- A Metal-Free Direct Arene C?H Amination
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The synthesis of aryl amines via the formation of a C?N bond is an essential tool for the preparation of functional materials, active pharmaceutical ingredients and bioactive products. Usually, this chemical connection is only possible by transition metal-catalyzed reactions, photochemistry or electrochemistry. Here, we report a metal-free arene C?H amination using hydroxylamine derivatives under benign conditions. A charge transfer interaction between the aminating reagents TsONHR and the arene substrates enables the chemoselective amination of the arene, even in the presence of various functional groups. Oxygen was crucial for an effective conversion and its accelerating role for the electron transfer step was proven experimentally. In addition, this was rationalized by a theoretical study which indicated the involvement of a dioxygen-bridged complex with a “Sandwich-like” arrangement of the aromatic starting materials and the aminating agents at the dioxygen molecule. (Figure presented.).
- Wang, Tao,Hoffmann, Marvin,Dreuw, Andreas,Hasagi?, Edina,Hu, Chao,Stein, Philipp M.,Witzel, Sina,Shi, Hongwei,Yang, Yangyang,Rudolph, Matthias,Stuck, Fabian,Rominger, Frank,Kerscher, Marion,Comba, Peter,Hashmi, A. Stephen K.
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supporting information
p. 2783 - 2795
(2021/04/05)
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- Iron-Catalyzed Alkyne Carboamination via an Isolable Iron Imide Complex
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Transition metal imide-mediated C-N bond formation is a powerful strategy for the introduction of nitrogen into organic compounds. We have discovered that the reaction ofN-mesityl(β-diketiminato)iron imide complextBuLFeNMes (tBuL = 3,5-bis(2,6-diisopropylphenylimino)-2,2,6,6-tetramethylheptyl and Mes = 2,4,6-trimethylphenyl) with a terminal alkyne substrate gives a β-alkynyl enamine product by a novel alkyne carboamination process. Stoichiometric experiments revealed a catalyst deactivation pathway involving generation of the acetylide complex,tBuLFeCCPh, and mesityl amine (MesNH2) from the acetylene complex,tBuLFe(HCCPh), and mesityl azide (MesN3). This reactivity is suppressed in the presence of coordinating additive 4-tert-butylpyridine (tBuPy), likely through formation of the four-coordinate complextBuLFe(HCCPh)(tBuPy). These insights were instrumental in identifying reaction conditions that allow for turnover of the iron catalyst.
- Richards, Corey A.,Rath, Nigam P.,Neely, Jamie M.
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supporting information
p. 2945 - 2950
(2021/09/07)
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- Visible light enables catalytic formation of weak chemical bonds with molecular hydrogen
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The synthesis of weak chemical bonds at or near thermodynamic potential is a fundamental challenge in chemistry, with applications ranging from catalysis to biology to energy science. Proton-coupled electron transfer using molecular hydrogen is an attractive strategy for synthesizing weak element–hydrogen bonds, but the intrinsic thermodynamics presents a challenge for reactivity. Here we describe the direct photocatalytic synthesis of extremely weak element–hydrogen bonds of metal amido and metal imido complexes, as well as organic compounds with bond dissociation free energies as low as 31 kcal mol?1. Key to this approach is the bifunctional behaviour of the chromophoric iridium hydride photocatalyst. Activation of molecular hydrogen occurs in the ground state and the resulting iridium hydride harvests visible light to enable spontaneous formation of weak chemical bonds near thermodynamic potential with no by-products. Photophysical and mechanistic studies corroborate radical-based reaction pathways and highlight the uniqueness of this photodriven approach in promoting new catalytic chemistry. [Figure not available: see fulltext.].
- Park, Yoonsu,Kim, Sangmin,Tian, Lei,Zhong, Hongyu,Scholes, Gregory D.,Chirik, Paul J.
