Articles de revues : « Carbon-hetero bond transformation reactions »

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Valdés, Carlos, Raquel Barroso et María Cabal. « Pd-catalyzed Auto-Tandem Cascades Based on N-Sulfonylhydrazones : Hetero- and Carbocyclization Processes ». Synthesis 28, n^o 19 (10 août 2017) : 4434–47. http://dx.doi.org/10.1055/s-0036-1588535.

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The Pd-catalyzed cross-coupling between N-tosylhydrazones and organic halides is a powerful method for the creation of C–C bonds. This transformation has been included recently in cascade processes in which the same catalyst promotes various independent catalytic steps, a process known as auto-tandem catalysis. This strategy proves to be very useful for the construction of relatively complex carbo- and heterocyclic structures, as well as for the generation of molecular diversity. This short review will cover the different Pd-catalyzed auto-tandem reactions involving N-tosylhydrazones organized by the bond-forming sequence: C–C/C–N and C–C/C–C. Some examples of related tandem reactions leading to acyclic compounds are also highlighted.1 Introduction2 Auto-Tandem C–C/C–N Bond-Forming Reactions3 Auto-Tandem C–C/C–C Bond-Forming Reactions4 Tandem Reactions for the Synthesis of Linear Molecules5 Summary and Outlook

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Rai, Vijai K., Fooleswar Verma, Suhasini Mahata, Smita R. Bhardiya, Manorama Singh et Ankita Rai. « Metal Doped-C3N4/Fe2O4 : Efficient and Versatile Heterogenous Catalysts for Organic Transformations ». Current Organic Chemistry 23, n^o 12 (20 septembre 2019) : 1284–306. http://dx.doi.org/10.2174/1385272823666190709113758.

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The polymeric graphitic carbon nitride (g-C3N4) has been one of the interesting earth abundant elements. Though g-C3N4 finds application as a photocatalyst, its photocatalytic behaviour is limited because of low efficiency, mainly due to rapid charge recombination. To overcome this problem, several strategies have been developed including doping of metal/non-metal in the cavity of g-C3N4. Moreover, the CoFe2O4 NPs have been used in many organic transformations because of its high surface area and easy separation due to its magnetic nature. This review describes the role of cobalt ferrite as magnetic nanoparticles and metal-doped carbon nitride as efficient heterogeneous catalysts for new carbon-carbon and carbon-hetero atom bond formation followed by heterocyclization. Reactions which involved new catalysts for selective activation of readily available substrates has been reported herein. Since nanoparticles enhance the reactivity of catalyst due to higher catalytic area, they have been employed in various reactions such as addition reaction, C-H activation reaction, coupling reaction, cyclo-addition reaction, multi-component reaction, ring-opening reaction, oxidation reaction and reduction reactions etc. The driving force for choosing this topic is based-on huge number of good publications including different types of spinels/metal doped-/graphitic carbon nitride reported in the literature and due to interest of synthetic community in recent years. This review certainly will represent the present status in organic transformation and for exploring further their catalytic efficiency to new organic transformations involving C-H activation reaction through coupling, cyclo-addition, multi-component, ring-opening, oxidation and reduction reactions.

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Tietze, L. F., et N. Rackelmann. « Domino reactions in the synthesis of heterocyclic natural products and analogs ». Pure and Applied Chemistry 76, n^o 11 (1 janvier 2004) : 1967–83. http://dx.doi.org/10.1351/pac200476111967.

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Domino reactions are defined as processes of two or more bond-forming reactions under identical conditions, in which the subsequent transformation takes place at the functionalities obtained in the former transformation. They allow the efficient synthesis of complex molecules from simple substrates in an ecologically and economically favorable way. A very powerful domino process is the domino Knoevenagel–hetero-Diels–Alder reaction, in which an aldehyde or an beta-ketoester is condensed with a 1,3-dicarbonyl compound or a heteroanalog to give a 1-oxa-1,3-butadiene, which can undergo an inter- or intramolecular hetero-Diels–Alder reaction with dienophiles such as enol ethers or alkenes. The products are dihydropyrans, which can be transformed in a variety of ways. Thus, an extension of the process is the synthesis of highly substituted pyrrolidines, piperidines, and azepanes using aminoaldehydes. The process has also been employed for the enantioselective total synthesis of a variety of alkaloids, such as indol- and ipecacuanha alkaloids. In another domino process, erythrina and homoerythrina alkaloids have been prepared from simple phenylethylamines and ketoesters.

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Smaligo, Andrew J., Manisha Swain, Jason C. Quintana, Mikayla F. Tan, Danielle A. Kim et Ohyun Kwon. « Hydrodealkenylative C(sp3)–C(sp2) bond fragmentation ». Science 364, n^o 6441 (16 mai 2019) : 681–85. http://dx.doi.org/10.1126/science.aaw4212.

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Chemical synthesis typically relies on reactions that generate complexity through elaboration of simple starting materials. Less common are deconstructive strategies toward complexity—particularly those involving carbon-carbon bond scission. Here, we introduce one such transformation: the hydrodealkenylative cleavage of C(sp3)–C(sp2) bonds, conducted below room temperature, using ozone, an iron salt, and a hydrogen atom donor. These reactions are performed in nonanhydrous solvents and open to the air; reach completion within 30 minutes; and deliver their products in high yields, even on decagram scales. We have used this broadly functionality tolerant transformation to produce desirable synthetic intermediates, many of which are optically active, from abundantly available terpenes and terpenoid-derived precursors. We have also applied it in the formal total syntheses of complex molecules.

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Poursharif, Akram, Mahmood Kazemzad et Nooshin Salman Tabrizi. « Fabrication of Carbon Nanotube Granules as Pd Catalyst Supports for Hydrogenation of Carbon-Carbon Triple Bond ». Advanced Materials Research 829 (novembre 2013) : 82–85. http://dx.doi.org/10.4028/www.scientific.net/amr.829.82.

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Hydrogenation is one of the most important transformation reactions widely used in a large variety of areas such as Chemical, pharmaceutical and agricultural industries. Granulated carbon supported palladium catalysts have been used here for hydrogenation of carbon-carbon triple bonds. Catalyst composites and granules were produced by using sodium alginate binder under the certain thermal treatment process. After that, metal salt precursors were deposited using impregnation method. The final catalysts obtained through reduction of metal oxides by hydrazine as reducing agent. After that, metal particles loaded catalysts were utilized to perform hydrogenation reaction. Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) techniques applied for investigation of catalysts. Reaction products were evaluated by High Performance Liquid Chromatography (HPLC) technique. It has been concluded that MWCNT as support exhibits high conversion in the hydrogenation of 2-butyne-1, 4-diol as a typical triple bond carbon-carbon precursor.

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Kumar, Sumit, et Kishor Padala. « The recent advances in K2S2O8-mediated cyclization/coupling reactions via an oxidative transformation ». Chemical Communications 56, n^o 96 (2020) : 15101–17. http://dx.doi.org/10.1039/d0cc06036d.

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Recently the K₂S₂O₈ mediated cyclization/coupling reactions to construct carbon–carbon/carbon–heteroatom bond via oxidative transformation is became much interesting in organic synthesis.

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Liu, Leping, Bo Xu et Gerald B. Hammond. « Construction of cyclic enones via gold-catalyzed oxygen transfer reactions ». Beilstein Journal of Organic Chemistry 7 (13 mai 2011) : 606–14. http://dx.doi.org/10.3762/bjoc.7.71.

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During the last decade, gold-catalyzed reactions have become a tour de force in organic synthesis. Recently, the gold-, Brønsted acid- or Lewis acid-catalyzed oxygen transfer from carbonyl to carbon–carbon triple bond, the so-called alkyne–carbonyl metathesis, has attracted much attention because this atom economical transformation generates α,β-unsaturated carbonyl derivatives which are of great interest in synthetic organic chemistry. This mini-review focuses on the most recent achievements on gold-catalyzed oxygen transfer reactions of tethered alkynones, diynes or alkynyl epoxides to cyclic enones. The corresponding mechanisms for the transformations are also discussed.

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Cho, Inha, Zhi-Jun Jia et Frances H. Arnold. « Site-selective enzymatic C‒H amidation for synthesis of diverse lactams ». Science 364, n^o 6440 (9 mai 2019) : 575–78. http://dx.doi.org/10.1126/science.aaw9068.

