Phosphine-free cobalt-(II) complexes for dehydrogenative c-c coupling reactions using alcohols: synthesis and applications thereof

Abstract

The invention provides a newly developed, inexpensive, and bench-stable Cobalt (II)-complexes encompassing phosphine-free N,N-bidentate ligand system. Particularly, the present invention utilizes Co(II)-complexes as catalyzing system for the sole purpose of studying the C-alkylation reaction through borrowing hydrogen strategy. The present invention also provides a catalytic methodology for selective alkylation, alkenylation of fluorene, and inactivated bulky indene utilizing alcohol under mild and benign conditions. In the present invention, fluorene and indene are alkylated using a range of substrates as an alkylating agent, such as primary and secondary aromatic, heteroaromatic, and aliphatic alcohols. The present invention indicates a sophisticated catalytic process with yields that range from high to exceptional yields and excellent regioselectivity of the C3-alkylated indenes.

Description

[0001] PHOSPHINE-FREE COBALT-(II) COMPLEXES FOR DEHYDROGENATIVE C-C COUPLING REACTIONS USING ALCOHOLS: SYNTHESIS AND APPLICATIONS THEREOF CROSS-REFERENCE TO RELATED PATENT APPLICATION: This application claims the priority to and benefit of Indian Patent Application No. 202441056658 filed on July 25, 2024; the disclosures of which are incorporated herein by reference FIELD OF THE INVENTION: The present invention relates to the field of organic, organometallic chemistry and sustainable catalysis. Particularly, the present invention relates to a catalytic process for alkylation of fluorene and indene. Specifically, the present invention involves the development of a phosphine-free (NN)PyMeMeCoBr2 complex that facilitates the process for the C-alkylation of fluorene and indene under optimized conditions. BACKGROUND OF THE INVENTION: Fluorene and its analogs are versatile chemical intermediates utilized in optical materials, polymer, electrochemistry, pharmacies, and organic solar cells. Meanwhile, the process benefits environmental protection because the fluorene is an essential component of coal tar, which needs to be better utilized. Therefore, the functionalization of fluorene as a means of converting coal tar into a value-added product has a favorable outlook in organic synthesis. In recent decades, there has been a lot of interest in the synthesis of 9- monoalkylated and 9,9-dialkylated fluorene monomers since they are essential building blocks for poly(alkylfluorene)s, which have diverse chemical, physical, and photoelectric properties. Earlier techniques required for their preparation depend mainly on the condensation of aldehydes and fluorene, followed by hydrogenation, or the SN2 reaction of fluorenes with an excess of haloalkanes mediated by a strong base (n-BuLi or NaOH). However, these techniques frequently use stoichiometric (or greater) alkyl halides, leading to hazardous byproducts, enabling over-alkylation, poor yield, and freezing temperatures for much of their operation. Indene (benzocyclopentadienes) moiety is a crucial carbocyclic derivative in organic and organometallic chemistry. Various indene derivatives have shown essential biological properties, such as antitumor, antiallergic, fungicidal, anti- hypercholesterolemic, anticonvulsant, herbicidal, and antimicrobial activities. They also have wide applications in material science. Moreover, they serve as important ligand precursors in group IV metallocene complexes that catalyze the olefin polymerization process with metallocene. Consequently, the progress on efficient synthesis of structurally diverse substituted indene continues to be a focus for synthetic chemists. Additionally, an abundance of research on the synthesis of mono- and multi-substituted indenes has been reported, using the existing indenyl core. Typically, the conventional method for the synthesis of 3-substituted indene starts with the in-situ generation of indenyl lithium, which is produced by deprotonating indene with n-butyl lithium and subsequently reacting with electrophiles. There are several disadvantages to this method, including an extended reaction time, the use of extremely low temperatures, the employment of hazardous reagents, insufficient regioselectivity, and the production of large volumes of copious amounts. Therefore, it is extremely desirable to establish an eco-friendly, cost-effective, and sustainable approach for investigating the alkylation of indene. In recent times, transition-metal-catalyzed hydrogen auto-transfer (HA) / borrowing hydrogenation (BH) and acceptorless dehydrogenation strategies utilizing abundantly available renewable feedstock alcohols for selective C-C or C-N bond formation have emerged as powerful tools in the field of chemical synthesis. The transition metal- catalyzed C-C coupling of carbonyl compounds via alcohol activation through the HA strategy overcomes the limitations of the conventional approach. It is important to note that there are significantly more commercial alcohols available than alkyl halides. The BH / HA approach is redox neutral, an atom-efficient and environmentally friendly alkylation strategy that diversifies the synthetic utility of widely accessible alcohols with the generation of water as the sole byproduct. The method consists of three steps, namely, dehydrogenation, condensation, and hydrogenation sequence, where a catalyst first oxidizes alcohol by removing hydrogen to form a reactive carbonyl compound (dehydrogenation). This intermediate can undergo a diverse range of subsequent transformations (condensation) before the catalyst returns the “borrowed” hydrogen (hydrogenation) to liberate the product and regenerate the catalyst. The strategy is quite facile for the alkylation of carbon with acidic protons using alcohol in the presence of a base to generate C-C bonds. Following the BH approach, the transition-metal catalyzed α-alkylation (C-C bond formation) of carbonyl compounds from various primary and secondary alcohols has been well studied. The transformation uses a limited group of compounds containing an activated methylene group adjacent to electron-withdrawing substituents, namely, ketone, ester, amide, nitrile and heteroarene. There are studies on selective C3-alkylation of indene catalyzed by inexpensive and readily available first-row transition metals and using alcohols as alkylating agents. Indeed, C3-bis-indentation of alcohols is unprecedented. The BH circumstances, however, allow for the formation of tetra-substituted olefin intermediates from secondary alcohols and disubstituted nucleophilic carbons during the condensation step, while steric factors prevent the reduction of olefin intermediates to the final product. However, the present invention provides hydrogenation and bis-alkylation of the olefin intermediates by employing ester, amide, imide and heterocyclic activation groups in few examples. The first significant exploration of this was published in 1955 by Becker in the Journal of the American Chemical Society (77: 6030-6031). Becker described the base-catalyzed alkylation of fluorene with certain aliphatic alcohols, a process that required an excess of base and high reaction temperatures of 210-220 °C, which are considered very harsh conditions. Recently, Ganaprakashan and co-workers, in J. Org. Chem. 2020, 85: 2277-2290, discloses Ru-catalyzed direct (sp3)C-H alkylation of fluorene using alcohols. Yong- Qiang Tu, in Angew. Chem. Int. Ed.2022, 61, e202206446, discloses three examples using spirocyclic NHC-Ir pincer complex and few reports on the 3d-metal catalyzed selective C(sp3)-H alkylation of fluorenes are disclosed. The publication, in Chem. Commun. 2021, 57, 10363-10366 and in Catal. Sci. Technol. 2023, 13, 611-617, Srimani-group separately explained Mn and Ni-based catalytic systems for the synthesis of monoalkylated fluorenes using alcohols. Adhikari, in Catal. Sci. Technol.2022, 12: 4211-4216, discloses ligand-assisted Ni- catalysis enabling C-alkylation of 9H-fluorene with alcohols. Very recently, the publication by Samanta and Paul group, in J. Org. Chem. 2024, 89: 1910-1926, discloses cobalt and Zn-based pincer complex proceeds through a non-innocent azo-anion radical pathway as shown in the pictorial representation below. Although a large variety of alcohols have been shown, the reactivity of fluorenes towards diol limits the substrate range. Functionalizing inactivated methylene of carbocycles such as 9H-fluorene has been explored insufficiently to date and is quite challenging. A pictorial representation of prior art on the alkylation of 9H-fluorene with alcohols: Despite the development of many synthetic techniques, there have been few studies on synthesizing indene derivatives from feedstock alcohols. The first time Hoveyda et al, in J. Am. Chem. Soc. 2000, 122: 5977–5983, discloses Zr-catalysed C1- alkylation of indene using tosylates via nucleophilic attack of substrate-derived zirconates as shown in pictorial representation. Furthermore, Chae S. Yi discloses Ru-catalyze selective C2-alkylation of indene with alcohols and the procedure through catalyst-driven vinylic C-H bond activation and oxidative addition of the C-O bond of alcohol published in Science, 2011, 333: 1613–1616. However, the present invention describes the selective BH / HA strategy-based C3-alkylation of less-activated indenes from alcohol. Tu et al. (2022), disclose facile benzylic C3-alkylation of indene with alcohols by spirocyclic NHC-Ir III pincer complex in Angew. Chem. Int. Ed. 2022, 61: e202206446. However, the bis-indenylation of unactivated olefin has not yet been accomplished. Therefore, the development of a new technique for the comprehensive investigation of the selective alkylation processes of indene moiety using alcohol is quite challenging. A pictorial representation of prior arts on the alkylation of indenes with alcohols:

