A method for preparing triarylphosphine and its oxides by light-induced cyanopyridine

Abstract

The invention discloses a method for preparing triarylphosphine and its oxide by light-induced cyanopyridine. The method comprises the following steps: 1) placing a cyanopyridine compound, diphenylphosphine, a photocatalyst, and a solvent in a reaction vessel, and subjecting the mixture to a coupling reaction under irradiation with a blue light source to generate a triarylphosphine compound; and 2) oxidizing the arylphosphine compound in air to obtain a corresponding phosphine oxide compound. The method uses a cyanopyridine compound and diarylphosphine, which are simple and readily available, as reaction substrates, 4-CzIPN as a photocatalyst, dimethyl sulfoxide as a solvent, and room temperature as a reaction temperature. The triarylphosphine compound is synthesized simply and efficiently under the condition of blue light as a light source, and the phosphine oxide compound is further oxidized. The method comprises the following steps: the reaction conditions are mild, the raw materials used are cheap and readily available, no metal reagents are used, and the method is environmentally friendly.

Description

Technical Field

[0001] The present invention relates to the technical field of organic intermediate synthesis, in particular to a method for preparing triarylphosphine and its oxides by light-induced cyanopyridine. Background Art

[0002] Triarylphosphines and their derivatives are advantageous structural scaffolds in organic catalysis, medicinal chemistry, and materials science. In particular, asymmetrically substituted PR2R′ structures have been widely used as chelating ligands in coordination chemistry and catalysis. Therefore, it is of great significance to develop a direct, mild, and efficient method for synthesizing triarylphosphines. Classical methods for synthesizing triarylphosphines mainly involve electrophilic reactions, nucleophilic reactions, or transition metal (Pd, Ni, etc.) catalysis. In recent years, the strategy of photochemically induced preparation of triarylphosphines has attracted much attention due to its green and environmentally friendly nature, high atom economy, and mild reaction conditions. Currently, the specific methods for synthesizing triarylphosphines are:

[0003] Method 1: Diarylphosphine oxides are reacted with the Tf2O / 2,6-lutidine system to generate an electrophilic phosphinating agent in situ, which then undergoes a tandem coupling reaction with alkynes to generate various triarylphosphines and their derivatives (J.Am.Chem.Soc.2017,139,6106-6109):

[0004]

[0005] This method uses the Tf2O / 2,6-lutidine system, has harsh reaction conditions, and is only applicable to the reaction of alkynes.

[0006] Method 2: Using diphenylphosphine and aryl halides / trifluorates as substrates, transition metal-catalyzed CP(III) cross-coupling reactions in DMF or NMP with KOAc or DABCO as bases and heterogeneous or homogeneous Pd or Ni catalysts, various triarylphosphines and their derivatives are obtained (Org. Lett. 2002, 4, 3541-3543):

[0007]

[0008] This method uses toxic and expensive metal catalysts, and the reaction temperature is as high as 180-200°C, and the reaction conditions are very harsh.

[0009] Method 3: Electron donor-acceptor complex (EDA) of arylsulfonium salt, diarylphosphine and potassium carbonate was used to promote the C(sp 2 )-P bond formation to obtain various triarylphosphines and their derivatives (Org.Lett.2023,25,8350-8355):

[0010]

[0011] The arylsulfonium salt used in this method needs to be pre-prepared in advance, and the experimental steps are relatively complicated. Summary of the Invention

[0012] In view of the above problems, the present invention aims to provide a method for preparing triarylphosphine and its oxides by light-induced cyanopyridine, which is simple to operate, does not involve heavy metals, and has mild reaction conditions.

[0013] In order to achieve the above object, the technical solution adopted by the present invention is as follows: a method for preparing triarylphosphine and its oxides by light-induced cyanopyridine, the method being as follows:

[0014]

[0015] Wherein, R1 is selected from C1~C4 alkyl, H, trifluoromethyl, cyano, C2~C5 ester group; the photocatalyst is selected from Ir[dF(CF3)ppy]2(dtbpy)PF6, 4-CzIPN, fac-Ir(ppy)3; and the light source is a blue light source.

[0016] The present invention places a cyanopyridine compound, diphenylphosphine, a photocatalyst, and a solvent in a reaction container. Under irradiation with a light source, the cyanopyridine compound and the diphenylphosphine undergo a coupling reaction under the action of the photocatalyst to generate a triarylphosphine compound. For the convenience of separation, the triarylphosphine compound is further oxidized to obtain the corresponding phosphine oxide compound.