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supporting information
p. 969 - 976
(2021/07/25)
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- Transformation of Formazanate at Nickel(II) Centers to Give a Singly Reduced Nickel Complex with Azoiminate Radical Ligands and Its Reactivity toward Dioxygen
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The heteroleptic (formazanato)nickel bromide complex LNi(μ-Br)2NiL [LH = Mes-NH-N═C(p-tol)-N═N-Mes] has been prepared by deprotonation of LH with NaH followed by reaction with NiBr2(dme). Treatment of this complex with KC8led to transformation of the formazanate into azoiminate ligands via N-N bond cleavage and the simultaneous release of aniline. At the same time, the potentially resulting intermediate complex L′2Ni [L′ = HN═C(p-tol)-N═N-Mes] was reduced by one additional electron, which is delocalized across the π system and the metal center. The resulting reduced complex [L′2Ni]K(18-c-6) has aS=1/2ground state and a square-planar structure. It reacts with dioxygen via one-electron oxidation to give the complex L′2Ni, and the formation of superoxide was detected spectroscopically. If oxidizable substrates are present during this process, these are oxygenated/oxidized. Triphenylphosphine is converted to phosphine oxide, and hydrogen atoms are abstracted from TEMPO-H and phenols. In the case of cyclohexene, autoxidations are triggered, leading to the typical radical-chain-derived products of cyclohexene.
- Ar, Deniz,Kilpatrick, Alexander F. R.,Cula, Beatrice,Herwig, Christian,Limberg, Christian
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p. 13844 - 13853
(2021/05/04)
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- Minimization of Back-Electron Transfer Enables the Elusive sp3 C?H Functionalization of Secondary Anilines
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Anilines are some of the most used class of substrates for application in photoinduced electron transfer. N,N-Dialkyl-derivatives enable radical generation α to the N-atom by oxidation followed by deprotonation. This approach is however elusive to monosubstituted anilines owing to fast back-electron transfer (BET). Here we demonstrate that BET can be minimised by using photoredox catalysis in the presence of an exogenous alkylamine. This approach synergistically aids aniline SET oxidation and then accelerates the following deprotonation. In this way, the generation of α-anilinoalkyl radicals is now possible and these species can be used in a general sense to achieve divergent sp3 C?H functionalization.
- Zhao, Huaibo,Leonori, Daniele
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supporting information
p. 7669 - 7674
(2021/03/08)
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- General and selective synthesis of primary amines using Ni-based homogeneous catalysts
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The development of base metal catalysts for industrially relevant amination and hydrogenation reactions by applying abundant and atom economical reagents continues to be important for the cost-effective and sustainable synthesis of amines which represent highly essential chemicals. In particular, the synthesis of primary amines is of central importance because these compounds serve as key precursors and central intermediates to produce value-added fine and bulk chemicals as well as pharmaceuticals, agrochemicals and materials. Here we report a Ni-triphos complex as the first Ni-based homogeneous catalyst for both reductive amination of carbonyl compounds with ammonia and hydrogenation of nitroarenes to prepare all kinds of primary amines. Remarkably, this Ni-complex enabled the synthesis of functionalized and structurally diverse benzylic, heterocyclic and aliphatic linear and branched primary amines as well as aromatic primary amines starting from inexpensive and easily accessible carbonyl compounds (aldehydes and ketones) and nitroarenes using ammonia and molecular hydrogen. This Ni-catalyzed reductive amination methodology has been applied for the amination of more complex pharmaceuticals and steroid derivatives. Detailed DFT computations have been performed for the Ni-triphos based reductive amination reaction, and they revealed that the overall reaction has an inner-sphere mechanism with H2metathesis as the rate-determining step.
