A method for breaking carbon-fluorine bonds and hydrogenating trifluoromethyl arenes

Abstract

The present application provides a new method to directly cleave sp 3 Hybrid carbon-fluorine bond, the method is under the condition of non-metal photocatalyst, N-heterocyclic carbene borane, after nitrogen replacement, under the irradiation of light source, reaction at 30~40 DEG C for 12-48h, get de-trifluoride hydrogenation aromatic compound. The method has the following advantages: 1) the scope of application of substrate is wide, and medium or more yield can be obtained. 2) the method does not need to add initiator, has the advantages of simple operation, high stability, can realize the scale-up of gram level, etc.

Description

Technical Field

[0001] This invention relates to a method for hydrogenating trifluoromethyl aromatics by completely breaking the carbon-fluorine bond to obtain aromatic compounds, and also to an organic photocatalyst suitable for this purpose. Background Technology

[0002] As is well known, the carbon-fluorine bond is the strongest single bond among carbon atoms, and the organic transformation of organofluorine compounds through carbon-fluorine bond breaking has attracted widespread interest from researchers. Oxidative addition processes mediated by low-valence transition metal complexes are considered an effective method for breaking carbon-fluorine bonds because these complexes are highly reactive to electron-deficient chemical bonds. Therefore, researchers have been dedicated to finding metal complexes or reactive substances capable of catalyzing carbon-fluorine bond oxidative addition processes. To date, many examples of carbon-fluorine bond oxidative addition using various transition metal complexes have been reported, but these processes are limited to sp... 2 Hybridized carbon-fluorine bonds, such as those in fluoroaromatics and fluoroalkenes. In contrast, the sp[] in the trifluoromethyl group of directly cleaved trifluoromethylaromatics... 3 Hybridized carbon-fluorine bonds are rare. Benzyl or allyl sp... 3 The cleavage of hybrid carbon-fluorine bonds occurs through a single-electron transfer system and electrophilic cationic species such as silicon ions. (Chen, K. et al. J. Am. Chem. Soc. 2017, 139, 18444-18447.; Wang, H. et al. Am. Chem. Soc. 2018, 140, 163-166. Luo, C. et al. J. Am. Chem. Soc. 2019, 141, 14120-14125. Scott, VJ et al. Am. Chem. Soc. 2005, 127, 2852-2853. Yoshida, S. et al. Angew. Chem. Int. Ed. 2017, 56, 5890-5893. Mandal, D. et al.) (J. Am. Chem. Soc. 2020, 142, 2572-2578.) In 2013, researchers used a niobium catalyst to achieve the conversion of the three carbon-fluorine bonds in trifluoromethyl aromatics. (Gianetti, T. Let al. J. Am. Chem. Soc. 2013, 135, 8145-8148.) In 2020, Hiroaki Iwamoto et al. first used a nickel complex to achieve the oxidative addition of carbon-fluorine bonds in trifluoromethyl aromatics, yielding the defluorination and hydrogenation product. (Hiroaki Iwamoto et al. J. Am. Chem. Soc. 2020, 142, 19360-19367.) While there is considerable research on transition metal-catalyzed defluorination and hydrogenation, research using non-metallic catalysts is relatively limited.

[0003] N-heterocyclic carbene boranes, as boron derivatives, can participate in a variety of reactions in different roles. Compared to traditional boron reagents, nitrogen-heterocyclic carbene (NHC) boranes have advantages such as being readily available, highly stable, and easy to handle. Furthermore, due to the presence of coordinate bonds in NHC boranes, a push-pull electron structure is formed between NHC and boron, with the boron center consisting of sp... 2 Hybridization to sp 3 Hybridization leads to a significant increase in the electron cloud density at the boron center. It is precisely this unique electronic structure that causes it to exhibit reactivity different from traditional borane reagents.

