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Journal ArticleDOI: 10.1021/ACSCATAL.0C05681

CO2-Promoted Reactions: An Emerging Concept for the Synthesis of Fine Chemicals and Pharmaceuticals

02 Mar 2021-ACS Catalysis (American Chemical Society)-Vol. 11, Iss: 6, pp 3414-3442
Abstract: Carbon dioxide is a nontoxic and abundant chemical and has been widely used as a C1 building block for the synthesis of highly important chemicals. This greenhouse gas also has the ability to trigg...

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11 results found

Journal ArticleDOI: 10.1016/J.JCOU.2021.101590
Qizhuang Zou1, Yun Yi1, Tianxiang Zhao1, Fei Liu1  +2 moreInstitutions (2)
Abstract: We describe herein an efficient and catalyst-free methodology for N-formylation and N-methylation of various amines using BH3N(C2H5)3 as a reductant and CO2 as C1 source. This system is compatible with a wide range of substrates, such as aromatic secondary amines, aliphatic secondary amines, heterocyclic amines, and primary amines. The desired methylamines and formamides are obtained in excellent yields by changing the reaction solvent, temperature, and the amount of BH3N(C2H5)3. The optimum yields of methylamines and formamides are up to 99 %, which are comparable to the data using different catalysts. Moreover, it has been demonstrated by mechanistic research that CO2 was activated by inserting into B–H bonds of BH3N(C2H5)3 and formamide can be regarded as an intermediate species during the N-methylation formation.

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Topics: Formamides (58%), Methylamines (57%)

2 Citations

Journal ArticleDOI: 10.1016/J.TETLET.2021.153362
Abstract: Exploiting earth-abundant, bio-compatible first-row transition metals in homogeneously catalysed hydrogenation and dehydrogenation reactions for the synthesis of diverse organic frameworks has emerged as an important area in academia and industry. Catalytic (de)hydrogenation reactions form the basis of the modern chemical industry and are atom-economical, green and sustainable approach towards several new environmentally benign transformations. Carbon dioxide and methanol serve as sustainable feedstock and cost-effective raw materials for the synthesis of fine and bulk chemicals. The utilization of CO2 and methanol as C1 building blocks for the formation of carbon–carbon, carbon–nitrogen bonds have gained considerable interest in organic synthesis. Particularly noteworthy is the synthesis of N-formylated, N-methylated, C-methylated products because these motifs are prevalent in a large number of biological molecules as well as value-added chemicals. In this review, we aim to provide an overview of homogeneous base metal catalysed formylation and methylation reactions using carbon dioxide and methanol as C1 sources based on hydrogenation and dehydrogenation strategies.

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Topics: Dehydrogenation (56%), Catalysis (54%), Organic synthesis (53%) ... read more

Journal ArticleDOI: 10.1021/ACS.INORGCHEM.1C02689
Abstract: The development of sustainable catalysts to get methanol from CO2 under milder conditions and without any additives is still considered an arduous task. In many instances, transition-metal-catalyzed carbon dioxide to formic acid formation is more facile than methanol formation. This article provides comprehensive density functional theoretic investigations of six new Mn(I)PNN complexes, which are designed to perform CO2 to methanol conversion under milder reaction conditions. All these six catalysts have similar structural features except at terminal nitrogen, -N (1), where adenine-inspired nitrogen heterocycles containing pyridine and pyrimidine moieties are attached to instill an electron withdrawing effect on the central metal and thus to facilitate dihydrogen polarization during the catalyst regeneration. All these computationally modeled Mn(I)PNN complexes demonstrate the promising catalytic activity to get methanol through cascade catalytic cycles at 298.15 K. The metal-ligand cooperative (MLC) as well as noncooperative (NC) pathways are investigated for each catalytic cycle. The NC pathway is the preferred pathway for formic acid and formaldehyde formation, whereas methanol formation proceeds through only the MLC pathway. Different nitrogen heterocycles attached to the -N (1) terminal manifested a considerable amount of impact on the Gibbs free energies, overall activation energies, and computed turnover frequencies (TOFs). Among all the catalysts, SPCAT02 provides excellent TOFs for HCO2H (500 151 h-1), HCHO (11 912 h-1), and CH3OH (2 372 400 h-1) formation at 50 °C. SPCAT04 is found to be a better catalyst for the selective formation of formic acid formation at room temperature than the rest of the catalysts. The computed TOF results are found reliable upon comparison with experimentally established catalysts. To establish the structure-activity relationship, the activation strain model and Fukui function calculations are performed on all the catalysts. Both these studies provide complementary results. The present study revealed a very important finding that a more electrophilic metal center could facilitate the CO2 hydrogenation reaction robustly. All computationally designed catalysts could be cheaper and better alternatives to convert CO2 to methanol under mild reaction conditions in an aqueous medium.

