A method for synthesizing an organic phosphine intermediate from inorganic phosphoric acid

Abstract

The present invention discloses a method for synthesizing an organophosphorus intermediate from inorganic phosphoric acid. Oxalyl chloride (COCl)2 is used as an activator to activate the inorganic phosphate [TBA][H2PO4] to synthesize a novel phosphine precursor [TBA][PO2Cl2], which is reduced to a low-valent organophosphorus intermediate [TBA][P(SiCl3)2] under the action of trichlorosilane. This preparation method overcomes the ultra-long reaction time of 6 d and the high-temperature condition above 110 °C in the existing methods, greatly improving the reaction efficiency and reducing the energy consumption. Moreover, the raw materials used in this method are cheap and easily available. [TBA][P(SiCl3)2] can be used to prepare organophosphorus compounds. Triphenylphosphine is prepared using [TBA][P(SiCl3)2] as a phosphorus-containing reagent, and the product can be used as an excellent ligand for organometals in organic synthesis.

Description

Technical Field

[0001] The present invention belongs to the field of organic synthesis and relates to a method for synthesizing an organophosphorus intermediate from inorganic phosphoric acid. Background Art

[0002] The synthesis of organophosphorus intermediates currently relies on the preparation from white phosphorus (1 million tons / year) produced by high-temperature carbothermal reduction of phosphate rock. The use of white phosphorus to synthesize organophosphorus intermediates has high energy consumption and harsh reaction conditions. Phosphoric acid (9,000 tons / year) prepared by the wet process has less pollution and high yield in the production process, and is cheap and easily available. However, it is currently mainly used in the production of phosphate fertilizers in agriculture. If phosphoric acid (or phosphate rock) can be directly converted into organophosphorus compounds, it can not only reduce the environmental pollution caused by using white phosphorus as a precursor to synthesize organophosphorus compounds, but also save energy, shorten the reaction cycle, improve production efficiency, and simultaneously achieve the diverse conversion from "inorganic phosphorus to organophosphorus". However, the method of directly using phosphoric acid or phosphate to prepare organophosphorus intermediates is currently in its infancy and still faces great challenges and opportunities. Summary of the Invention

[0003] The object of the present invention is to provide a method for synthesizing an organophosphorus intermediate using inorganic phosphoric acid as a phosphorus source.

[0004] I. Synthesis of Organophosphorus Intermediate

[0005] The method for synthesizing an organophosphorus intermediate from inorganic phosphoric acid uses tetrabutylammonium dihydrogen phosphate ([TBA][H2PO4]) as a phosphorus source, oxalyl chloride as an activator, and reacts at room temperature for 2 - 2.5 h under the conditions of having a solvent or no solvent and argon to obtain the active phosphorus substance [TBA][PO2Cl2]. Then, the reducing agent trichlorosilane is added and reacted at 60 - 110 °C for 1 - 12 h, and the organophosphorus intermediate - bis(trichlorosilyl)phosphide anion [TBA][P(SiCl3)2] is obtained by recrystallization with dichloromethane and n-pentane. Among them, the molar ratio of [TBA][H2PO4] to oxalyl chloride is 1:1 - 1:10; the molar ratio of [TBA][PO2Cl2] to trichlorosilane is 1:10 - 1:30.

[0006] The structural formula of the organophosphorus intermediate [TBA][P(SiCl3)2] is:

[0007] .

[0008] II. Synthesis of Organophosphorus

[0009] Using the synthesized [TBA][P(SiCl3)2] as the phosphorus-containing reagent and iodobenzene as the coupling raw material, a method for palladium-catalyzed synthesis of triphenylphosphine was achieved. In the presence of dichlorobis(diphenylphosphino)ferrocene palladium(II) (PdCl2(dppf)), with THF as the solvent, DMAP as the base, and TBAF as the assistant (desilylating reagent, also known as "F source"), [TBA][P(SiCl3)2] and iodobenzene were heated to 80 - 110 °C in an argon atmosphere and reacted for 20 - 25 h. After cooling to room temperature, the reaction mixture was extracted with dichloromethane, all organic layers were collected, dried over anhydrous sodium sulfate, the solvent was evaporated by a rotary evaporator under vacuum, and then purified using a chromatography column to obtain triphenylphosphine PPh3. 31 P NMR, 1 H NMR and 13 C NMR spectra are as Figure 1 , Figure 2 , Figure 3 .

