C2-boron substituted indoline compound and preparation method thereof
By activating the C=C bond of indole with a photocatalyst, the efficient synthesis of C2-boron-substituted dihydroindole was achieved, solving the problem of indole dearomatization reaction in the existing technology and providing a simple, low-cost and highly selective preparation method.
Patent Information
- Application Number
- CN202511669468.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-14
- Publication Date
- 2026-02-06
AI Technical Summary
In the existing technology, the dearomatization reaction of indole has problems such as harsh reaction conditions, poor regioselectivity, high cost, heavy metal residues and narrow substrate applicability, especially insufficient activation efficiency for neutral or electron-rich indole.
The synthesis of C2-boron-substituted dihydroindole was achieved by using nitrogen-containing heterocyclic carbene borane and N-substituted indole derivatives via a hydroboration reaction in the presence of a photocatalyst and additives. The C=C bond was activated by single-electron transfer or energy transfer using a photocatalyst, and the reaction was carried out under blue LEDs.
It achieves zero heavy metal residue, few side reactions, simple operation, convenient separation and purification, wide applicability, good regional selectivity, low cost, and is suitable for the derivatization of drug molecules with complex structures.
Smart Images
Figure SMS_1 
Figure SMS_12 
Figure SMS_14
Abstract
Description
Technical Field
[0001] This invention relates to the field of pharmaceutical intermediate synthesis technology, and specifically to a C2-boron-substituted dihydroindole compound and its preparation method. Background Technology
[0002] Structural modification of heterocyclic compounds is a crucial technique in drug development and functional material design. Among these, the dihydroindole skeleton, an important class of nitrogen-containing heterocycles, is widely found in natural products and drug molecules, exhibiting diverse pharmacological activities. For example, the dihydroindole unit in the core structure of physostigmine, an anticholinesterase drug, is essential for its activity; Corynoxine and other Uncaria alkaloids exert neuromodulatory effects through this skeleton. Notably, these natural molecules rarely contain boron atoms. The introduction of boron not only significantly improves drug targeting and metabolic stability but also serves as a key synthetic site, allowing for the construction of more structurally diverse dihydroindole derivatives through reactions such as Suzuki coupling and oxidative hydroxylation, thereby expanding the pharmaceutical chemistry space.
[0003] Traditionally, the dearomatization of indole has relied primarily on transition metal catalysis or electrochemical redox strategies. Transition metal catalysis typically requires metal catalysts (such as Pd, Rh, Ni, etc.), which suffer from harsh reaction conditions, poor regioselectivity, high cost, and heavy metal residues, limiting its application in drug synthesis. While electrochemical methods avoid the use of metal catalysts, they still face challenges such as complex reaction apparatus, low current efficiency, and a narrow substrate applicability, particularly with generally insufficient activation efficiency for neutral or electron-rich indole. Summary of the Invention
[0004] To address the technical problems existing in the prior art, the present invention provides a C2-boron-substituted dihydroindole compound and its preparation method.
[0005] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a C2-boron-substituted dihydroindole compound, wherein the compound has the following structure:
[0006] (I) Where X is NH, N-SO2Ph, N-Boc, N-Troc, NCH3, NTs, O or S; R 1 The electron-donating group is H, an electron-donating group, or an electron-withdrawing group, wherein the electron-donating group is methyl, methoxy, phenyl, or tert-butyl, and the electron-withdrawing group is fluorine, chlorine, bromine, cyano, or trifluoromethyl. R2 It is methyl or isopropyl; R 3 It can be methyl, isopropyl, benzyl, n-butyl, or cyclohexyl; Y represents either H or N atoms.
[0007] Furthermore, the C2-boron-substituted dihydroindole compound is selected from any of the following compounds: , , , , , , , , , .
[0008] A method for preparing a C2-boron-substituted dihydroindole compound includes the following steps: Compound 1 and compound 2 undergo a hydroboration reaction. The reaction proceeds via a free radical process, involving indole dearomatization and hydroboration, ultimately yielding a C2-boron-substituted dihydroindole compound. The reaction equation is as follows.
