A heterogeneous catalyst for the catalytic reaction of alkynes with B 2 Pin 2 Application in hydroboration reactions

Abstract

The present invention discloses an application of a heterogeneous catalyst in the hydroboration reaction of alkynes with B2Pin2. The heterogeneous catalyst is prepared by sequentially adding copper nitrate trihydrate, trimesic acid, and pyridine-3,5-dicarboxylic acid to a mixed solvent of N,N-dimethylformamide and absolute ethanol under stirring conditions. After mixing evenly, the mixture is transferred to a hydrothermal reaction kettle and reacted at 80-160 °C to produce crystals. After the reaction, it is naturally cooled to room temperature, and the solid catalyst is collected by centrifugation and washed. The washed catalyst is immersed in absolute ethanol at 75-85 °C for purification for 12 h, centrifuged, and the solid is collected. After washing 3-4 times with absolute ethanol, it is dried under vacuum. The catalyst of the present invention has broad substrate generality and high catalytic activity in the hydroboration reaction of alkynes.

Description

Technical Field

[0001] The present invention relates to a novel use of a heterogeneous catalyst and its application in catalyzing the reaction of alkynes with B 2 Pin 2 Application in hydroboration reactions. Background Art

[0002] Chiral borate esters and their derivatives are powerful building blocks for asymmetric synthesis in organic synthesis, and they show higher configurational stability than any other chiral organometallic reagents (such as organolithium, organomagnesium, organocopper, etc.); as a multifunctional building block in organic synthetic chemistry and medicinal chemistry, vinyl borate has attracted much attention due to its high activity, low toxicity and good stability in air. Among them, vinyl boron compounds, especially (E)-vinyl borate esters, are usually used to form new CC and CX (X=N, O, S) bonds through cross-coupling reactions, and are also widely used in various cross-coupling reactions such as Suzuki-Miyaura cross-coupling, Chan-Lam coupling, and rhodium-catalyzed additions. The general methods for synthesizing (E)-vinyl borate esters are as follows: (1) transition metal-catalyzed dehydrogenative borylation of olefins. Since the activity of borane is uncontrollable, transition metal-catalyzed dehydrogenative borylation of olefins produces saturated alkyl borate esters; (2) hydroboration of alkynes by adding boron-containing reagents to the triple bond without the need for pre-functionalization. It is worth noting that how to control the regioselectivity and chemical selectivity of the addition process is the biggest challenge in the hydroboration of alkynes. Among them, transition metal-catalyzed hydroboration of alkynes has been shown to be a direct and effective method for the generation of (E)-vinyl borate esters. In recent years, a variety of catalysts have been used to catalyze the reaction of alkynes with B 2 Pin 2 Hydroboration reactions such as Pd(OAc) 2 , CuO / MgO, copper powder, NHC-Cu complex, etc. However, in order to achieve high conversion and high selectivity in the synthesis of vinyl borane, most of the catalysts used in this reaction have low conversion frequency (TOF), and the reaction conditions are harsh, the solvents are toxic, additives are added, and the reaction time is long. Therefore, it is necessary to develop efficient catalytic reactions of alkynes with B 2 Pin 2 Heterogeneous catalysts for hydrogenation reactions are very necessary for practical applications.

[0003] Unlike heterogeneous catalysts such as coordination polymers, pure inorganic metal zeolites, mesoporous silica and metal oxides, MOFs are 3D coordination networks formed by metal nodes (metal clusters or metal ions) and organic ligands, involving crystalline and porous compounds with strong metal-ligand interactions. Due to their high porosity, adjustable pore size, large specific surface area, well-dispersed active species and original single metal sites, they have been considered to be the most promising heterogeneous catalysts. At the same time, they are widely used in adsorption, degradation, photocatalysis, electrocatalysis and thermal catalysis. However, for the catalytic reaction of alkynes with B 2 Pin 2 In the hydroboration reaction, MOFs also show the disadvantages of requiring a long time and high temperature to achieve high selectivity and high conversion rate.

