Cu4 cluster catalytic material with synergistic double catalytic sites and application thereof in borohydration reaction

Abstract

This invention discloses a Cu4 cluster catalytic material with synergistic dual catalytic sites and its application in the hydroboration reaction, belonging to the interdisciplinary field of coordination chemistry and nanomaterials. This copper cluster, using N-heterocyclic thiones (methimazole) as protecting ligands, is synthesized in high yield via a simple one-pot method. The chemical formula of the cluster is: C 16 H 20 Cu4N8S4, abbreviated as Cu4NC, belongs to the tetragonal crystal system and has a space group of 1. P 42 / n, a =10.01930(10)Å, b =10.01930(10)Å, c =11.6512(2)Å, α =90°, β =90°, gamma =90°, V =1169.62(3)Å 3 This catalyst utilizes the advantages of its synergistic dual catalytic sites to achieve highly efficient and selective catalytic hydroboration of alkynes. It exhibits excellent chemoselectivity (up to 100%), high efficiency (conversion number (TON) = 77786), high yield (up to 99%), a broad substrate range (28), mild conditions (room temperature and air), and high recovery rate, which are beneficial for the development of functionalized cluster catalysts.

Description

Technical Field

[0001] This invention belongs to the interdisciplinary field of coordination chemistry and nanomaterials, and relates to a novel Cu4 cluster catalyst material modified with N-heterocyclic thionone ligands, and its efficient application in the hydroboration reaction. Background Technology

[0002] The preparation and study of atomically precise metal nanoclusters has become a promising new research direction in the field of nanoscience. Metal nanoclusters are a class of clusters with precise atomic structures, typically composed of tens to hundreds of metal atoms linked by organic ligands. As bridges connecting atoms and nanoparticles, metal nanoclusters exhibit unique optical, electrical, and chemical properties. Compared to gold and silver, copper has many advantages, including lower cost, higher abundance in the Earth's crust, and wider availability. However, due to the difficulty in synthesizing copper clusters and their susceptibility to oxidation in air, synthesizing highly active copper cluster catalysts remains a significant challenge. Research on copper clusters, especially atomically precise carbene-modified copper cluster catalysts, is still in its early stages.

[0003] The hydroboration of alkynes is an important class of organic chemical reactions. Through the hydroboration of alkynes, new CB bonds can be directly constructed, creating multifunctional organic reaction modules. This allows for the directional, controllable, and diverse functionalization of alkynes, enabling the direct construction of various complex organic molecules in a streamlined and efficient manner. Therefore, it is very important in various fields of chemistry, especially in pharmaceutical and other fine chemical research. Its products, vinyl boron compounds, are important organic intermediates in organic synthesis, drug synthesis, and the synthesis of high-value-added industrial compounds.

[0004] Copper catalysts are among the most representative catalysts for catalytic hydroboration reactions, but achieving high chemoselectivity and considerable conversion rates for targeted functional groups remains a significant challenge in the research of catalytic alkyne hydroboration reactions. Summary of the Invention

[0005] The purpose of this invention is to synthesize a Cu4 cluster catalyst with high efficiency and multifunctionality protected by N-heterocyclic thionone ligands, and to develop a high efficiency, multifunctional and practical method for preparing important organic reaction modules such as vinyl boron compounds.

[0006] To this end, the present invention has developed a Cu4 cluster material modified with an N-heterocyclic thione ligand, characterized in that its chemical formula is: C 16 H 20 Cu4N8S4, abbreviated as Cu4NC, belongs to the tetragonal crystal system and has the space group P42 / n. α=90°, β=90°, γ=90°,

[0007] The shell ligand used is methimazole, with the following structural formula:

[0008]

[0009] The preparation method of Cu4 cluster material of the present invention is achieved through the following steps:

[0010] Under air atmosphere, copper salt Cu(MeCN)4PF6 was dissolved in MeCN, and a methanol solution containing methimazole was added while stirring vigorously at room temperature. After the solution turned blue, stirring was continued; then excess triethylamine was added to the stirring reaction to form microcrystals. The suspension was centrifuged, the microcrystals were collected, and dried under vacuum.

[0011] The core of the copper nanoclusters consists of four copper atoms and four N-heterocyclic thion ligands ( Figure 1 (As shown) Protects and stabilizes the Cu4 metal core; the NHT ligand contains S and N donors and can be firmly anchored to the surface of the Cu4NC cluster through Cu-S and Cu-N bonds. In the Cu4 unit, an average Cu-Cu distance of [value missing] was observed. Less than twice the van der Waals radius ( Figure 2 (As shown).

[0012] The N-heterocyclic thionone ligand-modified copper cluster catalyst of this invention can be used for highly efficient and multifunctional catalytic hydroboration of alkynes, and its properties are specifically described below:

[0013] This cluster-based catalyst fully leverages its synergistic dual-catalytic site advantage in the hydroboration of alkynes, achieving highly efficient and selective catalytic hydroboration of alkynes, including excellent chemoselectivity (reaching 100%), high efficiency (TON = 77786), high yield (reaching 99%), and a broad substrate range (28 examples). Figure 3 As shown), mild conditions (room temperature and air), high stability (5 cycles of catalysis), high recovery rate, and scale-up experiments were conducted. Figure 4 (as shown) and the directional derivatization of vinyl boron compounds to achieve the development of functionalized cluster catalysts.