[0004] Free radical reactions are a powerful and efficient means of constructing complex organic compounds, offering advantages such as mild reaction conditions, rapid reaction rates, and good functional group tolerance. Therefore, utilizing free radical reaction mechanisms to achieve functional group transformations has attracted widespread attention from researchers. Summary of the Invention

[0005] Currently, the defluorination and hydrogenation reaction of trifluoromethyl aromatics uses transition metal catalysis, which has disadvantages such as high cost, difficult post-processing, and heavy metal pollution. To overcome the shortcomings of existing methods, this invention provides a new method for directly cleaving the sp(s) group in the trifluoromethyl group of trifluoromethyl aromatics. 3 The method involves reacting a hybridized carbon-fluorine bond under the conditions of a non-metallic photocatalyst and N-heterocyclic carbene borane, with nitrogen replacement, and under light source irradiation at 30–40 °C for 12–48 h, to obtain an aromatic compound with detrifluorinated hydrogenation.

[0006] This method has the following advantages: 1) It has a wide range of applicable substrates, and the applicable trifluoromethyl aromatic compounds include trifluoromethyl aromatics with only cyano substitution, trifluoromethyl aromatics with cyano and halogen, trifluoromethyl aromatics with cyano and amino groups, trifluoromethyl aromatics with amide groups, trifluoromethyl aromatics with ester groups, trifluoromethyl aromatics with sulfonamide groups, and trifluoromethyl aromatics with methoxy groups, all of which can achieve yields of over 70%. 2) This method does not require the addition of an initiator, and has the advantages of simple operation, high stability, and the ability to achieve gram-scale scale-up.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] Using trifluoromethyl aromatic hydrocarbon (0.25 mmol) as a raw material, under the conditions of an organic photocatalyst (0.0025 mmol to 0.0125 mmol) and N-heterocyclic carbene borane (0.30 mmol to 0.75 mmol), 1 to 3 mL of solvent was added, and after nitrogen purging, the reaction was carried out at 30 to 40 °C for 12 to 48 h under light irradiation to obtain aromatic compounds that have undergone defluorination and hydrogenation (from water) (e.g., 4-methylbenzonitrile obtained by defluorination and hydrogenation of 4-trifluoromethylbenzonitrile).

[0009] The trifluoromethyl aromatic compound has the following structure, wherein R 1 R 2 R 3 R 4 R 5 R 6 R 7 R 8 Each of these represents a single substituent on its corresponding benzene ring, and the substituents are H, halogens (F, Cl, Br, I), amino groups, or alkoxy groups (with the molecular formula OC). n H 2n+1 One of the following (n = 1-5).

[0010]

[0011] The aforementioned nitrogen-containing heterocyclic carbene borane is Or compounds having the following structure, wherein R a R b R c R d R e R f These are halogens (F, Cl, Br, I) and alkyl groups (with the molecular formula C). n H 2n+1 (n = 1-20), substituted arylalkyl (X) m C6H 5-m C n H 2n n = 0-10, m = 0-4, X = F, Cl, Br, I) or alkoxy group (molecular formula OC) n H 2n+1 (n = 1-10), alkyl halide (molecular formula C n H 2n X, n = 1-20, X = one of F, Cl, Br, I, R a R b R c R d R e R f Same or different.

[0012]

[0013] The organic photocatalyst is a compound having the following structure, and the catalyst used is one or more of the following catalysts. Wherein R 1 R 2 R 3 R 4 R 5 R 6 R 7R 8 R 9 R 10 Each of these represents a single substituent on its corresponding benzene ring, and the substituents are H, halogens (F, Cl, Br, I), or alkyl groups (with the molecular formula C). n H 2n+1 (n = 1-5) or alkoxy group (molecular formula OC) n H 2n+1 One of the following (n = 1-5), R 1 R 2 R 3 R 4 R 5 R 6 R 7 R 8 R 9 R 10 Same or different.