[0004] Due to the changes in the pore structure, coordination environment and electronic structure formed by metals and organic ligands in DEMOFs, defect engineering strategies have been proven to be an effective method to improve the activity of MOFs. Recently, with the continuous development of characterization technology, DEMOFs have received more and more attention. The general methods for synthesizing DEMOFs materials are: (1) mixed joint method; (2) rapid precipitation method resulting in missing linking ligands; (3) inorganic acid post-synthesis treatment method; (4) acid regulator resulting in ligand loss. Among these studies, the main focus is on the synthesis and application of defective MOFs materials, among which DEMOFs have been used in catalyzing the reaction of alkynes with B. 2 Pin 2 The hydroboration reaction of is rarely studied. Summary of the invention

[0005] The present invention aims to solve the problems of harsh conditions for the catalytic hydroboration of alkynes in existing homogeneous catalytic systems and heterogeneous catalytic systems (metal oxides, metal coordination compounds, MOFs materials), and provides a catalyst for the hydroboration of alkynes with B. 2 Pin 2 Heterogeneous catalysts for hydroboration reactions.

[0006] The chemicals and reagents used in the method of the present invention can all be commercially available.

[0007] The heterogeneous catalyst is prepared by sequentially adding copper nitrate trihydrate, trimesic acid and pyridine 3,5-dicarboxylic acid into a mixed solvent of N,N-dimethylformamide-anhydrous ethanol under stirring conditions, mixing the mixture, transferring the mixture into a hydrothermal reactor, reacting at 80-160° C. to produce crystals, naturally cooling to room temperature after the reaction, collecting and washing the solid catalyst by centrifugation, washing the catalyst with N,N-dimethylformamide and anhydrous ethanol in sequence, immersing the catalyst in anhydrous ethanol at 75-85° C. for purification for 12 hours, centrifuging, collecting the solid, washing the solid with anhydrous ethanol for 3-4 times, and vacuum drying to obtain the heterogeneous catalyst DE-HKUST-1.

[0008] The molar ratio of copper nitrate trihydrate to trimesic acid is 1.5:1, and the molar ratio of trimesic acid to pyridine 3,5-dicarboxylic acid is 5:1-6; the N,N-dimethylformamide-anhydrous ethanol mixed solvent is prepared by mixing N,N-dimethylformamide and anhydrous ethanol in a volume ratio of 3-5:1.

[0009] The alkyne is selected from phenylacetylene, 4-acetyltylene, 3-acetyltylene, 2-acetyltylene, 4-methoxyphenylacetylene, 4-fluorophenylacetylene, 1-chloro-4-ethynylbenzene, 1-chloro-3-ethynylbenzene, 1-chloro-2-ethynylbenzene, 4-bromophenylacetylene, 4-ethynylbenzonitrile, 3-ethynylthiophene, 1-hexyne, and cyclopropylacetylene.

[0010] Application of heterogeneous catalyst DE-HKUST-1 in catalytic reaction of alkynes with B 2 Pin 2 In the hydroboration reaction, DE-HKUST-1, a base, B 2 Pin 2 A mixture of , alkyne, and anhydrous ethanol was added to a Shrek reaction tube equipped with a magnetic stirrer in sequence, and the reaction tube was evacuated and filled with nitrogen gas with a volume concentration of 99.99% through a double-row tube, and this process was repeated three times. The reaction tube containing the reaction mixture was then reacted at 35° C. under magnetic stirring for 1 hour. After the reaction was completed, the solid catalyst was removed by filtration, and the reaction mixture was stirred for 1 hour. 1 The yield was determined by HNMR analysis, and the filtrate was filtered and chromatographed on a silica gel column (petroleum ether:ethyl acetate volume ratio of 80:1 to 40:1 as eluent) to obtain a pure (E)-vinyl borate product.