- Beller, Matthias,Chandrashekhar, Vishwas G.,Jagadeesh, Rajenahally V.,Jiao, Haijun,Murugesan, Kathiravan,Wei, Zhihong
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p. 4332 - 4339
(2020/05/18)
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- Mild deprotection of the: N-tert -butyloxycarbonyl (N -Boc) group using oxalyl chloride
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We report a mild method for the selective deprotection of the N-Boc group from a structurally diverse set of compounds, encompassing aliphatic, aromatic, and heterocyclic substrates by using oxalyl chloride in methanol. The reactions take place under room temperature conditions for 1-4 h with yields up to 90percent. This mild procedure was applied to a hybrid, medicinally active compound FC1, which is a novel dual inhibitor of IDO1 and DNA Pol gamma. A broader mechanism involving the electrophilic character of oxalyl chloride is postulated for this deprotection strategy. This journal is
- Awuah, Samuel G.,George, Nathaniel,Ofori, Samuel,Parkin, Sean
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p. 24017 - 24026
(2020/07/23)
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- Cu(II)-Mediated N-H and N-Alkyl Aryl Amination and Olefin Aziridination
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Cu(II)-mediated direct NH2 and NH alkyl aryl aminations and olefin aziridinations are described. These room-temperature, one-pot, environmentally friendly procedures replace costly Rh2 catalysts and, in some instances, display important differences with comparable Rh2- and Fe-supported reactions.
- Munnuri, Sailu,Anugu, Raghunath Reddy,Falck, John R.
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supporting information
p. 1926 - 1929
(2019/03/11)
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- Deacetylative Amination of Acetyl Arenes and Alkanes with C-C Bond Cleavage
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The Br?nsted acid-catalyzed synthesis of primary amines from acetyl arenes and alkanes with C-C bond cleavage is described. Although the conversion from an acetyl group to amine has traditionally required multiple steps, the method described herein, which uses an oxime reagent as an amino group source, achieves the transformation directly via domino transoximation/Beckmann rearrangement/Pinner reaction. The method was also applied to the synthesis of γ-aminobutyric acids, such as baclophen and rolipram.
- Hyodo, Kengo,Hasegawa, Genna,Maki, Hiroya,Uchida, Kingo
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supporting information
p. 2818 - 2822
(2019/04/25)
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- Metal-free chemoselective reduction of nitroaromatics to anilines via hydrogen transfer strategy
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A novel protocol for chemoselective reduction of aromatic nitro compounds to aromatic amines has been established. The metal-free reduction goes through a hydrogen transfer process. Various easily reducible functional groups can be well tolerated under the optimized reaction conditions.
- Shuai, Qi,Li, Jun,Zhao, Feng,Su, Weike,Deng, Guojun
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p. 965 - 975
(2019/04/13)
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- Cobalt in N-doped carbon matrix catalyst for chemoselective hydrogenation of nitroarenes
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Anilines as important intermediates for both organic synthesis and industrial manufactory are densely substituted with a variety of functional moieties, and the transformation of nitroarenes into corresponding anilines requires catalytically selective hydrogenation catalyst. Herein, we describe a simple pyrolysis strategy to prepare cobalt catalysts in nitrogen-doped carbon matrix applied in the selective hydrogenation of nitroarenes with molecular hydrogen. The Co/NC catalysts are obtained through thermal treatment of mixed precursors of cobalt phthalocyanine and melamine. The surface-modified Co particles with Co3O4 and CoNx sites are surrounded by N-doped carbon layers according to a series of structural characterization results. These Co/NC catalysts are capable of efficiently selective hydrogenation of nitrobenzene and various substituted nitroarenes into corresponding anilines under relatively mild reaction conditions. The optimal catalytic hydrogenation performance is contributed to the fast rate of H2 dissociated activation on the CoNx active sites and the facile adsorption of the reactant substances, which is verified by the isotopic H2-D2 exchange experiments, reactant adsorption and the ORR reaction tests. Furthermore, the heterogeneous Co/NC catalyst is highly stable without the Co leaching and deactivation issues during the recycling reaction runs.