[0002] There is need to explore of functionalizing inactivated methylene of carbocycles such as 9H-fluorene. The present invention also provides an extensive study on a well-defined phosphine-free N,N-bidentate ligand-based cobalt catalytic functionalization of 9H-carbon in fluorenes (Scheme 2). The catalytic system worked well with several types of benzylic, hetero-aromatic, and aliphatic alcohols and fluorene. Specifically with bulky secondary alcohol, it proceeds via fluorene alkenylation to obtain tetra-substituted olefin. Specially, with the aliphatic diol case, the developed protocol in the present invention reacted differently and generated late-stage functionalized Spiro compounds for the first time in the present invention. Therefore, the development of a new technique for the comprehensive investigation of the selective alkylation processes of indene moiety using alcohol is required. The present invention provides an earth-abundant base-metal cobalt-catalyzed divergence in alkylation reaction with indene, primarily selective C3-alkylation, C1,C3-bis-alkylation of indenes and synthesis of bis-indenyl-alkane using abundantly available alcohols as potential alkylating agents. The reaction is catalyzed by a well-defined (NN)Co(II)-bidentate complex and it operates via the HA / BH strategy (Scheme 4). OBJECTS OF THE INVENTION: The primary object of the present invention is to develop an efficient catalyst for the selective alkylation processes of indene or fluorenes. Another object of the present invention is to provide a novel process for synthesis of phosphine-free (NN)PyMeMeCoBr2 complex to show an efficient catalytic activity in the functionalization of fluorene and regioselective alkylation of indene. Yet another object of the present invention is to provide a process for development of transition metal-catalyzed selective C(sp3)-H alkylation of fluorene. Another object of the present invention is to provide a novel spiro compounds from fluorenes by using the catalytic activity of the catalyst (NN)PyMeMeCoBr2complex. Another object of the present invention is to furnish a process for the synthesis of novel sprio compounds by catalyzed selective alkylation of fluorene. Yet another object of the present invention is to provide a process for the development of transition-metal catalysed chemo-divergence in alkylation of indene. Another object of the present invention is to provide a process for the synthesis of bis-indenyl-alkane. Yet another object of the present invention is to provide a optimize reaction conditions to maximize yield and quality of the produced alkylated flourenes and alkylated indenes. SUMMARY OF THE INVENTION: Accordingly, in one aspect, the present invention provides a process for the synthesis of (NN)PyMeMeCoBr2 complex, comprising th i. reacting pyridine derivative with compound in the prese se and a solvent to yield NNPyMeMebidentate ligand (L1); and ii. ligand (L1) with anhydrous CoBr2 in presence of a solvent at a particular temperature to yield (NN)PyMeMeCoBr2 complex. According to the present invention, the pyridine derivative in step (i) is selected from the group comprising 2-(chloromethyl) pyridine hydrochloride, 2-(2,6- bis(bromomethyl)pyridine, 2-(bromomethyl) pyridine, 2-(2,6- bis(chloromethyl)pyridine, 2-(2-chloroethyl) pyridine hydrochloride, or 4-(2- chloroethyl) pyridine hydrochloride, wherein the pyridine derivative is 2- (chloromethyl) pyridine hydrochloride. The heterocyclic compound in step (i) is selected from group comprising 3-methyl pyrazole, 3,5-dimethyl pyrazole, morpholine, 3-ethyl-1H pyrazole, 3-ethyl-5 methyl 1H pyrazole, wherein the heterocyclic compound is 3,5-dimethyl pyrazole. The solvent in step (i) is selected from the group comprising of diethyl ether, dimethylformamide tetrahydrofuran, dichloromethane, methanol, DMSO, dimethoxy ethane, dimethoxy methane, dibutyl ether, ethanol, isopropyl alcohol, acetonitrile or diisopropyl ether, wherein the solvent is acetonitrile. The base in step (i) is selected from a group comprising of potassium hydroxide, potassium tert-butoxide, sodium carbonate, caesium carbonate, lithium carbonate, calcium carbonate, sodium bicarbonate, ammonium hydroxide, potassium carbonate, potassium bicarbonate or magnesium carbonate, wherein the base is potassium hydroxide. The solvent in step (ii) is selected from the group comprising of diethyl ether, dimethylformamide tetrahydrofuran, dichloromethane, methanol, DMSO, dimethoxy ethane, dimethoxy methane, dibutyl ether, ethanol, isopropyl alcohol, acetonitrile or diisopropyl ether, wherein the solvent is acetonitrile. According to the process for synthesis of catalyst, the temperature in step ii) is maintained between 25 to 50 °C. Another aspect of the present is to furnish a process for transition metal-catalyzed selective C(sp3)-H alkylation of fluorene, comprising step of reacting fluorene with an alkyl presence of a catalyst, a solvent, and a base to yield alkylated fluorenes. According to the present invention, the alkylating agent is an alcohol and the alcohol is selected from the group comprising aromatic alcohols, benzylic alcohols, hetero-aromatic alcohols, aliphatic primary or secondary alcohols. The catalyst is (NN)PyMeMeCoBr2complex. The solvent is selected from the group comprising toluene, n-octane, diethyl ether, dimethylformamide tetrahydrofuran, dichloromethane, methanol, DMSO, dimethoxy ethane, dimethoxy methane, dibutyl ether, ethanol, isopropyl alcohol, acetonitrile or diisopropyl ether, wherein the solvent is toluene or n-octane. The base is selected from a group comprising potassium hydroxide, potassium tert- butoxide, sodium hydroxide, sodium carbonate, caesium carbonate, lithium carbonate, calcium carbonate, sodium bicarbonate, ammonium hydroxide, potassium carbonate, potassium bicarbonate or magnesium carbonate, wherein the base is potassium tert-butoxide or sodium hydroxide. In another aspect, the present invention provides a novel spiro compound