[0009] Compound 1 is an N-substituted indole derivative; compound 2 is a nitrogen-containing heterocyclic carbene borane.
[0010] Furthermore, the specific steps include: Compound 1, compound 2, photocatalyst and additives were mixed in an organic solvent and reacted for 12-18 h under nitrogen protection and light irradiation at a wavelength of 440-450 nm. The reaction was completed, yielding C2-boron-substituted dihydroindole compounds; The reaction formula is as follows: .
[0011] Furthermore, the photocatalyst is 4-DPAIPN.
[0012] Furthermore, the organic solvent is anhydrous toluene, anhydrous methyl tert-butyl ether, or anhydrous 1,4-dioxane. Furthermore, the additive is thiophenol and alkali, wherein the molar ratio of thiophenol to alkali is (1~3):10.
[0013] Furthermore, the molar ratio of compound 1, compound 2, photocatalyst, thiophenol and base is 1:1.5:(0.02~0.05):(0.1~0.3):(1~2).
[0014] Furthermore, the thiophenol is 4-methylthiophenol, 4-trifluoromethylthiophenol, or methyl thiosalicylate.
[0015] Furthermore, the base is pyridine, TEBA, or TBAB.
[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The preparation method of the present invention is simple to operate, has no heavy metal residue, few side reactions, and is easy to separate and purify.
[0017] (2) In this invention, the photocatalyst can efficiently activate the C=C bond of indole through a single electron transfer or energy transfer mechanism, thereby achieving borylation and dearomatization. Photocatalysis does not require a strong coordination environment, and the reaction selectivity can be controlled by adjusting the redox potential of the photosensitizer, making it suitable for the derivatization of complex drug molecules.
[0018] (3) In the preparation process of the present invention, the reaction conditions are mild, the substrate has a wide range of applicability, good regioselectivity, and strong functional group tolerance.
[0019] (4) The reaction apparatus used in the preparation process of the present invention is very simple and the overall preparation efficiency is high.
[0020] (5) The raw materials used in this invention are simple and readily available, with low cost, and the activation efficiency of neutral or electron-rich indole is high, which has a good application prospect. Detailed Implementation
[0021] It is readily understood that, based on the technical solution of this invention, those skilled in the art can propose various interchangeable structural methods and implementations without altering the essential spirit of the invention. Therefore, the following specific embodiments are merely illustrative examples of the technical solution of this invention and should not be considered as the entirety of the invention or as limitations or restrictions on the technical solution of this invention.
[0022] This invention provides a C2-boron-substituted dihydroindole compound, specifically the structure shown in formula (I):
[0023] (I) Where X is NH, N-SO2Ph, N-Boc, N-Troc, NCH3, NTs, O or S; R 1 It can be H, an electron-donating group, or an electron-withdrawing group; wherein, the electron-donating group is methyl, methoxy, phenyl, or tert-butyl; and the electron-withdrawing group is fluorine, chlorine, bromine, cyano, or trifluoromethyl. R 2 Methyl, isopropyl, etc.; R3 It can be methyl, isopropyl, benzyl, n-butyl, or cyclohexyl, etc.; Y can be an H or N atom, etc.
[0024] In an organic solvent (anhydrous methyl tert-butyl ether), using 4-DPAIPN as a photosensitizer and TBAB and methyl thiosalicylate as additives, N-substituted indole undergoes a hydroboration reaction with NHC-BH3 under 30 W blue LED light irradiation. The reaction proceeds via a free radical process to finally yield boron-containing dihydroindole compounds. The reaction formula is as follows:
[0025] Example 1 In an 18 × 180 mm glass tube, N-(p-toluenesulfonyl)indole (0.2 mmol, 1.0 equivalent), 1,3-dimethylimidazolium borane (1.5 equivalent), 4-DPAIPN (2 mol%), TBAB (1.0 equivalent), methyl thiosalicylate (0.2 equivalent), and anhydrous methyl tert-butyl ether (2 mL) were added. The reaction was carried out under nitrogen protection and irradiated with a 30 W blue LED for 12 hours until complete reaction was observed by TLC. The reaction solution was concentrated and separated by column chromatography to obtain the corresponding C2-boron-substituted dihydroindole compound 3a. The product was a green oily liquid, and the separation yield was 85%. Its chemical formula is […]. .