[0017] In the preparation method of the present invention, the molar ratio of diphenylphosphine to cyanopyridine compound is 1 to 3:1; the molar ratio of photocatalyst to cyanopyridine compound is 0.0005 to 0.05:1; the molar ratio of diphenylphosphine to cyanopyridine compound is preferably 2:1; and the molar ratio of photocatalyst to cyanopyridine compound is preferably 0.03:1. When the preferred molar ratio of photocatalyst, diphenylphosphine, and cyanopyridine compound is selected, the yield of the final product is the highest.

[0018] In the preparation method of the present invention, the photocatalyst is preferably 4-CzIPN; when the photocatalyst is 4-CzIPN, the yield of the final product is the highest.

[0019] In the preparation method of the present invention, the reaction solvent is one of dichloromethane, tetrahydrofuran, acetonitrile and dimethyl sulfoxide; the molar concentration of the cyanopyridine compound in the reaction solvent is 0.07 mmol / mL; the reaction solvent is preferably dimethyl sulfoxide; when the solvent is dimethyl sulfoxide, the yield of the final product is the highest.

[0020] The wavelength of the blue light source described in the preparation method of the present invention is 465nm.

[0021] In the preparation method of the present invention, the reaction temperature is 15-35°C, the first step reaction time is 10-16 hours, and the second step reaction time is 18-30 hours. The first step reaction time is preferably 12 hours, the second step reaction time is preferably 24 hours, and the reaction temperature is preferably 25°C, which provides the highest yield of the final product.

[0022] The reaction of the present invention is carried out under the condition of the presence of a solvent, and the oxidation potential of diphenylphosphine hydrogen is E ox = +1.08V, which can be excited by 4-CzIPN (E ox (PC * / PC -· )=+1.65V vs Ag / AgCl) oxidation. Due to the reduction potential (E red (PC / PC -· )=-1.18V vs Ag / AgCl), which is insufficient to reduce 4-cyanopyridine (E red = -1.85V vs Ag / AgCl). Cyanopyridine compounds may undergo proton coupling with diphenylphosphine, enabling their reaction. Cyclic voltammetry revealed a new reduction peak at -0.7V when 4-cyanopyridine, diphenylphosphine, and DMSO were mixed, confirming the presence of proton coupling.

[0023] The advantages of this invention are that it uses readily available cyanopyridine compounds and diarylphosphines as reaction substrates, 4-CzIPN as a photocatalyst, dimethyl sulfoxide as a solvent, and room temperature under blue light to simply and efficiently synthesize triarylphosphines. Further oxidation yields phosphine oxide compounds. Compared to other methods for synthesizing triarylphosphines, this method offers milder reaction conditions, uses readily available and inexpensive raw materials, avoids the use of metal reagents, and is environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is the H NMR spectrum of diphenyl(pyridin-4-yl)phosphine oxide in Example 1;

[0025] Figure 2 is the nuclear magnetic phosphorus spectrum of diphenyl(pyridin-4-yl)phosphine oxide in Example 1;

[0026] Figure 3 This is the C NMR spectrum of diphenyl(pyridin-4-yl)phosphine oxide in Example 1.

[0027] Figure 4 is the H NMR spectrum of (2-methylpyridin-4-yl)diphenylphosphine oxide in Example 2;

[0028] Figure 5is the nuclear magnetic phosphorus spectrum of (2-methylpyridin-4-yl)diphenylphosphine oxide in Example 2;

[0029] Figure 6 This is the C NMR spectrum of (2-methylpyridin-4-yl)diphenylphosphine oxide in Example 2.

[0030] Figure 7 is the H NMR spectrum of (2,6-dimethylpyridin-4-yl)diphenylphosphine oxide in Example 3;

[0031] Figure 8 is the nuclear magnetic phosphorus spectrum of (2,6-dimethylpyridin-4-yl)diphenylphosphine oxide in Example 3;

[0032] Figure 9 This is the C NMR spectrum of (2,6-dimethylpyridin-4-yl)diphenylphosphine oxide in Example 3.

[0033] Figure 10 is the H NMR spectrum of (2-(tert-butyl)pyridin-4-yl)diphenylphosphine oxide in Example 4;

[0034] Figure 11 is the nuclear magnetic phosphorus spectrum of (2-(tert-butyl)pyridin-4-yl)diphenylphosphine oxide in Example 4;

[0035] Figure 12 This is the C NMR spectrum of (2-(tert-butyl)pyridin-4-yl)diphenylphosphine oxide in Example 4.