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A major challenge in carbon‒hydrogen (C‒H) bond functionalization is to have the catalyst control precisely where a reaction takes place. In this study, we report engineered cytochrome P450 enzymes that perform unprecedented enantioselective C‒H amidation reactions and control the site selectivity to divergently construct β-, γ-, and δ-lactams, completely overruling the inherent reactivities of the C‒H bonds. The enzymes, expressed in Escherichia coli cells, accomplish this abiological carbon‒nitrogen bond formation via reactive iron-bound carbonyl nitrenes generated from nature-inspired acyl-protected hydroxamate precursors. This transformation is exceptionally efficient (up to 1,020,000 total turnovers) and selective (up to 25:1 regioselectivity and 97%, please refer to compound 2v enantiomeric excess), and can be performed easily on preparative scale.

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Quan, Zheng-Jun, Xi-Cun Wang, Ming-Xia Liu et Hai-Peng Gong. « Palladium-Catalyzed Copper-Promoted Hiyama-Type Carbon–Carbon Cross-Coupling Reactions of Dihetaryl Disulfides as Electrophiles ». Synlett 29, n^o 03 (26 octobre 2017) : 330–35. http://dx.doi.org/10.1055/s-0036-1589116.

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Dihetaryl disulfides were used as electrophiles in a palladium-catalyzed carbon–carbon cross-coupling reaction with arylsilanes to realize a Hiyama-type reaction. This unique transformation shows high reactivity, excellent functional-group tolerance, and mild reaction conditions, making it an attractive alternative to conventional cross-coupling approaches for carbon−carbon bond construction.

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Yang, Qiaoyu, Xiaoxian Guo, Yuwan Liu et Huifeng Jiang. « Biocatalytic C-C Bond Formation for One Carbon Resource Utilization ». International Journal of Molecular Sciences 22, n^o 4 (14 février 2021) : 1890. http://dx.doi.org/10.3390/ijms22041890.

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The carbon-carbon bond formation has always been one of the most important reactions in C1 resource utilization. Compared to traditional organic synthesis methods, biocatalytic C-C bond formation offers a green and potent alternative for C1 transformation. In recent years, with the development of synthetic biology, more and more carboxylases and C-C ligases have been mined and designed for the C1 transformation in vitro and C1 assimilation in vivo. This article presents an overview of C-C bond formation in biocatalytic C1 resource utilization is first provided. Sets of newly mined and designed carboxylases and ligases capable of catalyzing C-C bond formation for the transformation of CO2, formaldehyde, CO, and formate are then reviewed, and their catalytic mechanisms are discussed. Finally, the current advances and the future perspectives for the development of catalysts for C1 resource utilization are provided.

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Heravi, Majid M., Mahzad Dehghani, Vahideh Zadsirjan et Manijheh Ghanbarian. « Alkynes as Privileged Synthons in Selected Organic Name Reactions ». Current Organic Synthesis 16, n^o 2 (26 mars 2019) : 205–43. http://dx.doi.org/10.2174/1570179416666190126100744.

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Background:Alkynes are actually basic chemicals, serving as privileged synthons for planning new organic reactions for assemblage of a reactive motif, which easily undergoes a further desirable transformation. Name reactions, in organic chemistry are referred to those reactions which are well-recognized and reached to such status for being called as their explorers, discoverers or developers. Alkynes have been used in various name reactions. In this review, we try to underscore the applications of alkynes as privileged synthons in prevalent name reactions such as Huisgen 1,3-dipolar cycloaddtion via Click reaction, Sonogashira reaction, and Hetero Diels-Alder reaction.Objective:In this review, we try to underscore the applications of alkynes as privileged synthons in the formation of heterocycles, focused on the selected reactions of alkynes as a synthon or impending utilization in synthetic organic chemistry, which have reached such high status for being included in the list of name reactions in organic chemistry.Conclusion:Alkynes (including acetylene) are an unsaturated hydrocarbon bearing one or more triple C-C bond. Remarkably, alkynes and their derivatives are frequently being used as molecular scaffolds for planning new organic reactions and installing reactive functional group for further reaction. It is worth mentioning that in general, the terminal alkynes are more useful and more frequently being used in the art of organic synthesis. Remarkably, alkynes have found different applications in pharmacology, nanotechnology, as well as being known as appropriate starting precursors for the total synthesis of natural products and biologically active complex compounds. They are predominantly applied in various name reactions such as Sonogashira, Glaser reaction, Friedel-crafts reaction, Castro-Stephens coupling, Huisgen 1.3-dipolar cycloaddtion reaction via Click reaction, Sonogashira reaction, hetero-Diels-Alder reaction. In this review, we tried to impress the readers by presenting selected name reactions, which use the alkynes as either stating materials or precursors. We disclosed the applications of alkynes as a privileged synthons in several popular reactions, which reached to such high status being classified as name reactions. They are thriving and well known and established name reactions in organic chemistry such as Regioselective, 1,3-dipolar Huisgen cycloaddtion reaction via Click reaction, Sonogashira reaction and Diels-Alder reaction.

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Fujihara, Tetsuaki, et Yasushi Tsuji. « Cobalt- and rhodium-catalyzed carboxylation using carbon dioxide as the C1 source ». Beilstein Journal of Organic Chemistry 14 (19 septembre 2018) : 2435–60. http://dx.doi.org/10.3762/bjoc.14.221.

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Carbon dioxide (CO2) is one of the most important materials as renewable chemical feedstock. In this review, the Co- and Rh-catalyzed transformation of CO2 via carbon–carbon bond-forming reactions is summarized. Combinations of metals (cobalt or rhodium), substrates, and reducing agents realize efficient carboxylation reactions using CO2. The carboxylation of propargyl acetates and alkenyl triflates using cobalt complexes as well as the cobalt-catalyzed reductive carboxylation of α,β-unsaturated nitriles and carboxyamides in the presence of Et2Zn proceed. A Co complex has been demonstrated to act as an efficient catalyst in the carboxylation of allylic C(sp3)–H bonds. Employing zinc as the reductant, carboxyzincation and the four-component coupling reaction between alkyne, acrylates, CO2, and zinc occur efficiently. Rh complexes also catalyze the carboxylation of arylboronic esters, C(sp2)–H carboxylation of aromatic compounds, and hydrocarboxylation of styrene derivatives. The Rh-catalyzed [2 + 2 + 2] cycloaddition of diynes and CO2 proceeds to afford pyrones.

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Tsuji, Yasushi, et Tetsuaki Fujihara. « Carbon dioxide as a carbon source in organic transformation : carbon–carbon bond forming reactions by transition-metal catalysts ». Chemical Communications 48, n^o 80 (2012) : 9956. http://dx.doi.org/10.1039/c2cc33848c.

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Guo, Fenghai, Jayla A. Young, Mina S. Perez, Holden A. Hankerson et Alex M. Chavez. « Progress on the Cu-Catalyzed 1,4-Conjugate Addition to Thiochromones ». Catalysts 13, n^o 4 (8 avril 2023) : 713. http://dx.doi.org/10.3390/catal13040713.

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Carbon–carbon bond formation is one of the most important tools in synthetic organic chemists’ toolbox. It is a fundamental transformation that allows synthetic chemists to synthesize the carbon framework of complex molecules from inexpensive simple starting materials. Among the many synthetic methodologies developed for the construction of carbon–carbon bonds, organocopper reagents are one of the most reliable organometallic reagents for this purpose. The versatility of organocuprate reagents or the reactions catalyzed by organocopper reagents were demonstrated by their applications in a variety of synthetic transformations including the 1,4-conjugate addition reactions. Sulfur-containing heterocyclic compounds are a much less studied area compared to oxygen-containing heterocycles but have gained more and more attention in recent years due to their rich biological activities and widespread applications in pharmaceuticals, agrochemicals, and material science. This paper will provide a brief review on recent progress on the synthesis of an important class of sulfur-heterocycles-2-alkylthiochroman-4-ones and thioflavanones via the conjugate additions of Grignard reagents to thiochromones catalyzed by copper catalysts. Recent progress on the synthesis of 2-substituted thiochroman-4-ones via alkynylation and alkenylation of thiochromones will also be covered in this review.

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Chinkov, Nicka, G. Sklute, Helena Chechik, Adi Abramovitch, Deborah Amsallem, J. Varghese, Swapan Majumdar et I. Marek. « New regio-, stereo-, diastereo- and enantioselective one-pot reactions mediated by organometallic derivatives ». Pure and Applied Chemistry 76, n^o 3 (1 janvier 2004) : 517–35. http://dx.doi.org/10.1351/pac200476030517.