[0011] The base is selected from sodium tert-butoxide and sodium hydroxide.

[0012]

[0013] Compared with the prior art, the present invention has the following advantages:

[0014] (1) The heterogeneous catalyst of the present invention has a high specific surface area, an easily adjustable pore structure, and uniformly dispersed active sites, and the heterogeneous catalyst is connected to the defective ligand pyridine 3,5-dicarboxylic acid through a one-pot synthesis method to form a catalyst with significantly increased catalytic activity;

[0015] (2) The present invention uses a heterogeneous catalyst for the reaction of alkynes with B 2 Pin 2 In the hydroboration reaction, it exhibits extremely high conversion rate and selectivity in the catalytic hydroboration reaction;

[0016] (3) The heterogeneous catalyst preparation method of the present invention is simple, easy to operate, low in cost, high in catalytic efficiency, excellent in selectivity, and easy to recover the catalyst, thus easily achieving the requirements of green industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a Fourier transform infrared spectroscopy (FT-IR) diagram of the heterogeneous catalyst DE-HKUST-1 of Example 1; wherein a is the HKUST-1 catalyst, bg are catalysts prepared by adding 1 mol, 2 mol, 3 mol, 4 mol, 5 mol, and 6 mol of pyridine 3,5-dicarboxylic acid, respectively, the upper figure is the full spectrum; the lower figure is an enlarged view of the light yellow transparent area;

[0018] Figure 2 1 is an X-ray photoelectron spectroscopy (XPS) diagram of the highly catalytically active heterogeneous catalyst DE-HKUST-1 prepared in Example 1, ag is the same as above, the upper diagram is a Cu2p diagram; the lower diagram is a N1s diagram;

[0019] Figure 3 It is a (E)-vinyl borate ester prepared from phenylacetylene as an alkyne. 1 H NMR spectra;

[0020] Figure 4 It is a (E)-vinyl borate ester prepared from phenylacetylene as an alkyne. 13 CNMR images;

[0021] Figure 5 It is a (E)-vinyl borate ester prepared from 4-ethynyltoluene as alkyne. 1 H NMR spectra;

[0022] Figure 6 It is a (E)-vinyl borate ester prepared from 4-ethynyltoluene as alkyne. 13 CNMR images

[0023] Figure 7 It is a (E)-vinyl borate ester prepared from 3-ethynyltoluene as alkyne. 1 H NMR spectra;

[0024] Figure 8 It is a (E)-vinyl borate ester prepared from 3-ethynyltoluene as alkyne. 13 CNMR images;

[0025] Fig. 9 It is a (E)-vinyl borate ester prepared from 2-ethynyltoluene as alkyne. 1 H NMR spectra;

[0026] Fig.10 It is a (E)-vinyl borate ester prepared from 2-ethynyltoluene as alkyne. 13CNMR image. DETAILED DESCRIPTION

[0027] The present invention is further described in detail below through examples and drawings, but the protection of the present invention is not limited to the contents described.

[0028] Embodiment 1:

[0029] (1) Under stirring conditions, copper nitrate trihydrate (7.5 mmol), trimesic acid (5 mmol), and pyridine 3,5-dicarboxylic acid (1 mmol, 2 mmol, 3 mmol, 4 mmol, 5 mmol, and 6 mmol, respectively) were added to 50 mL of a mixed solvent of N,N-dimethylformamide and anhydrous ethanol (volume ratio of 4:1) in sequence, and mixed thoroughly until completely dissolved. The mixture was transferred to a 100 mL polytetrafluoroethylene-lined stainless steel hydrothermal reactor, and reacted at 120°C in an oven for 24 h to produce crystals. After the reaction was completed, the reaction mixture was naturally cooled to room temperature, and the solid was obtained by centrifugation at 10000 r / min. The solid was washed with N,N-dimethylformamide and anhydrous ethanol in sequence, each for 3 times. After washing, the catalyst was immersed in anhydrous ethanol at 80°C for 12 h to remove residual reagents, and the solid was collected by centrifugation at 10000 r / min. The solid was washed with anhydrous ethanol for another 3 times, and then dried at 80°C in vacuum for 12 h to obtain a heterogeneous catalyst DE-HKUST-1;