[0036] Figure 13 is the H NMR spectrum of diphenyl(2-phenylpyridin-4-yl)phosphine oxide in Example 5;

[0037] Figure 14 is the nuclear magnetic phosphorus spectrum of diphenyl (2-phenylpyridin-4-yl) phosphine oxide in Example 5;

[0038] Figure 15 This is the C NMR spectrum of diphenyl (2-phenylpyridin-4-yl) phosphine oxide in Example 5.

[0039] Figure 16 is the H NMR spectrum of 2-(diphenylphosphoryl)isobutyronitrile in Example 6;

[0040] Figure 17 is the nuclear magnetic phosphorus spectrum of 2-(diphenylphosphoryl)isobutyronitrile in Example 6;

[0041] Figure 18 This is the C NMR spectrum of 2-(diphenylphosphoryl)isobutyronitrile in Example 6.

[0042] Figure 19 is the H NMR spectrum of methyl 2-(diphenylphosphoryl)isonicotinate in Example 7;

[0043] Figure 20 is the nuclear magnetic phosphorus spectrum of methyl 2-(diphenylphosphoryl)isonicotinate in Example 7;

[0044] Figure 21 This is the C NMR spectrum of methyl 2-(diphenylphosphoryl)isonicotinate in Example 7.

[0045] Figure 22 is the H NMR spectrum of diphenyl(4-(trifluoromethyl)pyridin-2-yl)phosphine oxide in Example 8;

[0046] Figure 23 is the NMR fluorine spectrum of diphenyl(4-(trifluoromethyl)pyridin-2-yl)phosphine oxide in Example 8;

[0047] Figure 24 is the nuclear magnetic phosphorus spectrum of diphenyl (4- (trifluoromethyl) pyridin-2-yl) phosphine oxide in Example 8;

[0048] Figure 25 This is the C NMR spectrum of diphenyl(4-(trifluoromethyl)pyridin-2-yl)phosphine oxide in Example 8. DETAILED DESCRIPTION

[0049] The present invention will be described in further detail below with reference to the accompanying drawings and specific implementation methods.

[0050] The raw materials used in the following specific examples can all be purchased commercially, and each reagent was purified by means known in the art before use when necessary.

[0051] In the present invention, "cyanopyridine compounds" have the meaning commonly understood by those skilled in the art, that is, compounds containing a cyano group (-CN) and a pyridine structure, for example: 4-cyanopyridine and its various derivatives.

[0052] The raw materials in the following specific examples can all be purchased commercially, and various reagents were purified by means known in the art before use when necessary.

[0053] 1 H NMR, 31 P NMR and 13 C NMR measurements were performed using a Bruker Avance 400 spectrometer. The test temperature was room temperature, the solvent was deuterated chloroform, and the reference was selected: 1 H NMR: CHCl3 7.260 ppm; 13 C NMR: CHCl3: 77.000 ppm.

[0054] Example 1: Synthesis of diphenyl(pyridin-4-yl)phosphine oxide

[0055] To an 8 mL vial equipped with a magnetic stirrer, the photocatalyst 4-CzIPN (4.7 mg, 3 mmol%) and 4-cyanopyridine (20.8 mg, 1.0 eq, 0.2 mmol) were added. The vial was capped and evacuated with nitrogen three times. Ultra-dry DMSO (3.0 mL) and diphenylphosphine (69.7 μL, 3.0 eq, 0.4 mmol) were then added. The mixture was then stirred at room temperature and irradiated with 465 nm LED blue light for 12 hours, followed by further irradiation in air for 24 hours. After completion of the reaction, extraction was performed, the solvent was removed in vacuo, and column chromatography was performed to yield 44.8 mg of diphenyl(pyridin-4-yl)phosphine oxide (80% yield).

[0056] The product diphenyl (pyridin-4-yl) phosphine oxide (such as Figure 1 、 2 and 3): 1 H NMR (400MHz, CDCl3) δ8.83-8.64(m,2H),7.68-7.59(m,4H),7.59-7.42(m,8H)ppm. 31 P NMR (162MHz, CDCl3) δ27.02ppm. 13 C NMR (101MHz, CDCl3) δ149.8 (d, J = 9.7Hz), 141.9 (d, J = 96.2Hz), 132.4 (d, J = 2.8Hz), 13 1.8(d,J=10.0Hz), 130.7(d,J=106.0Hz), 128.7(d,J=12.4Hz), 125.6(d,J=8.0Hz)ppm.