[0003] According to another aspect, the present invention provides a process for the synthesis of novel Spiro compound, comprising step of reacting fluorene with an alkylating agent in presence of a catalyst, a solvent, and a base to produce spiro compound. According to the present invention, the process for preparation of spiro compound, wherein the alkylating agent is a diol. The diol is selected from group comprising 1,3-propanediol, 1,4-butanediol, 1,5-pentandiol, 1,2-ethanediols, methanediol, 1,6- hexanediol, or 10-decanediol, wherein the diol is 1,3-propanediol, 1,4-butanediol or 1,5-pentandiol. The solvent is selected from the group comprising of toluene, n-octane, diethyl ether, dimethylformamide tetrahydrofuran, dichloromethane, methanol, DMSO, dimethoxy ethane, dimethoxy methane, dibutyl ether, ethanol, isopropyl alcohol, acetonitrile or diisopropyl ether, wherein the solvent is toluene or n-octane. Accordingly, the base is selected from a group comprising of potassium hydroxide, potassium tert-butoxide, sodium hydroxide, sodium carbonate, caesium carbonate, lithium carbonate, calcium carbonate, sodium bicarbonate, ammonium hydroxide, potassium carbonate, potassium bicarbonate or magnesium carbonate, wherein the base is potassium tert-butoxide or sodium hydroxide. Yet another aspect, the present invention provides a process for transition-metal catalyzed chemo-divergence in C-H alkylation of indene or synthesis of bis- (indenyl)alkane, comprising step of reacting indene with alkylating agent in presence of a catalyst, a solvent, and a base to yield alkylated indene products or bis-(indenyl)alkane. According to the process for preparation of spiro compound, wherein the alkylating agent is an alcohol, the alcohol is selected from the group comprising aromatic alcohols, benzylic alcohols, hetero-aromatic alcohols, aliphatic primary or secondary alcohols. The catalyst is (NN)PyMeMeCoBr2 complex. According to the process, wherein the solvent is selected from the group comprising toluene, n-octane, diethyl ether, dimethylformamide tetrahydrofuran, dichloromethane, methanol, DMSO, dimethoxy ethane, dimethoxy methane, dibutyl ether, ethanol, isopropyl alcohol, acetonitrile or diisopropyl ether, wherein the solvent is toluene or n-octane. The base is selected from a group comprising potassium hydroxide, potassium tert- butoxide, sodium hydroxide, sodium carbonate, caesium carbonate, lithium carbonate, calcium carbonate, sodium bicarbonate, ammonium hydroxide, potassium carbonate, potassium bicarbonate or magnesium carbonate, wherein the base is potassium tert-butoxide or sodium hydroxide. According to the process, alkylated indene compounds are producing through borrowing hydrogen (BH) strategy and bis-indenyl-alkanes are producing through the interrupted borrowing hydrogenation pathway (IBHS). BRIEF DESCRIPTION OF THE DRAWINGS: FIG. 1: ORTEP diagram of (NN)PyMeMeCoBr2 complex with 50% probability ellipsoids. Hydrogen atoms are omitted for clarity. FIG. 2: ORTEP diagram of spiro compound 40 with 50% probability ellipsoids. Hydrogen atoms are omitted for clarity. DETAILED DESCRIPTION OF THE INVENTION: Accordingly, in one aspect, the present invention provides a simple, phosphine-free (NN)PyMeMeCoBr2 complex and effectively using for the present catalytic applications. (N mplex This Co-complex is an air-stable, crystalline substance that can be kept for many months in both solid and solution phases. It can be synthesized quantitatively on a gram scale. According to another aspect, the present invention provides a process for the synthesis of (NN)PyMeMeCoBr2 complex, comprising steps of: a) reacting pyridine derivative with a heterocyclic compound in the presence of a base and a solvent to yield NNPyMeMebidentate ligand (L1) as shown in Scheme 1; and b) reacting NNPyMeMebidentate ligand (L1) with anhydrous CoBr2in a solvent at room temperature, resulting in the corresponding (NN)PyMeMeCoBr2 complex in 87 % isolated yield as shown in Scheme 1. Scheme 1: Synthesis of (NN)PyMeMeCoBr2 bidentate complex. Accordi ng to the present invention, the pyridine derivative is selected from the group comprising 2-(chloromethyl) pyridine hydrochloride, 2-(2,6- bis(bromomethyl)pyridine, 2-(bromomethyl) pyridine, 2-(2,6- bis(chloromethyl)pyridine, 2-(2-chloroethyl) pyridine hydrochloride, 4-(2- chloroethyl) pyridine hydrochloride. The preferred pyridine derivative is 2- (chloromethyl) pyridine hydrochloride. The heterocyclic compound is selected from the group comprising 3-methyl pyrazole, 3,5-dimethyl pyrazole, morpholine, 3 ethyl-1H pyrazole, 3-ethyl-5 methyl 1H pyrazole. The preferred heterocyclic compound is 3,5-dimethyl pyrazole. The process as above, wherein the solvent in step (i) is selected from the group comprising of diethyl ether, dimethylformamide tetrahydrofuran, dichloromethane, methanol, DMSO, dimethoxy ethane, dimethoxy methane, dibutyl ether, ethanol, isopropyl alcohol, acetonitrile or diisopropyl ether, wherein the preferred solvent is acetonitrile. The process as above wherein the base in step (i) is selected from a group comprising of potassium hydroxide, potassium tert-butoxide, sodium carbonate, cesium carbonate, lithium carbonate, calcium carbonate, sodium bicarbonate, ammonium hydroxide, potassium carbonate, potassium bicarbonate or magnesium carbonate, wherein the preferred base is potassium hydroxide. The process as above, wherein the solvent in step (ii) is selected from the group comprising of diethyl ether, dimethylformamide tetrahydrofuran, dichloromethane, methanol, DMSO, dimethoxy ethane, dimethoxy methane, dibutyl ether, ethanol, isopropyl alcohol, acetonitrile or diisopropyl ether, wherein the preferred solvent is acetonitrile. The ligand and Co(II) complexes were characterized by various analytical and spectroscopic methods. Single-crystal XRD studies determined the molecular structures of complexes as shown in FIG.1. Accordingly, in another aspect, the present invention provides a process for transition metal-catalyzed selective C(sp3)-H alkylation of fluorene, comprising the step of reacting fluorene with an alkylating agent in the presence of a catalyst, a solvent, and a base to yield the alkylated fluorenes as shown in Scheme 2. Scheme 2: Development of transition metal-catalyzed selective C(sp3)-H alkylation of fluorene. According to the present invention, the catalytic protocol exhibited a broad reaction scope with various fluorenes; the alkylating agent is alcohol, including benzylic, heteroaromatic, aliphatic primary, or secondary alcohols, and the catalyst is (NN)PyMeMeCoBr2 bidentate complex. In the process as above, the solvent is selected from the group comprising of toluene, n-octane, diethyl ether, dimethylformamide tetrahydrofuran, dichloromethane, methanol, DMSO, dimethoxy ethane, dimethoxy methane, dibutyl ether, ethanol, isopropyl alcohol, acetonitrile or diisopropyl ether, wherein the preferred solvent is toluene, or n-octane. In the process as above, the base is selected from a group comprising potassium hydroxide, potassium tert-butoxide, sodium hydroxide, sodium carbonate, caesium carbonate, lithium carbonate, calcium carbonate, sodium bicarbonate, ammonium hydroxide, potassium carbonate, potassium bicarbonate, and magnesium carbonate, wherein the preferred base is potassium tert-butoxide or sodium hydroxide. In the reaction with steric bulky alcohol proceeds with alkenylation and furnished the tetra-substituted olefine as the primary product. Accordingly, the present invention, the cobalt complexes, are showing efficient catalytic activity in the facile C(sp3)-H functionalization of 9H-fluorene. In another aspect, present invention provides a novel spiro compound. wherein, n is 2,3. According to the present invention, a process for the synthesis of a novel spiro compound comprising the step of reacting fluorene with an alkylating agent in the presence of a catalyst, a solvent and a base resulting the relatively novel spiro compound as shown in Scheme 3. Scheme 3: A process for synthesis of a novel spiro compound. According to the present invention, the alkylating agent is a diol, the suitable diol is selected from groups comprising 1,3-propanediol, 1,4-butanediol, 1,5- pentandiol, 1,2-ethanediols, methanediol, 1,6-hexanediol, or 10-decanediol. The preferred diol is 1,3-propanediol, 1,4-butanediol or 1,5-pentandiol. The present invention provides the synthesis of spiro compounds utilizing diol and earth-abundant cobalt complex broadened the efficiency and applicability of the methodology. The process as above, the solvent is selected from the group comprising of toluene, n-octane, diethyl ether, dimethylformamide tetrahydrofuran, dichloromethane, methanol, DMSO, dimethoxy ethane, dimethoxy methane, dibutyl ether, ethanol, isopropyl alcohol, acetonitrile or diisopropyl ether, wherein the preferred solvent is toluene or n-octane. The process as above, the base is selected from a group comprising of potassium hydroxide, potassium tert-butoxide, sodium hydroxide, sodium carbonate, cesium carbonate, lithium carbonate, calcium carbonate, sodium bicarbonate, ammonium hydroxide, potassium carbonate, potassium bicarbonate and magnesium carbonate, wherein the preferred base is potassium tert-butoxide or sodium hydroxide. However, the present invention focused on the reaction of fluorene with diol to demonstrate the synthetic applicability. Remarkably, 1,3-propanediol, 1,4- butanediol and 1,5-pentandiol were linked preferentially with 9h-fluorene after undergoing alkylation and alkenylation on either side to form olefinated product. As per the present invention, the cobalt complexes show efficient catalytic activity in the facile C(sp3)-H functionalization of 9H-fluorene. Yet another aspect, the present invention provides a process for transition-metal catalysed chemo-divergence in C-H alkylation of indene or synthesis of bis- (indenyl)alkane comprising a step of reacting indene with an alkylating agent in the presence of a catalyst, a solvent, and a base to yield alkylated indene products or bis-(indenyl)alkane as shown in Scheme 4. Additionally, regioselective C(3)-H alkylation of inactivated indene involving alcohols via the borrowing hydrogen (BH) strategy and the catalytic procedure effectively produced the first report on bis-indenyl-alkane by using the interrupted borrowing hydrogenation pathway (IBHS). Scheme 4: Development of transition-metal catalyzed chemo-divergence in C- H alkylation of indene and synthesis of bis-(indenyl)alkane. Gram scale synthesis was also demonstrated with 4-methylbenzyl alcohol. The utility of the developed catalytic protocol, in the present invention, is extended successfully for the diversification in alkylation reaction with indene. The alkylating agent is an alcohol; the alcohol is selected from the group comprising aromatic, aliphatic, and hetero-aromatic primary, as well as secondary alcohols bearing substituents at the o-, p-, and m-positions. The catalyst is (NN)PyMeMeCoBr2 complex. In the process as above, the solvent is selected from the group comprising toluene, n-octane, diethyl ether, dimethylformamide tetrahydrofuran, dichloromethane, methanol, DMSO, dimethoxy ethane, dimethoxy methane, dibutyl ether, ethanol, isopropyl alcohol, acetonitrile or diisopropyl ether, wherein the preferred solvent is toluene or n-octane. The process as above, the base is selected from a group comprising potassium hydroxide, potassium tert-butoxide, sodium hydroxide, sodium carbonate, cesium carbonate, lithium carbonate, calcium carbonate, sodium bicarbonate, ammonium hydroxide, potassium carbonate, potassium bicarbonate and magnesium carbonate, wherein the preferred base is potassium tert-butoxide or sodium hydroxide Significantly, the derivatives of benzyl alcohol exhibited distinct reactivity with Indene, resulting in a mixture of C2 / C3-alkylated products with a high degree of selectivity towards the C3-position of indene. On the other hand, sp2(C3) / sp3(C1)- dialkylation of substituted indene with alcohols is made possible by a long reaction time and higher temperature in prior arts. In one embodiment of the present invention, using this catalytic approach, the first- ever synthesis of bis-indenyl-alkane using aliphatic alcohol was produced. However, the present invention provides phosphine-free N,N-bidentate ligand- based cobalt catalytic activity of alkylation of flourene and indene, which offers several technical advantages, they are: Technical Advantages of the present invention: i). Availability: Compared to many noble metals, the metal (cobalt), in the present invention, is abundant in the Earth's crust, ensuring a more steady supply as well as lower material cost. ii). Reduced Toxicity: Phosphine ligands can be toxic and challenging to handle, posing environmental and safety risks. Phosphine-free ligands reduce these risks, leading to safer and more environmentally friendly catalytic processes. iii). Environmental Sustainability: The use of Phosphine-free N,N-bidentate ligand-based cobalt, a more abundant and less toxic metal, aligns with green chemistry principles aimed at developing sustainable and environmentally benign chemical processes. iv). Catalytic Efficiency: N,N-bidentate ligands can be designed to optimize the electronic and steric properties of the cobalt center, enhancing the catalyst's activity in the facile C(sp3)-H functionalization of 9H-fluorene and regioselective C(3)-H alkylation of inactivated indene. v). Cost-Effectiveness: The catalyst, in the present invention, is significantly cheaper than many other transition metals commonly used in catalysis, such as palladium, platinum, and rhodium. vi). Scalability: The catalyst, in the present invention, is economically viable for large-scale industrial processes. vii). Versatility: The catalysts with N,N-bidentate ligands have been successfully used in the present invention for various reactions, including dehydrogenation, C-H activation, and C-C coupling, demonstrating their versatility in organic chemistry. viii). Production of novel Spiro compound: The reaction of flourene with diols in the presence of the catalyst produced a novel Spiro compound. ix). Production of bis-indenyl-alkane: The catalytic procedure, in the present invention, by utilizing the catalyst effectively to produce the bis-indenyl- alkane. Certain specific aspects and embodiment of the present invention will be explained in detail with reference to the following examples, which are provided only for purposes of illustration and should not be construed as limiting the scope of the invention in any manner. EXAMPLES: EXAMPLE 1. Synthesis of (NN)PyMeMeCoBr2 bidentate complex: The complex was synthesized by reacting the NNPyMeMebidentate ligand (L1) with anhydrous CoBr2 in acetonitrile at room temperature, resulting in the corresponding Co-complex with an 87 % isolated yield. EXAMPLE 2. The characterization of (NN)PyMeMeCoBr2 bidentate complex: The (NN)PyMeMeCoBr2complex was thoroughly characterized using a variety of spectroscopic (IR, UV-Vis, and1H NMR) and analytical (elemental analysis, high- resolution mass techniques. The magnetic behaviour of (NN)PyMeMeCoBr2 was confirmed using the Evans method, suggesting a magnetic moment of 1.91 BM at CoII-center (S = 1 / 2). EXAMPLE 3. Structural analysis of (NN)PyMeMeCoBr2 bidentate complex: The complex was synthesized by reacting the NNPyMeMebidentate ligand (L1) with anhydrous CoBr2in acetonitrile at room temperature, resulting in the corresponding Co-complex in 87 % isolated yield. The complex crystallized in the orthorhombic space group ‘P b c a’. The molecular structure of the complex was confirmed by a single-crystal X-ray diffraction study, as shown in FIG. 1. The X-ray diffraction investigation reveals that the complex's Co(II) core exhibited four coordinated, distorted tetrahedral structures with two nitrogen donor atoms of ligand (L1) and two bromide ions. The bong angle of N(1)-Co(1)-N(3), Br(1)-Co(1)-Br(2), N(1)- Co(1)-Br(1), N(1)-Co(1)-Br(2), N(3)-Co(1)-Br(1) and N(3)-Co(1)-Br(2) are found at 91.5(3), 114.19(7), 110.4(3), 110.3 (3), 112.4(3) and 115.7(3), respectively. EXAMPLE 4. Screening of catalytic conditions: To investigate the optimized reaction conditions, a combination of 9H-fluorene and 4-methyl benzyl alcohol was used as a model substrate. The selected catalytic conditions are mentioned below in Table 1. Complete screening of reaction parameters, such as the nature and amount of the base, solvent, temperature, and catalyst loading, was performed to obtain the optimal reaction conditions. Thus, overall, the optimized reaction condition was as followed by adding 0.5 mmol of fluorene, 5.5 mmol of 4-methylbenzyl alcohol, 0.20 mmol of KOtBu, 0.01 mmol Cobalt-catalyst (2.0 mol %) loading in toluene solvent refluxed at 130 °C for 24 h. Table 1. Screening of catalytic conditions.

