Application of heterogeneous catalyst in catalysis of hydroboration reaction of alkyne and B2Pin2

Abstract

The invention discloses an application of a heterogeneous catalyst in catalysis of alkyne and B2Pin2 hydroboration reaction, and the heterogeneous catalyst is prepared by the following steps: mixing copper salt, pyrazole-3, 5-dicarboxylic acid and an N, N-dimethylformamide-absolute ethyl alcohol mixed solvent, fully stirring until complete dissolution, carrying out solvothermal reaction at 100-150 DEG C, after the reaction is completed, naturally cooling, and carrying out solid-liquid separation to obtain the heterogeneous catalyst. And washing and drying the solid to obtain the product. The heterogeneous catalyst is simple in preparation process, has good stability and recoverability, and is mild in condition, wide in universality and high in product yield when being used for catalyzing an alkyne hydroboration reaction.

Description

Technical Field

[0001] This invention relates to the use of a heterogeneous catalyst in the catalytic hydroboration reaction of alkynes with B2Pin2. Background Technology

[0002] Vinyl boronates are an important class of organoboron compounds with the general structural formula R-CH=CH-B(OR')2, possessing the dual characteristics of both alkenes and boronates, and playing a crucial role in modern organic synthesis. These compounds are mainly synthesized via metal-catalyzed boronization reactions, Peterson alkenylation reactions, and Matteson reactions. The most important application of vinyl boronates lies in the Suzuki-Miyaura coupling reaction, which can efficiently construct C(sp...)... 2 )-C(sp 2 Chan-Lam bonds play an irreplaceable role in the synthesis of drug molecules (such as antitumor compounds) and functional materials (such as OLEDs). Furthermore, they can participate in various transformation reactions such as Chan-Lam coupling and conjugated addition, and are used as important monomers in the preparation of conjugated polymers and self-healing materials.

[0003] Currently, the hydroboration reaction of alkynes with pinacol diboronate (B2Pin2) is an effective method for synthesizing vinyl borate esters. For decades, noble metal-based materials such as Rh, Ir, and Pd have been the preferred catalysts for hydroboration, but their high cost and toxicity have limited their widespread application. In recent years, alkaline earth metals and transition metals such as Fe, Co, and Ni have flourished in the field of catalytic hydroboration due to their abundant reserves, low cost, and good catalytic performance. Metal-organic frameworks (MOFs) possess advantages such as high specific surface area, excellent thermal stability, and well-dispersed metal active sites, enabling them to exhibit superior performance in catalytic reactions across various fields. Synthesizing MOFs for catalytic hydroboration by rationally designing the coordination environment between organic ligands and metal nodes provides a green route for the preparation of organoborides.

[0004] Metal-organic frameworks (MOFs) exhibit significant advantages in heterogeneous catalysis. Compared to traditional catalysts (such as metal oxides, zeolites, mesoporous silica, and enzymes), their unique properties offer new opportunities for catalytic reactions, particularly in the hydroboration reaction, where they hold significant research value. First, the rigid framework structure of MOFs effectively stabilizes catalytic active sites, avoiding the aggregation or degradation problems common in homogeneous catalysts, thus significantly improving catalyst stability and lifetime. Second, the highly ordered crystallinity of MOFs enables uniform dispersion of active sites at the molecular level, which not only improves catalytic efficiency but also provides an ideal model for in-depth exploration of reaction mechanisms. Furthermore, the structural tunability of MOFs allows for precise control of the chemical environment of catalytic sites, enabling precise control over chemoselectivity, regioselectivity, stereoselectivity, and even enantioselectivity. Another prominent feature of MOFs is their multi-component synergistic catalytic capability; metal nodes, organic ligands, and porous structures can all serve as active sites in the catalytic process, giving them broader applicability. Meanwhile, numerous studies have shown that MOFs can maintain excellent crystallinity and catalytic activity even after multiple cycles of use, a characteristic that gives them a significant advantage in industrial applications.