[0026] Green oil (85%, 64.8 mg). 1 H NMR (400 MHz, CDCl3) δ 7.54 (d, J = 7.9Hz, 1H), 7.37 (d, J = 7.9 Hz, 2H), 7.14-7.11 (m, 1H), 7.07-7.03 (m, 3H), 7.00-6.97 (m, 1H), 6.84 (s, 2H), 3.92 (brs, 1H), 3.78 (s, 6H), 2.65-2.58 (m,1H), 2.49-2.46 (m, 1H), 2.28 (s, 3H) ppm. 13 C NMR (100 MHz, CDCl3) δ 142.8,142.1, 137.7, 136.3, 129.2, 126.9, 126.6, 125.4, 124.4, 120.4, 118.4, 36.2,35.6, 21.6 ppm. HRMS-ESI (m / z): [M+Na] +calcd for C 20 H 24 BN3O2SNa + , 424.0528;found, 424.0524. Example 2
[0027] In an 18 × 180 mm glass tube, the reaction substrate N-Boc-indole (0.2 mmol, 1.0 equivalent), 1,3-dimethylimidazolium borane (1.5 equivalent), 4-DPAIPN (2 mol%), TBAB (1.0 equivalent), methyl thiosalicylate (0.2 equivalent), and anhydrous methyl tert-butyl ether (2 mL) were added. The reaction was carried out under nitrogen protection and irradiated with a 30 W blue LED for 18 hours until complete reaction was observed by TLC. The reaction solution was concentrated and separated by column chromatography to obtain the corresponding C2-boron-substituted dihydroindole compound 3b. The product was a white solid with a separation yield of 65%, and its chemical formula is […]. .
[0028] White solid (65%, 40.3 mg). 1 H NMR (400 MHz, CDCl3) δ 7.69-7.41 (m,1H), 7.15 (d, J = 7.1 Hz, 1H), 7.09-7.05 (m, 1H), 6.90-6.86 (m, 1H), 6.76 (s,2H), 4.09 (brs, 1H), 3.69 (s, 6H), 3.34-3.30 (m, 1H), 2.75-2.71 (m, 1H) ppm. 13 C NMR (100 MHz, CDCl3) δ 126.3, 121.8, 120.1, 115.7, 36.0, 28.6 ppm. HRMS-ESI (m / z): [M+Na] + calcd for C 18 H 26 BN3O2Na + , 350.2010; found, 350.2012. Example 3
[0029] In an 18 × 180 mm glass tube, the reaction substrate N-(p-toluenesulfonyl)-5-methoxyindole (0.2 mmol, 1.0 equivalent), 1,3-dimethylimidazolium borane (1.5 equivalent), 4-DPAIPN (2 mol%), TBAB (1.0 equivalent), methyl thiosalicylate (0.2 equivalent), and anhydrous methyl tert-butyl ether (2 mL) were added. The reaction was carried out under nitrogen protection and irradiated with a 30 W blue LED for 12 hours until complete reaction was observed by TLC. The reaction solution was concentrated and separated by column chromatography to obtain the corresponding C2-boron-substituted dihydroindole compound 3c. The product was a white solid with a separation yield of 84%, and its chemical formula is […]. .
