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Open accessJournal ArticleDOI: 10.1039/D0SC05924B

Mangana(III/IV)electro-catalyzed C(sp3)–H azidation

04 Mar 2021-Chemical Science (The Royal Society of Chemistry)-Vol. 12, Iss: 8, pp 2890-2897
Abstract: Manganaelectro-catalyzed azidation of otherwise inert C(sp3)-H bonds was accomplished using most user-friendly sodium azide as the nitrogen-source. The operationally simple, resource-economic C-H azidation strategy was characterized by mild reaction conditions, no directing group, traceless electrons as the sole redox-reagent, Earth-abundant manganese as the catalyst, high functional-group compatibility and high chemoselectivity, setting the stage for late-stage azidation of bioactive compounds. Detailed mechanistic studies by experiment, spectrophotometry and cyclic voltammetry provided strong support for metal-catalyzed aliphatic radical formation, along with subsequent azidyl radical transfer within a manganese(iii/iv) manifold.

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Topics: Chemoselectivity (53%)

16 results found

Open accessJournal ArticleDOI: 10.1021/ACSCENTSCI.0C01413
Toryn Dalton1, Teresa Faber1, Frank Glorius1Institutions (1)
Abstract: Since the definition of the "12 Principles of Green Chemistry" more than 20 years ago, chemists have become increasingly mindful of the need to conserve natural resources and protect the environment through the judicious choice of synthetic routes and materials. The direct activation and functionalization of C-H bonds, bypassing intermediate functional group installation is, in abstracto, step and atom economic, but numerous factors still hinder the sustainability of large-scale applications. In this Outlook, we highlight the research areas seeking to overcome the sustainability challenges of C-H activation: the pursuit of abundant metal catalysts, the avoidance of static directing groups, the replacement of metal oxidants, and the introduction of bioderived solvents. We close by examining the progress made in the subfield of aryl C-H borylation from its origins, through highly efficient but precious Ir-based systems, to emerging 3d metal catalysts. The future growth of this field will depend on industrial uptake, and thus we urge researchers to strive toward sustainable C-H activation.

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46 Citations

Open accessJournal ArticleDOI: 10.1039/D1CS00223F
Luiz F. T. Novaes1, Jinjian Liu1, Yifan Shen1, Lingxiang Lu1  +2 moreInstitutions (1)
Abstract: Electrochemistry has recently gained increased attention as a versatile strategy for achieving challenging transformations at the forefront of synthetic organic chemistry. Electrochemistry's unique ability to generate highly reactive radical and radical ion intermediates in a controlled fashion under mild conditions has inspired the development of a number of new electrochemical methodologies for the preparation of valuable chemical motifs. Particularly, recent developments in electrosynthesis have featured an increased use of redox-active electrocatalysts to further enhance control over the selective formation and downstream reactivity of these reactive intermediates. Furthermore, electrocatalytic mediators enable synthetic transformations to proceed in a manner that is mechanistically distinct from purely chemical methods, allowing for the subversion of kinetic and thermodynamic obstacles encountered in conventional organic synthesis. This review highlights key innovations within the past decade in the area of synthetic electrocatalysis, with emphasis on the mechanisms and catalyst design principles underpinning these advancements. A host of oxidative and reductive electrocatalytic methodologies are discussed and are grouped according to the classification of the synthetic transformation and the nature of the electrocatalyst.

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30 Citations

Open accessJournal ArticleDOI: 10.1016/J.GRESC.2021.03.002
Na Chen1, Hai-Chao Xu2Institutions (2)
01 May 2021-
Abstract: There is a resurgence of interests in organic electrochemistry, which is generally accepted as a green synthetic tool. In this context, many electrochemical methods have been developed in the past decade to access various nitrogen-centered radicals (NCRs) from readily available precursors in a controlled fashion, enabling the rapid development of many NCR-mediated new reactions for the construction of nitrogen-containing organic compounds. In this review, recent advances in the chemistry of electrochemically generated NCRs are critically highlighted, based on the electrochemical strategies for their formation and the types of NCRs. Focus is put on the mechanism for the electrochemical generation of different NCRs and their synthetic applications.

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16 Citations

Journal ArticleDOI: 10.1021/ACS.CHEMREV.0C01124
26 Feb 2021-Chemical Reviews
Abstract: Aliphatic azides are a versatile class of compounds found in a variety of biologically active pharmaceuticals. These compounds are also recognized as useful precursors for the synthesis of a range of nitrogen-based scaffolds of therapeutic drugs, biologically active compounds, and functional materials. In light of the growing importance of aliphatic azides in both chemical and biological sciences, a vast array of synthetic strategies for the preparation of structurally diverse aliphatic azides have been developed over the past decades. However, to date, this topic has not been the subject of a dedicated review. This review aims to provide a concise overview of modern synthetic strategies to access aliphatic azides that have emerged since 2010. The discussed azidation reactions include (a) azidation of C-C multiple bonds, (b) azidation of C-H bonds, (c) the direct transformation of vinyl azides into other aliphatic azides, and (d) miscellaneous reactions to access aliphatic azides. We critically discuss the synthetic outcomes and the generality and uniqueness of the different mechanistic rationale of each of the selected reactions. The challenges and potential opportunities of the topic are outlined.

