Method for hydroboration of styrene compound
By induced photoinduced heterogeneous semiconductor catalyst to catalyze the borohydrogenation reaction of styrene compounds and azacyclic carbeneborane at low temperature, the problem of high toxicity, expensive and difficult to recover in the prior art is solved, and efficient, environmentally friendly and economical reaction effects are achieved.
Patent Information
- Application Number
- CN202311222144.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-09-21
- Publication Date
- 2025-03-21
AI Technical Summary
The prior art has defects in catalyzing the borohydrogenation reaction of styrene compounds and azacyclic carbeneborane, which has high free radical initiator loading, high reaction temperature, high catalyst toxicity, expensive and difficult to recover, which affects the efficiency and environmental protection of the reaction.
The reaction is carried out under light source irradiation by controlling the molar ratio of styrene-based compounds to azacyclic carbineborane, using appropriate organic solvents and inert gases, and reacting under light source irradiation, reducing the reaction temperature and improving the recovery and utilization of the catalyst.
The efficient hydroborohydrogenation reaction of styrene compounds and azacyclic carbeneborane at low temperatures is achieved, which reduces the toxicity and cost of the catalyst, improves the recovery and utilization rate of the catalyst, and improves the environmental protection and economicality of the reaction.
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Abstract
Description
Technical Field
[0001] The present invention specifically relates to a method for the photoinduced hydroboration of styrene compounds and nitrogen heterocyclic carbene borane compounds by using heterogeneous semiconductor catalysis. Background Art
[0002] Styrene compounds are important reaction building blocks due to the presence of unsaturated olefinic groups, and selective hydroboration of the olefinic groups of styrene can transform them into functionally diverse coupling building blocks with boron reactive sites. Reactions involving boron radicals have received widespread attention in the industry due to their special activity, but the instability of boron radicals has also been affecting the development of this field. Nitrogen heterocyclic carbene borane is a solid borane that is stable to air, water, and weak acids. At the same time, due to the presence of coordinated nitrogen heterocyclic carbenes, boron radicals can be stabilized by π-electron conjugation, which provides the necessary conditions for the hydroboration reaction involving boron radicals and has developed several methods ( E.et al., J.Am.Chem.Soc.2011,133,10312–10321; Yang,H.et al.,Angew.Chem.Int.Ed.2020,59,6706-6710.), but these methods require the use of excessive free radical initiators or expensive iridium salts, and there are also problems such as catalyst residue and high reaction temperature. There are also methods that use iodine to catalyze the hydroboration reaction of styrene compounds with nitrogen heterocyclic carbene boranes through non-free radical mechanisms, but the use of toxic and easily sublimated iodine has a certain negative impact on environmental protection and operator safety. Heterogeneous semiconductor catalysts can produce catalytic effects under light induction. In addition, they can be separated and recycled by simple filtration. From the perspectives of practicality, economy, and environmental protection, the development of photoinduced heterogeneous catalytic methods for the hydroboration of styrene compounds with nitrogen heterocyclic carbene boranes is a very meaningful and challenging task. Summary of the invention
[0003] In view of a series of problems faced in the hydroboration of styrene compounds with nitrogen heterocyclic carbene boranes, such as high loading of free radical initiators, high reaction temperature, high catalyst toxicity, expensive catalysts, difficulty in catalyst recovery and catalyst residue, the present invention provides a method for the hydroboration of styrene compounds with nitrogen heterocyclic carbene boranes using photoinduced heterogeneous semiconductor catalysis.
[0004] To achieve the above purpose, the technical solution adopted by the present invention is as follows:
[0005] Styrene compounds and nitrogen heterocyclic carbene borane are used as raw materials, heterogeneous semiconductors are used as catalysts, the molar ratio of styrene compounds to nitrogen heterocyclic carbene borane is 1:0.1-1:5, 1-150 mg of heterogeneous semiconductors are used for each millimole of styrene compounds, an organic solvent is added (0.5-25 mL (preferably 5-10 mL) is required for each millimole of styrene compounds), and after inert gas replacement, the reaction is carried out at 0-50° C. for 1-100 hours under light source irradiation to obtain a hydroboration product.
[0006] The styrene compound includes one or more of the following structures, wherein R 1 ~R 3 They are H, halogen (F, Cl, Br, I), alkyl (molecular formula C n H 2n+1 , n = 1 to 20), alkoxy (molecular formula OC n H 2n+1 , n = 1 to 10) one or more of phenyl, thienyl, benzoyl, R 1 ~R 3 The same or different.
