Method for fluorocarbon fracture boronation of polyfluorinated aromatic hydrocarbon compound

Abstract

The invention provides a novel method for preparing polyfluoroaryl borane through fluorocarbon fracture boronation of a polyfluoroaromatic hydrocarbon compound. According to the method, a heterogeneous semiconductor is used as a catalyst, polyfluorinated aromatic hydrocarbon and N-heterocyclic carbene borane are used as raw materials, in an inert gas atmosphere, under irradiation of a light source, a reaction is performed at 0-50 DEG C for 1-100 h, and a defluorinated boronation product is obtained. The method has the advantages of simplicity in operation, wide substrate application range, easiness in catalyst recovery, low catalyst residue, mild conditions and the like.

Description

Technical Field

[0001] The present invention specifically relates to a method for photoinduced heterogeneous semiconductor catalyzed carbon-fluorine bond breaking boronization of polyfluoroaromatic compounds and nitrogen heterocyclic carbene borane compounds. Background Art

[0002] As a chemical bond with high bond energy, carbon-fluorine bonds are widely present in many important organic compounds. According to statistics, about 20% of drugs and 30% of pesticides contain carbon-fluorine bonds. In addition, carbon-fluorine bonds also exist in many new catalysts and new materials (Senaweera S. et al., Tetrahedron 2014, 70, 7413–7428; Nozaki K. et al., J. Am. Chem. Soc. 2017, 139, 3861–3867; Bao Z. et al., Chem. Mater. 2011, 23, 446–455.). Fluorine-substituted aromatic compounds, as one of the important skeleton structures, cannot be obtained in nature and all need to be prepared by artificial synthesis. For polyfluorinated aromatic compounds among them, selectivity in synthesis is a huge challenge.

[0003] As a versatile reaction module, polyfluoroaromatic boranes use the borane part as the reaction active site and can be used to prepare a series of compounds containing polyfluoroaromatic skeletons through a variety of mature chemical transformations including Suzuki coupling. Therefore, the synthesis of this type of boranes has also attracted the attention of many chemists in the industry. The main synthetic strategy is the defluorination boration of polyfluoroaromatics: (1) through Rh (Braun T. et al., Angew. Chem. Int. Ed. 2010, 49, 3947–3951; Zhang X. et al., Angew. Chem. Int. Ed. 2015, 54, 9075–9078) and Ni (Radius U. et al., Angew. Chem. Int. Ed. 2015, 54, 9075–9078). al., J.Am.Chem.Soc.2016,138,5250–5253) and other transition metal catalyzed selective defluorination boration. This type of reaction often requires high temperature and high catalyst loading. These harsh reaction conditions severely limit the scope of substrates and the application of the method; (2) Free radical defluorination boration process involving free radical initiators (Taniguchi,T.etal.,Organic Letters2020,22,2054-2059.). This type of reaction requires high temperature to induce excess free radical initiators. Such harsh conditions and low atom economy limit the application of the reaction; (3) Photocatalytic selective defluorination boration (Wu,J.et al.,Angew Chem Int Ed.2020,59,4009-4016.). This type of reaction requires the use of Ir salts or organic dyes as catalysts. This homogeneous catalytic reaction has problems such as catalyst residue and catalyst recovery, which affects the application of the reaction.

[0004] Heterogeneous semiconductor catalysts can produce catalytic effects under light induction. In addition, they can be separated and recycled by simple filtration. From the perspectives of practicality, economy, and environmental protection, the development of photoinduced heterogeneous catalytic defluorination and boration of polyfluoroaromatics is a very meaningful and challenging task. At the same time, due to the presence of special coordination bonds, nitrogen heterocyclic carbene (NHC) borane has a unique electronic structure and exhibits a different reactivity from traditional borane reagents. In addition, it has the advantages of being easy to obtain, highly stable, and easy to operate. Its application in such reactions can further increase the practicality of the method. Summary of the invention