[0004] EXAMPLE 5. (NN)MeMeCoBr2 catalysed C9-Alkylation of 9H-Fluorene with primary aromatic alcohols: The alkylation of 9H-fluorene using primary aromatic alcohols as the alkyl source resulted in good to excellent yields of the desired C9-alkylated fluorenes. In the developed protocol, 0.5 mmol of fluorene, 0.55 mmol of alcohols or primary aromatic benzylic alcohol, 0.010 mmol of Co-complex (2.0 mol %), and 0.2 mmol KOtBu were added to toluene and refluxed in a silicon oil bath at 130 °C for 24 hours. It was observed that the presence of ortho-substituted methoxy groups on benzyl alcohols led to a lower yield of 56% for the 2,4,6-trimethoxy alkylated fluorene. Further, meta-substituted benzyloxy and 3,4-bismethoxymethoxy groups also yielded the desired products in 78 and 80 % yield, respectively as shown in Table 2 (Compounds 4-5). Similarly, the electron-withdrawing groups such as -F and - OCF3 substituted benzyl alcohol were well-tolerated and afforded the corresponding C9-alkylated products in moderate yields. Moreover, meta- substituted amine on benzyl alcohol, coupled chemoselectively with 9H-fluorene in 63% of a good yield (Compound 8). It is worth revealing that an amine (-NH2) substituent on the benzyl group can be a suitable entry point for late-stage synthetic elaboration, as shown in Table 2. Table 2. (NN)MeMeCoBr2catalysed C9-Alkylation of 9H-Fluorene with primary aromatic alcohols. EXAMPLE 6. (NN)MeMeCoBr2 catalyzed C9-Alkylation of 9H-Fluorene with primary aliphatic alcohols: The result of activated primary benzylic alcohol intends to broaden the scope of the present reaction system by using aliphatic alcohols as the alkylating partner. In particular, utilizing aliphatic alcohol as an alkyl source is considerably more challenging than using benzyl alcohol. Correspondingly, the addition of 0.5 mmol of fluorene, 0.55 mmol of aliphatic alcohols, 0.015 mmol of Co-complex, and 0.2 mmol KOtBu in toluene refluxed in silicon oil-bath at a temperature of 130 °C for 30 h. Under optimal conditions, the compounds 9-11 were obtained from the corresponding starting materials in moderate to high yield (64-81%). Positively, long-chain aliphatic alcohol such as 1-pentanol was found to be suitable coupling partners for the reaction and furnished great yield of the alkylated compound 12. Cyclohexylmethyl alcohol also afforded respective compound 13 in ideal yield about 74% as shown in Table 3. Table 3. (NN)MeMeCoBr2catalyzed C9-Alkylation of 9H-Fluorene with primary aliphatic alcohols. Me N N N EXAMPLE 7. (NN)MeMeCoBr2 catalyzed C9-Alkylation of 9H-Fluorene with secondary alcohols: As indicated in Table 4, the reaction generality for the alkylation of 9H-fluorene utilizing secondary alcohols was evaluated. Alkylation using secondary alcohols is more challenging because the alkylated product of tetrasubstituted olefins requires hydrogenation. Therefore, a stronger catalyst, higher base loading, and a longer reaction time are necessary to achieve a decent yield of the products. The reaction was initiated by adding 0.5 mmol of fluorene, 0.55 mmol of aliphatic alcohols, 0.015 mmol of Co-complex, and 0.2 mmol KOtBu in toluene, then refluxed in a silicon oil bath at 130 °C for 36 hours. However, the -NMe2substituted 1-phenylethanol was successfully employed to alkylate fluorene to furnish a compound 14 with a moderate yield of 71%. Cyclic alcohol, such as cycloheptanol, was proved to be an appropriate coupling partner and afforded low yields (43%) of compound 15. Further, switching to exploring the long-chain aliphatic secondary alcohol, the secondary aliphatic alcohols with symmetrical arms, such as 4-heptanol, produced (compound 16) poor yields about 61% due to steric congestion. Furthermore, long-chain unsymmetrical 2-ol coupled gently and generated the corresponding compound 17 in a moderate yield of 64%, as shown in Table 4. Table 4. (NN)MeMeCoBr2 catalyzed C9-Alkylation of 9H-Fluorene with secondary alcohols. EXAMPLE 8. (NN)MeMeCoBr2 catalysed C9-Alkylation of 9H-Fluorene with heteroaromatic alcohols: Heteroatoms constitute a very common fragment of a number of active pharmaceutical ingredients as well as excipients. Most frequently, nitrogen heterocycles or various positional combinations of nitrogen atoms, sulfur, and oxygen can be found in five or six-membered rings. The application of heterocycles provides a useful tool for modifying the solubility, lipophilicity, polarity, and hydrogen bonding capacity of biologically active agents. Significantly, there are very few examples related to hetero-aromatic alcohol coupled 9H-fluorene in the previous reports. The reaction of alkylation of fluorene was initiated by the addition of 0.5 mmol of fluorene, 0.55 mmol of heteroaromatic alcohols, 0.025 mmol of Co-complex, and 0.2 mmol KOtBu in toluene refluxed in silicon oil-bath at temperature 140°C for 36 h. The heteroaryl methanol was well tolerated under this catalytic 9H-alkylation reaction of fluorene, as shown in Table 5. It is important to mention here that, due to the coordination nature of nitrogen, the developed catalytic method was less effective with all kinds of pyridine methanol and resulted in 47% of the desired compound 18. Delightfully, sulphur- containing various thiophene alcohols were found to be suitable coupling partners for the reaction and furnished moderate to moderate yield (49-74%) of the alkylated compounds 19-21as shown in Table 5. Table 5. (NN)MeMeCoBr2catalysed C9-Alkylation of 9H-Fluorene with heteroaromatic alcohols. Me