[0030] Meanwhile, HKUST-1 catalyst was prepared according to the above method, except that pyridine 3,5-dicarboxylic acid was not added;

[0031] The present invention uses Fourier transform infrared spectroscopy (FT-IR) to characterize the obtained catalyst. The results are as follows Figure 1 As shown; the infrared spectra of all DE-HKUST-1 catalysts are typical HKUST-1 band patterns, which indicates that all DE-HKUST-1 catalysts maintain the framework of HKUST-1 and no significant unreacted ligands remain in them after washing and purification; 1644cm -1 The peaks at 1565, 1448 and 1372 cm are attributed to the stretching vibration of C=O. -1 The peak at 925 cm corresponds to the C=C stretching vibration of the trisubstituted benzene ring. -1 The peak at 694 cm -1 A weak absorption peak appears at -COO - When the ligand ratio increases, the 1448 cm-1 in the FT-IR spectrum of the DE-HKUST-1 catalyst increases. -1 The band at 1267 cm-1 (corresponding to the C=C stretching vibration on the aromatic ring) gradually shifts to low frequencies.-1 The CN stretching vibration peak at appeared and gradually strengthened. These results confirmed the successful synthesis of DE-HKUST-1 catalyst.

[0032] In order to further confirm the successful synthesis of DE-HKUST-1 heterogeneous catalyst and study the effect of defective ligand pyridine-3,5-dicarboxylic acid on the metal center Cu 2+ The XPS experiment was carried out on the DE-HKUST-1 catalyst to find out the binding properties. Figure 2 As shown in the figure, N1s has a peak at 399eV, while HKUST-1 catalyst has no peak in this region, and its intensity increases with the increase of doping ratio. This further proves that the nitrogen-containing species pyridine 3,5-dicarboxylic acid is successfully inserted into the HKUST-1 framework. In addition, the XPS spectrum of the Cu2p binding energy region is shown in the figure, showing strong Cu2p at binding energies of 954eV and 934eV. 1 / 2 and Cu2p 3 / 2 peaks, and vibration satellite peaks appear at about 943eV and 939eV, which are the metal center Cu in the HKUST-1 structure. 2+ The intrinsic state of Cu in the framework is not significantly changed after modification with pyridine 3,5-dicarboxylic acid. 2+ The oxidation state remains unchanged during the modification process.

[0033] (2) DE-HKUST-1 catalyst (0.012 mmol, prepared from 4 mmol of pyridine 3,5-dicarboxylic acid), sodium tert-butoxide (0.02 mmol), B 2 Pin 2 (2.5mmol), alkyne (2mmol), and anhydrous ethanol (5mL) were added sequentially to a Shrek reaction tube (20mL) equipped with a magnetic stirrer, and the reaction tube was evacuated through a double-row tube and filled with nitrogen gas with a volume concentration of 99.99%, which was repeated three times. The reaction tube containing the reaction mixture was then reacted at 35°C under magnetic stirring for 1h. After the reaction was completed, the solid catalyst was removed by filtration, and the filtrate was purified by silica gel column chromatography (petroleum ether: ethyl acetate 80-40:1 as eluent) to obtain the (E)-vinyl borate product. 1 HNMR analysis determined the yield of (E)-vinyl borate;

[0034]

[0035]

[0036] At the same time, HKUST-1 catalyst was used to catalyze the reaction of phenylacetylene with B 2 Pin 2The hydroboration reaction was carried out under the same reaction conditions as above, and the product yield was 32.4% and the selectivity was 99%.