[0005] In view of a series of problems faced in the preparation of polyfluoroaromatic boranes, such as high catalyst or free radical initiator loading, high reaction temperature, expensive catalyst, difficulty in catalyst recovery and catalyst residue, the present invention provides a method for preparing polyfluoroaromatic borane compounds by light-induced heterogeneous semiconductor catalysis of polyfluoroaromatic compounds and nitrogen heterocyclic carbene borane compounds.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] Polyfluoroaromatic hydrocarbons and nitrogen heterocyclic carbene boranes are used as raw materials, heterogeneous semiconductors are used as catalysts, the molar ratio of polyfluoroaromatic hydrocarbons to nitrogen heterocyclic carbene boranes is 1:0.1-1:5, 1-20 mg of heterogeneous semiconductors are used for each millimole of polyfluoroaromatic hydrocarbons, an organic solvent is added (0.5-2.5 mL is required for each millimole of polyfluoroaromatic hydrocarbons), and after inert gas replacement, the reaction is carried out at 0-50° C. for 1-100 hours under light source irradiation to obtain a defluorinated boronation product.

[0008] The polyfluoroaromatic compounds include one or more of the following structures, wherein R 1 ~R 11 They are H, trifluoromethyl, cyano, halogen (F, Cl, Br, I), alkyl (molecular formula C n H 2n+1 , n = 1 to 20), ester group (molecular formula COOC n H 2n+1 , n = 1 ~ 10), acyl (molecular formula COC n H 2n+1 , n=1~10) one or more, R 1 ~R 11 The same or different.

[0009]

[0010] The nitrogen heterocyclic carbene borane is diMe-Imd-BH3

[0011]

[0012] The heterogeneous semiconductor includes one or more of TiO2 (P25), nanotubular TiO2, nanosheet TiO2, nanosheet CdS, nanorod CdS, nanowire CdS, nanosphere CdS, ZnIn2S4, In2S3, and g-C3N4.

[0013] The inert gas includes one or more of helium, nitrogen and argon.

[0014] The light source is one or more of visible violet light (390nm-435nm), visible blue light (435nm-490nm), and visible green light (490nm-560nm).

[0015] The light source power is 1W to 80W, preferably 5W to 45W.

[0016] The organic solvent includes one or more of tetrahydrofuran, toluene, dichloromethane, 1,2-dichloroethane, acetonitrile, 1,4-dioxane, N,N-dimethylformamide, and N,N-dimethylacetamide.

[0017] The method has the advantages of simple operation, wide application range of substrates, easy recovery of catalysts, low catalyst residues, mild conditions, etc. DETAILED DESCRIPTION

[0018] The following embodiments are helpful for understanding the present invention, but are not intended to limit the content of the present invention.

[0019] Example 1

[0020] Preparation of Heterogeneous Semiconducting Nanotube TiO2

[0021] 2.0g TiO2 (P25) was mixed with 160mL 10mol / L sodium hydroxide aqueous solution, and the mixture was completely poured into a 200mL stainless steel autoclave with a polytetrafluoroethylene liner, and the autoclave was placed in an oven at 150°C and heated for 48h, and then the autoclave was slowly cooled to room temperature, and the solid precipitate was filtered, and washed with deionized water to neutrality (pH = 6.0-7.5), and after drying, the obtained solid was placed in a quartz boat, and the quartz boat was wrapped with two layers of aluminum foil. Subsequently, the quartz boat was calcined at 450°C in a nitrogen stream for 3h to obtain nanotubular TiO2 with an inner diameter of 50-150nm and a length of 3-6μm.

[0022] Example 2

[0023] Preparation of Heterogeneous Semiconductor Nanosheets of TiO2

[0024] Dissolve 40 mmol TiF4 in 1.0 L of hydrochloric acid aqueous solution with a pH of 2.0, take 14.5 mL of the above solution, 13.38 mL of isopropanol and 0.5 mL of hydrofluoric acid (10% w / w) and add them into a 50 mL stainless steel autoclave with a polytetrafluoroethylene liner, place the autoclave in an oven at 180°C and heat for 44 h, then slowly cool the autoclave to room temperature, filter out the solid precipitate, wash it three times with deionized water, dry it, and calcine it at 600°C for 1.5 h to obtain nano-flaky TiO2 with a thickness of 2 to 7 nm.