[0014] The beneficial effects of this invention are as follows: The Cu4 cluster of this invention has a precisely structured atomic size, which can be accurately characterized at the atomic level; the N-heterocyclic thion ligand endows it with both rigidity and flexibility, enabling efficient and multifunctional catalysis of alkyne hydroboration under mild conditions. It has excellent application value for the preparation of vinyl boron compounds, an important organic reaction module, and this cluster catalyst has a promising application prospect in the field of organic catalysis. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the shell protection ligand structure of the Cu4 copper cluster material of the present invention.

[0016] Figure 2 This is a schematic diagram of the structure of the Cu4 copper cluster material of the present invention.

[0017] Figure 3 This is a table of substrates for the hydroboration reaction of alkynes catalyzed by the Cu4 copper cluster material of this invention.

[0018] Figure 4 This invention relates to a scale-up experiment of the hydroboration of alkynes catalyzed by Cu4 copper cluster material and the directional derivatization of vinyl boron compounds. Detailed Implementation

[0019] The invention will be further illustrated by the following examples:

[0020] Example 1: Synthesis of Cu4 Copper Cluster Material of the Present Invention

[0021] Under air atmosphere, copper salt Cu(MeCN)4PF6 (4.0 mmol) was dissolved in 100 mL of MeCN. At room temperature, 100 mL of methanol solution containing methimazole (4.0 mmol) was added with vigorous stirring. After the solution turned blue, stirring was continued for 10 minutes. Then, excess triethylamine (2.0 mL) was added to the stirred reaction, and microcrystals formed immediately. The suspension was centrifuged, and the microcrystals were collected. The microcrystals were dissolved in DCM, and after 2 days at room temperature, the resulting solution was diffused with MeCN to obtain colorless Cu4NC crystals with a yield of 75%. The crystals were then dried under vacuum.

[0022] The Cu4 copper cluster material of the present invention prepared in Example 1 was further characterized as follows:

[0023] (1) Crystal structure determination

[0024] X-ray single-crystal diffraction data of the complexes were determined using appropriately sized single-crystal samples on a Rigaku XtaLAB Pro single-crystal diffractometer. All data were obtained using graphite-monochromated CuKα rays. The diffraction source was collected at 200 K using ω-scan mode, and corrected for Lp factor and semi-empirical absorption. Structural analysis was performed by first obtaining the initial structure using the direct method with the SHELXL-97 program, and then refining it using the full-matrix least squares method with the SHELXL-97 program. All non-hydrogen atoms were refined using anisotropic thermal parameter methods. All hydrogen atoms were refined using isotropic thermal parameter methods. Detailed crystal measurement data are shown in Table 1.

[0025] Table 1. Main crystallographic data of the copper nanocluster material of the present invention.

[0026]

[0027]

[0028] Application Example 1: Cu4 copper cluster catalyst catalyzes the hydroboration of alkynes, using ethinylestradiol as the reaction substrate.

[0029]

[0030] Under air atmosphere, ethinylestradiol 1aa (59.3 mg, 0.2 mmol, 1.0 eq), B2Pin2 2 (111.8 mg, 0.44 mmol, 2.2 eq.), microcrystalline Cu4NC catalyst (2.8 mg, 2.0 mol%), K2CO3 (60.7 mg, 0.44 mmol, 2.2 equiv.), and a mixed solvent (2.0 mL, MeCN-H2O, v / v 4 / 1) were added to a reaction flask. The reaction mixture was stirred at room temperature for 1 hour. The reaction was monitored by TLC (PE-EA, v / v 2 / 1). The reaction was quenched when the alkyne was consumed, and 0.2 mmol of mesitylene was added as an internal standard. The catalytic yield was determined by NMR internal standard method. The experiment was repeated three times, and the average value was used to calculate the catalytic yield. Finally, the crude product was concentrated. The crude product was then purified by column chromatography (PE-EA, v / v 7 / 3) to obtain the target product 4aa as a white solid, with an overall yield of 85% (71.9 mg). Figure 3 ,4aa).

[0031] Other implementations, as shown in the reaction route above, yield different products and yields using different substrates.

[0032] The above embodiments are only used to illustrate the content of this invention. Other embodiments of this invention are also possible. However, all technical solutions formed by equivalent substitution or equivalent modification fall within the protection scope of this invention.

Claims

1. Use of N-heterocyclic thione ligand-modified Cu4 cluster materials in borohydration reactions, characterized in that: As a catalyst for the hydroboration reaction of alkyne; the N-heterocyclic thione ligand modified Cu4 cluster material has a chemical formula of: C 16 H 20 Cu4N8S4, abbreviated as: Cu4NC, belongs to tetragonal system, and the space group is P 42 / n, a = 10.01930(10) Å, b =10.01930(10) Å, c = 11.6512(2) Å, α = 90°, β = 90°, gamma = 90°, V = 1169.62(3) Å 3 ; wherein the N-heterocyclic thioenone ligand is a methanethioimidazole, having the structural formula: 。 2. Use of the N-heterocyclic thio ketone modified Cu4 cluster material according to claim 1 in a borohydration reaction, characterized in that: The N-heterocyclic thioenone ligand modified Cu4 cluster material has a core composed of four copper atoms, and the Cu4 metal core is protected by four N-heterocyclic thioenone ligands. The N-heterocyclic thioenone ligand is firmly anchored on the surface of the Cu4 cluster through Cu-S and Cu-N bonds.

3. Use of the N-heterocyclic thioketone-modified Cu4 cluster material according to claim 1 or 2 in a borohydration reaction, characterized in that: The borohydration reaction route of the alkyne is as follows: R 1 selected from one of the following substituents, 。

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