[0014]

[0015] The light source is one of the following: visible light violet (390nm-435nm), visible light blue (435nm-490nm), or visible light green (490nm-560nm), with visible light blue (435nm-490nm) being preferred. The power of the light source is 1W to 100W, preferably 20W to 30W.

[0016] The solvent used is one or more of tetrahydrofuran, 1,4-dioxane, toluene, N,N-dimethylformamide, acetonitrile, H2O, and 1,2-dichloroethane.

[0017] This method has the following advantages: 1) It has a wide range of applicable substrates, and the applicable trifluoromethyl aromatic compounds include trifluoromethyl aromatics with only cyano substitution, trifluoromethyl aromatics with cyano and halogen, trifluoromethyl aromatics with cyano and amino groups, trifluoromethyl aromatics with amide groups, trifluoromethyl aromatics with ester groups, trifluoromethyl aromatics with sulfonamide groups, and trifluoromethyl aromatics with methoxy groups, all of which can achieve moderate to high yields. 2) This method does not require the addition of an initiator, and has the advantages of simple operation, high stability, and the ability to achieve gram-scale scale-up. Detailed Implementation

[0018] The following examples illustrate the specific implementation steps of the present invention in detail. These examples should not be construed as limiting the scope of the present invention.

[0019] Example 1

[0020] Organic photocatalyst 4-DPA-IPN(R) 1 ~R 8 Synthesis of H (all H):

[0021]

[0022] First, the apparatus was dried and its internal chamber was purged with nitrogen three times. Then, under nitrogen purging, diphenylamine (1.69 g, 10.00 mmol) and 40 mL THF were added to the internal chamber. NaH solid (0.48 g, 12.00 mmol) was added under ice-water bath (0-4 °C). After the addition was complete, the mixture was stirred for 2 hours to obtain the reaction solution. Next, 2,4,5,6-tetrafluoroisophthalonitrile (0.40 g, 2.00 mmol) was weighed, dissolved in 2 mL THF, and transferred to a constant-pressure dropping funnel. This solution was added dropwise to the reaction solution. After the addition was complete, the ice-water bath was removed, the temperature was raised to 50 °C, and the mixture was stirred overnight. Once the raw materials were consumed, the mixture was cooled to room temperature, and excess NaH was slowly quenched with 10 mL of water. The mixture was filtered, and then washed with 200 mL of methanol to obtain the crude product. The crude product was further purified by column chromatography (dichloromethane / n-hexane = 2 / 3, V / V) to obtain 1.4 g of the product. 1 H NMR (400MHz, CDCl3): δ7.22–7.18(m,4H),7.03–6.99(m,12H),6.95(tt,J= 7.4,1.1Hz,2H),6.86–6.78(m,8H),6.64–6.60(m,10H),6.50–6.47(m,4H). 13 C NMR (CDCl3, 100MHz): δ154.20,151.75,145.55,144.68,143.17,140.30,129.40,128.61,127.58,124.20,123.97,122.94,122.61,12 1.09,113.17,113.03.IR(solid,ν,cm-1):3045,2214,1597,1540,1489,1478,1444,1332,1308,1222,1149,926,739,717.ESI:Calcd for C 56 H 40 N6Na + ([M+Na)) + )817.3212,found:817.3147.

[0023] Example 2

[0024] Organic photocatalyst 3-DPAFIPN(R) 1 ~R 6 Synthesis of H (all H):

[0025]

[0026] First, the apparatus was dried and its internal chambers were purged with nitrogen three times. Then, under nitrogen purging, diphenylamine (1.27 g, 7.50 mmol) and 40 mL of THF were added to the internal chambers. NaH solid (0.36 g, 9.00 mmol) was added under ice-water bath conditions (0–4 °C). After the addition was complete, the mixture was stirred for 2 hours to obtain the reaction solution. Next, 2,4,5,6-tetrafluoroisophthalonitrile (0.40 g, 2.00 mmol) was weighed, dissolved in 2 mL of THF, and transferred to a constant-pressure dropping funnel. This solution was added dropwise to the reaction solution. After the addition was complete, the ice-water bath was removed, and the mixture was stirred overnight at room temperature. Once the raw materials were consumed, excess NaH was slowly quenched with 10 mL of H₂O. The mixture was filtered and washed with 200 mL of methanol to obtain the crude product. The crude product was further purified by column chromatography (dichloromethane / n-hexane = 2 / 3, V / V) to obtain 1.06 g of the product.