[0005] Based on these characteristics, MOFs exhibit great potential in catalyzing hydroboration reactions. Hydroboration is a crucial transformation process in organic synthesis, and the designability and high selectivity of MOFs make them ideal catalysts for optimizing this reaction. Therefore, systematically studying the application of MOFs in hydroboration reactions will not only contribute to the development of efficient and stable catalytic systems but may also provide new insights for green chemistry and sustainable synthesis. Summary of the Invention

[0006] This invention provides a novel application of a heterogeneous catalyst, namely its use in the hydroboration reaction of alkynes with B2Pin2. The heterogeneous catalyst Cu-3,5-PzDC is specifically prepared by mixing copper salt, pyrazole-3,5-dicarboxylic acid, and N,N-dimethylformamide-anhydrous ethanol in a mixed solvent. After thorough stirring until completely dissolved, a solvothermal reaction is carried out at 100-150°C. After the reaction is completed, the mixture is naturally cooled, the solid and liquid are separated, and the solid is washed and dried to obtain the final product.

[0007] 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.

[0008] The catalytic hydroboration reaction of alkynes with B2Pin2 involves sequentially adding Cu-3,5-PzDC, a base, B2Pin2, alkynes, and a mixed solvent to a Shrek reaction tube equipped with a magnetic stirrer. The reaction is carried out at 25°C with magnetic stirring for 30 minutes. After the reaction is complete, the solid catalyst is removed by filtration, and the reaction proceeds through… 1The yield was determined by 1H NMR analysis, and the filtrate was purified by silica gel column chromatography (petroleum ether:ethyl acetate volume ratio of 80:1 to 40:1 as eluent) to obtain pure (E)-vinyl borate product.

[0009] The molar ratio of alkyne to B2Pin2 is 1:1-2, and the amount of heterogeneous catalyst added is 1-2% of the molar amount of alkyne.

[0010] The alkyne is selected from phenylacetylene, 4-ethynyltoluene, 3-methylphenylacetylene, 2-ethynyltoluene, 4-fluorophenylacetylene, 1-chloro-4-ethynylbenzene, (4-bromophenyl)acetylene, 4-iodophenylacetylene, 1-ethyl-4-ethynylbenzene, 4-tert-butylphenylacetylene, 3-ethynylthiophene, 4-methoxyphenylacetylene, and methyl 4-ethynylbenzoate.

[0011] The alkali is sodium tert-butoxide.

[0012]

[0013] Compared with the prior art, the advantages of the present invention are as follows:

[0014] (1) The heterogeneous catalyst of the present invention is applied to the hydroboration reaction of alkynes and B2Pin2. It exhibits extremely high conversion rate and selectivity in the hydroboration reaction at room temperature and in air atmosphere for a short time.

[0015] (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, easy to recover catalyst, and easy to meet the requirements of green industrial production. Attached Figure Description

[0016] Figure 1 This is the X-ray diffraction (XRD) pattern of the heterogeneous catalyst Cu-3,5-PzDC in Example 1.

[0017] Figure 2 These are transmission electron microscope (TEM) images of the heterogeneous catalyst Cu-3,5-PzDC from Example 1. Figure a shows the microstructure of the Cu-3,5-PzDC catalyst, and Figures b and f show the elemental EDS spectra. Detailed Implementation

[0018] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the content described. The methods used in the embodiments are all conventional technical means in the art, and the reagents used are all commercially available conventional reagents or prepared according to standard methods unless otherwise specified.

[0019] Example 1: Preparation of heterogeneous catalyst Cu-3,5-PzDC

[0020] Under stirring conditions, copper nitrate trihydrate (3 mmol) and pyrazole 3,5-dicarboxylic acid monohydrate (3 mmol) were added sequentially to 50 mL of a mixed solvent of N,N-dimethylformamide and anhydrous ethanol (volume ratio 4:1). The mixture was thoroughly mixed until completely dissolved. The mixture was then transferred to a 100 mL stainless steel hydrothermal reactor lined with polytetrafluoroethylene and reacted in an oven at 120 °C for 8 h to produce crystals. After the reaction was completed, the mixture was naturally cooled to room temperature and centrifuged at 8000 r / min to obtain the solid. The solid was washed sequentially with N,N-dimethylformamide and anhydrous ethanol, three times each. After washing, the solid was dried under vacuum at 80 °C for 12 h to obtain the heterogeneous catalyst Cu-3,5-PzDC.

[0021] The X-ray diffraction (XRD) pattern of the prepared heterogeneous catalyst is shown in the figure. Figure 1 The spectrum shows multiple sharp diffraction peaks, indicating that the sample is a highly crystalline material, consistent with the typical characteristics of MOF (metal-organic framework) materials. No obvious diffuse peaks were observed, indicating that the catalyst has high purity and no significant amorphous components.