[0010] Among them, the molar ratio of the organophosphorus intermediate [TBA][P(SiCl3)2] to iodobenzene is 1:2 - 1:4; the molar ratio of the organophosphorus intermediate [TBA][P(SiCl3)2] to DMAP is 1:3 - 1:5; the molar ratio of the organophosphorus intermediate [TBA][P(SiCl3)2] to TBAF is 1:1 - 1:2; the molar ratio of the organophosphorus intermediate [TBA][P(SiCl3)2] to dichlorobis(diphenylphosphino)ferrocene palladium(II) is 20:1.

[0011] The method for preparing [TBA][P(SiCl3)2] overcomes the 6-day reaction time and high-temperature conditions in the existing methods, greatly improving the reaction efficiency and reducing the reaction energy consumption. [TBA][P(SiCl3)2] can be used to prepare organophosphorus compounds. Triphenylphosphine was prepared using [TBA][P(SiCl3)2] as the phosphorus-containing reagent, and the product can be used as an excellent ligand for organometals in organic synthesis.

[0012] The raw materials used in the synthesis method of the organophosphorus intermediate are cheap and easily available: [H3PO4] is obtained from phosphate rock through a wet process, with an annual output of up to 90 million tons. The activator oxalyl chloride used is synthesized from oxalic acid, which is cheap and easily available, and trichlorosilane is an industrial by-product.

[0013] The advantages of the present invention compared with the prior art are as follows:

[0014] (1) Using phosphate as the phosphorus source, it has a rich source;

[0015] (2) The activator and reducing agent used are all easily available and relatively cheap products in industry;

[0016] (3) Overcomes the reaction conditions of high temperature and high pressure, reduces the reaction temperature, shortens the reaction time, and reduces energy consumption;

[0017] (4) The reaction can be carried out with or without a solvent;

[0018] (5) The reaction generates a stable phosphorus intermediate, providing conditions for subsequent further transformation. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 1H NMR of PPh3 31 1H NMR;

[0020] Figure 2 31P NMR of PPh3 1 31P NMR;

[0021] Figure 3 13C NMR of PPh3 13 13C NMR;

[0022] Figure 4 31P NMR of [TBA][PO2Cl2] 31 31P NMR;

[0023] Figure 5 1H NMR of [TBA][PO2Cl2] 1 1H NMR;

[0024] Figure 6 13C NMR of [TBA][PO2Cl2] 13 13C NMR;

[0025] Figure 7 31P NMR of [TBA][P(SiCl3)2] 31 31P NMR;

[0026] Figure 8 1H NMR of [TBA][P(SiCl3)2] 1 1H NMR;

[0027] Figure 9 13C NMR of [TBA][P(SiCl3)2] 13 13C NMR. DETAILED DESCRIPTION OF THE INVENTION

[0028] The synthesis of organic phosphine intermediates using inorganic phosphoric acid as a phosphorus source in the present invention will be further described below through specific examples.

[0029] Example 1 Synthesis of [TBA][PO2Cl2]

[0030] In the glove box, 0.6 mmol of [TBA][H2PO4] was dissolved in 4 mL of dichloromethane, and 1 eq of oxalyl chloride (0.6 mmol) was added. The reaction tube was sealed and removed from the glove box, and the reaction was carried out at room temperature for 2 h. After the reaction was completed, the excess oxalyl chloride was removed on a vacuum line, and dichloromethane was added to dissolve and concentrate to an oily state. Subsequently, [TBA][PO2Cl2] was obtained by recrystallization using acetone and ether. 31 P NMR (162 MHz, Chloroform- d ) δ = -7.85 ppm. 1 H NMR (400 MHz,Chloroform- d ) δ = 3.51 – 3.42 (m, 8H), 1.89 – 1.78 (m, 8H), 1.67 – 1.56 (m,8H), 1.17 (t, J =8.0, 12H) ppm. 13 C NMR (101 MHz, Chloroform- d ) δ = 58.88, 24.18,19.90, 13.92 ppm. 31 P NMR, 1 H NMR and 13 C NMR spectra are as shown in Figure 4 , Figure 5 , Figure 6 .

[0031] Example 2 Synthesis of [TBA][PO2Cl2]

[0032] In the glove box, 0.6 mmol of [TBA][H2PO4] was dissolved in 4 mL of acetonitrile, and 1 eq of oxalyl chloride (0.6 mmol) was added. The reaction tube was sealed and removed from the glove box, and the reaction was carried out at room temperature for 2 h. After the reaction was completed, the excess oxalyl chloride was removed on a vacuum line, and dichloromethane was added to dissolve and concentrate to an oily state. Subsequently, [TBA][PO2Cl2] was obtained by recrystallization using acetone and ether. 31 P NMR (162 MHz, Chloroform- d ) δ = -7.85 ppm. 1 H NMR (400 MHz,Chloroform- d ) δ = 3.51 – 3.42 (m, 8H), 1.89 – 1.78 (m, 8H), 1.67 – 1.56 (m,8H), 1.17 (t, J=8.0, 12H) ppm. 13 C NMR (101 MHz, Chloroform- d ) δ = 58.88, 24.18,19.90, 13.92 ppm.