[0027] 1 H NMR (400MHz, CDCl3): δ7.30–7.20(12H), 7.11–7.01(6H), 7.01–6.93(12H). 13 CNMR (101MHz, CDCl 3) δ152.48(d,J=258.5Hz),151.81(d,J=3.2Hz),151.19,145.55,145.33,143.07(d,J=11.1Hz ),129.45,129.37,124.60,124.02,122.76,122.73,112.61(d,J=3.2Hz),109.05(d,J=3.0Hz). 19 F NMR(377MHz, CDCl3)δ-121.30.IR(solid,ν,cm-1):3033,2104,1547,1456,1428,1414,1310,1219,1179,930,714,704.ESI:Calcd forC 44 H 30 FN5([M+Na)) + )670.2378,found:670.2378.

[0028] Example 3

[0029] Nitrogen heterocyclic carbene borane diMe-Imd-BH3(R) a R d All are methyl, R b R c R e R f Synthesis of H (all H):

[0030]

[0031] First, the apparatus was dried and its internal chamber was purged with nitrogen three times. Then, under nitrogen purging, 1-methylimidazole (9.85 g, 0.12 mol) and 24 mL of DCM (dry dichloromethane) were added to the internal chamber. Iodomethane (20.44 g, 0.144 mol) was added dropwise through a constant pressure dropping funnel under ice-water bath (0-4 °C). After the addition was complete, the mixture was moved to room temperature and stirred for 12 h. The solvent was then evaporated to obtain the first product. Next, NaBH4 (5.83 g, 0.154 mol) was directly weighed and added to the first product. 110 mL of toluene was added, and the mixture was heated to 125 °C and refluxed for 20 h. After reflux, the supernatant was evaporated to obtain the crude product. The crude product was then recrystallized with 140 mL of H2O to obtain 7.07 g of diMe-Imd-BH3, with a yield of 58.4%.

[0032] 1 H NMR (400MHz, CDCl3): δ6.80(s,2H),3.74(s,6H),1.02(m,3H). 13 CNMR (101MHz, CDCl3) δ 170.2 (q, J B-C =50.3Hz), 120.0, 35.9. 11 B(128MHz, CDCl3)-37.5(q,J=86.4Hz).IR(solid,ν,cm-1):3133,3167,3051,2985,2953,2275,1574,1419,1445,1266,1232,1187,876,714,704.ESI:Calcd for C5H 10 BN2([M+Na)) + )109.0932,found:109.0935.

[0033] Example 4

[0034] The substrate 4-(trifluoromethyl)benzonitrile (0.30 mmol), the organic photocatalyst 3-DPAFIPN (0.0075 mmol), the nitrogen-containing heterocyclic carbene borane diMe-Imd-BH3 (0.33 mmol), and acetonitrile:H2O = 95:5 (v / v, 2 mL) were weighed sequentially into a dried glass bottle. A magnetic swirl was added, the bottle was sealed with a rubber stopper, and the atmosphere inside the glass bottle was purged with nitrogen three times (the gas purging can be performed by inserting the tip of a syringe needle through the rubber stopper into the glass bottle; this procedure can be followed in the following examples and comparative examples). The reaction was carried out at 35°C for 12 h under 20 W blue light source at 455 nm. After the reaction was stopped, the internal standard naphthalene (15 mg) was added to the reaction solution. After complete dissolution, the yield of 4-methylbenzonitrile was quantitatively analyzed by GC-MS, and the yield was 80%.