[0022] Transmission electron microscopy (TEM) images of the prepared heterogeneous catalysts are shown below. Figure 2 As shown in Figure a, the catalyst has a layered morphology and is composed of nanosheets. EDS mapping analysis shows that C, O, N and Cu are uniformly distributed in the catalyst Cu-3,5-PzDC.

[0023] Example 2: Preparation of (E)-vinylboronic ester by hydroboration of phenylacetylene with B2Pin2 catalyzed by heterogeneous catalyst Cu-3,5-PzDC

[0024]

[0025] Heterogeneous catalyst (8.905 μmol), phenylacetylene (0.5 mmol), sodium tert-butoxide (0.5 mmol), B2Pin2 (0.75 mmol), and anhydrous ethanol (1 mL) were sequentially added to a Shrek reaction tube (5 mL) equipped with a magnetic stirrer. The resulting reaction tube containing the reaction mixture was then incubated at 25 °C with magnetic stirring for 30 min. After the reaction was complete, the solid catalyst was removed by filtration. The filtrate was purified by silica gel column chromatography (using petroleum ether:ethyl acetate 80:1 as eluent) to obtain the (E)-vinyl borate product. 1 1H NMR analysis confirmed that the yield of (E)-vinyl borate was 99.9% and the selectivity was 99.9%.

[0026] (E)-vinyl borate 1 H NMR and 13 C NMR data: 1H NMR(600MHz,Chloroform-d)δ7.49(d,J=7.1Hz,2H),7.41(d,J=18.4Hz,1H),7.3 4(t,J=7.4Hz,2H),7.30(d,J=7.2Hz,1H),6.18(d,J=18.4Hz,1H),1.32(s,12H). 13 C NMR (151MHz, Chloroform-d) δ149.64,137.51,129.04,128.70,127.18,116.39,83.48,24.93.

[0027] Example 3: Preparation of (E)-vinylboronic ester by hydroboration of 4-fluorophenylacetylene with B2Pin2 catalyzed by heterogeneous catalyst Cu-3,5-PzDC

[0028]

[0029] Heterogeneous catalyst (8.905 μmol), 4-fluorophenylacetylene (0.5 mmol), sodium tert-butoxide (0.5 mmol), B2Pin2 (0.75 mmol), and anhydrous ethanol (1 mL) were sequentially added to a Shrek reaction tube (5 mL) equipped with a magnetic stirrer. The resulting reaction tube containing the reaction mixture was then incubated at 25 °C with magnetic stirring for 30 min. After the reaction was complete, the solid catalyst was removed by filtration. The filtrate was purified by silica gel column chromatography (using petroleum ether:ethyl acetate 40:1 as eluent) to obtain the (E)-vinyl borate product. 1 1H NMR analysis determined that the yield of (E)-vinyl borate was 75.2% with a selectivity of 99%.

[0030] (E)-vinyl borate 1 H NMR and 13 C NMR data: 1 H NMR (600MHz, Chloroform-d) δ7.50-7.42(m,2H),7.35(d,J=18.4Hz,1H),7.02(t,J=8.7Hz,2H),6.07(d,J=18.4Hz,1H),1.31(s,12H). 13 C NMR (151MHz, Chloroform-d) δ164.07, 162.42, 148.30, 133.76, 128.84 (d, J = 7.8Hz), 115.69 (d, J = 21.1Hz), 83.53, 24.92.

[0031] Example 4: Preparation of (E)-vinylboronic ester by hydroboration of (4-bromophenyl)acetylene with B2Pin2 catalyzed by heterogeneous catalyst Cu-3,5-PzDC

[0032]

[0033] Heterogeneous catalyst (8.905 μmol), (4-bromophenyl)acetylene (0.5 mmol), sodium tert-butoxide (0.5 mmol), B2Pin2 (0.75 mmol), and anhydrous ethanol (1 mL) were sequentially added to a Shrek reaction tube (5 mL) equipped with a magnetic stirrer. The resulting reaction tube containing the reaction mixture was then incubated at 25 °C with magnetic stirring for 30 min. After the reaction was complete, the solid catalyst was removed by filtration. The filtrate was purified by silica gel column chromatography (using petroleum ether:ethyl acetate 40:1 as eluent) to obtain the (E)-vinyl borate product. 1 1H NMR analysis determined that the yield of (E)-vinyl borate was 80%, with a selectivity of 99%.