[0057]

[0058]

[0059]

[0060] Standard conditions: 4-cyanopyridine 0.2 mmol (1.0 eq), diphenylphosphine 0.4 mmol (2.0 eq), 4-CzIPN (3 mol%), DMSO (3.0 mL), reaction time 12 h, oxidation time 24 h, room temperature, yield is isolated yield. DMSO = dimethyl sulfoxide.

[0061] Example 2: (2-methylpyridin-4-yl)diphenylphosphine oxide

[0062] An 8 mL vial equipped with a magnetic stirrer was charged with the photocatalyst 4-CzIPN (4.7 mg, 3 mol%) and 2-methylpyridine-4-carbonitrile (23.6 mg, 1.0 eq, 0.2 mmol). The vial was capped and evacuated with nitrogen three times. Ultra-dry DMSO (3.0 mL) and diphenylphosphine (69.7 μL, 3.0 eq, 0.4 mmol) were then added. The mixture was then stirred at room temperature and irradiated with 465 nm LED blue light for 12 hours, followed by further irradiation in air for 24 hours. After completion of the reaction, extraction was performed, the solvent was removed in vacuo, and column chromatography was performed to yield 44.2 mg of (2-methylpyridin-4-yl)diphenylphosphine oxide (75% yield).

[0063] The product (2-methylpyridin-4-yl) diphenylphosphine oxide (such as Figure 4 、 5 and 6): 1 H NMR (400MHz, CDCl3) δ8.59(t,J=4.8Hz,1H),7.68-7.61(m,4H),7.60-7.54(m,2H),7.51-7.45(m,5H),7.28-7.22(m,1H),2.58(s,3H)ppm. 31 P NMR (162MHz, CDCl3) δ27.15ppm. 13 C NMR (101MHz, CDCl3) δ 159.0 (d, J = 9.7Hz), 149.1 (d, J = 10.2Hz), 142.1 (d, J = 97.3Hz), 132.4 (d, J = 2.8Hz), 131. 9(d,J=10.0Hz), 131.0(d,J=105.6Hz), 128.7(d,J=12.3Hz), 125.2(d,J=7.7Hz), 122.6(d,J=8.2Hz), 24.5ppm.

[0064] Example 3: (2,6-dimethylpyridin-4-yl)diphenylphosphine oxide

[0065] An 8 mL vial equipped with a magnetic stirrer was charged with the photocatalyst 4-CzIPN (4.7 mg, 3 mol%) and 2,6-dimethyl-4-cyanopyridine (26.4 mg, 1.0 eq, 0.2 mmol). The vial was capped and evacuated with nitrogen three times. Ultra-dry DMSO (3.0 mL) and diphenylphosphine (69.7 μL, 3.0 eq, 0.4 mmol) were then added. The mixture was then stirred at room temperature and irradiated with 465 nm LED blue light for 12 hours, followed by further irradiation in air for 24 hours. After completion of the reaction, extraction and removal of the solvent in vacuo were performed, followed by column chromatography to yield 38.4 mg of (2,6-dimethylpyridin-4-yl)diphenylphosphine oxide (62%).

[0066] The product (2,6-dimethylpyridin-4-yl) diphenylphosphine oxide (such as Figure 7 、 8 and 9): 1 H NMR (400MHz, CDCl3) δ7.67-7.60(m,4H),7.59-7.53(m,2H),7.51-7.44(m,4H),7.19(d,J=12.0Hz,2H),2.52(s,6H)ppm. 31 P NMR (162MHz, CDCl3) δ27.39ppm. 13 C NMR (101MHz, CDCl3) δ158.2(d,J=10.5Hz), 142.2(d,J=97.6Hz), 132.3(d,J=2.9Hz), 131.9(d,J= 10.1Hz), 131.1(d,J=105.2Hz), 128.6(d,J=12.4Hz), 122.0(d,J=8.1Hz), 24.5(d,J=1.5Hz)ppm.