[0025] Example 3

[0026] Preparation of Heterogeneous Semiconductor Nanosheets CdS

[0027] 2.0 mmol of Cd(OAc)2·2H2O and 6.0 mmol of thiourea were dissolved in 60 mL of ethylenediamine, and then the mixture was completely poured into a 100 mL stainless steel autoclave with a polytetrafluoroethylene liner. The autoclave was placed in an oven at 100°C and heated for 8 h. The autoclave was then slowly cooled to room temperature, and the solid precipitate was filtered out. The solid precipitate was washed three times with ethanol, and then washed three times with ethanol deionized water, and vacuum dried to obtain nanosheet CdS with a thickness of 2 to 7 nm.

[0028] Example 4

[0029] Preparation of Heterogeneous Semiconductor Nanorods of CdS

[0030] 10 mmol of Cd(OAc)2·2H2O and 30 mmol of thiourea were dissolved in 50 mL of ethylenediamine, and then the mixture was completely poured into a 100 mL stainless steel autoclave with a polytetrafluoroethylene liner. The autoclave was placed in an oven at 160°C and heated for 48 hours. The autoclave was then slowly cooled to room temperature, and the solid precipitate was filtered out. The solid precipitate was washed three times with ethanol and then three times with deionized water, and vacuum dried to obtain nanorod-shaped CdS with a diameter of 30 to 100 nm and a length of 100 to 300 nm.

[0031] Example 5

[0032] Preparation of Heterogeneous Semiconductor Nanowires CdS

[0033] 1.6 g of Cd(NO3)2·4H2O and 1.19 g of thiourea were dissolved in 50 mL of ethylenediamine, and then the mixture was completely poured into a 100 mL stainless steel autoclave with a polytetrafluoroethylene liner. The autoclave was placed in an oven at 180°C and heated for 72 h. The autoclave was then slowly cooled to room temperature, and the solid precipitate was filtered out. It was washed three times with ethanol and then three times with deionized water, and vacuum dried to obtain nanowire CdS with a diameter of 30 to 100 nm and a length of 2 to 6 μm.

[0034] Example 6

[0035] Preparation of Heterogeneous Semiconductor Nano-spherical CdS

[0036] 0.6 mmol of Cd(OAc)2·2H2O and 15 mmol of thiourea were dissolved in 15 mL of deionized water, and then the mixture was completely poured into a 30 mL stainless steel autoclave with a polytetrafluoroethylene liner. The autoclave was placed in an oven at 140°C and heated for 5 h. The autoclave was then slowly cooled to room temperature, and the solid precipitate was filtered out. The solid precipitate was washed three times with ethanol and then three times with deionized water, and then vacuum dried to obtain nano-spherical CdS with a diameter of 40 to 80 nm.

[0037] Example 7

[0038] Preparation of Heterogeneous Semiconductor ZnIn2S4

[0039] Dissolve 304.2 mg of Zn(NO3)2·6H2O, 624.2 mg of InCl3·4H2O and 260.6 mg of hexadecyltrimethylammonium bromide in 20 mL of deionized water, then add 604.8 mg of thiourea to the mixture, stir for 30 min, transfer the mixture to a 50 mL stainless steel autoclave with a polytetrafluoroethylene liner, seal the autoclave, and heat it in an oven at 160°C for 16 h. Then cool the autoclave naturally to room temperature, filter out the solid precipitate, wash it three times with ethanol, then wash it three times with a mixture of ethanol and water (1:3, v / v), and dry it in vacuo to obtain ZnIn2S4.