[0007]
[0008] The nitrogen heterocyclic carbene borane is diMe-Imd-BH3
[0009]
[0010] The heterogeneous semiconductor includes one or more of TiO2 (P25), nanotube TiO2, nanosheet TiO2, nanorod CdS, nanosheet CdS, nanosphere CdS, nanowire CdS, ZnIn2S4, In2S3, and g-C3N4.
[0011] The inert gas includes one or more of helium, nitrogen and argon.
[0012] The light source is one or more of visible violet light (390nm-435nm), visible blue light (435nm-490nm), and visible green light (490nm-560nm).
[0013] The light source power is 1W to 80W, preferably 5W to 45W.
[0014] The organic solvent includes one or more of tetrahydrofuran, toluene, dichloromethane, 1,2-dichloroethane, acetonitrile, 1,4-dioxane, N,N-dimethylformamide, and N,N-dimethylacetamide. DETAILED DESCRIPTION
[0015] The following embodiments are helpful for understanding the present invention, but are not intended to limit the content of the present invention.
[0016] Example 1
[0017] Preparation of Heterogeneous Semiconducting Nanotube TiO2
[0018] 2.0g TiO2 (P25) was mixed with 160mL 10mol / L sodium hydroxide aqueous solution, and the mixture was completely poured into a 200mL stainless steel autoclave with a polytetrafluoroethylene liner, and the autoclave was placed in an oven at 150°C and heated for 48h, and then the autoclave was slowly cooled to room temperature, and the solid precipitate was filtered, and washed with deionized water until neutral (pH = 6.0-7.5), and after drying, the obtained solid was placed in a quartz boat, and the quartz boat was wrapped with two layers of aluminum foil. Subsequently, the quartz boat was calcined at 450°C in a nitrogen stream for 3h to obtain nanotubular TiO2 with an inner diameter of 50-150nm, a length of 3-6μm, and a wall thickness of 10-75nm.
[0019] Example 2
[0020] Preparation of Heterogeneous Semiconductor Nanosheets of TiO2
[0021] 40mmol TiF4 was dissolved in 1.0L of hydrochloric acid aqueous solution with a pH of 2.0. 14.5mL of the above solution, 13.38mL of isopropanol and 0.5mL of hydrofluoric acid (10% w / w) were added to a 50mL stainless steel autoclave with a polytetrafluoroethylene liner. The autoclave was placed in an oven at 180°C and heated for 44h. The autoclave was then slowly cooled to room temperature. The solid precipitate was filtered out, washed three times with deionized water, dried, and calcined at 600°C for 1.5h to obtain nano-flaky TiO2 with a thickness of 2 to 7nm.
[0022] Example 3
[0023] Preparation of Heterogeneous Semiconductor Nanosheets CdS
[0024] 2.0 mmol of Cd(OAc)2·2H2O and 6.0 mmol of thiourea were dissolved in 60 mL of ethylenediamine, and then the mixture was completely poured into a 100 mL stainless steel autoclave with a polytetrafluoroethylene liner. The autoclave was placed in an oven at 100°C and heated for 8 h. The autoclave was then slowly cooled to room temperature, and the solid precipitate was filtered out. The solid precipitate was washed three times with ethanol, and then washed three times with ethanol deionized water, and vacuum dried to obtain nanosheet CdS with a thickness of 2 to 7 nm.
[0025] Example 4
[0026] Preparation of Heterogeneous Semiconductor Nanorods of CdS
[0027] 10 mmol of Cd(OAc)2·2H2O and 30 mmol of thiourea were dissolved in 50 mL of ethylenediamine, and then the mixture was completely poured into a 100 mL stainless steel autoclave with a polytetrafluoroethylene liner. The autoclave was placed in an oven at 160°C and heated for 48 hours. The autoclave was then slowly cooled to room temperature, and the solid precipitate was filtered out. The solid precipitate was washed three times with ethanol and then three times with deionized water, and vacuum dried to obtain nanorod-shaped CdS with a diameter of 30 to 100 nm and a length of 100 to 300 nm.
[0028] Example 5
[0029] Preparation of Heterogeneous Semiconductor Nanowires CdS
[0030] 1.6 g of Cd(NO3)2·4H2O and 1.19 g of thiourea were dissolved in 50 mL of ethylenediamine, and then the mixture was completely poured into a 100 mL stainless steel autoclave with a polytetrafluoroethylene liner. The autoclave was placed in an oven at 180°C and heated for 72 h. The autoclave was then slowly cooled to room temperature, and the solid precipitate was filtered out. It was washed three times with ethanol and then three times with deionized water, and vacuum dried to obtain nanowire CdS with a diameter of 30 to 100 nm and a length of 2 to 6 μm.