[0033] Example 3 Synthesis of [TBA][PO2Cl2]

[0034] In the glove box, 0.6 mmol of [TBA][H2PO4] was added to the reaction, and 1 eq of oxalyl chloride (0.6 mmol) was added. The reaction tube was sealed and removed from the glove box, and the reaction was carried out at room temperature for 2 h. After the reaction was completed, the excess oxalyl chloride was removed on the vacuum line, and dichloromethane was added to dissolve and concentrated to an oily state. Subsequently, [TBA][PO2Cl2] was obtained by recrystallization using acetone and ether. 31 P NMR (162 MHz, Chloroform- d ) δ = -7.85 ppm. 1 H NMR (400 MHz, Chloroform- d ) δ= 3.51 – 3.42 (m, 8H), 1.89 – 1.78 (m, 8H), 1.67 – 1.56 (m, 8H), 1.17 (t, J =8.0, 12H) ppm. 13 C NMR (101 MHz, Chloroform- d ) δ = 58.88, 24.18, 19.90, 13.92ppm.

[0035] Example 4 Synthesis of Organic Phosphine Intermediate

[0036] In the glove box, 0.6 mmol of [TBA][H2PO4] was added to the reaction tube, and 1 eq of oxalyl chloride (0.6 mmol) was added. The reaction tube was sealed and removed from the glove box, and the reaction was carried out at room temperature for 2 h. After the reaction was completed, the excess oxalyl chloride was removed on the vacuum line, and 15 eq of trichlorosilane (9 mmol) was added. It was placed at 60 °C for reaction for 24 h. Subsequently, the organic phosphine intermediate [TBA][P(SiCl3)2] was obtained by recrystallization using dichloro and pentane at -35 °C. 31 P NMR (162 MHz,Chloroform-d) δ = -172.03 ppm. 1 H NMR (400 MHz, Chloroform- d ) δ = 3.21 (t,J = 7.2, 8H), 1.59 (t, J = 8.0, 8H), 1.43 – 1.33 (m, 8H), 0.95 (t, J = 7.2, 12H) ppm. 13 C NMR (101 MHz, Chloroform- d ) δ = 58.55, 23.64, 19.42, 13.39 ppm. 31 P NMR, 1 1H NMR and 13 13C NMR spectra are as Figure 7 , Figure 8 , Figure 9 .

[0037] Synthesis of Organophosphorus Intermediate in Example 5

[0038] In the glove box, 0.6 mmol of [TBA][H2PO4] was added to the reaction tube, and 1 eq of oxalyl chloride (0.6 mmol) was added. The reaction tube was sealed and removed from the glove box, and reacted at room temperature for 2 h. After the reaction was completed, the excess oxalyl chloride was removed on the vacuum pipeline, and 15 eq of trichlorosilane (9 mmol) was added. It was placed at 80 °C and reacted for 12 h. Subsequently, recrystallization was carried out with dichloromethane and pentane at -35 °C to obtain the organophosphorus intermediate [TBA][P(SiCl3)2]. 31 P NMR (162 MHz, Chloroform-d) δ = -172.03 ppm. 1 1H NMR (400 MHz, Chloroform- d ) δ = 3.21 (t, J = 7.2, 8H), 1.59 (t, J = 8.0, 8H), 1.43 – 1.33 (m, 8H), 0.95 (t, J = 7.2, 12H) ppm. 13 13C NMR (101 MHz, Chloroform- d ) δ = 58.55, 23.64, 19.42, 13.39 ppm.

[0039] Synthesis of Organophosphorus Intermediate in Example 6

[0040] In the glove box, 0.6 mmol of [TBA][H2PO4] was added to the reaction tube, and 1 eq of oxalyl chloride (0.6 mmol) was added. The reaction tube was sealed and removed from the glove box, and the reaction was carried out for 2 h. After the reaction was completed, the excess oxalyl chloride was removed on the vacuum line, and 15 eq of trichlorosilane (9 mmol) was added. It was placed at 110 °C and reacted for 12 h. Subsequently, it was recrystallized with dichloromethane and pentane at -35 °C to obtain the organophosphorus intermediate [TBA][P(SiCl3)2]. 31 P NMR (162 MHz, Chloroform-d) δ = -172.03 ppm. 1 H NMR (400 MHz, Chloroform- d ) δ = 3.21 (t, J = 7.2, 8H),1.59 (t, J = 8.0, 8H), 1.43 – 1.33 (m, 8H), 0.95 (t, J = 7.2, 12H) ppm. 13 C NMR(101 MHz, Chloroform- d ) δ = 58.55, 23.64, 19.42, 13.39 ppm.

