as follows: synthesis of 4' -trifluoromethyl-biphenyl-2-thiol

Weighing 10g of 2-bromo-4' -trifluoromethyl biphenyl in 100mL of THF, cooling to about-78 ℃, slowly dropwise adding n-butyl lithium (2.5M, 26mL), controlling the internal temperature to be less than-70 ℃, and stirring for 1h after dropwise adding; slowly dripping ethanedithiol (4.5g), controlling the internal temperature to be less than-70 ℃, stopping cooling after dripping, and stirring for 5 hours. Cooling to 0 ℃, dropwise adding 4M HCl aqueous solution for quenching, adjusting the pH value of the system to be about 6, stirring for 10min, standing to separate out an aqueous phase, and washing an organic phase by using saturated sodium chloride aqueous solution; drying with anhydrous sodium sulfate, concentrating the organic phase under reduced pressure, adding PE 60mL, stirring at 60 deg.C for 0.5h, cooling, filtering, pulping with MTBE 30mL, pulping at 50 deg.C for 0.5h, filtering, and drying to obtain 7.4g of the target compound.

The second step is that: synthesis of 3-trifluoromethyl dibenzothiophene

Adding 7g of 4' -trifluoromethyl-biphenyl-2-thiol, 0.14g of palladium dichloride and 0.16g of cuprous chloride into 70mL of DMSO (dimethylsulfoxide), protecting by N2, reacting at 140 ℃ in an oil bath for 8h, pouring into ice water after the reaction is finished, filtering, dissolving DCM, drying by using anhydrous sodium sulfate, decoloring by using silica gel, concentrating, adding 60mL of acetonitrile, stirring at 60 ℃ for 0.5h, cooling, filtering to obtain 6.0g of solid, and detecting by using thin layer chromatography to obtain the target compound.

The above description is only an example of the present invention, and is not intended to limit the scope of the present invention, and all equivalent modifications made by the present invention in the specification or other related fields directly or indirectly are included in the scope of the present invention.