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In the first part of the lecture, we will discuss the one-pot preparation of chiral homoallylic alcohol and amine derivatives by a copper-catalyzed four-component reaction. In this process, three new carbon-carbon bonds as well as a quaternary and a tertiary chiral center are created with excellent regio- and diastereoselectivities. When the reaction was performed without adding external electrophiles, a β-elimination reaction took place to give polysubstituted allenes in good overall yields. This strategy of zinc-homologation followed by a β-elimination reaction was also synthetically used for the transformation of sp3 sulfoxides into olefins with potential application in asymmetric synthesis. Finally, in the second part of this lecture, the stereoselective preparation of metallated dienes in only two chemical steps from commercially available products will be described. This new strategy is based on a tandem allylic C-H bond activation of a remote ω-double bond followed by an elimination reaction.

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Prasanna, Pitchaimani, Pethaiah Gunasekaran, Subbu Perumal et J. Carlos Menéndez. « A catalyst-free multicomponent domino sequence for the diastereoselective synthesis of (E)-3-[2-arylcarbonyl-3-(arylamino)allyl]chromen-4-ones ». Beilstein Journal of Organic Chemistry 10 (21 février 2014) : 459–65. http://dx.doi.org/10.3762/bjoc.10.43.

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The three-component domino reactions of (E)-3-(dimethylamino)-1-arylprop-2-en-1-ones, 3-formylchromone and anilines under catalyst-free conditions afforded a library of novel (E)-3-(2-arylcarbonyl-3-(arylamino)allyl)-4H-chromen-4-ones in good to excellent yields and in a diastereoselective transformation. This transformation generates one C–C and one C–N bond and presumably proceeds via a reaction sequence comprising a Michael-type addition–elimination reaction, a nucleophilic attack of an enamine to a carbonyl reminiscent of one of the steps of the Bayllis–Hilman condensation, and a final deoxygenation. The deoxygenation is assumed to be induced by carbon monoxide resulting from the thermal decomposition of the dimethylformamide solvent.

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Tsuji, Yasushi, et Tetsuaki Fujihara. « ChemInform Abstract : Carbon Dioxide as a Carbon Source in Organic Transformation : Carbon-Carbon Bond Forming Reactions by Transition-Metal Catalysts ». ChemInform 43, n^o 50 (29 novembre 2012) : no. http://dx.doi.org/10.1002/chin.201250235.

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Pires, Marina, Sara Purificação, A. Santos et M. Marques. « The Role of PEG on Pd- and Cu-Catalyzed Cross-Coupling Reactions ». Synthesis 49, n^o 11 (26 avril 2017) : 2337–50. http://dx.doi.org/10.1055/s-0036-1589498.

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Carbon–carbon and carbon–heteroatom coupling reactions are among the most important transformations in organic synthesis as they enable complex structures to be formed from readily available compounds under different routes and conditions. Several metal-catalyzed cross-coupling reactions have been developed creating many efficient methods accessible for the direct formation of new bonds between differently hybridized carbon atoms.During the last decade, much effort has been devoted towards improvement of the sustainability of these reactions, such as catalyst recovery and atom efficiency. Polyethylene glycol (PEG) can be used as a medium, as solid-liquid phase transfer catalyst, or even as a polymer support. PEG has been investigated in a wide variety of cross-coupling reactions either as an alternative solvent to the common organic solvents or as a support for catalyst, substrate, and ligand. In this review we will summarize the different roles of PEG in palladium- and copper-catalyzed cross-coupling reactions, with the focus on Heck, Suzuki–Miyaura, Sonogashira, Buchwald–Hartwig, Stille, Fukuyama, and homocoupling reactions. We will highlight the role of PEG, the preparation of PEGylated catalysts and substrates, and the importance for the reaction outcome and applicability.1 Introduction2 PEG in Heck Reactions3 PEG in Homocoupling Reactions4 PEG in Suzuki–Miyaura Reactions5 PEG in Sonogashira Reactions6 PEG in Buchwald–Hartwig Reactions7 PEG in Stille Reactions8 PEG in Fukuyama Reactions9 PEG in Miscellaneous Cross-Coupling Routes10 Conclusions

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Pagar, Vinayak Vishnu, et T. V. RajanBabu. « Tandem catalysis for asymmetric coupling of ethylene and enynes to functionalized cyclobutanes ». Science 361, n^o 6397 (5 juillet 2018) : 68–72. http://dx.doi.org/10.1126/science.aat6205.

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Transformation of simple precursors into structurally complex cyclobutanes, present in many biologically important natural products and pharmaceuticals, is of considerable interest in medicinal chemistry. Starting from 1,3-enynes and ethylene, both exceptionally inexpensive starting materials, we report a cobalt-catalyzed route to vinylcyclobutenes, as well as the further enantioselective addition of ethylene to these products to form complex cyclobutanes with all-carbon quaternary centers. These reactions can proceed in discrete stages or in a tandem fashion to achieve three highly selective carbon-carbon bond formations in one pot using a single chiral cobalt catalyst.

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Chatterjee, Rupak, et Asim Bhaumik. « Carboxylation of Alkenes and Alkynes Using CO2 as a Reagent : An Overview ». Current Organic Chemistry 26, n^o 1 (janvier 2022) : 60–70. http://dx.doi.org/10.2174/1385272825666211206090621.

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: CO2 fixation reactions are of paramount interest both from economical and environmental perspectives. As an abundant, non-toxic, and renewable C1 feedstock, CO2 can be utilized for the synthesis of fuels and commodity chemicals under elevated reaction conditions. The major challenge in the CO2 utilization reactions is its chemical inertness due to high thermodynamic stability and kinetic barrier. The carboxylation of unsaturated hydrocarbons with CO2 is an important transformation as it forms high-value reaction products having industrial as well as medicinal importance. This mini-review is mainly focused on the recent developments in the homogeneously and heterogeneously catalyzed carboxylation of alkenes and alkynes by using carbon dioxide as a reagent. We have highlighted various types of carboxylation reactions of alkenes and alkynes involving different catalytic systems, which comprise mainly C-H bond activation, hydrocarboxylation, carbocarboxylation, heterocarboxylation, and ring-closing carboxylation, including visible-light assisted synthesis processes. The mechanistic pathways of these carboxylation reactions have been described. Moreover, challenges and future perspectives of these carboxylation reactions are discussed.

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Liu, Wei-Bing, Cui Chen, Qing Zhang et Zhi-Bo Zhu. « Organic synthesis using (diacetoxyiodo)benzene (DIB) : Unexpected and novel oxidation of 3-oxo-butanamides to 2,2-dihalo-N-phenylacetamides ». Beilstein Journal of Organic Chemistry 8 (7 mars 2012) : 344–48. http://dx.doi.org/10.3762/bjoc.8.38.

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A novel and reliable method for the direct preparation of 2,2-dihalo-N-phenylacetamides is reported. The key transformation involves the cleavage of a carbon–carbon bond in the presence of DIB and a Lewis acid as the halogen source, and thus this method significantly expands the value of DIB as a unique and powerful tool in chemical synthesis. This protocol not only adds a new aspect to reactions that use other hypervalent iodine reagents but also provides a wide space for the synthesis of disubstituted acetamides.

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Lv, Ze-Jie, Junnian Wei, Wen-Xiong Zhang, Ping Chen, Dehui Deng, Zhang-Jie Shi et Zhenfeng Xi. « Direct transformation of dinitrogen : synthesis of N-containing organic compounds via N−C bond formation ». National Science Review 7, n^o 10 (23 juin 2020) : 1564–83. http://dx.doi.org/10.1093/nsr/nwaa142.