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Topics: Catalysis (57%), Methanol (54%), Catalytic cycle (54%) ... read more

Open accessJournal ArticleDOI: 10.1039/D1GC03161A
19 Nov 2021-Green Chemistry
Abstract: Three-component Strecker reaction of aldehydes, amines and KCN has been performed for the first time in supercritical carbon dioxide. In the proposed procedure non-toxic and non-flammable carbon dioxide acts not only as an environmentally benign reaction medium but also as the reaction promoter via in situ formation of carbonic acid which provides a gradual release of the true cyanating agent (HCN) from available KCN. The reaction conditions (pressure, temperature, concentrations of reagents) were optimized, and various aromatic and aliphatic amines and aldehydes were transformed into valuable α-amino nitriles including perspective pharmacological substances. The equimolar amount of used cyanogen reagent, carrying out the process in a sealed autoclave in ‘green’ solvent medium under mild conditions (90 bar, 35 °C) along with the high yields of products and the scalability of the developed procedure make it suitable for sustainable industrial applications.

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Topics: Strecker amino acid synthesis (58%), Supercritical carbon dioxide (56%), Reagent (54%) ... read more


232 results found

Open accessJournal ArticleDOI: 10.1021/CR300503R
10 Jul 2013-Chemical Reviews
Abstract: A fundamental aim in the field of catalysis is the development of new modes of small molecule activation. One approach toward the catalytic activation of organic molecules that has received much attention recently is visible light photoredox catalysis. In a general sense, this approach relies on the ability of metal complexes and organic dyes to engage in single-electron-transfer (SET) processes with organic substrates upon photoexcitation with visible light. Many of the most commonly employed visible light photocatalysts are polypyridyl complexes of ruthenium and iridium, and are typified by the complex tris(2,2′-bipyridine) ruthenium(II), or Ru(bpy)32+ (Figure 1). These complexes absorb light in the visible region of the electromagnetic spectrum to give stable, long-lived photoexcited states.1,2 The lifetime of the excited species is sufficiently long (1100 ns for Ru(bpy)32+) that it may engage in bimolecular electron-transfer reactions in competition with deactivation pathways.3 Although these species are poor single-electron oxidants and reductants in the ground state, excitation of an electron affords excited states that are very potent single-electron-transfer reagents. Importantly, the conversion of these bench stable, benign catalysts to redox-active species upon irradiation with simple household lightbulbs represents a remarkably chemoselective trigger to induce unique and valuable catalytic processes. Open in a separate window Figure 1 Ruthenium polypyridyl complexes: versatile visible light photocatalysts.

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Topics: Photoredox catalysis (62%), Ruthenium (54%), Visible spectrum (51%) ... read more

4,920 Citations

Open accessJournal ArticleDOI: 10.1021/CR900184E
Thomas W. Lyons1, Melanie S. Sanford1Institutions (1)
10 Feb 2010-Chemical Reviews
Abstract: 1.1 Introduction to Pd-catalyzed directed C–H functionalization The development of methods for the direct conversion of carbon–hydrogen bonds into carbon-oxygen, carbon-halogen, carbon-nitrogen, carbon-sulfur, and carbon-carbon bonds remains a critical challenge in organic chemistry. Mild and selective transformations of this type will undoubtedly find widespread application across the chemical field, including in the synthesis of pharmaceuticals, natural products, agrochemicals, polymers, and feedstock commodity chemicals. Traditional approaches for the formation of such functional groups rely on pre-functionalized starting materials for both reactivity and selectivity. However, the requirement for installing a functional group prior to the desired C–O, C–X, C–N, C–S, or C–C bond adds costly chemical steps to the overall construction of a molecule. As such, circumventing this issue will not only improve atom economy but also increase the overall efficiency of multi-step synthetic sequences. Direct C–H bond functionalization reactions are limited by two fundamental challenges: (i) the inert nature of most carbon-hydrogen bonds and (ii) the requirement to control site selectivity in molecules that contain diverse C–H groups. A multitude of studies have addressed the first challenge by demonstrating that transition metals can react with C–H bonds to produce C–M bonds in a process known as “C–H activation”.1 The resulting C–M bonds are far more reactive than their C–H counterparts, and in many cases they can be converted to new functional groups under mild conditions. The second major challenge is achieving selective functionalization of a single C–H bond within a complex molecule. While several different strategies have been employed to address this issue, the most common (and the subject of the current review) involves the use of substrates that contain coordinating ligands. These ligands (often termed “directing groups”) bind to the metal center and selectively deliver the catalyst to a proximal C–H bond. Many different transition metals, including Ru, Rh, Pt, and Pd, undergo stoichiometric ligand-directed C–H activation reactions (also known as cyclometalation).2,3 Furthermore, over the past 15 years, a variety of catalytic carbon-carbon bond-forming processes have been developed that involve cyclometalation as a key step.1b–d,4 The current review will focus specifically on ligand-directed C–H functionalization reactions catalyzed by palladium. Palladium complexes are particularly attractive catalysts for such transformations for several reasons. First, ligand-directed C–H functionalization at Pd centers can be used to install many different types of bonds, including carbon-oxygen, carbon-halogen, carbon-nitrogen, carbon-sulfur, and carbon-carbon linkages. Few other catalysts allow such diverse bond constructions,5,6,7 and this versatility is predominantly the result of two key features: (i) the compatibility of many PdII catalysts with oxidants and (ii) the ability to selectively functionalize cyclopalladated intermediates. Second, palladium participates in cyclometalation with a wide variety of directing groups, and, unlike many other transition metals, promotes C–H activation at both sp2 and sp3 C–H sites. Finally, the vast majority of Pd-catalyzed directed C–H functionalization reactions can be performed in the presence of ambient air and moisture, making them exceptionally practical for applications in organic synthesis. While several accounts have described recent advances, this is the first comprehensive review encompassing the large body of work in this field over the past 5 years (2004–2009). Both synthetic applications and mechanistic aspects of these transformations are discussed where appropriate, and the review is organized on the basis of the type of bond being formed.