- Dai, Yihu,Jiang, Chunyang,Xu, Min,Bian, Bo,Lu, Di,Yang, Yanhui
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p. 158 - 166
(2019/06/03)
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- Catalytic Transfer Hydrodebenzylation with Low Palladium Loading
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A highly-efficient catalytic system for hydrodebenzylation reaction is described. The cleavage of O-benzyl and N-benzyl protecting groups was performed using an uncommonly low palladium loading (0.02–0.3 mol%; TON up to 5000) in a relatively short reaction time. The approach was used for a variety of substrates including pharmaceutically important precursors, and gram-scale deprotection reaction was shown. Transfer conditions together with easy-to-make Pd/C catalyst are the key features of this debenzylation scheme. (Figure presented.).
- Yakukhnov, Sergey A.,Ananikov, Valentine P.
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supporting information
p. 4781 - 4789
(2019/09/16)
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- Generation and Reactivity of a One-Electron-Oxidized Manganese(V) Imido Complex with a Tetraamido Macrocyclic Ligand
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The synthesis and X-ray structure of a new manganese(V) mesitylimido complex with a tetraamido macrocyclic ligand (TAML), [MnV(TAML)(N-Mes)]? (1), are reported. Compound 1 is oxidized by [(p-BrC6H4)3N]+.[SbCl6]? and the resulting MnVI species readily undergoes H-atom transfer and nitrene transfer reactions.
- Shi, Huatian,Xie, Jianhui,Lam, William W. Y.,Man, Wai-Lun,Mak, Chi-Keung,Yiu, Shek-Man,Lee, Hung Kay,Lau, Tai-Chu
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supporting information
p. 12895 - 12899
(2019/09/13)
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- DIRECT C-H AMINATION AND AZA-ANNULATION
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In some aspects, the present disclosure provides methods of aminating an aromatic compound comprising reacting an aminating agent with an aromatic compound in the presence of a rhodium catalyst. In some embodiments, the methods may comprise aminating an aromatic compound which contains multiple different functional groups. The methods described herein may also be used to create bicyclic system comprising reacting an intramolecular aminating agent with an aromatic ring to obtain a second ring containing a nitrogen atom. In another aspect, the methods described herein may also be used to create a cyclic aliphatic cyclic/poly cyclic amine system comprising a reacting an intramolecular aminating agent by insertion into a C(sp3)-H bond.
- -
-
Paragraph 0132; 0148; 0149
(2019/06/07)
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- AMINATION AND HYDROXYLATION OF ARYLMETAL COMPOUNDS
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In one aspect, the present disclosure provides methods of preparing a primary or secondary amine and hydroxylated aromatic compounds. In some embodiments, the aromatic compound may be unsubstituted, substituted, or contain one or more heteroatoms within the rings of the aromatic compound. The methods described herein may be carried out without the need for transition metal catalysts or harsh reaction conditions.
- -
-
Paragraph 0098; 0134; 0135; 0154
(2018/03/25)
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- A P?P Bond as a Redox Reservoir and an Active Reaction Site
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The carbonylation of a nickel(II) anilido species 2 led to the formation of a dinickel(0)–CO complex (P2P-PP2){Ni(CO)}2 3 with a P?P bond along with isocyanate generation. In this reaction, the central phosphide moiety of an anionic PPP ligand (PPP?=?P[2-PiPr2C6H4]2) acts as a single-electron donor to form a P radical. Alternatively, 3 can be synthesized from the reduction of (PPP)NiCl (1) in the presence of CO; thus, the reaction proceeds by radical coupling of a .P?Ni0?CO species. The reverse reaction occurred to generate 1 when 3 was treated with AgCl. Since the P?P bond is light-sensitive, its homolysis is possible and was explored by EPR spectroscopy and DFT analysis. Finally, various bond-activation reactions of 3 occurred under visible-light conditions, thus indicating that a P?P bond can act as an active reaction site.