[0030] White solid (84%, 69.1 mg). 1 H NMR (400 MHz, CDCl3) δ 7.45-7.43 (m,1H), 7.36-7.35 (m, 2H), 7.08-7.06 (m, 2H), 6.86 (s, 2H), 6.69-6.67 (m, 1H),6.66-6.60 (m, 1H), 3.88 (brs, 1H), 3.80 (s, 6H), 3.76 (s, 3H), 2.50-2.47 (m,1H), 2.41-2.37 (m, 1H), 2.32 (s, 3H) ppm. 13 C NMR (100 MHz, CDCl3) δ 157.2,142.7, 139.6, 136.1, 135.6, 129.2, 127.1, 120.4, 119.3, 111.9, 110.0, 55.6,36.2, 35.8, 21.6 ppm. HRMS-ESI (m / z): [M+Na] + calcd for C 21 H 26 BN3O3SNa + ,434.1680; found, 434.1678. Example 4
[0031] In an 18 × 180 mm glass tube, N-(p-toluenesulfonyl)indole (0.2 mmol, 1.0 equivalent), 1-n-butyl-3-methylimidazolium borane (1.5 equivalent), 4-DPAIPN (2 mol%), TBAB (1.0 equivalent), methyl thiosalicylate (0.2 equivalent), and anhydrous methyl tert-butyl ether (2 mL) were added. The reaction was carried out under nitrogen protection and irradiated with a 30 W blue LED for 12 hours until complete reaction was observed by TLC. The reaction solution was concentrated and separated by column chromatography to obtain the corresponding C2-boron-substituted dihydroindole compound 3d. The product was a white solid with a separation yield of 74%, and its chemical formula is […]. .
[0032] White solid (74%, 62.6 mg). 1 H NMR (400 MHz, CDCl3) δ 7.54 (d, J = 7.9Hz, 1H), 7.38-7.33 (m, 2H), 7.16-7.11 (m, 1H), 7.08-7.04 (m, 2H), 7.04-6.96(m, 2H), 6.90-6.89 (m, 1H), 6.88-6.87 (m, 1H), 4.20-4.12 (m, 2H), 3.86 (brs,1H), 3.82 (s, 3H), 2.63-2.57 (m, 1H), 2.48-2.44 (m, 1H), 2.30 (s, 3H), 1.85-1.77 (m, 2H), 1.43-1.30 (m, 2H), 0.95 (t, J = 7.4 Hz, 3H) ppm. 13 C NMR (100MHz, CDCl3) δ 142.7, 142.2, 137.8, 136.3, 129.2, 126.9, 126.5, 125.4, 124.4,120.6, 118.9, 118.5, 48.5, 36.2, 35.7, 32.5, 21.6, 20.0, 13.8 ppm. HRMS-ESI(m / z): [M+Na] + calcd for C 23 H 30 BN3O2SNa + , 446.2044; found, 446.2036. Example 5
[0033] In an 18 × 180 mm glass tube, N-(p-toluenesulfonyl)-4-chloroindole (0.2 mmol, 1.0 equivalent), 1,3-dimethylimidazolium borane (1.5 equivalent), 4-DPAIPN (2 mol%), TBAB (1.0 equivalent), methyl thiosalicylate (0.2 equivalent), and anhydrous methyl tert-butyl ether (2 mL) were added. The reaction was carried out under nitrogen protection and irradiated with a 30 W blue LED for 12 hours until complete reaction was observed by TLC. The reaction solution was concentrated and separated by column chromatography to obtain the corresponding C2-boron-substituted dihydroindole compound 3e as a white solid in a yield of 62%. Its chemical formula is […]. .