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Abstract N-containing organic compounds are of vital importance to lives. Practical synthesis of valuable N-containing organic compounds directly from dinitrogen (N2), not through ammonia (NH3), is a holy-grail in chemistry and chemical industry. An essential step for this transformation is the functionalization of the activated N2 units/ligands to generate N−C bonds. Pioneering works of transition metal-mediated direct conversion of N2 into organic compounds via N−C bond formation at metal-dinitrogen [N2-M] complexes have generated diversified coordination modes and laid the foundation of understanding for the N−C bond formation mechanism. This review summarizes those major achievements and is organized by the coordination modes of the [N2-M] complexes (end-on, side-on, end-on-side-on, etc.) that are involved in the N−C bond formation steps, and each part is arranged in terms of reaction types (N-alkylation, N-acylation, cycloaddition, insertion, etc.) between [N2-M] complexes and carbon-based substrates. Additionally, earlier works on one-pot synthesis of organic compounds from N2 via ill-defined intermediates are also briefed. Although almost all of the syntheses of N-containing organic compounds via direct transformation of N2 so far in the literature are realized in homogeneous stoichiometric thermochemical reaction systems and are discussed here in detail, the sporadically reported syntheses involving photochemical, electrochemical, heterogeneous thermo-catalytic reactions, if any, are also mentioned. This review aims to provide readers with an in-depth understanding of the state-of-the-art and perspectives of future research particularly in direct catalytic and efficient conversion of N2 into N-containing organic compounds under mild conditions, and to stimulate more research efforts to tackle this long-standing and grand scientific challenge.

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Kumagai, Naoya, et Masakatsu Shibasaki. « 7-Azaindoline Auxiliary : A Versatile Attachment Facilitating Enantioselective C–C Bond-Forming Catalysis ». Synthesis 51, n^o 01 (30 novembre 2018) : 185–93. http://dx.doi.org/10.1055/s-0037-1610412.

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This short review provides an overview of 7-azaindoline auxiliaries in asymmetric catalysis. 7-Azaindoline serves as a useful attachment to carboxylic acids, and the thus-formed 7-azaindoline amides are amenable to atom-economical C–C bond-forming reactions with high stereoselectivity. The attachment is used for the sake of gaining traction in promoting the reaction of interest and can be easily removed after enantioselective reactions. Both nucleophilic and electrophilic catalyses are realized with broad tolerance for functional groups, showcasing the usefulness of 7-azaindoline auxiliaries for practical and streamlined synthesis of a wide range of acyclic chiral building blocks.1 Introduction2 7-Azaindoline as a Key Auxiliary3 7-Azaindoline Amide as a Pronucleophile3.1 α-Carbon-Substituted 7-Azaindoline Amide3.2 α-Nitrogen-Substituted 7-Azaindoline Amide3.3 α-Oxygen-Substituted 7-Azaindoline Amide3.4 α-Fluorocarbon-Substituted 7-Azaindoline Amide3.5 α-Halogen-Substituted 7-Azaindoline Amide3.6 α-Sulfur-Substituted 7-Azaindoline Amide4 7-Azaindoline Amide as an Electrophile4.1 Conjugate Addition of Butenolides4.2 1,3-Dipolar Cycloaddition of Nitrones5 Transformation of 7-Azaindoline Amide6 Conclusion

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Obydennov, Dmitrii L., Vyacheslav D. Steben’kov, Konstantin L. Obydennov, Sergey A. Usachev, Vladimir S. Moshkin et Vyacheslav Y. Sosnovskikh. « Reactions of 4-Pyrones with Azomethine Ylides as a Chemoselective Method for the Construction of Multisubstituted Pyrano[2,3-c]pyrrolidines ». Synthesis 53, n^o 15 (13 avril 2021) : 2621–31. http://dx.doi.org/10.1055/s-0040-1706032.

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Abstract4-Pyrones bearing electron-donating and electron-withdrawing groups react with nonstabilized azomethine ylides to form pyrano[2,3-c]pyrrolidines in moderate to good yields. The reaction proceeds chemoselectively as a 1,3-dipolar cycloaddition of the azomethine ylide at the carbon–carbon double bond of the pyrone activated by the electron-withdrawing substituent. The reactivity of 4-pyrones toward azomethine ylides was rationalized by computational studies with the use of reactivity indexes. The pyrano[2,3-c]pyrrolidine moiety could be modified, for example by a ring-opening transformation under the action of hydrazine to provide pyrazolyl-substituted pyrrolidines.

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Hölscher, Markus, Christoph Gürtler, Wilhelm Keim, Thomas E. Müller, Martina Peters et Walter Leitner. « Carbon Dioxide as a Carbon Resource – Recent Trends and Perspectives ». Zeitschrift für Naturforschung B 67, n^o 10 (1 octobre 2012) : 961–75. http://dx.doi.org/10.5560/znb.2012-0219.

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With the growing perception of industrialized societies that fossil raw materials are limited resources, academic chemical research and chemical industry have started to introduce novel catalytic technologies which aim at the development of economically competitive processes relying much more strongly on the use of alternative carbon feedstocks. Great interest is given world-wide to carbon dioxide (CO2) as it is part of the global carbon cycle, nontoxic, easily available in sufficient quantities anywhere in the industrialized world, and can be managed technically with ease, and at low cost. In principle carbon dioxide can be used to generate a large variety of synthetic products ranging from bulk chemicals like methanol and formic acid, through polymeric materials, to fine chemicals like aromatic acids useful in the pharmaceutical industry. Owing to the high thermodynamic stability of CO2, the energy constraints of chemical reactions have to be carefully analyzed to select promising processes. Furthermore, the high kinetic barriers for incorporation of CO2 into C-H or C-C bond forming reactions require that any novel transformation of CO2 must inevitably be associated with a novel catalytic technology. This short review comprises a selection of the most recent academic and industrial research developments mainly with regard to innovations in CO2 chemistry in the field of homogeneous catalysis and processes.

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Kim, Yohan, Seongmin Kim, Minyoung Shim, Yusik Oh, Kug-Seung Lee, Yousung Jung et Hye Ryung Byon. « Alteration of Oxygen Evolution Mechanisms in Layered LiCoO₂ Structures By Intercalation of Alkali Metal Ions ». ECS Meeting Abstracts MA2022-01, n^o 34 (7 juillet 2022) : 1356. http://dx.doi.org/10.1149/ma2022-01341356mtgabs.

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The word ‘Sustainability’, including carbon neutrality, has dominated the direction of social development over the past decade. In particular, energy conversion reactions through electrochemical methods are one of the efficient methods of obtaining small carbon footprint fuels. The oxygen evolution reaction (OER) is a key step in determining the overall reaction efficiency of fuel-related electrochemical reactions such as CO2 reduction reaction and H2 evolution reaction. However, electron transfer is sluggish for OER due to 4 electrons per one O2 molecule. This promotes multiple studies on the metal oxide electrocatalyst structure. The Alkali-transition metal oxides with the layered structure are one of the attractive OER electrocatalyst series. For example, lithium cobalt oxide (LiCoO2, LCO) presented OER activity through Li+ extraction (delithiation) from the lattice structure. In this work, we investigated the insertion effect of large alkaline cations (A+: Na+, K+, and Cs+) at the delithiated LCO for OER activity and stability. The intercalations of hydrated Na+ and K+ induced significant phase transformation of the delithiated LCO structure. In addition, the relative ratio between Co and alkali metal species determined the average Co oxidation state of LCO. We found that OER activity was improved in the order of Li+ < Na+ < K+, which was associated with the increased Co valence state and the Co-O bond covalency. Consistently, density functional theory (DFT) simulation also predicted the formation of efficient OER active sites by the K+ insertion. In comparison, Cs+ insertion exhibited the highest OER activity and demonstrated different OER processes. Due to the larger Cs+ size, the cation insertion was predominantly achieved at the delithiated LCO surface, resulting in imposing tensile strain to the surface edge. This catalyst showed the significant pH dependency on the OER property, suggesting the lattice-oxygen-based pathway for LCO. However, the bulk structure was preserved with little phase transformation, demonstrating better OER stability than others. In the presentation, I will discuss the catalytic activity responsible for the cation sizes and two different mechanisms in detail. Figure 1

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Kannath, Suraj, Paweł Adamczyk, Langping Wu, Hans H. Richnow et Agnieszka Dybala-Defratyka. « Can Alkaline Hydrolysis of γ-HCH Serve as a Model Reaction to Study Its Aerobic Enzymatic Dehydrochlorination by LinA ? » International Journal of Molecular Sciences 20, n^o 23 (26 novembre 2019) : 5955. http://dx.doi.org/10.3390/ijms20235955.

