Method for electrochemical synthesis of 3, 3 '-bisphenyl-2, 2'-bisbenzothiophene compound

Abstract

The invention discloses a method for electrochemical synthesis of 3, 3 '-difluorobenzene. The invention relates to a method for preparing a substituted 3, 3 '-bisphenyl-2, 2'-bisbenzothiophene compound, which comprises the following specific synthesis steps: by taking a substituted 3-phenylbenzothiophene compound as a reaction raw material, tetrabutyl ammonium hexafluorophosphate as an electrolyte and 2, 3-dichloro-5, 6-dicyanobenzoquinone as an additive, reacting at the temperature of 50-60 DEG C for 2-4 hours, thereby obtaining the substituted 3, 3 '-bisphenyl-2, 2'-bisbenzothiophene compound. And reacting in an organic solvent under the conditions of oxygen-free atmosphere and platinum electrode oxidation at 20-40 DEG C to obtain the target product 3, 3 '-bisphenyl-2, 2'-bisbenzothiophene compound. The platinum electrode is used as an oxidation electrode to oxidize and replace the 3-phenylbenzothiophene compound, so that the defect of high cost caused by using excessive oxidant and transition metal catalyst can be effectively avoided; different series of 3, 3 '-bisphenyl-2, 2'-dibenzothiophene compounds can be prepared, and the method has a good substrate application range.

Description

Technical Field

[0001] The invention belongs to the technical field of synthesis of functional materials for organic electroluminescent devices, relates to a new synthesis process of 3,3'-biphenyl-2,2'-bibenzothiophene compounds, and specifically relates to a method for electrochemically synthesizing 3,3'-biphenyl-2,2'-bibenzothiophene compounds. Background Art

[0002] Benzothiophene is a very common structural unit in the synthesis of heterocyclic compounds. In the past few decades, chemical researchers have devoted themselves to the synthesis of polycyclic heterocyclic compounds. Many technologies have been reported for the synthesis of benzothiophene polycyclic condensed ring compounds using benzothiophene as the structural skeleton. In the past few decades, the conjugated π bond system containing heteroatoms has been recognized as a typical structural unit in the field of organic optoelectronics. The electronic structure of benzothiophene can be controlled by the replacement of heteroatoms, the change of substitution pattern and the expansion of conjugated π bonds, thereby showing unique and ever-changing photophysical properties. Patent document WO 2014 / 075382A1 discloses benzothiophene derivatives and their applications in the field of organic electroluminescence, and specifically discloses the application of benzothiophene derivatives in organic electroluminescent devices, especially as hole transport materials, hole injection materials or main materials of organic light-emitting materials in OLED devices. Benzothiophene is one of the most common core structural units constituting sulfur heterocyclic compounds. Benzothiophene derivatives have functional functional group skeletons with unique physiological and pathological activities. Due to their unique pharmacological and pathological effects, sulfur-containing compounds are widely used in the pharmaceutical treatment of various diseases such as anti-tumor, anti-inflammatory, antibacterial and anti-diabetic. Therefore, exploring effective construction of benzothiophene compounds is a difficult task.

[0003] Existing methods for constructing benzothiophene compounds have certain defects, such as the Suzuk coupling reaction of benzothiophene boronic acid and bromobenzothiophene; the reaction of benzothiophene with butyl lithium to generate a benzothiophene lithium reagent, which is then reacted with benzothiophene to obtain a bisbenzothiophene compound. These methods cannot avoid the use of strong bases, transition metal catalysts or Grignard reagents, and the preparation of Grignard reagents is dangerous. Summary of the invention

[0004] The technical problem solved by the present invention is to provide a method for electrochemically synthesizing 3,3'-biphenyl-2,2'-bibenzothiophene compounds with a simple process and an effective and convenient method. The method starts with simple and readily available reagents and undergoes simple operation steps. Under mild reaction conditions, the target product 3,3'-biphenyl-2,2'-bibenzothiophene compounds are obtained by electrochemical oxidation, thereby effectively avoiding the disadvantages of complex raw materials and high catalyst costs in traditional synthesis methods.

[0005] The present invention adopts the following technical solution to solve the above technical problems: a method for electrochemically synthesizing 3,3'-biphenyl-2,2'-bibenzothiophene compounds, wherein the specific synthesis steps are: replacing the 3-phenylbenzothiophene compound with 1 is used as the reaction raw material, tetrabutylammonium hexafluorophosphate is used as the electrolyte, and 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) is used as the additive. The target product 3,3'-biphenyl-2,2'-bibenzothiophene compound 2 is obtained in an organic solvent, an oxygen-free atmosphere, and a platinum electrode under oxidation conditions at 20-40 °C. The corresponding reaction equation in the synthesis process is:

[0006] Where R is H, C 1~10 Alkyl, C 1~10 One or more of an alkoxy group, a hydroxyl group, a halogen atom, a phenyl group or a substituted phenyl group, and R is a mono- or poly-substituted group on the benzene ring.

[0007] It is further defined that the C 1~10 The alkyl group is preferably methyl, C 1~10 The alkoxy group is preferably a methoxy group, and the halogen atom is preferably fluorine or chlorine.