- Kim, Yeong-Eun,Lee, Yunho
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supporting information
p. 14159 - 14163
(2018/10/15)
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- Rapid heteroatom transfer to arylmetals utilizing multifunctional reagent scaffolds
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Arylmetals are highly valuable carbon nucleophiles that are readily and inexpensively prepared from aryl halides or arenes and widely used on both laboratory and industrial scales to react directly with a wide range of electrophiles. Although C-C bond formation has been a staple of organic synthesis, the direct transfer of primary amino (-NH2) and hydroxyl (-OH) groups to arylmetals in a scalable and environmentally friendly fashion remains a formidable synthetic challenge because of the absence of suitable heteroatom-transfer reagents. Here, we demonstrate the use of bench-stable N-H and N-alkyl oxaziridines derived from readily available terpenoid scaffolds as efficient multifunctional reagents for the direct primary amination and hydroxylation of structurally diverse aryl- and heteroarylmetals. This practical and scalable method provides one-step synthetic access to primary anilines and phenols at low temperature and avoids the use of transition-metal catalysts, ligands and additives, nitrogen-protecting groups, excess reagents and harsh workup conditions.
- Gao, Hongyin,Zhou, Zhe,Kwon, Doo-Hyun,Coombs, James,Jones, Steven,Behnke, Nicole Erin,Ess, Daniel H.,Kürti, László
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p. 681 - 688
(2017/06/30)
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- Fe-Catalyzed Amination of (Hetero)Arenes with a Redox-Active Aminating Reagent under Mild Conditions
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A novel and efficient Fe-catalyzed direct C?H amination (NH2) of arenes is reported using a new redox-active aminating reagent. The reaction is simple, and can be performed under air, mild, and redox-neutral conditions. This protocol has a broad substrate scope and could be used in the late-stage modification of bioactive compounds. Mechanistic studies demonstrate that a radical pathway could be involved in this transformation.
- Liu, Jianzhong,Wu, Kai,Shen, Tao,Liang, Yujie,Zou, Miancheng,Zhu, Yuchao,Li, Xinwei,Li, Xinyao,Jiao, Ning
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supporting information
p. 563 - 567
(2017/01/18)
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- Continuous-Flow Electrophilic Amination of Arenes and Schmidt Reaction of Carboxylic Acids Utilizing the Superacidic Trimethylsilyl Azide/Triflic Acid Reagent System
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A continuous flow protocol for the direct stoichiometric electrophilic amination of aromatic hydrocarbons and the Schmidt reaction of aromatic carboxylic acids using the superacidic trimethylsilyl azide/triflic acid system is described. Optimization of reagent stoichiometry, solvent, reaction time, and temperature led to an intensified protocol at elevated temperatures that allows the direct amination of arenes to be completed within 3 min at 90 °C. In order to improve the selectivity and scope of this direct amination protocol, aromatic carboxylic acids were additionally chosen as substrates. Selected carboxylic acids could be converted to their corresponding amine counterparts in good to excellent yields (11 examples, 55-83%) via a Schmidt reaction employing similar flow reaction conditions (5 min at 90 °C) and a similar reactor setup as for the amination. The safety issues derived from the explosive, toxic, and volatile hydrazoic acid intermediate, the corrosive nature of triflic acid, and the exothermic quenching were addressed by designing a suitable continuous flow reaction setup for both types of transformations.
- Chen, Yuesu,Gutmann, Bernhard,Kappe, C. Oliver
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p. 9372 - 9380
(2016/10/14)
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- Electrochemical Amination of Less-Activated Alkylated Arenes Using Boron-Doped Diamond Anodes
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The anodic C-H amination of aromatic compounds is a powerful and versatile method for the synthesis of aniline derivatives. By using boron-doped diamond (BDD) anodes, a method initially described by Yoshida et al. for electron-rich arenes was expanded to less-activated aromatic systems e.g., simple alkylated benzene derivatives. Anodes based on sp3 carbon seem to be the key for the electrochemical amination reaction. The corresponding primary anilines are obtained in good yields. Despite the cationic intermediates of the electrolytic reaction tert-butyl moieties are tolerated.