[0067] Example 4: (2-(tert-Butyl)pyridin-4-yl)diphenylphosphine oxide

[0068] An 8 mL sample vial equipped with a magnetic stirrer was charged with the photocatalyst 4-CzIPN (4.7 mg, 3 mol%) and 2-tert-butyl-4-cyanopyridine (32.0 mg, 1.0 eq, 0.2 mmol). The vial was capped and evacuated with nitrogen three times. Ultra-dry DMSO (3.0 mL) and diphenylphosphine (69.7 μL, 3.0 eq, 0.4 mmol) were then added. The mixture was then stirred at room temperature and irradiated with 465 nm LED blue light for 12 hours, followed by further irradiation in air for 24 hours. After completion of the reaction, extraction and removal of the solvent in vacuo were performed, followed by column chromatography to yield 42.5 mg of (2-(tert-butyl)pyridin-4-yl)diphenylphosphine oxide (63% yield).

[0069] The product (2-(tert-butyl)pyridin-4-yl)diphenylphosphine oxide (such as Figure 10 、 11 and 12): 1 H NMR (400MHz, CDCl3) δ8.63 (t, J = 4.8Hz, 1H), 7.75-7.69 (m, 1H), 7.66-7.60 (m, 4H),7.57-7.51(m,2H),7.48-7.43(m,4H),7.19-7.13(m,1H),1.31(s,9H)ppm. 31 P NMR (162MHz, CDCl3) δ27.67ppm. 13 C NMR (101MHz, CDCl3) δ170.0(d,J=8.9Hz), 148.4(d,J=10.5Hz), 141.7(d,J=97.7Hz), 132.3(d,J=2.8Hz), 131.8(d,J=10.1Hz ),131.2(d,J=105.3Hz),128.6(d,J=12.4Hz),122.5(d,J=8.9Hz),121.2(d,J=7.9Hz),37.7,29.9ppm.HRMS(ESI)m / z:[M+H] + Calcd for C 21 H 23 NOP + 336.1512; Found 336.1511.

[0070] Example 5: Diphenyl (2-phenylpyridin-4-yl) phosphine oxide

[0071] An 8 mL vial equipped with a magnetic stirrer was charged with the photocatalyst 4-CzIPN (4.7 mg, 3 mol%) and 2-phenylpyridine-4-carbonitrile (36.0 mg, 1.0 eq, 0.2 mmol). The vial was capped and evacuated with nitrogen three times. Ultra-dry DMSO (3.0 mL) and diphenylphosphine (69.7 μL, 3.0 eq, 0.4 mmol) were then added. The mixture was then stirred at room temperature and irradiated with 465 nm LED blue light for 12 hours, followed by further irradiation in air for 24 hours. After completion of the reaction, extraction and removal of the solvent in vacuo were performed, followed by column chromatography to yield 15.1 mg of diphenyl(2-phenylpyridin-4-yl)phosphine oxide (21% yield).

[0072] The product diphenyl (2-phenylpyridin-4-yl) phosphine oxide (such as Figure 13 、 14 and 15): 1H NMR(400MHz, CDCl3)δ8.80(t,J=4.6Hz,1H),8.08(d,J=12.4Hz,1H),8.00-7.94(m,2 H),7.73-7.67(m,4H),7.62-7.57(m,2H),7.53-7.42(m,7H),7.41-7.36(m,1H)ppm. 31 P NMR (162MHz, CDCl3) δ27.36ppm. 13 C NMR (101MHz, CDCl3) δ157.8 (d, J = 9.8Hz), 149.6 (d, J = 10.3Hz), 142.8 (d, J = 97.4Hz), 138.3, 132.5 (d, J = 2.7Hz), 131.9 (d ,J=10.1Hz),130.9(d,J=105.7Hz),129.5,128.8(d,J=3.0Hz),128.7,127.0,123.8(d,J=8.4Hz),122.5(d,J=8.2Hz)ppm.

[0073] Example 6: 2-(Diphenylphosphoryl)isobutyronitrile

[0074] To an 8 mL vial equipped with a magnetic stirrer, the photocatalyst 4-CzIPN (4.7 mg, 3 mol%) and pyridine-2,4-dicarbonitrile (20.7 μL, 1.0 eq, 0.2 mmol) were added. The vial was capped and evacuated with nitrogen three times. Ultra-dry DMSO (3.0 mL) and diphenylphosphine (69.7 μL, 3.0 eq, 0.4 mmol) were then added. The mixture was then stirred at room temperature and irradiated with 465 nm LED blue light for 12 hours, followed by further irradiation in air for 24 hours. After completion of the reaction, extraction and removal of the solvent in vacuo were performed, followed by column chromatography to yield 29.4 mg of 2-(diphenylphosphoryl)isobutyronitrile (48% yield).