[0005] EXAMPLE 9. (NN)MeMeCoBr2 catalyzed C9-Alkylation of various arenes with primary alcohols: Following an extensive investigation of the catalytic reactivity of various varieties of alcohols with fluorene. Further, the extent of the reaction can be explored by employing several substituted fluorenes, as shown in Table 6. Initially, the reaction was by the addition of 0.5 mmol of substituted arenes, 0.55 mmol of benzylic alcohols, 0.01 mmol of Co-complex, and 0.2 mmol KOtBu in toluene refluxed in a silicon oil-bath at a temperature of 140°C for 24 h. The reaction of a symmetrically disubstituted tert-butyl group on fluorene derivatives with benzyl alcohol afforded the corresponding alkylated compound 22 in 75% yield. Similarly, heteroaromatic alcohols such as benzothiophene-1-methanol and thiophene-1-methanol also efficiently reacted to produce the C9 alkylated compounds 23-24 in moderate to excellent yields about 52-67%. Significantly, the catalytic protocol was also effective with the mono and di-halo (I, Br, F) substituted fluorene. Di-iodo and dibromo substituted fluorene and benzyl alcohol interacted nicely and furnished compounds 25-28 with 71%-78% yields, respectively. Moreover, mono (I, Br and F) substituted fluorene was reacted slowly with benzyl alcohol and provided a lower yield about 47-57% of desired compounds 26, 27 and 29. A sulfur-containing hetero-arene, such as 4H-cyclopenatadithiophene, was selectively 4H-alkylated with alcohols. It was crucial to remember that 4H- cyclopentadithiophene and benzyl alcohol interacted well to produce compound 30 in a reasonable yield of 74%. Notably, thiophene methanol furnished a 69% isolated yield of the desired compound 31. Meanwhile, furfuryl alcohol yielded a 49% lower yield for C4-alkylated compound 32, as shown in Table 6. Table 6. (NN)MeMeCoBr2 catalyzed C9-Alkylation of various arenes with primary alcohols.