[0034] White solid (62%, 51.6 mg). 1 H NMR (400 MHz, CDCl3) δ 7.45-7.42 (m,1H), 7.39-7.37 (m, 2H), 7.10-7.05 (m, 3H), 6.98-6.95 (m, 1H), 6.86 (s, 2H), 3.96 (brs, 1H), 3.81 (s, 6H), 2.63-2.62 (m, 2H), 2.33 (s, 3H) ppm. 13 C NMR (100 MHz, CDCl3) δ 143.6, 143.6, 143.2, 136.1, 136.0, 131.0, 129.4, 128.0,126.9, 124.4, 120.5, 116.2, 36.2, 35.2, 21.6 ppm.HRMS-ESI (m / z): [M+Na] + calcd for C 20 H 23 BClN3O2SNa + , 438.1185; found, 438.1178. Example 6
[0035] In an 18 × 180 mm glass tube, N-(p-toluenesulfonyl)-5-fluoroindole (0.2 mmol, 1.0 equivalent), 1,3-dimethylimidazolium borane (1.5 equivalent), 4-DPAIPN (2 mol%), TBAB (1.0 equivalent), methyl thiosalicylate (0.2 equivalent), and anhydrous methyl tert-butyl ether (2 mL) were added. The reaction was carried out under nitrogen protection and irradiated with a 30 W blue LED for 12 hours until complete reaction was observed by TLC. The reaction solution was concentrated and separated by column chromatography to obtain the corresponding C2-boron-substituted dihydroindole compound 3f. The product was a white solid with a separation yield of 65%, and its chemical formula is […]. .
[0036] White solid (65%, 51.9 mg). 1 H NMR (400 MHz, CDCl3) δ 7.49-7.45 (m,1H), 7.36-7.34 (m, 2H), 7.08 (d, J = 8.0 Hz, 2H), 6.87 (s, 2H), 6.84-6.80 (m,1H), 6.74-6.73 (m, 1H), 3.92 (brs, 1H), 3.80 (s, 6H), 2.56-2.51 (m, 1H),2.44-2.40 (m, 1H), 2.32 (s, 3H) ppm. 13 C NMR (100 MHz, CDCl3) δ 160.4 ( C -F, d, J = 240.3 Hz), 143.0, 140.2 ( C -F, d, J = 8.5 Hz), 138.2 ( C -F, d, J = 2.1 Hz),135.9, 129.3, 127.0, 120.4, 119.3 ( C -F, d, J = 8.7 Hz), 113.1 ( C -F, d, J =23.2 Hz), 112.5 ( C -F, d, J = 23.3 Hz), 36.2, 35.7, 21.6 ppm. 19F NMR (376 MHz, CDCl3) δ -119.3 (s, 1F). HRMS-ESI (m / z): [M+Na] + calcd for C 20 H 23 BFN3O2SNa + ,422.1480; found, 422.1472. Example 7
[0037] In an 18 × 180 mm glass tube, N-(p-toluenesulfonyl)indole (0.2 mmol, 1.0 equivalent), 1-benzyl-3-methylimidazolium borane (1.5 equivalent), 4-DPAIPN (2 mol%), TBAB (1.0 equivalent), methyl thiosalicylate (0.2 equivalent), and anhydrous methyl tert-butyl ether (2 mL) were added. The reaction was carried out under nitrogen protection and irradiated with a 30 W blue LED for 12 hours until complete reaction was observed by TLC. The reaction solution was concentrated and separated by column chromatography to obtain 3 g of the corresponding C2-boron-substituted dihydroindole compound. The product was a colorless liquid with a separation yield of 44%, and its chemical formula is [insert chemical formula here]. .
[0038] Colorless oil (44%, 40.3 mg). 1 H NMR (400 MHz, CDCl3) δ 7.56-7.54 (m,1H), 7.40-7.32 (m, 7H), 7.14-7.09 (m, 1H), 7.08-7.02 (m, 3H), 6.98 (t, J =7.3 Hz, 1H), 6.89-6.86 (m, 1H), 6.74-6.72 (m, 1H), 5.46-5.32 (m, 2H), 3.92(brs, 1H) 3.87 (s, 3H), 2.63-2.59 (m, 1H), 2.57-2.46 (m, 1H), 2.31 (s, 3H)ppm. 13 C NMR (100 MHz, CDCl3) δ 142.8, 142.1, 137.8, 136.2, 136.1, 129.2,129.0, 128.6, 128.3, 127.0, 126.6, 125.4, 124.5, 120.9, 119.0, 118.5, 52.3,36.3, 36.7, 21.6 ppm. HRMS-ESI (m / z): [M+Na] +calcd for C 26 H 28 BN3O2SNa + ,480.1887; found, 480.1889. Example 8
[0039] Benzothiophene (0.2 mmol, 1.0 equivalent), 1,3-dimethylimidazolium borane (1.5 equivalent), 4-DPAIPN (2 mol%), TBAB (1.0 equivalent), methyl thiosalicylate (0.2 equivalent), and anhydrous methyl tert-butyl ether (2 mL) were added to an 18 × 180 mm glass test tube. The reaction was carried out under nitrogen protection and irradiated with a 30 W blue LED for 12 hours until complete reaction was observed by TLC. The reaction solution was concentrated and separated by column chromatography for 3 hours to obtain the corresponding C2-boron-substituted dihydroindole compound. The product was a white solid with a separation yield of 40%, and its chemical formula is [insert chemical formula here]. .