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11 Citations

Journal ArticleDOI: 10.1016/J.SCIB.2021.07.011
Cong Ma1, Ping Fang1, Zhao-Ran Liu1, Shi-Shuo Xu1  +6 moreInstitutions (5)
Abstract: Organic electrosynthesis has been widely used as an environmentally conscious alternative to conventional methods for redox reactions because it utilizes electric current as a traceless redox agent instead of chemical redox agents. Indirect electrolysis employing a redox catalyst has received tremendous attention, since it provides various advantages compared to direct electrolysis. With indirect electrolysis, overpotential of electron transfer can be avoided, which is inherently milder, thus wide functional group tolerance can be achieved. Additionally, chemoselectivity, regioselectivity, and stereoselectivity can be tuned by the redox catalysts used in indirect electrolysis. Furthermore, electrode passivation can be avoided by preventing the formation of polymer films on the electrode surface. Common redox catalysts include N-oxyl radicals, hypervalent iodine species, halides, amines, benzoquinones (such as DDQ and tetrachlorobenzoquinone), and transition metals. In recent years, great progress has been made in the field of indirect organic electrosynthesis using transition metals as redox catalysts for reaction classes including C–H functionalization, radical cyclization, and cross-coupling of aryl halides-each owing to the diverse reactivity and accessible oxidation states of transition metals. Although various reviews of organic electrosynthesis are available, there is a lack of articles that focus on recent research progress in the area of indirect electrolysis using transition metals, which is the impetus for this review.

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Topics: Electrosynthesis (62%), Redox (54%), Electrolysis (53%) ... show more

6 Citations


129 results found

01 Jun 2001-Angewandte Chemie
Abstract: Examination of nature's favorite molecules reveals a striking preference for making carbon-heteroatom bonds over carbon-carbon bonds-surely no surprise given that carbon dioxide is nature's starting material and that most reactions are performed in water. Nucleic acids, proteins, and polysaccharides are condensation polymers of small subunits stitched together by carbon-heteroatom bonds. Even the 35 or so building blocks from which these crucial molecules are made each contain, at most, six contiguous C-C bonds, except for the three aromatic amino acids. Taking our cue from nature's approach, we address here the development of a set of powerful, highly reliable, and selective reactions for the rapid synthesis of useful new compounds and combinatorial libraries through heteroatom links (C-X-C), an approach we call "click chemistry". Click chemistry is at once defined, enabled, and constrained by a handful of nearly perfect "spring-loaded" reactions. The stringent criteria for a process to earn click chemistry status are described along with examples of the molecular frameworks that are easily made using this spartan, but powerful, synthetic strategy.

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Topics: Click chemistry (60%)

8,828 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

Journal ArticleDOI: 10.1038/417507A
Jay A. Labinger1, John E. Bercaw1Institutions (1)
30 May 2002-Nature
Abstract: The selective transformation of ubiquitous but inert C–H bonds to other functional groups has far-reaching practical implications, ranging from more efficient strategies for fine chemical synthesis to the replacement of current petrochemical feedstocks by less expensive and more readily available alkanes. The past twenty years have seen many examples of C–H bond activation at transition-metal centres, often under remarkably mild conditions and with high selectivity. Although profitable practical applications have not yet been developed, our understanding of how these organometallic reactions occur, and what their inherent advantages and limitations for practical alkane conversion are, has progressed considerably. In fact, the recent development of promising catalytic systems highlights the potential of organometallic chemistry for useful C–H bond activation strategies that will ultimately allow us to exploit Earth's alkane resources more efficiently and cleanly.

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2,100 Citations

Journal ArticleDOI: 10.1002/ANIE.200400657
19 Aug 2005-Angewandte Chemie
Abstract: Since the discovery of organic azides by Peter Griess more than 140 years ago, numerous syntheses of these energy-rich molecules have been developed. In more recent times in particular, completely new perspectives have been developed for their use in peptide chemistry, combinatorial chemistry, and heterocyclic synthesis. Organic azides have assumed an important position at the interface between chemistry, biology, medicine, and materials science. In this Review, the fundamental characteristics of azide chemistry and current developments are presented. The focus will be placed on cycloadditions (Huisgen reaction), aza ylide chemistry, and the synthesis of heterocycles. Further reactions such as the aza-Wittig reaction, the Sundberg rearrangement, the Staudinger ligation, the Boyer and Boyer-Aube rearrangements, the Curtius rearrangement, the Schmidt rearrangement, and the Hemetsberger rearrangement bear witness to the versatility of modern azide chemistry.

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Topics: Azide (56%), Curtius rearrangement (52%), Ylide (50%)

1,602 Citations

Open accessJournal ArticleDOI: 10.1002/CHEM.201001363
Tetsuya Satoh1, Masahiro Miura1Institutions (1)
Abstract: Aromatic substrates with oxygen- and nitrogen-containing substituents undergo oxidative coupling with alkynes and alkenes under rhodium catalysis through regioselective C-H bond cleavage. Coordination of the substituents to the rhodium center is the key to activate the C-H bonds effectively. Various fused-ring systems can be constructed through these reactions.

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Topics: Homogeneous catalysis (57%), Rhodium (53%), Catalysis (53%) ... show more

1,449 Citations

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