[0006] EXAMPLE 10. (NN)MeMeCoBr2 catalysed C9-Alkenylation of 9H-Fluorene with various alcohols: Alkylidenefluorenes are widely utilized as optoelectronic materials 35 and are found in a wide range of bioactive chemicals. Traditionally, they were produced via Peterson olefination or Wittig olefination, which produces hazardous waste. Therefore, it was extremely desirable to dehydrogenative produce alkylidenefluorenes directly from fluorene and alcohols catalyzed by an Earth- abundant cobalt catalyst. It is interesting to note that a greater selectivity for olefine synthesis was observed in the case of secondary alcohols. This might be because the sterically hindered alkene finds it harder to coordinate with the co-catalyst for a subsequent hydrogenation process. The reaction was initiated by the addition of 0.5 mmol of fluorene, 0.55 mmol of alcohols, 0.02 mmol of Co-complex, and 0.2 mmol KOtBu in a toluene refluxed in a silicon oil-bath at a temperature of 120 °C for 24 h. While performing the experiments of 9H-fluorene with secondary alcohol, in particular, diphenylmethanol under the above-optimized reaction condition, failed to deliver the alkylated fluorene, and interestingly, tetrasubstituted olefine was obtained as a major project. Intrigued by the result, upon fine-tuning the reaction temperature (120 °C) and time (24 h) of the catalytic condition, diphenymethanol bearing di- substituted methyl group smoothly reacted with fluorene gave the alkenylated compound 33 in 58% yield as shown in Table 7. Meanwhile, benzhydrol substituted chlorine afforded relatively low alkenylated compound 34 in 54% yield. Moreover, cyclopropanemethanol and 1-phenyl-1- propanol worked well under the established reaction condition and furnished a moderate yield about 53-57% of the respective compounds 35-36. Notably, extremely packed ortho-substituted benzyl alcohol and anthracene-9-ylmethanol as extended aromatic alcohol delivered the desired products in poor yield about 31-42% of the respective compounds 37-38, as shown in Table 7. Table 7. (NN)MeMeCoBr2catalysed C9-Alkenylation of 9H-Fluorene with various alcohols: Me N EXAMPLE 11. (NN)MeMeCoBr2 catalyzed fluorene reaction with diol (Synthesis of Spiro Compound): Following attempts at selective C9-alkylation of fluorene with primary, secondary, aromatic and aliphatic alcohols focused on the reaction of fluorene with diol to demonstrate the synthetic applicability of the present methodology. The reaction was initiated by the addition of 0.5 mmol of fluorene, 0.25 mmol of 1,3- propanediol, 0.02 mmol of Co-complex, and 0.1 mmol KOtBu in toluene 2ml refluxed in a silicon oil-bath at a temperature of 140 °C for 24 h. Remarkably, 1,3- propanediol linked preferentially with 9H-fluorene after undergoing alkylation and alkenylation on either side to form olefinated compound 39, which had a respectable yield of about 58%. In addition, the reaction was again initiated by the addition of 0.5 mmol of fluorene, 0.25 mmol of 11,4-butanediol or 1,5-pentandiol, 0.02 mmol of Co-complex, and 0.1 mmol KOtBu in toluene 2ml refluxed in silicon oil-bath at temperature 140 °C for 24 h. In contrast, the present catalytic procedure functionalized 1,4-butanediol and 1,5-pentandiol one step ahead, proceeded through alkylation, alkenylation and further cyclization, provided the versatile and novel Spiro compounds 40-41 with a lower yield 35-42% as shown in Table 8.1H,13C and single-crystal XRD confirmed the characterization of the Spiro compound as shown in FIG. 2. Interestingly, the synthesis of Spiro compounds utilizing the diol and earth-abundant cobalt complex broadened the efficiency and applicability of the methodology. Table 8. (NN)MeMeCoBr2catalyzed fluorene reaction with the diol (Synthesis of Spiro Compound):

[0007] EXAMPLE 12. Screening of catalytic conditions: To investigate the optimized reaction conditions, a combination of 3-methyl indene and 4-methoxy benzyl alcohol as the model substrate as shown in Table 9. Initially, the reactivity of Co-complex was examined with 0.5 mmol of 3-methylindene, and 0.55 mmol of 4-methoxybenzyl alcohol in the presence of catalyst (0.01 mmol, 2 mol%), 0.2 mmol KOtBu under the solventless conditions for 12 h of reaction time at 120°C. The results indicated that the C3-alkylated product had the lowest yield, at 41%, and that 59% was unreacted starting material, as shown in Table 9 (entry 1). In contrast, adding toluene as a solvent to a reaction medium produced a somewhat greater yield of 45%, as shown in Table 9 (in the entry 2). Interestingly, the isolated yield of compounds changed significantly when the reaction temperature was raised to 140 °C and the reaction time was increased to 18 hours, 56% and 78%, (entries 3-4). This implies that the reaction temperature and time substantially impacted the final yields of the compounds. Moreover, the highest isolated yield of 87% of the selective C3-alkylated product was obtained by further extending the reaction time to 24 hours (entry 5). When NaOH was used in place of base KOtBu, the yield of the product dropped to 54%, as shown in Table 9 (entry 6), this implies that the strong base worked well to activate the inactive indenes. Consequently, the conditions were found to be optimal by the addition of 0.5 mmol of 3-methylindene, 0.55 mmol of alcohol, 0.20 mmol of KOtBu, and 2.0 mol% Co-catalyst loaded in toluene, refluxed in silicon oil-bath at temperature 140 °C for 24 h. Table 9. Screening of catalytic conditions. EXAMPLE 13. (NN)MeMeCoBr2 catalyzed C3-alkylation of 3-methylindene with alcohols. The scope of the reaction between various alcohols and 3-methylindene (1a) was investigated under the optimized reaction conditions, as shown in Table 10. The conditions involved adding 0.5 mmol of 3-methylindene, 0.55 mmol of alcohol, 0.01 mmol of cobalt complex (2 mol%), and 0.2 mmol of KOtBu (12 mg) in toluene. The mixture was refluxed at 140 °C (silicon oil bath) for 24 hours. A wide variety of aliphatic, heteroaromatic and aromatic primary alcohols with substituents at the o-, p-, and m-positions were employed as the alkyl group, reacted smoothly to afford the desired C3-alkylated 3-methylindene in moderate to excellent yields. Electron donating groups such as -Me, -Et, -Pr, and -Ph, on the phenyl ring of the benzyl alcohol were successfully alkylated with 3-methylindene afforded 73-91% moderated to high yield of compounds 42-45 as shown in Table 10. Conversely, para-substituted alkoxy groups such as -OMe and -OBu gave the desired compounds 47 and 48 with maximum yields. However, meta-disubstituted benzyl alcohols were well tolerated and afforded the corresponding C3-alkylated products with moderate yields ranging from 67-78% of compounds 46 and 49-50, as shown in Table 10. Furthermore, the reaction with the substrate having halogen group (-I, -Cl) successfully underwent and yielded 3-benzylated 3-methylindenes 51-52 up to 82% of excellent yield. Table 10. (NN)MeMeCoBr2 catalyzed C3-alkylation of 3-methylindene with alcohols. In addition, the electron-withdrawing group (-F, -CF3) substituted benzyl alcohols furnished a moderate yield of the desired compounds 53-54 as shown in Table 10. These findings were revealed a major role for the electronic character of substituents in the current state of co-catalysis. The heteroaryl methanol was well tolerated under this catalytic C3-alkylation reaction of 3-methylindene. Benzo[b]thiophene-2-methanol provided C3-alkylated compound 55 in high yield of 79%. However, the established catalytic technique was less successful with pyridine methanol and produced only 52% of the final product because of the coordination nature of nitrogen of compound 56, as shown in Table 10. Additionally, 2- naphthalenemethanol reacted slowly due to steric reasons, providing 63% of the medium yield of the comparable compound 57. Interestingly, unactivated aliphatic alcohols such as 1-hexanol, with 3-methylindene afforded the corresponding compound 58 in yields 71% as shown in Table 10. EXAMPLE 14. (NN)MeMeCoBr2 catalyzed C3-alkylation of Substituted indene with alcohols: The synthetic approach was modified to include substituted indene only by increasing the catalyst’s concentration to 5 mol%. The reaction was initiated by addition of 0.5 mmol of substituted indene, 0.55 mmol of alcohol, 0.20 mmol (24 mg) of KOtBu, and 0.025 mmol co-catalyst (cobalt complex) (5.0 mol%) loaded in toluene, refluxed in silicon oil-bath at temperature 140 °C for 24 h. The expected indene C3-alkylation products were produced with moderate to high yields. There was minimal impact of the β-bromo substituents on the reactions efficiency and afforded C3-alkylated 2-bromoindene compound 59 in moderate yield 73% as shown in Table 11. The β-phenyl group of indene enhanced the reactivity significantly, resulting in an impressive yield 86% of compound 60 with n-pentanol. In contrast, biphenyl-4-methanol reacted slowly and produced a moderate yield 63% of compound 61 because of its bulkiness. TIPS (Triisopropylsily) group has the potential of being a selective protection and deprotection of -OH group and a useful control element in organic synthesis due to its extraordinary bulk, in that steric screening was provided for the atom to which TIPS is attached. Under standard reaction conditions, β-substituted -OTIPS indene was easily combined with 4-methylbenzyl alcohol and benzo thiophene-methanol to produce the corresponding compounds 62-63 in moderate yields. In addition, the aryl ring of indene exhibited bromo-substitution, indicating the production of a combination of C2 / C3-alkylated compounds 64-65 as shown in Table 11. Table 11. (NN)MeMeCoBr2catalyzed C3-alkylation of Substituted indene with alcohols. EXAMPLE 15. (NN)MeMeCoBr2 catalyzed C2 / C3-alkylation of indene with alcohol: A thorough study was conducted to evaluate the catalytic reactivity of different alcohols with substituted indene. The reaction conditions included indene (0.5 mmol), alcohols (0.55 mmol), cobalt complex (0.01 mmol, 2 mol%), and KOtBu (30 mg, 0.25 mmol) in toluene, refluxed at 130 °C (silicon oil bath) for 24 hours as shown in Table 12. A noteworthy observation was that the derivatives of benzyl alcohol exhibited distinct reactions, resulting in a mixture of C2 / C3-alkylated products that exhibited a high degree of selectivity towards the C3-alkylation of indene. The compounds comparable polarity made it challenging to separate using column chromatography. Consequently, a mixture of the compound was separated, and1H NMR was used to calculate the ratio. As a result of the mixed product's started evaluating the substrate's scope with slight alteration in the standard condition by lowering the reaction temperature to 130 °C. Furthermore, benzyl alcohol-bearing electron donating group and weak electron withdrawing group such as -Me, -tBu, -SMe, -OMe, -OnBu, and -Ph reacted smoothly under the optimized condition to form the corresponding C2 / C3-alkylated compounds 66-72 in moderate to high yield as shown in Table 12. The 4- Butoxybenzyl alcohol was shown to have the highest C3-selectivity of alkylated compound 71. Nevertheless, due to the steric bulk nature of 2-methylbenzyl alcohol, target compound 67 exhibited the lowest yield of 44% as expected. Moreover, the substrates bearing electron-withdrawing groups, such as -F and -CF3 reacted slowly with indene and provided a moderate yield 52-61% of compounds 73-74 as shown in Table 12. Remarkably, an exclusive C3-selective alkylated product was obtained in the case of unactivated aliphatic alcohols. A variety of aliphatic alcohols, including 1-hexanol, 1-heptanol, and 1-decanol, when combined with indene, generated the corresponding compounds 75-77 in moderate to great yield about 61–81%. In addition, secondary alcohols were reacted with indene, both cyclic and acyclic secondary alcohols underwent moderate reactions to generate the selective C3-alkylated compounds 78-79 as shown in Table 12. Significantly, resulted from the steric hindrance of the tetrasubstituted olefin intermediates. Meanwhile, thiophenemethanol, a hetero-aromatic alcohol, produced compound 80 in a respectable yield. As predicted, pyridine-1-methanol furnished the alkylation compound 81 in less than 50% yield under the optimized reaction condition. The varying patterns of alcohol reactivity towards indene suggested that benzyl alcohol was extremely active and produced a mixture of products, whereas secondary, aliphatic, and hetero-aromatic alcohols reacted more slowly and afforded specific C3-alkylated products under cobalt-catalysis as shown in Table 12. Table 12. (NN)MeMeCoBr2 catalyzed C2 / C3-alkylation of indene with alcohol: EXAMPLE 16. (NN)MeMeCoBr2 catalysed sp2(C3) / sp3(C1)-dialkylation of indene with While investigating the reactivity of alcohols with 3-methylindene, in GCMS, a low yield of bis-alkylated by-product was found. The reaction was initiated by adding 0.25 mmol of 3-Me / Ph-Indene, 0.52 mmol of alcohol, 0.5 mmol of KOtBu (40 mg), and 0.025 mmol co-catalyst (5.0 mol%) loaded in toluene, refluxed in silicon oil- bath at temperature 140 °C for 48 h which was yielded bis-alkylation product in improved yields as shown in Table 13. Further, under the optimized conditions, 4-chlorobenzyl alcohol was well tolerated and bis-alkylation compound 82 was obtained in moderate yield. Meanwhile, as expected naphthalene-2-methanol gave the desired compound 83 in low yield. Significantly, β-phenyl group of indene increased the reactivity, and unsaturated 9- decen-1-ol was furnished bis-alkylated 2-phenylindene compound 84 with poor yield, where terminal olefin did not undergo reduction as shown in Table 13. Importantly, under standard reaction conditions, normal indene was not amenable to the synthesis of the C1 / C3-double alkylation product; instead, this bis-alkylation product were only detected with β-substituted indene. Table 13. (NN)MeMeCoBr2 catalysed sp2(C3) / sp3(C1)-dialkylation of indene with alcohols. Me

