A novel cobalt catalyst for organic reactions and process thereof

Abstract

There are many benefits to organometallic catalysis, especially in homogeneous catalysis for C(sp2)-H bond activation and new C-C bond formation reactions. These catalysts, which are mainly transition metal complexes with organic ligands, are very reactive and selective, which increases the range and effectiveness of different synthetic transformations. Their capacity to activate C-H bonds under mild reaction conditions is a key advantage as it allows for the direct C-H alkylation of aryl ketones without the need for transient functional groups. This reduces utilization of chemicals, cost and energy used in addition to streamlining synthetic routes. Furthermore, complex molecular architectures with high stereo- and regioselectivity may be formed with the help of organometallic homogenous catalysts, making precise synthesis of complex molecules possible. The present catalyst is easy to use, industrially scalable, recyclable, and provides excellent yields of C-H alkylated products from nonactivated alkyl halides. The reported methods need the use of excess (2-6 equivalent) of alkyl halides but this catalyst performs the catalytic reaction in the stoichiometric quantities of aryl ketone and alkyl halides.

Description

A NOVEL COBALT CATALYST FOR ORGANIC REACTIONS ANDPROCESS THEREOFTECHNICAL FIELD

[0001] The present invention relates to a homogeneous cobalt catalyst, r]3-fluorenyl-(|J2- hydoxy) cobalt(II) dimer or [Co(p2-OH)-(r|3-Fluorenyl)]2 for room temperature C-H alkylation of aryl ketones with alkyl halides reactions. The catalyst is industrially scalable, easy to use and cost effective.

[0002] Organometallic catalysis is a type of catalysis where chemical reactions are sped up by using organometallic molecules. Organometallic catalysts are made entirely of metals connected to carbon and other elements that are frequently found in organometallic compounds, in contrast to conventional metal -based catalysts. These catalysts may catalyze a variety of transformations in organic synthesis like C-C, C-N, C-O, C-S bond formation reactions etc organometallic catalysis is a popular strategy in contemporary synthetic chemistry because it has a number of benefits, such as low reaction conditions, high selectivity, and environmental friendliness.

[0003] Catalysts accelerate chemical reactions by providing an alternative reaction pathway with lower activation energy, allowing reactions to proceed more rapidly than they would without the catalyst. They may promote specific pathways or products in a reaction, enhancing selectivity and reducing the formation of unwanted by-products. By lowering the activation energy required for a reaction, catalysts enable reactions to occur at lower temperatures and pressures, leading to energy savings and milder reaction conditions. They enable atom economy and achieve an excellent yield of products, thereby improving the overall efficiency of the reaction process. Many catalysts are compatible with green chemistry principles, such as the use of renewable resources, non-toxic reagents, and solvent- free conditions, contributing to more sustainable chemical processes. Some catalysts may be recovered and reused multiple times without losing their activity, reducing costs, and minimizing site generation. They may be designed and tailored to promote specific reactions or to work under different reaction conditions, offering versatility and applicability across various chemical transformations. They may enable the feasibility of reactions that might otherwise be difficult or impossible to achieve under ambient conditions, expanding the synthetic toolbox available to chemists.

[0004] Catalysts may become deactivated or inhibited by various substances present in the reaction mixture, such as impurities, reaction by-products, or intermediate species, leading to decreased catalytic activity over time. Some catalysts may undergo degradation or structural changes during the course of a reaction, resulting in reduced catalytic efficiency or selectivity and limiting their lifespan. In certain cases, catalysts may promote undesired side reactions or product pathways, leading to decreased selectivity and lower overall reaction efficiency. The synthesis or acquisition of certain catalysts may be expensive, particularly precious transition metal catalysts, which may hinder their widespread application in large- scale industrial processes catalyst performance may be highly dependent on reaction parameters such as temperature, pressure, pH, presence of air and moisture and solvent choice, requiring careful optimization to achieve optimal results. Some catalysts may contain toxic or environmentally harmful components, posing risks to human health and the environment during their synthesis, use, or disposal. The design and development of efficient catalysts for specific reactions often require significant research efforts and may involve trial- and-error approaches, limiting the pace of progress in certain areas of catalysis.