[0075] The product 2-(diphenylphosphoryl)isobutyronitrile (such as Figure 16 、 17 and 18): 1 H NMR (400MHz, CDCl3) δ8.95(d,J=4.8Hz,1H),8.54(d,J=5.6Hz,1H),7.90-7.84(m,4H),7.61-7.53(m,3H),7.50-7.44(m,4H)ppm. 31 P NMR (162MHz, CDCl3) δ19.94ppm. 13C NMR (101MHz, CDCl3) δ 159.2 (d, J = 128.2Hz), 150.8 (d, J = 18.6Hz), 132.3 (d, J = 2.8Hz), 132.0 (d, J = 9.7Hz), 130.8 (d, J = 106. 2Hz), 129.3 (d, J = 20.6Hz), 128.5 (d, J = 12.4Hz), 126.5 (d, J = 3.1Hz), 121.1 (d, J = 10.7Hz), 115.7ppm. HRMS (ESI) m / z: [M+H] + Calcd for C 18 H 14 N2OP + 305.0838; Found 305.0831.

[0076] Example 7: Methyl 2-(diphenylphosphoryl)isonicotinate

[0077] To an 8 mL sample vial equipped with a magnetic stirrer, photocatalyst 4-CzIPN (4.7 mg, 3 mol%) and methyl 2-cyano-4-pyridinecarboxylate (32.4 mg, 1.0 eq, 0.2 mmol) were added. The vial was capped and evacuated with nitrogen three times. Ultra-dry DMSO (3.0 mL) and diphenylphosphine (69.7 μL, 3.0 eq, 0.4 mmol) were then added. The mixture was then stirred at room temperature and irradiated with 465 nm LED blue light for 12 hours, followed by further irradiation in air for 24 hours. After completion of the reaction, extraction was performed, the solvent was removed in vacuo, and column chromatography was performed to yield 37.8 mg of methyl 2-(diphenylphosphoryl)isonicotinate (56% yield).

[0078] The product 2-(diphenylphosphoryl)isonicotinate methyl ester (such as Figure 19 、 20 and 21): 1 H NMR (400MHz, CDCl3) δ8.91(d,J=5.2Hz,1H),8.84(d,J=6.0Hz,1H),7.95-7.91(m ,1H),7.90-7.83(m,4H),7.54-7.48(m,2H),7.46-7.40(m,4H),3.93(s,3H)ppm. 31 P NMR (162MHz, CDCl3) δ20.66ppm. 13C NMR (101MHz, CDCl3) δ 164.8 (d, J = 2.0Hz), 157.8 (d, J = 131.0Hz), 150.9 (d, J = 19.2Hz), 137.6 (d, J = 9.5Hz), 132.0 (d, J = 2.8Hz), 131. 9(d,J=9.5Hz),131.5(d,J=105.2Hz),128.3(d,J=12.3Hz),127.1(d,J=20.5Hz),124.3(d,J=3.0Hz),52.7ppm.HRMS(ESI)m / z:[M+H] + Calcd for C 19 H 17 NO3P + 338.0941; Found 338.0934.

[0079] Example 8: Diphenyl (4- (trifluoromethyl) pyridin-2-yl) phosphine oxide

[0080] An 8 mL vial equipped with a magnetic stirrer was charged with the photocatalyst 4-CzIPN (4.7 mg, 3 mol%) and 2-cyano-4-trifluoromethylpyridine (34.4 mg, 1.0 eq, 0.2 mmol). The vial was capped and evacuated with nitrogen three times. Ultra-dry DMSO (3.0 mL) and diphenylphosphine (69.7 μL, 3.0 eq, 0.4 mmol) were then added. The mixture was then stirred at room temperature and irradiated with 465 nm LED blue light for 12 hours, followed by further irradiation in air for 24 hours. After completion of the reaction, extraction and solvent removal in vacuo were performed, followed by column chromatography to yield 26.0 mg of diphenyl(4-(trifluoromethyl)pyridin-2-yl)phosphine oxide in a 37% yield.