[0008] EXAMPLE 17. (NN)MeMeCoBr2 catalysed synthesis of bis-indenylalkane using aliphatic alcohols: In addition, the reactivity of alcohol in the presence of the catalyst was evaluated by interacting 0.22 mmol of indene, 0.1 mmol of aliphatic alcohols, 0.25 mmol of KOtBu (24 mg), and 0.01 mmol co-catalyst (5.0 mol%) loaded in 1 ml of n-octane, refluxed in silicon oil-bath at temperature 110 °C for 36 h; as a result bis-indenyl- alkane as unique final product was produced for the first time via interrupted borrowing hydrogenation (IBH) strategy as shown in Table 14. Significantly, yields of the respective compounds were obtained using n-octane as a solvent compared to toluene. Following a number of modifications, the catalytic procedure only yielded a low to moderate yield of the product; the residual starting material remained as such. Further, these initial results started examining the extent of primary alcohol in the alkane chains; catalytic process could not activate methanol as the basic alcohol; GCMS revealed traces of the product. However, biomass- derived ethanol was quite sluggish, obtained the desired product, bis-Indenylethane 85, in low yields (28%) under the standard applied conditions. Notably, 3- phenylpropanol reacted smoothly under the optimized conditions and yielded compound 86 in 43% yield. Analogously, a range of inactivated aliphatic alcohols such as 1-butanol, 1- pentanol, 1-hexanol, 1-heptanol, and 1-dodecanol with indene afforded the corresponding compounds 87-91 in moderate yields about 52-63%. Interestingly, primary alcohol accompanied by terminal olefine, including 7-octen-1-ol and 9- decen-1-ol, successfully furnished the bis-indenylation compound 92-93 in less than 50% yield without reduction of the double bond. Additionally, indene selectively bis-indenylate the challenging cyclic aliphatic methanol such as cyclopropanol and cyclohexanol under the present catalytic protocol and yielded the expected compounds 94-95 in low yield. Examining the entire substrate scope, the results suggested that indene was likely unable to bis-indenylate activated aromatic alcohols under present cobalt catalysis, probably due to electronic effect and steric hindrance caused by the trisubstituted olefin intermediates. Notably, the substituted bromine on the aryl ring of indene slowly bis-indenylated and the aromatic benzylic alcohol, 4-methylbenzyl alcohol, resulting in the desired compound 96 in a low yield. Table 14. (NN)MeMeCoBr2catalysed the synthesis of bis-indenylalkane using aliphatic alcohols. A novel phosphine-free cobalt bidentate complex was catalyzed by selective alkylation, alkenylation of fluorene, and inactivated cum bulky indene utilizing alcohol under mild and benign conditions. Fluorene was alkylated using a range of substrates, including aliphatic, heteroaromatic, and primary and secondary aromatic alcohols. This indicates a sophisticated catalytic process with yields that ranged from excellent to remarkable. A high yield and astounding regioselectivity of the C3-alkylated 3-methylindenes were achieved. Most astonishingly, the present catalytic technique demonstrated the synthesis of a flexible spiro molecule by the alkylation of fluorene with diol. Additionally, Due to the high reactivity of benzylic alcohol, a mixture of C2 / C3-alkylated indene was isolated. It furnished the C1, C3-bis-alkylated substituted indene at high temperatures and prolonged reaction time. Notably, aliphatic alcohol reacted differently with indene, and at lowered temperatures, a unique product, bis-indanyl- alkane, was obtained through an interrupted borrowing hydrogen strategy. Furthermore, the replacement of tridentate pincer ligands with bidentate ligands in the metal complex system represents a promising avenue for future research.