[0005] CN107051566B discloses preparation method of a nitrogen-doped carbon-coated heterogeneous cobalt catalyst disclosed in the invention: uniformly combining a source of carbon, a source of nitrogen, a cobalt salt, and a solvent in accordance with a mass ratio of x (6-x) to (1-6) to (1-10), where x is an integer between 0 and 6; drying the mixture; roasting it in an inert gas vacuum tube furnace; placing the roasted mixture in diluted acid to acidify it; performing solid-liquid separation; and finally ishing and drying the solid to produce the cobalt catalyst coated with aza-carbon. The invention also describes a procedure for catalyzing the transfer hydrogenation of unsaturated compounds, such as quinoline, vanillin, benzaldehyde, and phenylpropyl aldehyde, using the catalyst prepared by the procedure. The process of preparation is too complex to be used industrially.

[0006] CN106552661B discloses a primary amine compound using a type of nitrogen- doped carbon material loaded heterogeneous cobalt catalysts and its catalytic hydrogenating reduction amination is disclosed in the invention. The catalyst is to be prepared by the following methods: 1) preparing MOF material ZIF-67; 2) calcining MOF material ZIF-67 for 1-10 hours at 200-1000 degrees Celsius while protected from nitrogen to produce nitrogen-doped carbon material load cobalt catalyst Co / N-C. The following is the procedure for making the primary amine compound by catalytic hydrogenating reduction amination:Ammonium hydroxide, carbonyls, nitrogen-doped carbon material load, and cobalt catalyst are added to an organic solvent. The mixture is then passed through hydrogen and allowed to react for 0.5-20.0 hours at a temperature of 50-150 DEG C and a pressure of 0.1-5 MPa to produce aminated compounds. The process of synthesis is too complex.

[0007] However, there is a demand for low-cost, easy-to-use, more easily adaptable technology.SUMMARY

[0008] This summary is not intended to define or limit the claimed subject matter, nor is it designed to identify key characteristics of the claimed subject matter.

[0009] Disclosed is a homogeneous cobalt catalyst for crucial C-H activation reactions to get a new organic compound under ambient conditions.

[0010] In one of the implementations, the reactions studied are C-H activation reactions for room temperature C-H alkylation of aryl ketones with all types of alkyl halides

[0011] In another implementation, the catalyst may be used selectively to generate desired organic molecules in one step.

[0012] In another implementation, the catalysts is given in Fig 1.

[0013] In another implementation, just 5 moles % of the catalyst is required to do C-H activation reactions.

[0014] In another implementation, the catalyst is r|3-fluorenyl-(p2-hydoxy) cobalt(II) dimer or [Co(p2-OH)-(r|3-Fluorenyl)]2 . 1 1 performs C-H activation of aryl ketones at room / lower temperature.

[0015] In another implementation, the catalyst is easy to prepare and the process is industrially scalable.

[0016] In another implementation, the catalysts work selectively to synthesize specific targeted compounds from aryl ketones in the presence of the other functional groups and thus, it saves cost by unnecessary isolation or separation of undesired products from mixtures.

[0017] In yet another implementation, the catalyst works at room temperature and reaction time varies from 4-7 hrs depending on structure of aryl ketones and alkyl halides.

[0018] In another implementation, the catalyst is used for C-H activation and C-C bond formation reactions and thereby reducing a lot of time for selective compounds preparation.

[0019] In yet another implementation, the solvent may be any alcoholic solvent as selected from methanol, ethanol, isopropanol, n butanol or tetrahydrofuran in which the reaction is being performed.