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Hexachlorocyclohexane (HCH) isomers constitute a group of persistent organic pollutants. Their mass production and treatment have led to a global environmental problem that continues to this day. The characterization of modes of degradation of HCH by isotope fractionation is a current challenge. Multi isotope fractionation analysis provides a concept to characterize the nature of enzymatic and chemical transformation reactions. The understanding of the kinetic isotope effects (KIE) on bond cleavage reaction contributes to analyses of the mechanism of chemical and enzymatic reactions. Herein, carbon, chlorine, and hydrogen kinetic isotope effects are measured and predicted for the dehydrochlorination reaction of γ-HCH promoted by the hydroxyl ion in aqueous solution. Quantum mechanical (QM) microsolvation with an implicit solvation model and path integral formalism in combination with free-energy perturbation and umbrella sampling (PI-FEP/UM) and quantum mechanical/molecular mechanical QM/MM potentials for including solvent effects as well as calculating isotope effects are used and analyzed with respect to their performance in reproducing measured values. Reaction characterization is discussed based on the magnitudes of obtained isotope effects. The comparative analysis between the chemical dehydrochlorination of γ-HCH in aqueous media and catalyzed reaction by dehydrochlorinase, LinA is presented and discussed. Based on the values of isotope effects, these two processes seem to occur via the same net mechanism.

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Akiba, Ikumi, Naoki Shida et Mahito Atobe. « Oxidative C-F Bonds Activation Using Electrochemical Techniques ». ECS Meeting Abstracts MA2023-02, n^o 52 (22 décembre 2023) : 2487. http://dx.doi.org/10.1149/ma2023-02522487mtgabs.

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Fluorinated organic compounds are widely used in diverse areas such as pharmaceuticals, agrochemicals, and materials science, and occupy an important position in modern chemistry.[1] Consequently, there has been a large library of fluorine-containing chemicals. Thus, the evolution of defluorination reactions using abundant fluorinated organic compounds as starting materials is expected to lead to further development in various fields. For example, it is expected to be applied to the synthesis of medical and agrochemical products with new functions using defluorination reactions, as well as to the defluorination process of polyfluorinated organic compounds that are highly persistent in the environment. The inherent challenge of C-F functionalization is the highly stable and strong nature of C-F bond. To tackle this problem, various methods have been proposed to activate C-F bonds using transition metal complexes, and Lewis acids. However, these methods have some issues that using expensive heavy metals and toxic reagents. Recent years have seen a focus on the development of economical and environmentally friendly defluorination reactions, especially C-F bonds activation based on efficient energy input using electrochemical or photochemical methods. As for photochemical methods, Gouverneur and co-workers developed photocatalytic methods for the selective hydrodefluorination and defluoroalkylation of trifluoromethyl(hetero)arenes using 2,4,5,6-tetrakis(diphenylamino)isophthalonitrile as an organophotocatalyst.[2] As for electrochemical methods, Cheng and co-workers reported a defluorinative method to convert α,α,α-trifluoromethyl cinnamates to gem-difluorostyrenes using electrochemical reduction.[3] These methods of defluorination still have limitations in terms of the versatility of the substrates where only substrates with π-system or have electron acceptors like carbonyl groups are suitable for cleaving C-F bonds presumably for the facile single electron reduction. Thus, the activation and functionalization of C-F bonds in the aliphatic backbone by electrochemical or photochemical means still remain a challenge. In this work, we have developed an electrochemical C-F bond activation and functionalization under oxidative conditions. After exploring the reaction conditions, the electrochemical defluorination reaction of 1-fluoroadamantane was found to proceed in weakly coordinating electrolyte composed of 0.1 M Bu4NB(C6F5)4/CH2Cl2. Nucleophiles such as allyltrimethylsilane and 4,4,5,5-tetramethyl-2-(p-tolyl)-1,3,2-dioxaborolane were applicable to affording 1-allyladamantane (72% yield) and p-(1-adamantyl)toluene (52% yield), respectively. In this reaction, the use of a divided cell was found to be necessary, evidencing that the defluorination reaction proceeds oxidatively at the anode. In conclusion, we have successfully developed the first electrochemical defluorinative functionalization system under oxidative conditions, which potentially become a complementary strategy of electro-reductive counterpart of the defluorinative transformation of organic molecules. In the presentation, an exploration of the substrate scope, electrochemical studies, and the mechanistic proposal of the reaction will also be discussed. [1] Y. Ogawa, E. Tokunaga, O. Kobayashi, K. Hirai, N. Shibata, iScience., 2020, 23, 101467–101467. [2] J. B. I. Sap, N. J. W. Straathof, T. Knauber, C. F. Meyer, M. Médebielle, L. Buglioni, C. Genicot, A. A. Trabanco, T. Noël, C. W. am Ende, V. Gouverneur, J. Am. Chem. Soc., 2020, 142, 20, 9181–9187. [3] J. Sheng, N. Wu, X. Liu, F. Liu, S. Liu, W. Ding, C. Liu and X. Cheng, Chin. J. Org. Chem., 2020, 40, 11, 3873–3880. Figure 1

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Kiss, Loránd, Márton Kardos, Csaba Vass et Ferenc Fülöp. « Application of Metathesis Reactions in the Synthesis and Transformations of Functionalized β-Amino Acid Derivatives ». Synthesis 50, n^o 18 (26 juillet 2018) : 3571–88. http://dx.doi.org/10.1055/s-0036-1591600.

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Because of their biological relevance, cyclic β-amino acids have generated increasing interest and had significant impact in drug research over the past two decades. Their preparation and further functionalization towards new types of molecular entities have received large interest in synthetic and medicinal chemistry. Various types of metathesis reactions, such as ring-opening (ROM), ring-closing (RCM), or cross metathesis (CM) are used widely for access to either alicyclic β-amino acids or other densely functionalized derivatives of this group of compounds. This account intends to provide an insight into the most relevant synthetic routes to this class of derivatives with the application of metathesis reactions. The review focuses on the presentation of selective and stereocontrolled methodologies in view of versatility, robustness, limitations and efficiency.1 Introduction2 Synthesis and Transformation of Cyclic β-Amino Acids through Metathesis Reactions2.1 Synthesis of Five- and Six-Membered Cyclic β-Amino Acids by Ring-Closing Metathesis2.2 Synthesis of Five- and Six-Membered Cyclic β-Amino Acids by Cross Metathesis2.3 Synthesis of β-Amino Acids with Larger Ring Systems by Ring- Closing Metathesis2.4 Synthesis of β-Amino Acids with Condensed Ring Systems by Ring-Rearrangement Metathesis2.5 Stereocontrolled One-Step Synthesis of Functionalized Cispentacin and Transpentacin Derivatives2.5.1 Stereocontrolled Synthesis of Functionalized Cispentacin and Transpentacin Derivatives through Ring-Opening Metathesis of Norbornene β-Amino Acid Derivatives2.5.2 Stereocontrolled Synthesis of Functionalized Azetidinones and β-Amino Acid Derivatives from Condensed Ring β-Lactams by Ring-Opening Metathesis2.5.3 Carbon–Carbon Double Bond Functionalization of β-Amino Acid Derivatives and β-Lactams with α,β-Unsaturated Carbonyl Compounds through Cross Metathesis2.5.4 Synthesis of Functionalized β-Amino Acid Derivatives and β-Lactams through Chemoselective Cross Metathesis3 Conclusions and Outlook

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Balci, Metin. « Acyl Azides : Versatile Compounds in the Synthesis of Various Heterocycles ». Synthesis 50, n^o 07 (1 février 2018) : 1373–401. http://dx.doi.org/10.1055/s-0036-1589527.