[0035] Example 5

[0036] The substrate 2-(trifluoromethyl)benzonitrile (0.30 mmol), the organic photocatalyst 3-DPAFIPN (0.0075 mmol), the azahexacyclic carbene borane diMe-Imd-BH3 (0.33 mmol), and acetonitrile:H2O = 95:5 (v / v, 2 mL) were weighed sequentially into a dried glass bottle. A magnetic swirl was added, the bottle was sealed with a rubber stopper, and the atmosphere inside the glass bottle was purged with nitrogen three times. The reaction was carried out at 35 °C for 12 h under irradiation with a 455 nm blue light source at 20 W. After the reaction was stopped, naphthalene (15 mg) was added to the reaction solution as an internal standard. After complete dissolution, the yield of 2-methylbenzonitrile was quantitatively analyzed by GC-MS and found to be 90%.

[0037] Example 6

[0038] The substrate methyl 4-(trifluoromethyl)benzoate (0.30 mmol), the organic photocatalyst 3-DPAFIPN (0.0075 mmol), the azahexacyclic carbene borane diMe-Imd-BH3 (0.33 mmol), and acetonitrile:H2O = 95:5 (v / v, 2 mL) were weighed sequentially into a dried glass bottle. A magnetic swirl was added, the bottle was sealed with a rubber stopper, and the atmosphere inside the glass bottle was purged with nitrogen three times. The reaction was carried out at 35 °C for 12 h under irradiation with a 20 W blue light source at 455 nm. After the reaction was stopped, the internal standard naphthalene (15 mg) was added to the reaction solution. After complete dissolution, the yield of methyl 4-methylbenzoate was quantitatively analyzed by GC-MS and found to be 95%.

[0039] Example 7

[0040] The substrate 4-(trifluoromethyl)benzamide (0.30 mmol), the organic photocatalyst 3-DPAFIPN (0.0075 mmol), the azahexacyclic carbene borane diMe-Imd-BH3 (0.33 mmol), and acetonitrile:H2O = 95:5 (v / v, 2 mL) were weighed sequentially into a dried glass bottle. A magnetic swirl was added, the bottle was sealed with a rubber stopper, and the atmosphere inside the glass bottle was purged with nitrogen three times. The reaction was carried out at 35 °C for 12 h under irradiation with a 20 W blue light source at 455 nm. After the reaction was stopped, the internal standard naphthalene (15 mg) was added to the reaction solution. After complete dissolution, the yield of 4-methylbenzamide was quantitatively analyzed by GC-MS, and the yield was 85%.

[0041] Example 8

[0042] The substrate methyl 2-(trifluoromethyl)benzoate (0.30 mmol), the organic photocatalyst 3-DPAFIPN (0.0075 mmol), the azahexacyclic carbene borane diMe-Imd-BH3 (0.33 mmol), and acetonitrile:H2O = 95:5 (v / v, 2 mL) were weighed sequentially into a dried glass bottle. A magnetic swirl was added, the bottle was sealed with a rubber stopper, and the atmosphere inside the glass bottle was purged with nitrogen three times. The reaction was carried out at 35 °C for 12 h under irradiation with a 455 nm blue light source at 20 W. After the reaction was stopped, the internal standard naphthalene (15 mg) was added to the reaction solution. After complete dissolution, the yield of methyl 2-methylbenzoate was quantitatively analyzed by GC-MS and found to be 65%.