- Herold, Sebastian,M?hle, Sabine,Zirbes, Michael,Richter, Frank,Nefzger, Hartmut,Waldvogel, Siegfried R.
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supporting information
p. 1274 - 1278
(2016/03/19)
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- Photochemistry of N-Arylsulfonimides: An Easily Available Class of Nonionic Photoacid Generators (PAGs)
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The photochemical behavior of differently substituted N-arylsulfonimides was investigated. Homolysis of the S?N bond took place as the exclusive path from the singlet state to afford both N-arylsulfonamides and photo-Fries adducts, the amount of which depended on reaction conditions and aromatic substituents. Sulfinic and sulfonic acids were released upon irradiation under deaerated and oxygenated conditions, respectively. The nature of the excited states and intermediates involved were proved by laser flash photolysis and EPR experiments. These results highlighted the potential of such compounds as nonionic photoacid generators able to photorelease up to two equivalents of a strong acid for each mole of substrate.
- Torti, Edoardo,Protti, Stefano,Merli, Daniele,Dondi, Daniele,Fagnoni, Maurizio
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supporting information
p. 16998 - 17005
(2016/11/16)
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- Dirhodium-catalyzed C-H arene amination using hydroxylamines
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Primary and N-alkyl arylamine motifs are key functional groups in pharmaceuticals, agrochemicals, and functional materials, as well as in bioactive natural products. However, there is a dearth of generally applicablemethods for the direct replacement of aryl hydrogens with NH2/NH(alkyl) moieties. Here, we present a mild dirhodium-catalyzed C-H amination for conversion of structurally diverse monocyclic and fused aromatics to the corresponding primary and N-alkyl arylamines using NH2/NH(alkyl)-O-(sulfonyl)hydroxylamines as aminating agents; the relatively weak RSO2O-N bond functions as an internal oxidant. The methodology is operationally simple, scalable, and fast at or below ambient temperature, furnishing arylamines in moderate-to-good yields and with good regioselectivity. It can be readily extended to the synthesis of fused N-heterocycles.
- Paudyal, Mahesh P.,Adebesin, Adeniyi Michael,Burt, Scott R.,Ess, Daniel H.,Ma, Zhiwei,Kürti, László,Falck, John R.
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p. 1144 - 1147
(2016/11/09)
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- A triazine-phosphite polymeric ligand bearing cage-like P,N-ligation sites: An efficient ligand in the nickel-catalyzed amination of aryl chlorides and phenols
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A novel P,N-ligand was introduced for efficient Ni-catalyzed amination of aryl chlorides. Reaction of cyanuric acid (1,3,5-triazine-2,4,6-triol) and trichlorophosphine (PCl3) resulted in the production of a new porous material (TPPM) containing triazine rings with phosphite moieties in a sheet morphology. Cavities in the prepared compound create sites on the surface of the material with appropriate ligation character to coordinate with metals for catalytic purposes. The nickel-catalyzed amination of aryl chlorides and of phenols in their 2,4,6-triaryloxy-1,3,5-triazine (TAT) protected form were efficiently accomplished in the presence of this easily prepared and reusable P,N-ligand under mild reaction conditions. More importantly, TPPM was reusable for 5 iterations following this protocol without significantly decreasing in its activity.
- Panahi, Farhad,Roozbin, Fatemeh,Rahimi, Sajjad,Moayyed, Mohammadesmaeil,Valaei, Aria,Iranpoor, Nasser
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supporting information
p. 80670 - 80678
(2016/10/12)
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- The 4.4′-benzidine rearrangement of 4-alkyl substituted hydrazobenzenes
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When treated with dilute inorganic acids N,N′-diarylhydrazines (hydrazobenzenes) with an alkyl substituent in the 4-position undergo [5,5]-sigmatropic rearrangement reactions to furnish 4-(4′-aminophenyl)-4-alkylcyclohexa-2,5-dienimines (ipso-benzidines) in moderate to excellent yields. Steric bulk of the 4-alkyl substituent in the starting material decreases the yield of the respective ipso-benzidine. Additional electron-donating alkyl substituents in the ortho- and/or meta-positions on both rings generally promote the reaction and consequently increase the yield of the 4.4′-benzidine rearrangement product. Described herein are our findings regarding the scope and limits of this unusual benzidine rearrangement.