[0020] In yet another implementation, the invention is very simple, economic, environment friendly and commercially viable.BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Reading the aforementioned extensive explanation of embodiments in conjunction with the attached figures may help you comprehend it better. An example of the construction of the present subject matter is provided as figures for the purpose of illustration; nevertheless, the invention is not restricted to the precise method described in the document and the figures.

[0022] With reference to the accompanying figures, the current subject matter is discussed in full. The leftmost digit(s) of a reference number in a figure designates the figure where the reference number first appears. The same numerals are consistently utilized in the drawings to relate to different aspects of the current subject matter.

[0023] Figure la illustrates the Structure of the catalyst

[0024] Figure lb depicts the 1H-NMR spectra of the catalyst

[0025] Figure 1c depicts the IR spectra of the catalyst.

[0026] Figure Id depicts the 13C-NMR spectra of the catalyst

[0027] Figure 1 e, mass spectra of the catalyst.

[0028] Figure 2 depicts process of synthesis of the of the catalyst

[0029] Figure 3. Various reactions studied using the catalyst

[0030] Figure 4, Images of laboratory use of catalyst.

[0031] Figure 5, Electron Paramagnetic Resonance spectrum of the catalyst.DETAILED DESCRIPTION

[0032] Disclosed is a novel cobalt catalyst for organic reactions

[0033] In one of the embodiments, the reactions studied are C-H reactions for room temperature C-H alkylation of aryl ketones with alkyl halides. In an exemplary embodiment, the Fluorene (3.0-4.0 mmol) is dissolved in dry methanol. The mixture is stirred for half an hour under an inert atmosphere. Then sodium metal (4 -5 mmole) is added, and the reaction mixture is stirred to generate sodium salt of fluorene. Then stirring for Co(III) or Co(II) salts (3-4 mmol) is added to the reaction and stirred until the color of the solution changed from dark green to dark orange. The progress of the reaction is monitored using TLC. The catalyst formation is completed in about seven to eight hours under room temperature. Once the catalyst is formed, the reaction mixture is fdtered to remove the residue, and kept in the refrigerator for further alkylation of substituted aryl ketones with alkyl halides. The catalyst is air and moisture stable in the methanol solution form. The yield of the catalyst is found to be 87% by using GCMS. The catalyst is characterized using 'H-NMR.13C-NMR, HRMS and IR.

[0034] In another embodiment, the catalyst may be used selectively for generating desired C-H alkylated products of aryl ketones.

[0035] In another embodiment, the structure of the catalysts is given in Fig la

[0036] In another embodiment, the catalyst is used in 5-10 mol % catalytic amount.

[0037] In another embodiment referring to figure la„ the catalyst is r|3-fluorenyl-(p2- hydoxy) cobalt(II) dimer or [Co(p2-OH)-(r|3-Fluorenyl)]2 . 1 1 performs C-H activation of aryl ketones at room temperature.

[0038] Referring to figure lb, the IR of the catalyst with peaks 3341- Broad -OH, 1599-CO.

[0039] Referring to figure 1 c, the1H NMR (400 MHz, CD3OD) 5 7.80 (s, 4H), 7.55 (s, 4H), 7.36 (s, 4H), 7.29 (s, 4H), 1.91 (s, 2H).

[0040] Referring to Figure Id,13C NMR (101 MHz, CD3OD) 5 143.01, 141.60, 126.41, 126.38, 124.67, 119.34, 48.25, 48.03, 47.82, 47.61, 47.40, 47.18, 46.97.

[0041] Referring to figure le, mass spectra revealing m / z at 242.28

[0042] In another embodiment, the catalyst is easy to prepare and the process is industrially scalable.

[0043] In another embodiment, the catalysts work selectively to synthesis C-H alkylated products of aryl ketones and thus, save cost by avoiding multistep synthesis and is also atom economic.

[0044] In yet another embodiment, the catalysts work at room temperature and reaction time varies from 4-8 hrs depending on structure of the aryl ketones and alkyl halide.

