A method for electrochemical synthesis of 3,3'-bisphenyl-2,2'-bisbenzothiophene compounds

Abstract

This invention discloses an electrochemical synthesis method for 3,3'-bisphenyl-2,2'-bisbenzothiophene compounds. The specific synthetic steps are as follows: using substituted 3-phenylbenzothiophene compounds as reactants, tetrabutylammonium hexafluorophosphate as the electrolyte, and 2,3-dichloro-5,6-dicyanobenzoquinone as an additive, the reaction is carried out in an organic solvent under an oxygen-free atmosphere and with a platinum electrode oxidation condition at 20-40°C to obtain the target product, 3,3'-bisphenyl-2,2'-bisbenzothiophene compounds. This invention uses a platinum electrode as the oxidation electrode to oxidize substituted 3-phenylbenzothiophene compounds, effectively avoiding the drawbacks of using excessive oxidants and high-cost transition metal catalysts. This invention can prepare different series of 3,3'-bisphenyl-2,2'-bisbenzothiophene compounds and has a good substrate applicability range.

Description

Technical Field

[0001] This invention belongs to the field of synthesis technology of functional materials for organic electroluminescent devices, and relates to a new process for synthesizing 3,3'-bisphenyl-2,2'-bisbenzothiophene compounds, specifically a method for electrochemically synthesizing 3,3'-bisphenyl-2,2'-bisbenzothiophene compounds. Background Technology

[0002] Benzothiophene is a common structural unit in the synthesis of heterocyclic compounds. Over the past few decades, chemical researchers have focused on methods for synthesizing multi-component heterocyclic compounds, and many techniques for synthesizing benzothiophene-based multi-component fused-ring compounds using benzothiophene as the structural backbone have been reported. In recent decades, conjugated π-bond systems containing heteroatoms have been recognized as typical structural units in the field of organic optoelectronics. The electronic structure of benzothiophene can be controlled by the substitution of heteroatoms, changes in substitution patterns, and the expansion of conjugated π bonds, thus exhibiting unique and highly variable photophysical properties. Patent document WO 2014 / 075382A1 discloses benzothiophene derivatives and their applications in the field of organic electroluminescence, specifically disclosing their applications in organic electroluminescent devices, particularly as the host material for hole transport materials, hole injection materials, or organic light-emitting materials in OLED devices. Benzothiophene is one of the most common core structural units constituting sulfur heterocyclic compounds. Benzothiophene derivatives possess 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 medicinal treatment of various diseases, including anti-tumor, anti-inflammatory, antibacterial, and anti-diabetic applications. Therefore, exploring compounds for the efficient construction of benzothiophenes is a challenging task.

[0003] Existing methods for constructing benzothiophene compounds have certain drawbacks. For example, the coupling reaction of benzothiophene boric acid with bromobenzothiophene-containing Suzuk; the reaction of benzothiophene with butyllithium to generate benzothiophene lithium reagent, which then reacts with benzothiophene to obtain bisbenzothiophene compounds. These methods cannot avoid the use of strong bases, transition metal catalysts or Grignard reagents, and the preparation of Grignard reagents is inherently dangerous. Summary of the Invention

[0004] The technical problem solved by this invention is to provide a simple, efficient and convenient electrochemical synthesis method for 3,3'-bisphenyl-2,2'-bisbenzothiophene compounds. This method starts with simple and readily available reagents, and through simple operation steps, the target product 3,3'-bisphenyl-2,2'-bisbenzothiophene compounds are obtained by electrochemical oxidation under mild reaction conditions. This effectively avoids the drawbacks of traditional synthesis methods, such as complex raw materials and high catalyst costs.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: an electrochemical synthesis method for 3,3'-bisphenyl-2,2'-bisbenzothiophene compounds, the specific synthesis steps of which are: replacing 3-phenylbenzothiophene compounds with...

[0006] Using 1 as the reactant, tetrabutylammonium hexafluorophosphate as the electrolyte, and 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) as the additive, the reaction was carried out in an organic solvent under an oxygen-free atmosphere and with a platinum electrode at 20–40 °C to obtain the target product 3,3'-bisphenyl-2,2'-bisbenzothiophene compound 2. The corresponding reaction equations during the synthesis process are as follows:

[0007] Where R represents H and C 1~10 Alkyl, C 1~10 One or more of alkoxy, hydroxyl, halogen atom, phenyl or substituted phenyl, wherein R is monosubstituted or polysubstituted on the benzene ring.

[0008] Further specifying, the C 1~10 Alkyl groups are preferably methyl groups, C 1~10 The alkoxy group is preferably a methoxy group, and the halogen atom is preferably fluorine or chlorine.

[0009] Further specifying, the organic solvent is a mixed solvent of dichloromethane and hexafluoroisopropanol or a mixed solvent of 1,2-dichloroethane and hexafluoroisopropanol.

[0010] Further specified, 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.

[0011] Furthermore, the preferred reaction temperature is room temperature.

[0012] Further specifying, the oxygen-free atmosphere is a nitrogen atmosphere.

[0013] Further specified, the oxidation current of the platinum electrode is 4~6mA.