[0043] Example 9

[0044] The substrate 5-fluoro-2-trifluoromethylbenzonitrile (0.30 mmol), the organic photocatalyst 3-DPAFIPN (0.0075 mmol), the nitrogen-containing heterocyclic carbene borane diMe-Imd-BH3 (0.33 mmol), and acetonitrile:H2O = 95:5 (v / v, 2 mL) were weighed sequentially into a dried glass bottle. A magnetic swirl was added, the bottle was sealed with a rubber stopper, and the atmosphere inside the glass bottle was purged with nitrogen three times. The reaction was carried out at 35 °C for 12 h under irradiation with a 20 W blue light source at 455 nm. After the reaction was stopped, the internal standard naphthalene (15 mg) was added to the reaction solution. After complete dissolution, the yield of 5-fluoro-2-methylbenzonitrile was quantitatively analyzed by GC-MS, and the yield was 70%.

[0045] Example 10

[0046] The substrate 2-bromo-4-(trifluoromethyl)benzonitrile (0.30 mmol), the organic photocatalyst 3-DPAFIPN (0.0075 mmol), the azahexacyclic carbene borane diMe-Imd-BH3 (0.33 mmol), and acetonitrile:H2O = 95:5 (v / v, 2 mL) were weighed sequentially into a dried glass bottle. A magnetic swirl was added, the bottle was sealed with a rubber stopper, and the atmosphere inside the glass bottle was purged with nitrogen three times. The reaction was carried out at 35 °C for 12 h under irradiation with a 20 W blue light source at 455 nm. After the reaction was stopped, the internal standard naphthalene (15 mg) was added to the reaction solution. After complete dissolution, the yield of 4-methylbenzonitrile was quantitatively analyzed by GC-MS and found to be 90%.

[0047] Example 11

[0048] The substrate 2-bromo-6-(trifluoromethyl)benzonitrile (0.30 mmol), the organic photocatalyst 3-DPAFIPN (0.0075 mmol), the azahexacyclic carbene borane diMe-Imd-BH3 (0.33 mmol), and acetonitrile:H2O = 95:5 (v / v, 2 mL) were weighed sequentially into a dried glass bottle. A magnetic swirl was added, the bottle was sealed with a rubber stopper, and the atmosphere inside the glass bottle was purged with nitrogen three times. The reaction was carried out at 35 °C for 12 h under irradiation with a 455 nm blue light source at 20 W. After the reaction was stopped, the internal standard naphthalene (15 mg) was added to the reaction solution. After complete dissolution, the yield of 2-methylbenzonitrile was quantitatively analyzed by GC-MS and found to be 86%.

[0049] Example 12

[0050] Weigh the substrate 2-amino-4-(trifluoromethyl)benzonitrile (0.30 mmol), the organic photocatalyst 3-DPAFIPN (0.0075 mmol), the nitrogen-containing heterocyclic carbene borane diMe-Imd-BH3 (0.33 mmol), and acetonitrile:H2O = 95:5 (v / v, 2 mL) sequentially into a dried glass bottle. Add a magnetic stir bar, seal the bottle with a rubber stopper, and purge the bottle with nitrogen three times. React at 35°C for 12 h under 20 W 455 nm blue light source irradiation. After stopping the reaction, take 0.5 mL of the reaction solution, add the internal standard dibromomethane (15 mg) and 0.5 mL of CDCl3, and mix thoroughly. 1 Quantitative analysis by ¹H NMR showed that the yield of 2-amino-4-methylbenzonitrile was 92%. The product was purified by column chromatography (ethyl acetate / n-hexane = 1 / 20 V / V) to give 32.1 mg (81%).

[0051] 1 H NMR (400MHz, CDCl3) δ7.24 (s, 1H), 6.54 (d, J = 8.0Hz, 2H), 4.29 (s, 2H), 2.27 (s, 3H); 13C NMR(101MHz, CDCl3)δ151.0,143.0,132.4,119.2,117.3,116.2,90.1,20.8.IR(solid,ν ,cm-1):3378,3323,3056,3049,3021,2947,2936,2620,1616,1561,1205,962,760,628.