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Carbon–nitrogen bond formation is one of the most important reactions in organic chemistry. Various synthetic strategies for the generation of C–N bonds are described in the literature. For example, primary amines can be easily synthesized by the thermal decomposition of an acyl azide to an isocyanate, i.e. the Curtis rearrangement, followed by hydrolysis; the Curtius rearrangement has been used extensively. Furthermore, the advantage of the Curtius rearrangement is the isolation of acyl azides as well as the corresponding isocyanates. The isocyanates can be converted into various nitrogen-containing compounds upon reaction with various nucleophiles that can be used as important synthons for cyclization, in other words, for the synthesis of heterocycles. Therefore, this review demonstrates the importance of acyl azides not only in the synthesis acyclic systems, but also in the synthesis of various nitrogen-containing heterocycles.1 Introduction2 Synthesis of Acyl Azides2.1 Acyl Azides from Carboxylic Acid Derivatives2.2 Acyl Azides by Direct Transformation of Carboxylic Acids2.3 Acyl Azides from Aldehydes2.4 Carbamoyl Azides from Haloarenes, Sodium Azide, and N-Formylsaccharin3 Mechanism of Formation of Isocyanates4 Synthesis of Diacyl Azides5 Synthetic Applications5.1 Synthesis of Pyrimidinone Derivatives5.2 Dihydropyrimidinone and Isoquinolinone Derivatives5.3 Synthesis of Tetrahydroisoquinoline Skeleton5.4 Synthesis of Five-Membered Heterocycles5.5 Heterocycles Synthesized Starting from Homophthalic acid5.6 Heterocycles Synthesized from 2-(Ethoxycarbonyl)nicotinic Acid5.7 Formation of Aza-spiro Compounds5.8 Parham-Type Cyclization5.9 Diazepinone Derivatives5.10 Synthesis of Pyridine Derivatives5.11 Synthesis of Indole Derivatives6 Miscellaneous7 Conclusion

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Kim, Taeho, Peter J. Stogios, Anna N. Khusnutdinova, Kayla Nemr, Tatiana Skarina, Robert Flick, Jeong Chan Joo, Radhakrishnan Mahadevan, Alexei Savchenko et Alexander F. Yakunin. « Rational engineering of 2-deoxyribose-5-phosphate aldolases for the biosynthesis of (R)-1,3-butanediol ». Journal of Biological Chemistry 295, n^o 2 (5 décembre 2019) : 597–609. http://dx.doi.org/10.1074/jbc.ra119.011363.

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Carbon–carbon bond formation is one of the most important reactions in biocatalysis and organic chemistry. In nature, aldolases catalyze the reversible stereoselective aldol addition between two carbonyl compounds, making them attractive catalysts for the synthesis of various chemicals. In this work, we identified several 2-deoxyribose-5-phosphate aldolases (DERAs) having acetaldehyde condensation activity, which can be used for the biosynthesis of (R)-1,3-butanediol (1,3BDO) in combination with aldo-keto reductases (AKRs). Enzymatic screening of 20 purified DERAs revealed the presence of significant acetaldehyde condensation activity in 12 of the enzymes, with the highest activities in BH1352 from Bacillus halodurans, TM1559 from Thermotoga maritima, and DeoC from Escherichia coli. The crystal structures of BH1352 and TM1559 at 1.40–2.50 Å resolution are the first full-length DERA structures revealing the presence of the C-terminal Tyr (Tyr224 in BH1352). The results from structure-based site-directed mutagenesis of BH1352 indicated a key role for the catalytic Lys155 and other active-site residues in the 2-deoxyribose-5-phosphate cleavage and acetaldehyde condensation reactions. These experiments also revealed a 2.5-fold increase in acetaldehyde transformation to 1,3BDO (in combination with AKR) in the BH1352 F160Y and F160Y/M173I variants. The replacement of the WT BH1352 by the F160Y or F160Y/M173I variants in E. coli cells expressing the DERA + AKR pathway increased the production of 1,3BDO from glucose five and six times, respectively. Thus, our work provides detailed insights into the molecular mechanisms of substrate selectivity and activity of DERAs and identifies two DERA variants with enhanced activity for in vitro and in vivo 1,3BDO biosynthesis.

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Barata-Vallejo, Sebastián, et Al Postigo. « Photocatalytic Difluoromethylation Reactions of Aromatic Compounds and Aliphatic Multiple C–C Bonds ». Molecules 24, n^o 24 (6 décembre 2019) : 4483. http://dx.doi.org/10.3390/molecules24244483.

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Among the realm of visible light photocatalytic transformations, late-stage difluoromethylation reactions (introduction of difluoromethyl groups in the last stages of synthetic protocols) have played relevant roles as the CF2X group substitutions exert positive impacts on the physical properties of organic compounds including solubility, metabolic stability, and lipophilicity, which are tenets of considerable importance in pharmaceutical, agrochemical, and materials science. Visible-light-photocatalyzed difluoromethylation reactions are shown to be accomplished on (hetero)aromatic and carbon–carbon unsaturated aliphatic substrates under mild and environmentally benign conditions.

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Lumb, Jean-Philip, et Kenneth Esguerra. « Cu(III)-Mediated Aerobic Oxidations ». Synthesis 51, n^o 02 (3 décembre 2018) : 334–58. http://dx.doi.org/10.1055/s-0037-1609635.

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CuIII species have been invoked in many copper-catalyzed transformations including cross-coupling reactions and oxidation reactions. In this review, we will discuss seminal discoveries that have advanced our understanding of the CuI/CuIII redox cycle in the context of C–C and C–heteroatom aerobic cross-coupling reactions, as well as C–H oxidation reactions mediated by CuIII–dioxygen adducts.1 General Introduction2 Early Examples of CuIII Complexes3 Aerobic CuIII-Mediated Carbon–Heteroatom Bond-Forming Reactions4 Aerobic CuIII-Mediated Carbon–Carbon Bond-Forming Reactions5 Bioinorganic Studies of CuIII Complexes from CuI and O2 5.1 O2 Activation5.2 Biomimetic CuIII Complexes from CuI and Dioxygen5.2.1 Type-3 Copper Enzymes and Dinuclear Cu Model Complexes5.2.2 Particulate Methane Monooxygenase and Di- and Trinuclear Cu Model Complexes5.2.3 Dopamine–β-Monooxygenase and Mononuclear Cu Model Complexes6 Conclusion

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Martin, Nelson, et Ruchi Bharti. « Arynes in Natural Product Synthesis ». International Journal for Research in Applied Science and Engineering Technology 11, n^o 4 (30 avril 2023) : 2633–44. http://dx.doi.org/10.22214/ijraset.2023.50703.

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Abstract: Arynes are a unique class of intermediates used in synthetic organic chemistry, and research interest has been intensely focused on their peculiar reactivities. Arynes have been researched for almost a century. However, difficulties in monitoring these reactive species, as well as difficulties in creating synthetically viable techniques for their synthesis and trapping, have restricted their application. A key tactic for achieving the racemic and enantiopure total synthesis of a broad variety of natural compounds or their structural derivatives. The chemistry of arynes has advanced significantly over the past thirty years, particularly in the field of transition metal carbon- carbon and carbon-heteroatom bond-forming mechanisms. The field’s fast growth is largely attributable to the development of mild aryne production processes. To create a natural product with complex organic molecules, the role of aryne intermediates was non-replaceable. These organic substances are often used in medicine, therapies, or as raw material for the synthesis of other substances. Moreover, they may perform important biological tasks. There are numerous methods for synthesizing natural compounds including total synthesis, semi-synthesis, and biosynthesis. Total synthesis is the process of creating natural products entirely chemically from basic precursors as well as it can be produced in large quantities and can reveal information about its biological activity. One of the developments in Arynes’ chemistry is the chemical rearrangements brought about by this electrophilic intermediate. It is not feasible to use conventional methods in a single step. This review article discusses how arynes are used to create natural products. Arynes has a wide range of functionality in the field of scientific research. The evolution of this method has made a tremendous change in the total synthesis of natural products. Benzynes enabled creative synthesis in mild conditions. The transformation has expanded to investigate various reaction classes such as nucleophilic addition, (4+2), and (2+2) cycloaddition strategies and metal-catalyzed reactions are shown and explained in this article. This review will provide an idea about how the arynes act as an intermediate in those reaction mechanisms and enlighten the scope of these aryne intermediate.

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Deng, Yu-Hua, Zhihui Shao et Hui Wang. « An Update of N-Tosylhydrazones : Versatile Reagents for Metal-Catalyzed and Metal-Free Coupling Reactions ». Synthesis 50, n^o 12 (23 mai 2018) : 2281–306. http://dx.doi.org/10.1055/s-0036-1591993.

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N-Tosylhydrazones have had widespread application in organic synthesis for more than a half century. In most of cases, N-tosylhydrazones, as masked diazo compounds, have been generally used in a series of important carbon–carbon and carbon–heteroatom bond-forming reactions. This review provides an update on progress in diverse coupling reactions of N-tosylhydrazones since 2012. The examples selected are mainly categorized by metal-catalyzed and metal-free systems, wherein four main types of transformations including insertion, olefination, alkynylation, and cyclization are discussed for each system.1 Introduction2 Transition-Metal-Catalyzed Coupling Reactions3 Metal-Free Coupling Reactions4 Conclusion and Outlook

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Cherkas, Andrew A., Nasim Hadj-Bagheri, Arthur J. Carty, Enrico Sappa, Maria Angela Pellinghelli et Antonio Tiripicchio. « Polynuclear acetylide chemistry : acetylide to acetylene transformation at a binuclear center via carbon-carbon and carbon-nitrogen bond-forming reactions. X-ray structure of Os2(CO)6[.mu.-.eta.2-.dblvert.-C[C(NHBu-tert)(NEt2)]CPh](.mu.-PPh2) ». Organometallics 9, n^o 6 (juin 1990) : 1887–92. http://dx.doi.org/10.1021/om00156a031.