[0040] Example 8

[0041] Preparation of heterogeneous semiconductor In2S3

[0042] 936.3 mg of InCl3·4H2O and 260.6 mg of hexadecyltrimethylammonium bromide were dissolved in 20 mL of deionized water, and then 604.8 mg of thiourea was added to the mixture and stirred for 30 min. The mixture was then transferred to a 50 mL stainless steel autoclave with a polytetrafluoroethylene liner. After sealing, the autoclave was placed in an oven at 160°C and heated for 16 h. The autoclave was then naturally cooled to room temperature, and the solid precipitate was filtered out. The solid precipitate was washed three times with ethanol, and then washed three times with a mixture of ethanol and water (1:3, v / v), and dried in vacuo to obtain In2S3.

[0043] Example 9

[0044] Preparation of heterogeneous semiconductor g-C3N4

[0045] 5.0 g of melamine was placed in a quartz boat, and the quartz boat was wrapped with two layers of aluminum foil. The quartz boat containing melamine was then calcined at 550° C. for 4 h in an air flow to obtain g-C3N4.

[0046] Example 10

[0047] Synthesis of Nitrogen Heterocyclic Carbene Borane diMe-Imd-BH3

[0048] First, the device was dried and the internal chamber of the device was replaced with nitrogen. Then, 9.85 g of 1-methylimidazole and 150 mL of anhydrous dichloromethane were added to the internal chamber of the device under a nitrogen flow. 20.44 g of iodomethane was added dropwise through a constant pressure dropping funnel under an ice-water bath (0-4°C). After the addition was completed, the mixture was moved to room temperature (23-30°C), stirred for 12 hours, and then the solvent was removed under reduced pressure to obtain the product intermediate.

[0049] 5.83 g of NaBH4 was directly weighed and added to the above product intermediate, and 150 mL of toluene was added. The reaction solution was heated to reflux for 20 h, and then the supernatant was removed by decompression to remove the solvent to obtain a crude product, which was then recrystallized with 200 mL of deionized water to obtain 6.88 g of diMe-Imd-BH3 with a yield of 56.8%.

[0050] 1 H NMR (400MHz, CDCl3): δ6.80(s,2H),3.74(s,6H),1.01(m,3H). 13 CNMR (101MHz, CDCl3)δ170.2(q,J B-C =50.3Hz),120.0,35.9. 11 B(128MHz, CDCl3)-37.4(q,J=86.4Hz).IR(solid,ν,cm-1):3140,3167,3051,2979,2956,2275,1574,1445,1266,1232,1187,876,714,704.ESI:Calcd for C5H 10 BN2([M+Na] + )109.0932,found:109.0939.

[0051] Embodiment 11

[0052] Take a dry Schlenk tube with a polytetrafluoroethylene stopper and a polytetrafluoroethylene magnetic stirrer, add 0.22mmol of the nitrogen heterocyclic carbene borane (diMe-Imd-BH3) prepared in Example 10, 0.20mmol of hexafluorobenzene, 10mg of the nanotubular TiO2 prepared in Example 1 and 2.5mL of tetrahydrofuran in sequence, seal it and replace the nitrogen three times, irradiate the reaction solution with a 10W 390nm light source (UV) at 30°C, stir for 24h, 11 The reaction progress was monitored by B-NMR, and the filtrate was filtered and concentrated under reduced pressure. The crude product was further purified by rapid column chromatography (ethyl acetate / n-hexane = 1 / 1 V / V) to obtain 30.4 mg of the product with a yield of 55%.

[0053] 1 H NMR (400MHz, CDCl3) δ6.86 (s, 2H), 3.75 (s, 6H), 2.19 (dd, J = 179.3, 86.6Hz, 2H). 13 C NMR (176MHz, CDCl3) δ148.7–147.2(m),139.1–136.1(m),120.8,36.1.11 B NMR (128MHz, CDCl3) δ-32.59 (t, J=89.8Hz). 19 F NMR (376MHz, CDCl3) δ-132.92–-133.28(m,2F),-161.85(t,J=20.1Hz,F),-164.80–-165.38(m,2F).