[0052] Example 13

[0053] Without an organic photocatalyst, the substrate 4-(trifluoromethyl)benzonitrile (0.30 mmol), the azahexacyclic carbene borane diMe-Imd-BH3 (0.33 mmol), and acetonitrile:H2O = 95:5 (v / v, 2 mL) were weighed sequentially into a dried glass bottle. A magnetic spool was added, the bottle was sealed with a rubber stopper, and the atmosphere inside the glass bottle was purged with nitrogen three times. The reaction was carried out at 35 °C for 12 h under irradiation with a 20 W blue light source at 455 nm. After the reaction was stopped, the internal standard naphthalene (15 mg) was added to the reaction solution. After complete dissolution, the yield of 4-methylbenzonitrile was quantitatively analyzed by GC-MS and found to be 0%.

[0054] Example 14

[0055] The substrate 4-(trifluoromethyl)benzonitrile (0.30 mmol), the organic photocatalyst EosinY (Sigma-Adrich, E4009-5G) (0.0075 mmol), the nitrogen-containing carbene borane diMe-Imd-BH3 (0.33 mmol), and acetonitrile:H2O = 95:5 (v / v, 2 mL) were weighed sequentially into a dried glass bottle. A magnetic stopper was added, the bottle was sealed with a rubber stopper, and the atmosphere inside the glass bottle was purged with nitrogen three times. The reaction was carried out at 35 °C for 12 h under irradiation with a 20 W blue light source at 455 nm. After the reaction was stopped, the internal standard naphthalene (15 mg) was added to the reaction solution. After complete dissolution, the yield of 4-methylbenzonitrile was quantitatively analyzed by GC-MS, and the yield was 1%.

[0056] Example 15

[0057] The substrate 4-(trifluoromethyl)benzonitrile (0.30 mmol), the organic photocatalyst 4-DPA-IPN (0.0075 mmol), the azahexacyclic carbene borane diMe-Imd-BH3 (0.33 mmol), and acetonitrile:H2O = 95:5 (v / v, 2 mL) were weighed sequentially into a dried glass bottle. A magnetic spool was added, the bottle was sealed with a rubber stopper, and the atmosphere inside the glass bottle was purged with nitrogen three times. The reaction was carried out under a 20 W blue light source at 455 nm for 12 h. After the reaction was stopped, the internal standard naphthalene (15 mg) was added to the reaction solution. After complete dissolution, the yield of 4-methylbenzonitrile was quantitatively analyzed by GC-MS and found to be 60%.

[0058] Example 16

[0059] The substrate 4-(trifluoromethyl)benzonitrile (0.30 mmol), the organic photocatalyst 3-DPAFIPN (0.0075 mmol), the azahexacyclic carbene borane diMe-Imd-BH3 (0.33 mmol), and THF (2 mL) were weighed sequentially into a dried glass bottle. A magnetic spool was added, the bottle was sealed with a rubber stopper, and the atmosphere inside the glass bottle was purged with nitrogen three times. The reaction was carried out at 35 °C for 12 h under irradiation with a 455 nm blue light source at 20 W. After the reaction was stopped, naphthalene (15 mg) was added to the reaction solution. After complete dissolution, the yield of 4-methylbenzonitrile was quantitatively analyzed by GC-MS and found to be 10%.

[0060] Example 17

[0061] The substrate 4-(trifluoromethyl)benzonitrile (0.30 mmol), the organic photocatalyst 3-DPAFIPN (0.0075 mmol), the nitrogen-containing heterocyclic carbene borane (as shown in the formula below, the synthesis method is as described in the literature Michael J. Ingleson. et al. Chem. Sci., 2019, 10, 1434) (0.33 mmol), and acetonitrile:H2O = 95:5 (v / v, 2 mL) were weighed sequentially into a dried glass bottle. A magnetic stopper was added, the bottle was sealed with a rubber stopper, and the atmosphere inside the glass bottle was replaced with nitrogen three times. The reaction was carried out at 35 °C for 12 h under irradiation with a 20 W blue light source at 455 nm. After the reaction was stopped, the internal standard naphthalene (15 mg) was added to the reaction solution. After complete dissolution, the yield of 4-methylbenzonitrile was quantitatively analyzed by GC-MS and found to be 70%.