[0045] In another embodiment, the catalyst is used for C-H and C-C bond reactions and thereby reducing a lot of time for C-H alkylation of ketones. Since reactions may be carried out using methanol it saves a lot on extraction and separation.

[0046] In yet another embodiment, the invention is very simple, economic, environment friendly and commercially viable.

[0047] The catalyst is air and moisture stable and hence it can be recyclable. The Figure 5 shows scale-up reactions to and recovered catalyst from the alumina column.

[0048] In one of the embodiments, referring to figure 2 and 3, the reactions studied are C-H reactions for room temperature C-H alkylation of aryl ketones with alkyl halides. In an exemplary embodiment, the Fluorene (3.0 mmol) is dissolved in dry methanol. The mixture is stirred for half an hour under an inert atmosphere. Then sodium metal (4 mmole) is added, and the reaction mixture is stirred to generate sodium salt of fluorene. Then stirring for Co(III) salt , CO(OAC)3 (3 mmol) is added to the reaction and stirred until the color of the solution changed from dark green to dark orange. The progress of the reaction is monitored using TLC. The catalyst formation is completed in about seven to eight hours under room temperature. Once the catalyst is formed, the reaction mixture is filtered to remove the residue, and kept in the refrigerator for further alkylation of substituted aryl ketones with alkyl halides. The catalyst is air and moisture stable in the methanol solution form. The yield of the catalyst is found to be 88% by using GCMS. The catalyst is characterized using H- NMR,13C-NMR, HRMS and IR. In yet another embodiment, the solvent may be any alcoholic solvent as selected from methanol, ethanol, isopropanol, n-butanol or tetrahydrofuran in which the reaction is being performed.

[0049] In another embodiment, figure 4 depicts the laboratory images of catalyst being synthesised and used is shown.

[0050] In another embodiment, referring to figure 5, Electron Paramagnetic Resonance spectrum, also known as Electron Spin Resonance (ESR) spectrum. It's a spectroscopic technique used to study materials with unpaired electrons, such as free radicals, transitionmetal ions, or defects in crystals. In an EPR experiment, a sample is placed in a strong magnetic field and exposed to microwave radiation. If the sample contains unpaired electrons, the spins of these electrons may be flipped by the microwave radiation, causing transitions between different energy levels. The frequency at which these transitions occur depends on the strength of the magnetic field and the properties of the sample. The EPR spectrum is typically plotted as signal intensity (y-axis) versus the applied magnetic field (x- axis). The shape and position of the peaks in the spectrum provide information about the number of unpaired electrons, their environment, and other properties of the sample.

[0051] In yet another embodiment, the catalyst is easy to synthesize and use and easily scalable.

Claims

We Claim:

1. A novel catalyst for C(sp2)-H activation and C(sp2)-C bond formation reactions comprising of: there structureWherein, the solvent may be any alcoholic solvent as selected from methanol, ethanol, isopropanol, n butanol or tetrahydrofuran in which the reaction is being performed.

2. A process of making the catalyst comprising of: a) dissolving Fluorene (3.0-4.0 mmol) in dry methanol, b) adding sodium metal (4-5 mmole), and the reaction mixture is stirred to generate sodium salt of fluorene; c) adding Co(OAc)3 salts (3-4 mmol) to the reaction and stirred until the color of the solution changed from dark green to reddish orange, d) raising the temperature to 45-50 °C and maintaining it for three to four hours. e) Filtration isolation, and refrigeration.

3. A catalyst as (r|3-fluorenyl)-(p2-hydoxy) cobalt(II) dimer or [Co(p2-OH)-(r|3- Fluorenyl)]2used as 5 mole percent in organic reactions.

4. A process as claimed in claim 2, the solvent may be any alcoholic solvent as selected from methanol, ethanol, isopropanol, n butanol or tetrahydrofuran in which the reaction is being performed.

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