[0054] Examples 12 to 22

[0055] Except for the light source, the catalysts (except for commercially available TiO2 (P25), all of which were prepared in the above examples) were different, and the remaining operations in Examples 12 to 22 were completely the same as in Example 11 to evaluate the catalytic effects of different catalysts. The specific conditions and results are shown in Table 1. It can be seen from Table 1 that TiO2 with different morphologies, CdS with different morphologies, ZnIn2S4, In2S3 and g-C3N4 all showed good catalytic activity.

[0056] Table 1

[0057]

[0058] Embodiments 23 to 30

[0059] Except for the different catalyst dosage, solvent, light source power, reaction temperature, reaction time, and the ratio of hexafluorobenzene to nitrogen heterocyclic carbene borane, the remaining operations in Examples 23 to 39 are exactly the same as those in Example 11 to evaluate the specific effects of the above parameters on the reaction. The specific conditions and results are shown in Table 2. It can be seen from Table 2 that a variety of solvents are suitable for the reaction.

[0060] Table 2

[0061]

[0062] Examples 31 to 42

[0063] Except for the different substrates, the rest of the operations in Examples 31-42 are completely the same as those in Example 11, and the reaction results are shown in Table 3. All polyfluoroaromatic hydrocarbons can undergo photoinduced heterogeneous catalytic defluorination and boration.

[0064] Table 3

[0065]

[0066]

[0067]

[0068]

[0069]

[0070]

[0071]

[0072] Comparative Example

[0073]

Claims

1. A method for carbon-fluorine cleavage boronization of polyfluoroaromatic compounds, characterized in that: Polyfluoroaromatic hydrocarbons and nitrogen heterocyclic carbene boranes are used as raw materials, semiconductors are used as heterogeneous catalysts, the molar ratio of polyfluoroaromatic hydrocarbons to nitrogen heterocyclic carbene boranes is 1:0.1-1:5 (preferably 1:0.5-1:3, more preferably 1:1-1:2), 1-20 mg (preferably 3-15 mg, more preferably 5-10 mg) of heterogeneous semiconductor is used for every 0.2 mmol of polyfluoroaromatic hydrocarbons, an organic solvent is added (0.5-2.5 mL, preferably 0.7-2.2 mL, more preferably 1.0-2.0 mL is required for every 0.2 mmol of polyfluoroaromatic hydrocarbons), the reaction is carried out at 0-50° C. (preferably 5-45° C., more preferably 10-30° C.) under inert atmosphere gas and light, and the reaction is carried out for 1-100 h (preferably 5-70 h, more preferably 10-50 h) to obtain a defluorinated boronation product.

2. The method according to claim 1, characterized in that The polyfluoroaromatic compounds include one or more of the following structures, wherein R 1 ~R 11 are independently H, trifluoromethyl, cyano, halogen (F, Cl, Br, I), alkyl (molecular formula C n H 2n+1 , n = 1 to 20), ester group (molecular formula COOC n H 2n+1 , n = 1 ~ 10), acyl (molecular formula COC n H 2n+1 , n=1~10) one or more, R 1 ~R 11 the same or different between them; 3. The method according to claim 1, characterized in that The nitrogen heterocyclic carbene borane is diMe-Imd-BH3 4. The method according to claim 1, characterized in that The heterogeneous semiconductor includes: one or more of TiO2 (P25), nanotube TiO2, nanosheet TiO2, nanorod CdS, nanosheet CdS, nanosphere CdS, nanowire CdS, ZnIn2S4, In2S3, and g-C3N4.

5. The method according to claim 1, characterized in that The inert atmosphere gas includes one or more of helium, nitrogen and argon.

6. The method according to claim 1, characterized in that The light source of the illumination is one or more of visible violet light (wavelength 390nm-435nm), visible blue light (wavelength 436nm-490nm), and visible green light (wavelength 491nm-560nm).

7. The method according to claim 1 or 6, characterized in that The light source power is 1W to 80W, preferably 5W to 45W.

8. The method according to claim 1, characterized in that The organic solvent includes one or more of tetrahydrofuran, toluene, dichloromethane, 1,2-dichloroethane, acetonitrile, 1,4-dioxane, N,N-dimethylformamide, and N,N-dimethylacetamide.

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