[0037] Among them, the (E)-vinyl borate ester prepared from phenylacetylene as the alkyne 1 1H NMR and 13 13C NMR spectra are shown in Figure 3 、 4 1H NMR(600MHz,Chloroform-d)δ7.49(d,J=7.1Hz,2H),7.41(d,J=18.4Hz,1H),7.34(t,J=7.4Hz,2H),7.30(d,J=7.2Hz,1H),6.18(d,J=18.4Hz,1H),1.32(s,12H). 13 13C NMR(151MHz,Chloroform-d)δ149.54,137.42,128.95,128.60,127.08,83.39,24.84.

[0038] The (E)-vinyl borate ester prepared from 4-ethynyltoluene as the alkyne 1 1H NMR and 13 13C NMR spectra are shown in Figure 5 、 6 , 1 1H NMR(600MHz,Chloroform-d)δ7.42–7.35(m,3H),7.15(d,J=7.8Hz,2H),6.12(d,J=18.4Hz,1H),2.35(s,3H),1.31(s,12H). 13C NMR(151MHz,Chloroform-d)δ149.50,139.01,134.74,129.32,127.04,83.30,24.84,21.39.

[0039] The (E)-vinyl borate ester prepared from 3-ethynyltoluene as the alkyne 1 1H NMR and 13 13C NMR spectra are shown in Figure 7 、 8 , 1H NMR(600MHz,Chloroform-d)δ7.41(d,J=18.4Hz,1H),7.34(s,1H),7.26(d,J=8.0Hz,2H),7.15(d,J=7.5Hz,1H),6.19(d,J=18.4Hz,1H),2.39(d ,J=3.0Hz,3H),1.35(s,12H).13CNMR(151MHz,Chloroform-d)δ149.71,138.11,137.41,129.76,128.48,127.80,124.26,83.34,24.84,21.45.

[0040] (E)-vinyl borate esters prepared from 2-ethynyltoluene as alkyne 1 H NMR and 13 CNMR images Fig. 9 , 10 , 1 HNMR(600MHz,Chloroform-d)δ7.70(d,J=18.3Hz,1H),7.61(d,J=6.2Hz,1H),7. 26–7.23(m,2H),7.20(s,1H),6.14(d,J=18.3Hz,1H),2.48(s,3H),1.37(s,12H). 13 C NMR (151MHz, Chloroform-d) δ147.13,136.66,136.34,130.43,128.62,126.13,125.75,83.33,24.85,19.89.

[0041] From the above results we can see that:

[0042] The present invention studies the influence of different functional groups on the generation of (E)-vinyl borate. The results are shown in the table above. The hydroboration reaction of most aromatic terminal alkynes and aliphatic terminal alkynes can generate the corresponding (E)-vinyl borate with excellent conversion rate and selectivity. For aliphatic internal alkynes and aromatic internal alkynes as reactants, only very few products can be obtained. Among them, the conversion rate of the meta position and the orthorium position gradually decreases compared with the para position (99.9-89%). It can be inferred that the steric effect has a certain inhibitory effect on the hydroboration reaction (3b-3d, 3g-3i). The electron-donating group -CH 3 、-OCH 3Various phenylacetylene derivatives with electron-withdrawing groups F, Cl, Br, and -CN can provide the corresponding products (3b, 3e-3g, 3j-3k) with moderate or excellent conversions (40%, 97.2-99.9%). When 1-ethynyltoluene substituted with a strong electron-withdrawing group -CN is used as a reaction substrate, it can still provide the corresponding target product (3k) with an excellent conversion of 99.9%. When 3-ethynylthiophene is used as a substrate, it can also provide promising products with a conversion of 99.9% and a selectivity of 99.9%. At the same time, aliphatic groups as reaction substrates also provide the target products 3m and 3n with high conversions (99.9%). Unlike terminal alkynes, almost no products 3o-3p were detected for the hydroboration of internal alkynes catalyzed by DE-KHUST-1, which indicates that the DE-HKUST-1 catalyst has extremely high selectivity for catalyzing the hydroboration of terminal alkynes.