[0034] 1H NMR and 13C NMR data for (E)-vinyl borate: 1 H NMR(600MHz,Chloroform-d)δ7.41(d,J=18.4Hz,1H),7.34(s,1H),7.26(d,J=8.0Hz,2 H),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). 13 C NMR (151MHz, Chloroform-d) δ148.20,136.43,131.87,128.63,127.87,123.03,83.59,77.37,77.16,76.95,24.92.

[0035] Example 5: Preparation of (E)-vinylboronic ester by hydroboration of 3-acetylthiophene with B2Pin2 catalyzed by heterogeneous catalyst Cu-3,5-PzDC.

[0036]

[0037] Heterogeneous catalyst (8.905 μmol), 3-acetylenthiophene (0.5 mmol), sodium tert-butoxide (0.5 mmol), B2Pin2 (0.75 mmol), and anhydrous ethanol (1 mL) were sequentially added to a Shrek reaction tube (5 mL) equipped with a magnetic stirrer. The resulting reaction mixture was then incubated at 25 °C with magnetic stirring for 30 min. After the reaction was complete, the solid catalyst was removed by filtration. The filtrate was purified by silica gel column chromatography (using petroleum ether:ethyl acetate 60:1 as eluent) to obtain the (E)-vinyl borate product. 1 1H NMR analysis determined that the yield of (E)-vinyl borate was 52.6%, with a selectivity of 99%.

[0038] 1H NMR and 13C NMR data for (E)-vinylboronic acid ester: 1H NMR (600 MHz, Chloroform-d) δ 7.39 (d, J = 18.3 Hz, 1H), 7.32–7.29 (m, 2H), 7.28–7.25 (m, 1H), 5.95 (d, J = 18.3 Hz, 1H), 1.31 (s, 12H). 13C NMR (151 MHz, Chloroform-d) δ 142.11, 140.11, 125.10, 123.92, 123.90, 82.26, 76.22, 76.01, 75.80, 23.76, 0.00.

[0039] Example 6: Preparation of (E)-vinylboronic ester by hydroboration of methyl 4-ethynylbenzoate with B2Pin2 catalyzed by heterogeneous catalyst Cu-3,5-PzDC

[0040]

[0041] Heterogeneous catalyst (8.905 μmol), methyl 4-ethynylbenzoate (0.5 mmol), sodium tert-butoxide (0.5 mmol), B2Pin2 (0.75 mmol), and anhydrous ethanol (1 mL) were sequentially added to a Shrek reaction tube (5 mL) equipped with a magnetic stirrer. The resulting reaction tube containing the reaction mixture was then incubated at 25 °C with magnetic stirring for 30 min. After the reaction was complete, the solid catalyst was removed by filtration. The filtrate was purified by silica gel column chromatography (using petroleum ether:ethyl acetate 80:1 as eluent) to obtain the (E)-vinylboronic acid ester product. 1 1H NMR analysis determined that the yield of (E)-vinyl borate was 82.6% and the selectivity was 99%.

[0042] (E)-vinyl borate 1 H NMR and 13 C NMR data:1 H NMR (600MHz, CDCl3) δ8.00(d,J=8.0Hz,2H),7.53(d,J=8.0Hz,2H),7.40(d,J=18.4Hz,1H),6.27(d,J=18.4Hz,1H),3.91(s,3H),1.31(s,12H). 13 C NMR (151MHz, Chloroform-dδ166.94,148.27,141.77,130.21,130.04,127.04,119.59,83.71,77.37,77.16,76.95,52.31,24.93.

[0043] Example 7: Preparation of (E)-vinylboronic esters from different alkynes catalyzed by the heterogeneous catalyst Cu-3,5-PzDC. The catalytic method in this example is the same as above. The specific results are shown in the table below:

[0044]

[0045]

[0046] The results above show that:

[0047] This invention investigated the effect of different functional groups on the formation of (E)-vinylboronic esters. Experimental results showed that the catalytic system exhibited excellent catalytic activity and stereoselectivity for both aromatic and aliphatic terminal alkynes, with the conversion rate of aromatic substrates significantly higher than that of aliphatic substrates. Notably, substituent position effect studies revealed that the conversion rates of meta- and ortho-substituted phenylacetylene derivatives decreased significantly (90.1-71.9%) compared to para-substituted derivatives, confirming the significant influence of steric hindrance on the hydroboration reaction. Further structure-activity relationship analysis showed that phenylacetylene derivatives containing various electron-effect substituents (including electron-donating groups -CH3, -OCH3 and electron-withdrawing groups F, Cl, Br, I) at the para position maintained high reactivity (70.4-90.1%). Of particular note is that substrates with sterically hindered electron-donating groups, such as -C2H5 and -C(CH3)3 substituted substrates (1-ethyl-4-ethynylbenzene and 4-tert-butylphenylacetylene), still achieved good conversions (88.5% and 76.3%, respectively). Furthermore, the heterocyclic substrate 3-ethynylthiophene also exhibited moderate conversion (52.6%) and extremely high selectivity (99%). These experimental results fully demonstrate the excellent regioselectivity and stereoselectivity of the Cu-3,5-PzDC catalyst in the hydroboration of terminal alkynes.

[0048] Example 8: Preparation of (E)-vinylboronic ester from phenylacetylene and B2Pin2 by heterogeneous catalyst Cu-3,5-PzDC under different solvent conditions

[0049]

[0050] The method in this embodiment is the same as in embodiment 2, except that anhydrous ethanol is replaced with anhydrous methanol, tert-butanol, acetonitrile, and N,N-dimethylformamide-water (volume ratio 1:1).

[0051] The results showed that the yield of (E)-vinyl borate was 98% when the solvent was anhydrous methanol, 4.3% when the solvent was tert-butanol, 58.7% when the mixed solvent was N,N-dimethylformamide and water (volume ratio 1:1), and no (E)-vinyl borate could be obtained when the solvent was acetonitrile.

[0052] Example 9: Preparation of (E)-vinylboronic ester from phenylacetylene and B2Pin2 by the heterogeneous catalyst Cu-3,5-PzDC prepared under different mixed solvent conditions.

[0053]

[0054] The preparation method of the heterogeneous catalyst is the same as in Example 1, except that the volume ratio of the solvent in the N,N-dimethylformamide-anhydrous ethanol mixed solvent is different, namely 0:1, 1:1, 1:4, and 1:0. When the mixed solvent is N,N-dimethylformamide:anhydrous ethanol = 0:1, the yield of (E)-vinyl borate is 44.4%; when the mixed solvent is N,N-dimethylformamide:anhydrous ethanol = 1:1, the yield of (E)-vinyl borate is 45.2%; when the mixed solvent is N,N-dimethylformamide:anhydrous ethanol = 1:4, the yield of (E)-vinyl borate is 39.84%; and when the mixed solvent is N,N-dimethylformamide:anhydrous ethanol = 1:0, the yield of (E)-vinyl borate is 46.1%.

[0055] Example 10: The catalyst preparation method in this example is the same as in Example 1, except that copper nitrate is replaced with cobalt nitrate. In the preparation of (E)-vinyl borate ester from phenylacetylene and B2Pin2, the yield of (E)-vinyl borate ester is only 1.2%.

Claims

1. The application of a heterogeneous catalyst in the hydroboration reaction of alkynes with B2Pin2; characterized in that: The heterogeneous catalyst is prepared by mixing copper salt, pyrazole-3,5-dicarboxylic acid, and N,N-dimethylformamide-anhydrous ethanol in a mixed solvent, stirring thoroughly until completely dissolved, and then carrying out a solvothermal reaction at 100-150℃. After the reaction is completed, the mixture is naturally cooled, the solid and liquid are separated, and the solid is washed and dried.

2. The application according to claim 1, characterized in that: 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.

3. The application according to claim 1, characterized in that: (E)-vinyl borate ester was prepared by hydroboration of alkynes with B2Pin2 under alkaline, solvent, ambient temperature, and air atmosphere using a heterogeneous catalyst.

4. The application according to claim 3, characterized in that: The molar ratio of alkyne to B2Pin2 is 1:1-2.

5. The application according to claim 3, characterized in that: The alkynes are selected from phenylacetylene, 4-ethynyltoluene, 3-methylphenylacetylene, 2-ethynyltoluene, 4-fluorophenylacetylene, 1-chloro-4-ethynylbenzene, (4-bromophenyl)acetylene, 4-iodophenylacetylene, 1-ethyl-4-ethynylbenzene, 4-tert-butylphenylacetylene, 3-ethynylthiophene, 4-methoxyphenylacetylene, and methyl 4-ethynylbenzoate.

Images