[0040] White solid (40%, 19.5 mg). 1 H NMR (400 MHz, CDCl3) δ 7.13-7.10 (m,2H), 7.01-6.96 (m, 1H), 6.92-6.88 (m, 1H), 6.83 (s, 2H), 3.83 (s, 6H), 3.45-3.39 (brs, 1H), 3.25-3.19 (m, 1H), 2.99-2.92 (m, 1H) ppm. 13 C NMR (100 MHz, CDCl3) δ 145.3, 144.5, 126.3, 123.7, 123.2, 121.8, 120.6, 45.5, 36.5 ppm. HRMS-ESI (m / z): [M+Na] + calcd for C 13 H 17 BN2SNa + , 267.1098; found, 267.1108. Example 9
[0041] In an 18 × 180 mm glass tube, N-(p-toluenesulfonyl)indole (0.2 mmol, 1.0 equivalent), 1,2,4-triazole-type borane (1.5 equivalent), 4-DPAIPN (2 mol%), TBAB (1.0 equivalent), methyl thiosalicylate (0.2 equivalent), and anhydrous methyl tert-butyl ether (2 mL) were added to the reaction mixture. The mixture was reacted under nitrogen protection and irradiated with a 30 W blue LED for 12 hours until complete reaction was observed by TLC. The reaction solution was concentrated and separated by column chromatography to obtain the corresponding C2-boron-substituted dihydroindole compound 3i. The product was a white solid with a separation yield of 31%, and its chemical formula is […]. .
[0042] White solid (31%, 23.7 mg). 1 H NMR (400 MHz, CDCl3) δ 7.94-7.93 (m,1H), 7.56-7.54 (m, 1H), 7.38-7.35 (m, 2H), 7.16-7.13 (m, 1H), 7.12-6.98 (m,4H), 4.03 (s, 3H), 3.88 (brs, 1H), 3.85 (s, 3H), 2.69-2.63 (m, 1H), 2.52-2.48(m, 1H), 2.31 (s, 3H) ppm. 13 C NMR (100 MHz, CDCl3) δ 143.0, 141.9, 141.5,137.2, 136.0, 129.3, 126.9, 126.8, 125.5, 124.6, 118.2, 38.4, 35.6, 34.0,21.6 ppm. HRMS-ESI (m / z): [M+Na] + calcd for C 19 H 23 BN4O2SNa + , 405.1527; found, 405.1524. Example 10
[0043] In an 18 × 180 mm glass tube, the reaction substrates benzofuran (0.2 mmol, 1.0 equivalent), 1,3-dimethylimidazolium borane (1.5 equivalent), 4-DPAIPN (2 mol%), TBAB (1.0 equivalent), methyl thiosalicylate (0.2 equivalent), and anhydrous methyl tert-butyl ether (2 mL) were added. The reaction was carried out under nitrogen protection and irradiated with a 30 W blue LED for 12 hours until complete reaction was observed by TLC. The reaction solution was concentrated and separated by column chromatography to obtain the corresponding C2-boron-substituted dihydroindole compound 3j. The product was a white solid with a separation yield of 39%, and its chemical formula is […]. .