[0031] Example 6
[0032] Preparation of Heterogeneous Semiconductor Nano-spherical CdS
[0033] 0.6 mmol of Cd(OAc)2·2H2O and 15 mmol of thiourea were dissolved in 15 mL of deionized water, and then the mixture was completely poured into a 30 mL stainless steel autoclave with a polytetrafluoroethylene liner. The autoclave was placed in an oven at 140°C and heated for 5 h. The autoclave was then slowly cooled to room temperature, and the solid precipitate was filtered out. The solid precipitate was washed three times with ethanol and then three times with deionized water, and then vacuum dried to obtain nano-spherical CdS with a diameter of 40 to 80 nm.
[0034] Example 7
[0035] Preparation of Heterogeneous Semiconductor ZnIn2S4
[0036] Dissolve 304.2 mg of Zn(NO3)2·6H2O, 624.2 mg of InCl3·4H2O and 260.6 mg of hexadecyltrimethylammonium bromide in 20 mL of deionized water, then add 604.8 mg of thiourea to the mixture, stir for 30 min, transfer the mixture to a 50 mL stainless steel autoclave with a polytetrafluoroethylene liner, seal the autoclave, and heat it in an oven at 160°C for 16 h. Then cool the autoclave naturally to room temperature, filter out the solid precipitate, wash it three times with ethanol, then wash it three times with a mixture of ethanol and water (1:3, v / v), and dry it in vacuo to obtain ZnIn2S4.
[0037] Example 8
[0038] Preparation of heterogeneous semiconductor In2S3
[0039] 936.3 mg of InCl3·4H2O and 260.6 mg of hexadecyltrimethylammonium bromide were dissolved in 20 mL of deionized water, and then 604.8 mg of thiourea was added to the mixture and stirred for 30 min. The mixture was then transferred to a 50 mL stainless steel autoclave with a polytetrafluoroethylene liner. After sealing, the autoclave was placed in an oven at 160°C and heated for 16 h. The autoclave was then naturally cooled to room temperature, and the solid precipitate was filtered out. The solid precipitate was washed three times with ethanol, and then washed three times with a mixture of ethanol and water (1:3, v / v), and dried in vacuo to obtain In2S3.
[0040] Example 9
[0041] Preparation of heterogeneous semiconductor g-C3N4
[0042] 5.0 g of melamine was placed in a quartz boat, and the quartz boat was wrapped with two layers of aluminum foil. The quartz boat containing melamine was then calcined at 550° C. for 4 h in an air flow to obtain g-C3N4.
[0043] Example 10
[0044] Synthesis of Nitrogen Heterocyclic Carbene Borane diMe-Imd-BH3
[0045] First, the device was dried and the internal chamber of the device was replaced with nitrogen. Then, 9.85 g of 1-methylimidazole and 150 mL of anhydrous dichloromethane were added to the internal chamber of the device under a nitrogen flow. 20.44 g of iodomethane was added dropwise through a constant pressure dropping funnel under an ice-water bath (0-4°C). After the addition was completed, the mixture was moved to room temperature (23-30°C), stirred for 12 hours, and then the solvent was removed under reduced pressure to obtain the product intermediate.
[0046] 5.83 g of NaBH4 was directly weighed and added to the above product intermediate, and 150 mL of toluene was added. The reaction solution was heated to reflux for 20 h, and then the supernatant was removed by decompression to remove the solvent to obtain a crude product, which was then recrystallized with 200 mL of deionized water to obtain 6.88 g of diMe-Imd-BH3 with a yield of 56.8%.
[0047] 1 H NMR (400MHz, CDCl3): δ6.80(s,2H),3.74(s,6H),1.01(m,3H). 13 CNMR (101MHz,CDCl3)δ170.2(q,J B-C =50.3Hz),120.0,35.9. 11 B(128MHz, CDCl3)-37.4(q,J=86.4Hz).IR(solid,ν,cm-1):3140,3167,3051,2979,2956,2275,1574,1445,1266,1232,1187,876,714,704.ESI:Calcd for C5H 10 BN2([M+Na] + )109.0932,found:109.0939.
[0048] Embodiment 11
[0049] Take a dry Schlenk tube with a polytetrafluoroethylene stopper and a polytetrafluoroethylene magnetic stirrer, add 0.30mmol of nitrogen heterocyclic carbene borane (diMe-Imd-BH3), 0.20mmol of styrene, 15mg of ZnIn2S4 and 2.0mL of acetonitrile in sequence, seal it and replace the nitrogen three times, irradiate the reaction solution with a 10W 455nm light source at 30°C, stir for 24h, 11 The reaction progress was detected by B-NMR, and the filtrate was filtered and concentrated under reduced pressure. The crude product was further purified by rapid column chromatography (ethyl acetate / n-hexane = 1 / 2 V / V) to obtain 27.8 mg of the product (1,3-dimethyl-1H-imidazol-3-ium-2-yl)(phenethyl)dihydroborate, with a yield of 65%. The structure is as follows.