[0014] Further specifying, the molar ratio of the substituted 3-phenylbenzothiophene compound 1, tetrabutylammonium hexafluorophosphate as electrolyte, to 2,3-dichloro-5,6-dicyanobenzoquinone is 1:0.8~1.2:0.05~0.15.

[0015] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0016] 1. This 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;

[0017] 2. This invention can prepare different series of 3,3'-bisphenyl-2,2'-bisbenzothiophene compounds, with a good substrate applicability range. Detailed Implementation

[0018] The following examples further illustrate the above-described content of the present invention, but it should not be construed as limiting the scope of the subject matter of the present invention to the following examples. All technologies implemented based on the above-described content of the present invention fall within the scope of the present invention.

[0019] Examples 1-17

[0020] Typical procedure: Under a nitrogen atmosphere, 0.30 mmol of compounds 1a-1f, 0.30 mmol of tetrabutylammonium hexafluorophosphate, and 0.030 mmol of DDQ were sequentially added to an electrolytic cell containing 10 mL of a mixed solvent of dichloromethane and hexafluoroisopropanol (volume ratio 3:7). The oxidation reaction was carried out at a constant current of 5.0 mA and room temperature for 5.0 h using a platinum electrode. After the reaction, the dichloromethane and hexafluoroisopropanol were removed by vacuum concentration, and the target products 2a-2f were then separated by column chromatography. The results are as follows:

[0021]

[0022] The characterization data of compounds 2a~2f are as follows:

[0023] 3,3'-Biphenyl-2,2'-Bibenzothiophene (2a):

[0024]

[0025] 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) d139.9, 139.2, 134.0, 134.3, 131.4, 130.1, 129.1, 128.2, 125.9, 125.5, 123.5, 123.0.

[0026] 3,3'-Bis-p-methylphenyl-2,2'-bisbenzothiophene (2b):

[0027]

[0028] 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.

[0029] 3,3'-bis(4-methoxyphenyl-2,2'-bisbenzothiophene) (2c):

[0030]

[0031] 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) d159.3, 139.8, 139.3, 136.7, 131.5, 131.0, 126.5, 125.9, 125.4, 123.5, 122.9, 114.6, 55.6.

[0032] 3,3'-Bis-4-fluorophenyl-2,2'-bisbenzothiophene (2d):

[0033]

[0034] 1 H 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.

[0035] 3,3'-Bis-4-chlorophenyl-2,2'-bisbenzothiophene (2e):

[0036]

[0037] 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) d139.9, 138.9, 135.3, 133.1, 131.8, 131.6, 129.1, 126.1, 125.8, 123.4, 123.1.

[0038] 3,3'-bis4-biphenyl-2,2'-bisbenzothiophene (2f):

[0039]

[0040] 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.

[0041] To better understand the present invention, the effects of different reaction conditions on the reaction results were investigated: 1) When the electrolyte tetrabutylammonium hexafluorophosphate in Example 1 was replaced with tetrabutylammonium tetrafluoroborate, and other conditions were the same as in Example 1, product 2a was obtained with a yield of 38%, which was much lower than the yield of product 2a of 78% in Example 1; 2) When the platinum electrode in Example 1 was replaced with glassy carbon electrode, carbon cloth electrode, and carbon felt electrode, respectively, and other conditions were the same as in Example 1, the yields of the target product 2a obtained were 41%, 32%, and 72%, respectively, all of which were lower than the yield of product 2a of 78% in Example 1.

[0042] 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 embodiments and descriptions in the specification are only illustrative of the principles of the present invention. Various changes and modifications can be made to the present invention without departing from the scope of the principles of the present invention, and all such changes and modifications fall within the protection scope of the present invention.

Claims

1. A method for the electrochemical synthesis of 3,3'-bisphenyl-2,2'-bisbenzothiophene compounds, characterized in that... The specific synthesis steps are as follows: using substituted 3-phenylbenzothiophene compound 1 as the reactant, tetrabutylammonium hexafluorophosphate as the electrolyte, and 2,3-dichloro-5,6-dicyano-p-benzoquinone as the additive, the reaction is carried out in an organic solvent under an oxygen-free atmosphere and platinum electrode oxidation conditions at 20-40℃ to obtain the target product 3,3'-bisphenyl-2,2'-bisbenzothiophene compound 2. The corresponding reaction equations during the synthesis process are as follows: Where R is one or more of a hydroxyl group or a halogen atom, and R is monosubstituted or polysubstituted on the benzene ring.

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

3. The method for electrochemically synthesizing 3,3'-bisphenyl-2,2'-bisbenzothiophene compounds according to claim 2, 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.

4. The method for electrochemically synthesizing 3,3'-bisphenyl-2,2'-bisbenzothiophene compounds according to claim 1, characterized in that: The reaction temperature was room temperature.

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

6. The method for electrochemically synthesizing 3,3'-bisphenyl-2,2'-bisbenzothiophene compounds according to claim 1, characterized in that: The oxidation current of the platinum electrode is 4~6mA.

7. The method for electrochemically synthesizing 3,3'-bisphenyl-2,2'-bisbenzothiophene 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-dicyanobenzoquinone is 1:0.8~1.2:0.05~0.15.

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