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Grossi, Vincent, Cristiana Cravo-Laureau, Alain Méou, Danielle Raphel, Frédéric Garzino et Agnès Hirschler-Réa. « Anaerobic 1-Alkene Metabolism by the Alkane- and Alkene-Degrading Sulfate Reducer Desulfatibacillum aliphaticivorans Strain CV2803T ». Applied and Environmental Microbiology 73, n^o 24 (26 octobre 2007) : 7882–90. http://dx.doi.org/10.1128/aem.01097-07.

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ABSTRACT The alkane- and alkene-degrading, marine sulfate-reducing bacterium Desulfatibacillum aliphaticivorans strain CV2803T, known to oxidize n-alkanes anaerobically by fumarate addition at C-2, was investigated for its 1-alkene metabolism. The total cellular fatty acids of this strain were predominantly C-(even number) (C-even) when it was grown on C-even 1-alkenes and predominantly C-(odd number) (C-odd) when it was grown on C-odd 1-alkenes. Detailed analyses of those fatty acids by gas chromatography-mass spectrometry after 6- to 10-week incubations allowed the identification of saturated 2- and 4-ethyl-, 2- and 4-methyl-, and monounsaturated 4-methyl-branched fatty acids with chain lengths that correlated with those of the 1-alkene. The growth of D. aliphaticivorans on (per)deuterated 1-alkenes provided direct evidence of the anaerobic transformation of these alkenes into the corresponding 1-alcohols and into linear as well as 10- and 4-methyl-branched fatty acids. Experiments performed with [13C]bicarbonate indicated that the initial activation of 1-alkene by the addition of inorganic carbon does not occur. These results demonstrate that D. aliphaticivorans metabolizes 1-alkene by the oxidation of the double bond at C-1 and by the subterminal addition of organic carbon at both ends of the molecule [C-2 and C-(ω-1)]. The detection of ethyl-branched fatty acids from unlabeled 1-alkenes further suggests that carbon addition also occurs at C-3. Alkylsuccinates were not observed as potential initial intermediates in alkene metabolism. Based on our observations, the first pathways for anaerobic 1-alkene metabolism in an anaerobic bacterium are proposed. Those pathways indicate that diverse initial reactions of 1-alkene activation can occur simultaneously in the same strain of sulfate-reducing bacterium.

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Majee, Suman, Devalina Ray et Bimal KrishnaBanik. « Samarium-Mediated Asymmetric Synthesis ». Catalysts 13, n^o 1 (24 décembre 2022) : 24. http://dx.doi.org/10.3390/catal13010024.

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Samarium is an efficient reducing agent, a radical generator in cyclization and a cascade addition reaction. Interestingly, samarium metal has crucial impact on numerous C-C and C-X (X = hetero atom) bond forming transformations. It has been established as an exceptional chemo-selective and stereoselective reagent. The reactivity of the samarium catalyst/reagent is remarkably enhanced in the presence of various additives, ligands and solvents through effective coordination and an increase in reduction potential. It has inherent character to act as electron donor for a wide range of transformations including the asymmetric version of various reactions. This review accentuates the developments in samarium-mediated/catalyzed asymmetric organic synthesis over the past 12 years, where the chirality has been induced from ligand, a nearby asymmetric center within the substrate or through coordination directed stereospecific reactions.

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Sarabia, Francisco, et Iván Cheng-Sánchez. « Recent Advances in Total Synthesis via Metathesis Reactions ». Synthesis 50, n^o 19 (18 juillet 2018) : 3749–86. http://dx.doi.org/10.1055/s-0037-1610206.

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The metathesis reactions, in their various versions, have become a powerful and extremely valuable tool for the formation of carbon–carbon bonds in organic synthesis. The plethora of available catalysts to perform these reactions, combined with the various transformations that can be accomplished, have positioned the metathesis processes as one of the most important reactions of this century. In this review, we highlight the most relevant synthetic contributions published between 2012 and early 2018 in the field of total synthesis, reflecting the state of the art of this chemistry and demonstrating the significant synthetic potential of these methodologies.1 Introduction2 Alkene Metathesis in Total Synthesis2.1 Total Synthesis Based on a Ring-Closing-Metathesis Reaction2.2 Total Synthesis Based on a Cross-Metathesis Reaction2.3 Strategies for Selective and Efficient Metathesis Reactions of Alkenes2.3.1 Temporary Tethered Ring-Closing Metathesis2.3.2 Relay Ring-Closing Metathesis2.3.3 Stereoselective Alkene Metathesis2.3.4 Alkene Metathesis in Tandem Reactions3 Enyne Metathesis in Total Synthesis3.1 Total Syntheses Based on a Ring-Closing Enyne-Metathesis Reaction3.2 Total Syntheses Based on an Enyne Cross-Metathesis Reaction3.3 Enyne Metathesis in Tandem Reactions4 Alkyne Metathesis in Total Synthesis4.1 Total Synthesis Based on a Ring-Closing Alkyne-Metathesis Reaction4.2 Other Types of Alkyne-Metathesis Reactions5 Conclusions

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Kataria, Meenal, Subhamay Pramanik, Navleen Kaur, Manoj Kumar et Vandana Bhalla. « Ferromagnetic α-Fe2O3 NPs : a potential catalyst in Sonogashira–Hagihara cross coupling and hetero-Diels–Alder reactions ». Green Chemistry 18, n^o 6 (2016) : 1495–505. http://dx.doi.org/10.1039/c5gc02337h.

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Applications of in situ generated ferromagnetic α-Fe₂O₃ NPs as an efficient and recyclable catalyst for carbon–carbon bond formation via Sonogashira–Hagihara coupling reactions and the synthesis of pyran derivatives by hetero-Diels–Alder reactions have been demonstrated.

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Menon, Rajeev S., Akkattu T. Biju et Vijay Nair. « Recent advances in N-heterocyclic carbene (NHC)-catalysed benzoin reactions ». Beilstein Journal of Organic Chemistry 12 (9 mars 2016) : 444–61. http://dx.doi.org/10.3762/bjoc.12.47.

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N-Heterocyclic carbenes (NHCs) have emerged as a powerful class of organocatalysts that mediate a variety of organic transformations. The Benzoin reaction constitutes one of the earliest known carbon–carbon bond-forming reactions catalysed by NHCs. The rapid growth of NHC catalysis in general has resulted in the development of a variety of benzoin and benzoin-type reactions. An overview of such NHC-catalysed benzoin reactions is presented.

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Li, Fang, W. Felix Zhu, Claire Empel, Oleksandr Datsenko, Adarsh Kumar, Yameng Xu, Johanna H. M. Ehrler et al. « Photosensitization enables Pauson-Khand–type reactions with nitrenes ». Science 383, n^o 6682 (2 février 2024) : 498–503. http://dx.doi.org/10.1126/science.adm8095.

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The Pauson-Khand reaction has in the past 50 years become one of the most common cycloaddition reactions in chemistry. Coupling two unsaturated bonds with carbon monoxide, the transformation remains limited to CO as a C 1 building block. Herein we report analogous cycloaddition reactions with nitrenes as an N 1 unit. The reaction of a nonconjugated diene with a nitrene precursor produces bicyclic bioisosteres of common saturated heterocycles such as piperidine, morpholine, and piperazine. Experimental and computational mechanistic studies support relaying of the diradical nature of triplet nitrene into the π-system. We showcase the reaction’s utility in late-stage functionalization of drug compounds and discovery of soluble epoxide hydrolase inhibitors.

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Puzanov, Andrey I., Dmitry S. Ryabukhin, Anna S. Zalivatskaya, Dmitriy N. Zakusilo, Darya S. Mikson, Irina A. Boyarskaya et Aleksander V. Vasilyev. « Synthesis of 5-arylacetylenyl-1,2,4-oxadiazoles and their transformations under superelectrophilic activation conditions ». Beilstein Journal of Organic Chemistry 17 (15 septembre 2021) : 2417–24. http://dx.doi.org/10.3762/bjoc.17.158.