Claims

1. We claim:

1. A process for the synthesis of (NN)PyMeMeCoBr2 complex,i). reacting pyridine derivative with ain thebase and a solvent to yield NNPyMeMebidentate ligand (L1); and ii).bidentate ligand (L1) with anhydrous CoBr2in the presence of a solvent at a particular temperature to yield (NN)PyMeMeCoBr2complex.

2. The process as claimed in claim 1, wherein the pyridine derivative in step (i) is selected from the group comprising 2-(chloromethyl) pyridine hydrochloride, 2-(2,6-bis(bromomethyl)pyridine, 2-(bromomethyl) pyridine, 2-(2,6-bis(chloromethyl)pyridine, 2-(2-chloroethyl) pyridine hydrochloride, or 4-(2-chloroethyl) pyridine hydrochloride.

3. The process as claimed in claim 2, wherein the pyridine derivative is 2- (chloromethyl) pyridine hydrochloride.

4. The process as claimed in claim 1, wherein the heterocyclic compound in step (i) is selected from the group comprising 3-methyl pyrazole, 3,5-dimethyl pyrazole, morpholine, 3 ethyl-1H pyrazole, or 3-ethyl-5 methyl 1H pyrazole.

5. The process, as claimed in claim 4, wherein the heterocyclic compound is 3,5- dimethyl pyrazole.

6. The process as claimed in claim 1, wherein the solvent in step (i) is selected from the group comprising diethyl ether, dimethylformamide tetrahydrofuran, dichloromethane, methanol, DMSO, dimethoxy ethane, dimethoxy methane, dibutyl ether, ethanol, isopropyl alcohol, and acetonitrile or diisopropyl ether.

7. The process as claimed in claim 6, wherein the solvent is acetonitrile.

8. The process as claimed in claim 1, wherein the base in step (i) is selected from the group comprising potassium hydroxide, potassium tert-butoxide, sodium carbonate, cesium carbonate, lithium carbonate, calcium carbonate, sodium bicarbonate, ammonium hydroxide, potassium carbonate, and potassium bicarbonate or magnesium carbonate.

9. The process, as claimed in claim 8, wherein the base is potassium hydroxide.

10. The process as claimed in claim 1, wherein the solvent in step (ii) is selected from the group comprising diethyl ether, dimethylformamide tetrahydrofuran, dichloromethane, methanol, DMSO, dimethoxy ethane, dimethoxy methane, dibutyl ether, ethanol, isopropyl alcohol, and acetonitrile or diisopropyl ether.

11. The process, as claimed in claim 10, wherein the solvent is acetonitrile.

12. The process, as claimed in claim 6, wherein the temperature in step (ii) is maintained between 25 to 50 °C.

13. A process for transition metal-catalyzed selective C(sp3)-H alkylation of fluorene, comprising the step of reacting fluorene with anin the presence of a catalyst, a solvent, and a base to yield alkylated fluorenes.

14. The process as claimed in claim 13, wherein the alkylating agent is an alcohol.

15. The process, as claimed in claim 14, wherein the alcohol is selected from the group comprising aromatic alcohols, benzylic alcohols, hetero-aromatic alcohols, and aliphatic primary or secondary alcohols.

16. The process, as claimed in claim 13, wherein the catalyst is (NN)PyMeMeCoBr2complex.

17. The process as claimed in claim 13, wherein the solvent is selected from the group comprising toluene, n-octane, diethyl ether, dimethylformamide tetrahydrofuran, dichloromethane, methanol, DMSO, dimethoxy ethane, dimethoxy methane, dibutyl ether, ethanol, isopropyl alcohol, and acetonitrile or diisopropyl ether.

18. The process, as claimed in claim 17, wherein the solvent is toluene or n- octane.

19. The process as claimed in claim 13, wherein the base is selected from the group comprising potassium hydroxide, potassium tert-butoxide, sodium hydroxide, sodium carbonate, cesium carbonate, lithium carbonate, calcium carbonate, sodium bicarbonate, ammonium hydroxide, potassium carbonate, and potassium bicarbonate or magnesium carbonate.

20. The process as claimed in claim 19, wherein the base is potassium tert- butoxide or sodium hydroxide.

21. A novel spiro compoundwherein,22. A process for the synthesis of a novel Spiro compound, comprising the step of reacting fluorene with an alkylating agent in the presence of a catalyst, a solvent, and a base to produce a spiro compound.

23. The process, as claimed in claim 22, wherein the alkylating agent is a diol.

24. The process as claimed in claim 23, wherein the diol is selected from the group comprising 1,3-propanediol, 1,4-butanediol, 1,5-pentandiol, 1,2- ethanediols, methanediol, and 1,6-hexanediol, or 10-decanediol.

25. The process as, claimed in claim 24, wherein the diol is 1,3-propanediol, 1,4- butanediol or 1,5-pentandiol.

26. The process as claimed in claim 22, the solvent is selected from the group comprising toluene, n-octane, diethyl ether, dimethylformamide tetrahydrofuran, dichloromethane, methanol, DMSO, dimethoxy ethane, dimethoxy methane, dibutyl ether, ethanol, isopropyl alcohol, and acetonitrile or diisopropyl ether.

27. The process, as claimed in claim 26, wherein the solvent is toluene or n- octane.

28. The process as claimed in claim 22, wherein the base is selected from the group comprising potassium hydroxide, potassium tert-butoxide, sodium hydroxide, sodium carbonate, cesium carbonate, lithium carbonate, calcium carbonate, sodium bicarbonate, ammonium hydroxide, potassium carbonate, and potassium bicarbonate or magnesium carbonate.

29. The process, as claimed in claim 28, wherein the base is potassium tert- butoxide or sodium hydroxide.

30. A process for transition-metal catalyzed chemo-divergence in C-H alkylation of indene or synthesis of bis-(indenyl)alkane, comprising the step of reacting indene with an alkylating agent in the presence of a catalyst, a solvent, and a base to yield products of alkylated indene or bis-(indenyl)alkane.

31. The process, as claimed in claim 30, wherein the alkylating agent is an alcohol.

32. The process, as claimed in claim 31, wherein the alcohol is selected from the group comprising aromatic alcohols, benzylic alcohols, hetero-aromatic alcohols, and aliphatic primary or secondary alcohols.

33. The process, as claimed in claim 30, wherein the catalyst is (NN)PyMeMeCoBr2 complex.

34. The process as claimed in claim 30, wherein the solvent is selected from the group comprising toluene, n-octane, diethyl ether, dimethylformamide tetrahydrofuran, dichloromethane, methanol, DMSO, dimethoxy ethane, dimethoxy methane, dibutyl ether, ethanol, isopropyl alcohol, and acetonitrile or diisopropyl ether.

35. The process, as claimed in claim 34, wherein the solvent is toluene or n- octane.

36. The process as claimed in claim 30, wherein the base is selected from the group comprising potassium hydroxide, potassium tert-butoxide, sodium hydroxide, sodium carbonate, cesium carbonate, lithium carbonate, calcium carbonate, sodium bicarbonate, ammonium hydroxide, potassium carbonate, and potassium bicarbonate or magnesium carbonate.

37. The process as claimed in claim 36, wherein the base is potassium tert- butoxide or sodium hydroxide.

38. The process, as claimed in claim 30, is alkylated indenes produced through the borrowing hydrogen (BH) strategy.

39. The process, as claimed in claim 30 is bis-indenyl-alkanes produced through the interrupted borrowing hydrogenation pathway (IBHS).

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