[0044] White solid (39%, 17.8 mg). 1 H NMR (400 MHz, CDCl3) δ 7.13-7.11 (m,1H), 6.98-6.96 (m, 1H), 6.78 (s, 2H), 6.72-6.68 (m, 1H), 6.62-6.60 (m, 1H), 4.57 (brs, 1H), 3.80-3.78 (m, 6H), 3.23-3.20 (m, 1H), 2.92-2.86 (m, 1H) ppm. 13 C NMR (100 MHz, CDCl3) δ 161.9, 131.0, 126.9, 124.8, 120.5, 118.6, 108.6,37.3, 36.4 ppm. HRMS-ESI (m / z): [M+Na] + calcd for C 13 H 17 BN2ONa + , 251.1326;found, 251.1324. The technical scope of this invention is not limited to the content described above. Those skilled in the art can make various modifications and variations to the above embodiments without departing from the technical concept of this invention, and all such modifications and variations should fall within the protection scope of this invention.
Claims
1. A method for preparing a C2-boron-substituted dihydroindole compound, characterized in that, The structure of the compound is as follows: ； （Ⅰ） Where X is NH, N-SO2Ph, N-Boc, N-Troc, NCH3, NTs, O or S; R 1 The electron-donating group is H, an electron-donating group, or an electron-withdrawing group, wherein the electron-donating group is methyl, methoxy, phenyl, or tert-butyl, and the electron-withdrawing group is fluorine, chlorine, bromine, cyano, or trifluoromethyl. R 2 It is methyl or isopropyl; R 3 It can be methyl, isopropyl, benzyl, n-butyl, or cyclohexyl; Y represents either H or N atoms.
2. The C2-boron-substituted dihydroindole compound according to claim 1, characterized in that, The C2-boron-substituted dihydroindole compound is selected from any of the following compounds: 、 、 、 、 、 、 、 、 、 。 3. The method for preparing C2-boron-substituted dihydroindole compounds according to claim 1 or 2, characterized in that, Includes the following steps: Compound 1 and compound 2 undergo a hydroboration reaction. The reaction proceeds via a free radical process, involving indole dearomatization and hydroboration, ultimately yielding a C2-boron-substituted dihydroindole compound. The reaction equation is as follows. ； Compound 1 is an N-substituted indole derivative; compound 2 is a nitrogen-containing heterocyclic carbene borane.
4. The method for preparing C2-boron-substituted dihydroindole compounds according to claim 3, characterized in that, Specifically, the following steps are included: Compound 1, compound 2, photocatalyst and additives were mixed in an organic solvent and reacted for 12-18 h under nitrogen protection and light irradiation at a wavelength of 440-450 nm. The reaction was completed, yielding C2-boron-substituted dihydroindole compounds; The reaction formula is as follows: 。 5. The method for preparing C2-boron-substituted dihydroindole compounds according to claim 4, characterized in that, The photocatalyst is 4-DPAIPN.
6. The method for preparing C2-boron-substituted dihydroindole compounds according to claim 4, characterized in that, The organic solvent is anhydrous toluene, anhydrous methyl tert-butyl ether, or anhydrous 1,4-dioxane.
7. The method for preparing C2-boron-substituted dihydroindole compounds according to claim 4, characterized in that, The additives are thiophenol and alkali, wherein the molar ratio of thiophenol to alkali is (1~3):
10.
8. The method for preparing C2-boron-substituted dihydroindole compounds according to claim 7, characterized in that, The molar ratio of compound 1, compound 2, photocatalyst, thiophenol, and base is 1:1.5:(0.02~0.05):(0.1~0.3):(1~2).
9. The method for preparing C2-boron-substituted dihydroindole compounds according to claim 7, characterized in that, The thiophenol is 4-methylthiophenol, 4-trifluoromethylthiophenol, or methyl thiosalicylate.
10. The method for preparing C2-boron-substituted dihydroindole compounds according to claim 7, characterized in that, The base is pyridine, TEBA, or TBAB.