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Acetylene derivatives of 1,2,4-oxadiazoles, i.e., 5-(2-arylethynyl)-3-aryl-1,2,4-oxadiazoles, have been obtained, for the first time reported, from 5-(2-arylethenyl)-3-aryl-1,2,4-oxadiazoles by their bromination at the carbon–carbon double bond followed by di-dehydrobromination with NaNH2 in liquid NH3. The reaction of the acetylenyl-1,2,4-oxadiazoles with arenes in neat triflic acid TfOH (CF3SO3H) at room temperature for 1 h resulted in the formation of E/Z-5-(2,2-diarylethenyl)-3-aryl-1,2,4-oxadiazoles as products of regioselective hydroarylation of the acetylene bond. The addition of TfOH to the acetylene bond of these oxadiazoles quantitatively resulted in E/Z-vinyl triflates. The reactions of the cationic intermediates have been studied by DFT calculations and the reaction mechanisms are discussed.

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Gu, Huoliang, Xiong Sun, Yong Wang, Haihong Wu et Peng Wu. « Highly efficient mesoporous polymer supported phosphine-gold(i) complex catalysts for amination of allylic alcohols and intramolecular cyclization reactions ». RSC Advances 8, n^o 4 (2018) : 1737–43. http://dx.doi.org/10.1039/c7ra12498h.

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Coates, Greg, Feriel Rekhroukh et Mark R. Crimmin. « Breaking Carbon–Fluorine Bonds with Main Group Nucleophiles ». Synlett 30, n^o 20 (12 novembre 2019) : 2233–46. http://dx.doi.org/10.1055/s-0039-1690738.

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In this Account we describe a series of new reactions that we, and others, have reported that involve the transformation of C–F bonds into C–Mg, C–Al, C–Si, C–Fe and C–Zn bonds. We focus on the use of highly reactive main group nucleophiles and discuss aspects of reaction scope, selectivity and mechanism.1 Introduction1.1 The Fluorocarbon Industry and Sustainability1.2 Production of Fluorocarbons1.3 Properties of Fluorocarbons1.4 Our Work2 Results and Discussion2.1 Low-Valent Main Group Compounds2.1.1 Reactions with Fluoroarenes2.1.2 Reactions with Fluoroalkanes2.1.3 Reactions with Fluoroalkenes2.2 Main Group Nucleophiles (M1–M2)2.2.1 Reactions of M1–M2 Nucleophiles with Fluoroarenes2.2.2 Reactions of M1–M2 Nucleophiles with Fluoroalkanes2.2.3 Reactions of M1–M2 Nucleophiles with Fluoroalkenes3 Summary and Perspective

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Sala, Roberto, Camilla Loro, Francesca Foschi et Gianluigi Broggini. « Transition Metal Catalyzed Azidation Reactions ». Catalysts 10, n^o 10 (12 octobre 2020) : 1173. http://dx.doi.org/10.3390/catal10101173.

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A wide range of methodologies for the preparation of organic azides has been reported in the literature for many decades, due to their interest as building blocks for different transformations and their applications in biology as well as in materials science. More recently, with the spread of the use of transition metal-catalyzed reactions, new perspectives have also materialized in azidation processes, especially concerning the azidation of C–H bonds and direct difunctionalization of multiple carbon-carbon bonds. In this review, special emphasis will be placed on reactions involving substrates bearing a leaving group, hydroazidation reactions and azidation reactions that proceed with the formation of more than one bond. Further reactions for the preparation of allyl and vinyl azides as well as for azidations involving the opening of a ring complete the classification of the material.

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Quiclet-Sire, Béatrice, et Samir Z. Zard. « Some aspects of radical cascade and relay reactions ». Proceedings of the Royal Society A : Mathematical, Physical and Engineering Sciences 473, n^o 2200 (avril 2017) : 20160859. http://dx.doi.org/10.1098/rspa.2016.0859.

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The ability to create carbon–carbon bonds is at the heart of organic synthesis. Radical processes are particularly apt at creating such bonds, especially in cascade or relay sequences where more than one bond is formed, allowing for a rapid assembly of complex structures. In the present brief overview, examples taken from the authors' laboratory will serve to illustrate the strategic impact of radical-based approaches on synthetic planning. Transformations involving nitrogen-centred radicals, electron transfer from metallic nickel and the reversible degenerative exchange of xanthates will be presented and discussed. The last method has proved to be a particularly powerful tool for the intermolecular creation of carbon–carbon bonds by radical additions even to unactivated alkenes. Various functional groups can be brought into the same molecule in a convergent manner and made to react together in order to further increase the structural complexity. One important benefit of this chemistry is the so-called RAFT/MADIX technology for the manufacture of block copolymers of almost any desired architecture.

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Constantino, Andre F., Carla S. Francisco, Diana C. Cubides-Roman et Valdemar Lacerda. « Hetero-Diels-Alder Reactions in the Synthesis of Biologically Active Nitrogen Compounds : A Review ». Current Organic Synthesis 15, n^o 1 (20 mars 2018) : 84–104. http://dx.doi.org/10.2174/1570179414666170517170230.

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Background: The Hetero-Diels-Alder reaction (HDAR) is a method extensively used in organic chemistry as a tool in the synthesis of innumerous polycyclic compounds in particular nitrogen compounds, presents in many natural products, medicinally relevant substances and organic materials. The literature describes innumerable studies of HDAR using classic methods and modern developments such as reactions on the solid phase, the use of catalysts, transformations in aqueous solution and under microwaves. Objective: This review describes a variety of HDAR focused on obtaining nitrogen-containing compounds of considerable chemical and biological interest, and highlighting reported biological activity. Conclusion: This review has shown the importance of the HDA reaction as a tool of organic chemistry in the synthesis of nitrogen compounds. This type of reaction presents important properties including bond-forming economy, high regio- and stereoselectivities and thus provides highly efficient routes to access a wide range of polycyclic compounds. In addition to the variety of nitrogen compounds synthetized successfully by this method, they present relevant biological properties.

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Brahmachari, Goutam, Nayana Nayek, Mullicka Mandal, Anindita Bhowmick et Indrajit Karmakar. « Ultrasound-promoted Organic Synthesis - A Recent Update ». Current Organic Chemistry 25, n^o 13 (2 septembre 2021) : 1539–65. http://dx.doi.org/10.2174/1385272825666210316122319.

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Abstract: Ultrasonication, nowadays, is well-regarded as an effective green tool in implementing a plethora of organic transformations. The last decade has seen quite useful applications of ultrasound irradiation in synthetic organic chemistry. Ultrasound has already come out as a unique technique in green chemistry practice for its inherent properties of minimizing wastes and reducing energy and time, thereby increasing the product yields with higher purities under milder reaction conditions. The present review summarizes ultrasound-promoted useful organic transformations involving both carbon-carbon and carbon-heteroatom (N, O, S) bond-forming reactions in the absence or presence of varying catalytic systems, reported during the period 2016-2020.

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Glover, Stephen A., Arvi Rauk, Jeanne M. Buccigross, John J. Campbell, Gerard P. Hammond, Guoning Mo, Luke E. Andrews et Ashley-Mae E. Gillson. « The HERON reaction Origin, theoretical background, and prevalence ». Canadian Journal of Chemistry 83, n^o 9 (1 septembre 2005) : 1492–509. http://dx.doi.org/10.1139/v05-150.

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The origin of the HERON reaction is reviewed from a historical perspective and shown to have its foundation in the unusual properties of bisheteroatom-substituted amides, so-called anomeric amides. The reaction involves migration of anomerically destabilized oxo-substituents on an amide nitrogen to the amide carbon and dissociation of the amide bond. Computational work providing a theoretical basis for the reaction is presented, together with physical organic measurements that support results therefrom. The rearrangement has been observed in a number of chemical transformations of N-alkoxy-N-aminoamides, reactions of 1-acyloxy-1-alkoxydiazenes, N-alkoxy-N-aminocarbamates, N-alkoxyhydroxamic acids, as well as in the gas-phase reactions of N-acyloxy-N-alkoxyamides.Key words: HERON reaction, anomeric amides, rearrangements, hindered esters, concerted reactions.

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