[0081] The product diphenyl (4- (trifluoromethyl) pyridin-2-yl) phosphine oxide (such as Figure 22 、 23 , 24 and 25): 1 H NMR(400MHz, CDCl3) δ8.97(d,J=4.8Hz,1H),8.60(d,J=5.6Hz,1H),7.93-7.8 6(m,4H),7.61(d,J=4.8Hz,1H),7.55(t,J=7.2Hz,2H),7.50-7.44(m,4H)ppm. 19 F NMR(376MHz, CDCl3)δ-64.75(s,3F)ppm. 31 P NMR (162MHz, CDCl3) δ20.19ppm. 13C NMR (101MHz, CDCl3) δ158.8 (d, J = 130.0 Hz), 150.9 (d, J = 18.8 Hz), 138.6 (dd, J = 34.9, 9.8 Hz), 132.2 (d, J = 2.7 Hz), 132.0 (d, J = 9.6 Hz), 131.2 (d, J = 105.7 Hz), 128.4 (d, J = 12.4 Hz), 123.9 (q, J = 3.5 Hz), 123.7 (q, J = 3.5 Hz), 120.8-120.5 (m) ppm. HRMS (ESI) m / z: [M+H] + Calcd for C 18 H 14 F3NOP + 348.0760; Found 348.0762.

[0082]

[0083]

[0084] As can be seen from Examples 1-8, the method of the present invention is to react various inexpensive and readily available cyanopyridine compounds with diphenylphosphine, using DMSO as the solvent, at room temperature, under the conditions of blue light as the light source, and 4-CzIPN as the photocatalyst, to simply and efficiently synthesize triarylphosphine compounds. To simplify the separation procedure, further oxidation is performed to obtain phosphine oxide compounds. This method is a general synthesis method with mild reaction conditions, inexpensive and readily available raw materials, no metal reagents, environmental friendliness, and industrial applicability.

[0085] Example 9: Lighting Experiment

[0086] With other conditions unchanged, the technical solution in Example 1 was tested using ultraviolet light, no light, and white light, and the results were as follows:

[0087] Experimental group Lighting conditions Yield of diphenyl(pyridin-4-yl)phosphine oxide Example 1 Blu-ray 80％ Comparative Example 1 No light 0 Comparative Example 2 UV rays 39％ Comparative Example 3 White light ＜5％

[0088] Therefore, the optimal light source for the reaction conditions of this process is a blue light source, at which time the final yield of the product can reach the maximum.

[0089] It should be noted that the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any combination or equivalent transformation based on the above embodiments falls within the scope of protection of the present invention.

Claims

1. A method for preparing triarylphosphine and its oxides by light-induced cyanopyridine, characterized in that: The method described is as follows: ； Wherein, R1 is selected from H, C1-C4 alkyl, trifluoromethyl, cyano, C2-C5 ester group; The photocatalyst is selected from Ir[dF(CF3)ppy]2(dtbpy)PF6, 4-CzIPN, fac-Ir(ppy)3; The light source is a blue light source; the reaction solvent is dimethyl sulfoxide.

2. The method for preparing triarylphosphine and its oxide according to claim 1, characterized in that: The steps of the method are as follows: 1) A cyanopyridine compound, diphenylphosphine, a photocatalyst, and a solvent are placed in a reaction vessel, and a coupling reaction occurs under irradiation with a blue light source to generate a triarylphosphine compound; 2) Oxidizing the triarylphosphine compound obtained in step 1) in air to obtain the corresponding phosphine oxide compound.

3. The method for preparing triarylphosphine and its oxide according to claim 1 or 2, characterized in that: The molar ratio of the diphenylphosphine to the cyanopyridine compound is 1-3:1; the molar ratio of the photocatalyst to the cyanopyridine compound is 0.0005-0.05:

1.

4. The method for preparing triarylphosphine and its oxide according to claim 3, characterized in that: The molar ratio of the diphenylphosphine to the cyanopyridine compound is 2:1; the molar ratio of the photocatalyst to the cyanopyridine compound is 0.03:

1.

5. The method for preparing triarylphosphine and its oxide according to claim 1 or 2, characterized in that: The photocatalyst is 4-CzIPN.

6. The method for preparing triarylphosphine and its oxide according to claim 2, characterized in that: The molar concentration of the cyanopyridine compound in the reaction solvent is 0.07 mmol / mL.

7. The method for preparing triarylphosphine and its oxide according to claim 1 or 2, characterized in that: The wavelength of the blue light source is 465nm.

8. The method for preparing triarylphosphine and its oxide according to claim 2, characterized in that: The reaction temperature is 15-35° C., the first step reaction time is 10-16 hours, and the second step reaction time is 18-30 hours.

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