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Topics: Functional group (51%)

4,799 Citations

Open accessJournal ArticleDOI: 10.1002/ANIE.200806273
29 Jun 2009-Angewandte Chemie
Abstract: Pick your Pd partners: A number of catalytic systems have been developed for palladium-catalyzed CH activation/CC bond formation. Recent studies concerning the palladium(II)-catalyzed coupling of CH bonds with organometallic reagents through a PdII/Pd0 catalytic cycle are discussed (see scheme), and the versatility and practicality of this new mode of catalysis are presented. Unaddressed questions and the potential for development in the field are also addressed. In the past decade, palladium-catalyzed CH activation/CC bond-forming reactions have emerged as promising new catalytic transformations; however, development in this field is still at an early stage compared to the state of the art in cross-coupling reactions using aryl and alkyl halides. This Review begins with a brief introduction of four extensively investigated modes of catalysis for forming CC bonds from CH bonds: PdII/Pd0, PdII/PdIV, Pd0/PdII/PdIV, and Pd0/PdII catalysis. A more detailed discussion is then directed towards the recent development of palladium(II)-catalyzed coupling of CH bonds with organometallic reagents through a PdII/Pd0 catalytic cycle. Despite the progress made to date, improving the versatility and practicality of this new reaction remains a tremendous challenge.

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Topics: Coupling reaction (51%)

3,302 Citations

Journal ArticleDOI: 10.1021/CR0509760
Dino Alberico1, Mark E. Scott1, Mark Lautens1Institutions (1)
10 Jan 2007-Chemical Reviews
Abstract: The biaryl structural motif is a predominant feature in many pharmaceutically relevant and biologically active compounds. As a result, for over a century 1 organic chemists have sought to develop new and more efficient aryl -aryl bond-forming methods. Although there exist a variety of routes for the construction of aryl -aryl bonds, arguably the most common method is through the use of transition-metalmediated reactions. 2-4 While earlier reports focused on the use of stoichiometric quantities of a transition metal to carry out the desired transformation, modern methods of transitionmetal-catalyzed aryl -aryl coupling have focused on the development of high-yielding reactions achieved with excellent selectivity and high functional group tolerance under mild reaction conditions. Typically, these reactions involve either the coupling of an aryl halide or pseudohalide with an organometallic reagent (Scheme 1), or the homocoupling of two aryl halides or two organometallic reagents. Although a number of improvements have developed the former process into an industrially very useful and attractive method for the construction of aryl -aryl bonds, the need still exists for more efficient routes whereby the same outcome is accomplished, but with reduced waste and in fewer steps. In particular, the obligation to use coupling partners that are both activated is wasteful since it necessitates the installation and then subsequent disposal of stoichiometric activating agents. Furthermore, preparation of preactivated aryl substrates often requires several steps, which in itself can be a time-consuming and economically inefficient process.

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Topics: Aryl (59%)

3,059 Citations

Journal ArticleDOI: 10.1021/CR068357U
13 Jun 2007-Chemical Reviews
Abstract: 4.3. Reaction Mechanism 2373 4.4. Asymmetric Synthesis 2374 4.5. Outlook 2374 5. Alternating Polymerization of Oxiranes and CO2 2374 5.1. Reaction Outlines 2374 5.2. Catalyst 2376 5.3. Asymmetric Polymerization 2377 5.4. Immobilized Catalysts 2377 6. Synthesis of Urea and Urethane Derivatives 2378 7. Synthesis of Carboxylic Acid 2379 8. Synthesis of Esters and Lactones 2380 9. Synthesis of Isocyanates 2382 10. Hydrogenation and Hydroformylation, and Alcohol Homologation 2382

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Topics: Enantioselective synthesis (58%), Hydroformylation (57%), Catalysis (57%) ... read more

2,899 Citations

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