[0008] It is further defined that the organic solvent is a mixed solvent of dichloromethane and hexafluoroisopropanol or a mixed solvent of 1,2-dichloroethane and hexafluoroisopropanol.

[0009] It is further defined that the volume ratio of dichloromethane to hexafluoroisopropanol in the mixed solvent of dichloromethane and hexafluoroisopropanol is 3:7, and the volume ratio of 1,2-dichloroethane to hexafluoroisopropanol in the mixed solvent of 1,2-dichloroethane and hexafluoroisopropanol is 3:7.

[0010] Further defined, the reaction temperature is preferably room temperature.

[0011] It is further defined that the oxygen-free atmosphere is a nitrogen atmosphere.

[0012] It is further defined that the oxidation current of the platinum electrode is 4-6 mA.

[0013] It is further defined that the molar ratio of the substituted 3-phenylbenzothiophene compound 1, tetrabutylammonium hexafluorophosphate as an electrolyte and 2,3-dichloro-5,6-dicyano-p-benzoquinone is 1:0.8~1.2:0.05~0.15.

[0014] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1. The present invention uses a platinum electrode as an oxidation electrode to oxidize and replace 3-phenylbenzothiophene compounds, which can effectively avoid the disadvantages of using excessive oxidants and high costs of transition metal catalysts; 2. The present invention can prepare different series of 3,3'-biphenyl-2,2'-bibenzothiophene compounds and has a good substrate application range. DETAILED DESCRIPTION

[0015] The above contents of the present invention are further described in detail below through examples, but this should not be understood as the scope of the above subject matter of the present invention being limited to the following examples, and all technologies implemented based on the above contents of the present invention belong to the scope of the present invention.

[0016] Embodiments 1 to 17 Typical operation process: Under nitrogen atmosphere, 0.30mmol of compound 1a~1f, 0.30mmol of tetrabutylammonium hexafluorophosphate and 0.030mmol of DDQ were added to an electrolytic cell containing 10mL of a mixed solvent of dichloromethane and hexafluoroisopropanol (volume ratio 3:7) in sequence, and the platinum electrode oxidation reaction was carried out at a constant current of 5.0mA and room temperature for 5.0h. After the reaction was completed, the dichloromethane and hexafluoroisopropanol were removed by vacuum concentration, and then the target products 2a~2f were separated by column chromatography. The results are as follows:

[0017] The characterization data of compounds 2a~2f are as follows: 3,3'-Bisphenyl-2,2'-bisbenzothiophene (2a):

[0018] 1 H NMR (400 MHz, DMSO- d 6) d 7.97 (d, J = 8.0 Hz, 2H), 7.51-7.46 (m, 2H), 7.44-7.36 (m, 4H), 7.34 (dt, J = 8.8, 3.6 Hz, 6H), 7.16-7.10 (m, 4H); 13 C{ 1 H} NMR (101 MHz, DMSO- d 6) d 139.9, 139.2, 134.0, 134.3, 131.4, 130.1, 129.1, 128.2,125.9, 125.5, 123.5, 123.0.

[0019] 3,3'-Bis(p-methylphenyl)-2,2'-bis(benzothiophene) (2b):

[0020] 1 H NMR (400 MHz, DMSO- d 6) d 7.97-7.91 (m, 2H), 7.50-7.47 (m, 2H), 7.42-7.35 (m, 4H), 7.17 (d, J = 8.0 Hz, 4H), 7.09 (d, J = 8.0 Hz, 4H), 2.33 (s, 6H); 13 C{ 1 H} NMR (101 MHz, DMSO- d 6) d 139.8, 139.3, 137.6, 137.1, 131.4, 131.2, 130.1,129.7, 125.8, 125.4, 123.5, 122.9, 21.4.

[0021] 3,3'-Bis(4-methoxyphenyl)-2,2'-bis(benzothiophene) (2c):

[0022] 1 H NMR (400 MHz, DMSO- d 6) d 7.96-7.88 (m, 2H), 7.52-7.46 (m, 2H), 7.42-7.34 (m, 4H), 7.12 (d, J = 8.7 Hz, 4H), 6.92 (d, J = 8.7 Hz, 4H), 3.77 (s, 6H); 13 C{ 1 H} NMR (101 MHz, DMSO- d 6) d 9, 114.6, 55.6.

[0023] 3,3'-Bis(4-fluorophenyl)-2,2'-bis(benzothiophene) (2d):

[0024] 1H NMR (400 MHz, DMSO- d 6) d 7.99 (d, J = 7.6 Hz, 2H), 7.49-7.45 (dt, J =8.0, 1.2 Hz, 2H), 7.45-7.35 (m, 4H), 7.16 (m, 2H), 7.14-7.09 (m, 6H); 13 C{ 1 H}NMR (101 MHz, DMSO- d 6) d 139.8, 139.1, 135.6, 132.0, 132.0, 131.4, 130.5,126.0, 125.7, 123.4, 123.0, 116.1, 115.9.