[0062]

Claims

1. A method for hydrogenating trifluoromethyl aromatic hydrocarbons by breaking carbon-fluorine bonds, characterized in that: Using 0.25-0.30 mmol of trifluoromethyl aromatic hydrocarbon as a starting material, in the presence of 0.0025 mmol to 0.0125 mmol of organic photocatalyst and 0.30 mmol to 0.75 mmol of nitrogen-containing heterocyclic carbene borane, 1 to 3 mL of aqueous organic solvent was added into a reaction vessel. After the atmosphere inside the vessel was replaced with an inert gas, the reactants in the vessel were reacted at 30 to 40 °C for 12 to 48 h under the illumination of a light source to obtain an aromatic compound that has undergone de-trifluoro hydrogenation. The trifluoromethyl aromatic compound has one or more of the following structures, wherein R 1 R 2 R 3 R 4 R 5 R 6 R 7 R 8 Each of these represents a single substituent on its corresponding benzene ring, which are independently H, halogen, amino, and have the molecular formula OC. n H 2n+1 It contains one or more alkoxy groups, each numbering 1 to 4, wherein the halogen is selected from one or more of F, Cl, Br, and I; OC n H 2n+1 In the case of n=1-5, ， The organic photocatalyst is a compound having the following structure, and the catalyst used is one or more of the following catalysts; wherein R 1 R 2 R 3 R 4 R 5 R 6 R 7 R 8 R 9 R 10 Each of these represents a single substituent on its corresponding benzene ring, which are independently H, halogen, and have the molecular formula C. n H 2n+1 alkyl groups or molecules with the formula OC n H 2n+1 One or more alkoxy groups, each numbering 1 to 4, and R 1 R 2 R 3 R 4 R 5 R 6 R 7 R 8 R 9 R 10 Any two or more of them are the same or different; halogens are selected from F, Cl, Br, I, C n H 2n+1 In the case of n=1-5, OC n H 2n+1 In the case of n=1-5, ， The aforementioned nitrogen-containing heterocyclic carbene borane is Or one or more compounds having the following structures, wherein R a R b R c R d R e R f The elements are H, halogen, and C, respectively. n H 2n+1 Alkyl, substituted aryl alkyl or with the molecular formula OC n H 2n+1 The alkoxy group, with the molecular formula C n H 2n X has one or more alkyl halides, each numbering between 1 and 4; and R a R b R c R d R e R f Any two or more of them are the same or different; the molecular formula is C n H 2n+1 In alkyl groups, n = 1-20, and the molecular formula of substituted aryl alkyl groups is X. m C6H 5-m C n H 2n n=0-10, m=0-4, X=one or more of F, Cl, Br, and I; molecular formula is OC n H 2n+1 In the alkoxy group, n = 1-10, and the molecular formula is C. n H 2n In the alkyl halide group of X, n = 1-20, and X = one or more of F, Cl, Br, and I; ， The light source is a visible blue light source with a wavelength of 435 nm to 490 nm.

2. The method according to claim 1, characterized in that: The power of the light source is 1 W to 100 W.

3. The method according to claim 2, characterized in that: The power of the light source is 20 W to 30 W.

4. The method according to claim 1, characterized in that: The water content in the aqueous organic solvent is 1-10% by volume, and the organic solvent used is tetrahydrofuran, 1,4-dioxane, toluene, etc. N,N One or more of dimethylformamide, acetonitrile, and 1,2-dichloroethane.

5. The method according to claim 4, characterized in that: The water content in the aqueous organic solvent is 4-8% by volume.

6. The method according to claim 4, characterized in that: The water content in the aqueous organic solvent is 5-6% by volume.

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