[0041] Example 7 Synthesis of Organophosphorus Intermediate

[0042] In the glove box, 3 mmol of [TBA][H2PO4] was added to the reaction tube, and 3 eq of oxalyl chloride (9 mmol) was added. The reaction tube was sealed and removed from the glove box, and the reaction was carried out at room temperature for 2 h. After the reaction was completed, the excess oxalyl chloride was removed on the vacuum line, and 15 eq of trichlorosilane (45 mmol) was added. It was placed at 110 °C and reacted for 12 h. Subsequently, it was recrystallized with dichloromethane and pentane at -35 °C to obtain the organophosphorus intermediate [TBA][P(SiCl3)2]. 31 P NMR (162 MHz, Chloroform-d) δ = -172.03 ppm. 1 H NMR (400 MHz, Chloroform- d ) δ = 3.21 (t, J = 7.2, 8H), 1.59 (t, J = 8.0, 8H), 1.43 – 1.33 (m, 8H), 0.95 (t, J = 7.2, 12H) ppm. 1313C NMR (101 MHz, Chloroform- d ) δ = 58.55, 23.64, 19.42, 13.39 ppm.

[0043] Example 8 Preparation of Triphenylphosphine

[0044] In the glove box, the organophosphorus intermediate (0.2 mmol) prepared in Example 4 and iodobenzene (0.6 mmol) were heated to 110 °C for 24 h in the presence of argon, using THF (2 mL) as the solvent, DMAP (0.8 mmol) as the base, and TBAF (0.4 mmol) as the desilylating reagent (also known as the "F source") in the presence of dichlorobis(1,1'-bis(diphenylphosphino)ferrocene)palladium(II) (PdCl2(dppf)) (5 mol %). After cooling to room temperature, the reaction mixture was extracted with dichloromethane (3 × 20 mL), all organic layers were collected, dried over anhydrous sodium sulfate, and the solvent was evaporated by a rotary evaporator under vacuum to obtain a white solid as the crude product. Then the crude product was purified using a chromatographic column (silica gel, eluent PE:DCM = 10:1~3:1) to obtain the target product triphenylphosphine PPh3. 31 31P NMR (162MHz, Chloroform- d ) δ = -5.29. 1 1H NMR (400 MHz, Chloroform- d ) δ = 7.58 – 7.49(m, 5H), 7.49 – 7.36 (m, 10H). 13 13C NMR (101 MHz, Chloroform- d ) δ = 137.46 (d, J J=11.1), 133.96 (d, J J=19.6), 128.93, 128.73 (d, J J=6.9). 31 31P NMR, 1 1H NMR and 13 13C NMR spectra are as shown in Figure 1 , Figure 2 , Figure 3 .

Claims

1. A method for synthesizing an organic phosphine intermediate from inorganic phosphoric acid, characterized in that: Using tetrabutylammonium dihydrogen phosphate as the inorganic phosphorus source and oxalyl chloride as the activator, under solvent-free or solvent conditions and in an argon atmosphere, react at room temperature for 2 - 2.5 h to obtain the active phosphorus substance [TBA][PO2Cl2]. Subsequently, add the reducing agent trichlorosilane and react at 60 - 110 °C for 1 - 12 h, and recrystallize with dichloromethane and n-pentane to obtain the organophosphorus intermediate [TBA][P(SiCl3)2]; The structural formula of the organophosphorus intermediate [TBA][P(SiCl3)2] is: 。 2. The method for synthesizing an organic phosphine intermediate from inorganic phosphoric acid as described in claim 1, characterized in that: Using oxalyl chloride as the activator, the molar ratio of [TBA][H2PO4] to oxalyl chloride is 1:1 - 1:

10.

3. The method for synthesizing an organophosphorus intermediate from inorganic phosphoric acid according to claim 1, characterized in that: The solvent is CH2Cl2, TBME, CH3CN or DME.

4. The method for synthesizing an organophosphorus intermediate from inorganic phosphoric acid according to claim 1, characterized in that: Using trichlorosilane as the reducing agent, the molar ratio of [TBA][PO2Cl2] to trichlorosilane is 1:10 - 1:30.

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