[0025] 3,3'-Bis(4-chlorophenyl)-2,2'-bis(benzothiophene) (2e):

[0026] 1 H NMR (400 MHz, DMSO- d 6) d 8.01 (d, J = 7.2 Hz, 2H), 7.49 (d, J = 8.0 Hz,2H), 7.46-7.38 (m, 4H), 7.37-7.32 (m, 4H), 7.09 (d, J = 8.4 Hz, 4H); 13 C{ 1 H} NMR (101 MHz, DMSO- d 6) d 139.9, 138.9, 135.3, 133.1, 131.8, 131.6, 129.1, 126.1,125.8, 123.4, 123.1.

[0027] 3,3'-Bis(4-biphenyl)-2,2'-bis(benzothiophene) (2f):

[0028] 1 H NMR (400 MHz, DMSO- d 6) d 8.02 (d, J= 7.6 Hz, 2H), 7.70-7.65 (m, 4H), 7.61-7.55 (m, 6H), 7.48 (t, J = 7.6 Hz, 4H), 7.45-7.36 (m, 6H), 7.23-7.16 (m, 4H). 13 C{ 1 H} NMR (101 MHz, DMSO- d 6) d 140.1, 134.0, 139.7, 136.3, 133.4, 130.6,129.5, 128.1, 127.2, 127.1, 126.0, 125.7, 123.6, 123.1.

[0029] In order to better understand the present invention, the effects of different reaction conditions on the reaction results were investigated: 1) The electrolyte tetrabutylammonium hexafluorophosphate in Example 1 was replaced with tetrabutylammonium tetrafluoroborate, and the other conditions were the same as in Example 1. The product 2a was obtained through the reaction with a yield of 38%, which was much lower than the yield of product 2a in Example 1 (78%); 2) The platinum electrode in Example 1 was replaced with a glassy carbon electrode, a carbon cloth electrode, and a carbon felt electrode, respectively. The other conditions were the same as in Example 1. The yields of the target product 2a obtained through the reaction were 41%, 32%, and 72%, respectively, which were all lower than the yield of product 2a in Example 1 (78%).

[0030] The above embodiments describe the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for illustrating the principles of the present invention. Without departing from the scope of the principles of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for electrochemically synthesizing 3,3'-biphenyl-2,2'-bibenzothiophene compounds, characterized in that The specific synthesis steps are: using substituted 3-phenylbenzothiophene compound 1 as a reaction raw material, tetrabutylammonium hexafluorophosphate as an electrolyte, and 2,3-dichloro-5,6-dicyano-p-benzoquinone as an additive, the target product 3,3'-biphenyl-2,2'-bibenzothiophene compound 2 is obtained in an organic solvent, an oxygen-free atmosphere, and a platinum electrode under oxidation conditions at 20-40°C. The corresponding reaction equation in the synthesis process is: ； Where R is H, C 1~10 Alkyl, C 1~10 One or more of an alkoxy group, a hydroxyl group, a halogen atom, a phenyl group or a substituted phenyl group, and R is a mono- or poly-substituted group on the benzene ring.

2. The method for electrochemically synthesizing 3,3'-biphenyl-2,2'-bibenzothiophene compounds according to claim 1, characterized in that: The C 1~10 The alkyl group is preferably methyl, C 1~10 The alkoxy group is preferably a methoxy group, and the halogen atom is preferably fluorine or chlorine.

3. The method for electrochemically synthesizing 3,3'-biphenyl-2,2'-bibenzothiophene compounds according to claim 1, characterized in that: The organic solvent is a mixed solvent of dichloromethane and hexafluoroisopropanol or a mixed solvent of 1,2-dichloroethane and hexafluoroisopropanol.

4. The method for electrochemically synthesizing 3,3'-biphenyl-2,2'-bibenzothiophene compounds according to claim 3, characterized in that: The volume ratio of dichloromethane to hexafluoroisopropanol in the mixed solvent of dichloromethane and hexafluoroisopropanol is 3:7, and the volume ratio of 1,2-dichloroethane to hexafluoroisopropanol in the mixed solvent of 1,2-dichloroethane and hexafluoroisopropanol is 3:

7.

5. The method for electrochemically synthesizing 3,3'-biphenyl-2,2'-bibenzothiophene compounds according to claim 1, characterized in that: The reaction temperature is preferably room temperature.

6. The method for electrochemically synthesizing 3,3'-biphenyl-2,2'-bibenzothiophene compounds according to claim 1, characterized in that: The oxygen-free atmosphere is a nitrogen atmosphere.

7. The method for electrochemically synthesizing 3,3'-biphenyl-2,2'-bibenzothiophene compounds according to claim 1, characterized in that: The platinum electrode oxidation current is 4-6 mA.

8. The method for electrochemically synthesizing 3,3'-biphenyl-2,2'-bibenzothiophene compounds according to claim 1, characterized in that: The molar ratio of the substituted 3-phenylbenzothiophene compound, tetrabutylammonium hexafluorophosphate as electrolyte and 2,3-dichloro-5,6-dicyano-p-benzoquinone is 1:0.8-1.2:0.05-0.15.

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