[0043] Embodiment 2:

[0044] (1) Under stirring conditions, copper nitrate trihydrate (7.5 mmol), trimesic acid (5 mmol), and pyridine 3,5-dicarboxylic acid (4 mol) were added to 50 mL of a mixed solvent of N,N-dimethylformamide and anhydrous ethanol (volume ratio of 4:1) in sequence, and mixed thoroughly until completely dissolved. The mixture was transferred to a 100 mL polytetrafluoroethylene-lined stainless steel hydrothermal reactor, and reacted at 100° C. in an oven for 24 h to produce crystals. After the reaction was completed, the mixture was naturally cooled to room temperature, and centrifuged at 10000 r / min to obtain a solid. The solid was washed with DMF and EtOH in sequence, each for 3 times. After washing, the catalyst was immersed in anhydrous ethanol at 80° C. for 12 h to remove residual reagents, and centrifuged at 10000 r / min to collect the solid. The solid was washed with anhydrous ethanol for another 4 times, and then dried at 80° C. in vacuum for 12 h to obtain a heterogeneous catalyst.

[0045] (2) The heterogeneous catalyst (DE-HKUST-1 0.012 mmol), sodium hydroxide (0.02 mmol), B 2 Pin 2 (2.5mmol), phenylacetylene (2mmol) and anhydrous ethanol (5mL) were added sequentially into a Shrek reaction tube (20mL) equipped with a magnetic stirrer. The reaction tube was evacuated and filled with nitrogen gas with a volume concentration of 99.99% through a double-row tube, and the process was repeated three times. The reaction tube containing the reaction mixture was then reacted at 35°C under magnetic stirring for 1h. After the reaction was completed, the solid catalyst was removed by filtration. The filtrate was purified by silica gel column chromatography (petroleum ether: ethyl acetate 80:1 as eluent) to obtain the (E)-vinyl borate product with a yield of 98% and a selectivity of 99%.

Claims

1. A heterogeneous catalyst for the reaction of alkynes with B 2 Pin 2 Application in hydroboration reactions; The heterogeneous catalyst is prepared by sequentially adding copper nitrate trihydrate, trimesic acid and pyridine 3,5-dicarboxylic acid to a N,N-dimethylformamide-anhydrous ethanol mixed solvent under stirring conditions, mixing the mixture, transferring the mixture to a hydrothermal reactor, reacting at 80-160° C. to produce crystals, cooling the reaction to room temperature naturally after the reaction, collecting and washing the solid catalyst by centrifugation, immersing the washed catalyst in anhydrous ethanol at 75-85° C. for purification for 12 hours, centrifuging, collecting the solid, washing it 3-4 times with anhydrous ethanol and then vacuum drying it; The alkyne is selected from phenylacetylene, 4-acetyltylene, 3-acetyltylene, 2-acetyltylene, 4-methoxyphenylacetylene, 4-fluorophenylacetylene, 1-chloro-4-ethynylbenzene, 1-chloro-3-ethynylbenzene, 1-chloro-2-ethynylbenzene, 4-bromophenylacetylene, 4-ethynylbenzonitrile, 3-ethynylthiophene, 1-hexyne, and cyclopropylacetylene.

2. The use according to claim 1, Features: The molar ratio of copper nitrate trihydrate to trimesic acid is 1.5:1, and the molar ratio of trimesic acid to pyridine 3,5-dicarboxylic acid is 5:1-6.

3. The use according to claim 1, Features: The N,N-dimethylformamide-anhydrous ethanol mixed solvent is prepared by mixing N,N-dimethylformamide and anhydrous ethanol in a volume ratio of 3-5:

1.

4. The use according to claim 1, Features: In alkali, solvent, N 2 In the presence of heterogeneous catalysts, alkynes react with B 2 Pin 2 Hydroboration reaction.

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