[0050]
[0051] 1H NMR(700MHz,Chloroform-d)δ7.23–7.16(m,4H),7.09–7.05(m,1H),6.76(s,2H ),3.76(s,6H),2.57–2.50(m,2H),1.54(dd,J=167.5,83.1Hz,2H),0.77(s,2H); 13 C NMR (176MHz, CDCl3) δ148.3,128.0,128.0,124.6,120.1,38.9,36.0; 11 B NMR (128MHz, Chloroform-d) δ-27.05 (t, J=83.9Hz).
[0052] Examples 12 to 23
[0053] Except for the light source and the different catalysts, the rest of the operations in Examples 12 to 23 are exactly the same as in Example 11 to evaluate the catalytic effects of different catalysts. The specific conditions and results are shown in Table 1. It can be seen from Table 1 that TiO2 with different morphologies, CdS, ZnIn2S4, In2S3 and g-C3N4 with different morphologies (prepared in Examples 1-9) all exhibit good catalytic activity.
[0054] Table 1
[0055]
[0056]
[0057] Embodiments 24 to 40
[0058] Except for the different catalyst dosage, solvent, light source power, reaction temperature, reaction time, and the ratio of styrene to nitrogen heterocyclic carbene borane, the remaining operations in Examples 24 to 40 are exactly the same as those in Example 11 to evaluate the specific effects of the above parameters on the reaction. The specific conditions and results are shown in Table 2. As can be seen from Table 2, a variety of solvents are suitable for the reaction.
[0059] Table 2
[0060]
[0061] Embodiments 41 to 54
[0062] Except for the different substrates, the rest of the operations in Examples 41 to 54 are completely the same as those in Example 11, and the reaction results are shown in Table 3. All styrene compounds can undergo photoinduced heterogeneous catalytic hydroboration.
[0063] Table 3
[0064]
[0065]
[0066]
[0067]
[0068]
[0069]
[0070]
[0071]
[0072]
Claims
1. A method for hydroboration of styrene compounds, characterized in that: Using styrene compounds and nitrogen heterocyclic carbene borane as raw materials and a heterogeneous semiconductor as a catalyst, an organic solvent is added and reacted at 0 to 50° C. for 1 to 100 hours under light to obtain a hydroboration product.
2. The method according to claim 1, characterized in that: The molar ratio of the styrene compound to the nitrogen heterocyclic carbene borane is 1:0.1-1:5, 1-150 mg of the heterogeneous semiconductor is used for each millimole of the styrene compound, and 0.5-25 mL of the organic solvent is required for each millimole of the styrene compound.
3. The method according to claim 1, characterized in that: An organic solvent is added and replaced with an inert gas before reacting under light.
4. The method according to claim 1, characterized in that: The styrene compound includes one or more of the following structures, wherein R 1 ~R 3 Each of them is independently H, halogen (F, Cl, Br, I), alkyl (molecular formula C n H 2n+1 , n = 1 to 20), alkoxy (molecular formula OC n H 2n+1 , n = 1 to 10), one or more of phenyl, thienyl, and benzoyl, R 1 ~R 3 the same or different between them; 5. The method according to claim 1 or 2, characterized in that: The nitrogen heterocyclic carbene borane is diMe-Imd-BH3 6. The method according to claim 1 or 2, characterized in that: The heterogeneous semiconductor includes one or more of: TiO2 (P25), nanotubular TiO2, nanosheet TiO2, nanorod CdS, nanosheet CdS, nanosphere CdS, nanowire CdS, ZnIn2S4, In2S3, and g-C3N4.
7. The method according to claim 3, characterized in that: The inert gas includes one or more of helium, nitrogen and argon.
8. The method according to claim 1 or 2, characterized in that: The light source of the illumination is one or more of visible violet light (390nm-435nm), visible blue light (435nm-490nm), and visible green light (490nm-560nm); The light source power is 1W to 80W, preferably 5W to 45W.
9. The method according to claim 1 or 2, characterized in that: The organic solvent includes one or more of tetrahydrofuran, toluene, dichloromethane, 1,2-dichloroethane, acetonitrile, 1,4-dioxane, N,N-dimethylformamide, and N,N-dimethylacetamide.