- Bouillon, Marc E.,Meyer, Hartmut H.
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p. 3151 - 3161
(2016/05/24)
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- Regioselectivity of the ortho- and para-semidine, and diphenyline rearrangements
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The regioselectivity of the o-semidine, p-semidine, and diphenyline rearrangements of unsymmetrical N,N′-diarylhydrazines was studied experimentally. The results indicate that their electron-rich nitrogen atom is first protonated and then the electron-poor non-protonated nitrogen atom undergoes an N[1,3]-sigmatropic shift to the ortho-position of the electron-rich aryl rings, generating key intermediates. The intermediates can undergo (1) a direct proton transfer to give o-semidines, (2) a second N[1,3]-shift of the electron-poor nitrogen atom and then proton transfer to furnish p-semidines, and (3) a [3,3]-sigmatropic shift and subsequent proton transfer to yield diphenylines. It is the first N[1,3]-sigmatropic shift step that plays an important role in controlling the regioselectivity in the three rearrangements, further determining the structures of o-semidines, p-semidines, and diphenylines. The current results provide new insights into the o/p-semidine and diphenyline rearrangements and useful information for controlling and predicting the structures of the rearrangement products.
- Yang, Zhanhui,Hou, Shili,He, Wei,Cheng, Baoxiang,Jiao, Peng,Xu, Jiaxi
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p. 2186 - 2195
(2016/04/09)
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- Efficient and highly selective boron-doped carbon materials-catalyzed reduction of nitroarenes
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Exploring the potential catalytic applications of boron-doped carbon materials is a fascinating challenge. Here we describe that boron-doped onion-like carbon and carbon nanotubes as metal-free catalysts exhibit excellent catalytic activity and stability in nitroarene reduction under a stoichiometric amount of reductant.
- Lin, Yangming,Wu, Shuchang,Shi, Wen,Zhang, Bingsen,Wang, Jia,Kim, Yoong Ahm,Endo, Morinobu,Su, Dang Sheng
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p. 13086 - 13089
(2015/08/18)
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- Copper-Promoted Tandem Reaction of Azobenzenes with Allyl Bromides via N=N Bond Cleavage for the Regioselective Synthesis of Quinolines
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A copper-promoted tandem reaction of a variety of azobenzenes and allyl bromides via N=N bond cleavage to regioselectively construct quinoline derivatives has been developed. The azobenzenes act as not only construction units but also an oxidant for quinoline formation.
- Yi, Xiangli,Xi, Chanjuan
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supporting information
p. 5836 - 5839
(2015/12/11)
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- One step C-N bond formation from alkylbenzene and ammonia over Cu-modified TS-1 zeolite catalyst
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A Cu doped TS-1 zeolite sample was applied to catalyze the formation of C-N bonds on both the ring and the side chain of toluene, as well as other alkylbenzenes. A yield of 3.4% of toluidine was obtained for the amination of toluene, with a 1.0% yield of nitrobenzene. Cyanobenzene was also obtained as the C-N bond product on the side chain with a yield of 1.0%. The selectivity for C-N bond formation was 52.4%. The catalyst promoted the formation of a hydroxylamine intermediate from ammonia and hydrogen peroxide, and then the instantaneously generated amino cation reacted with the substrate to form C-N bonds on both the ring and side chain. Cyanobenzene was produced from the dehydration of benzylamine, formed via the reaction of ammonia and toluene. The formation of C-N bonds on the ring had an ortho-orientation advantage for mono-substituted-benzenes. With the increase in the number of methyl substituents, the yield of the ring products decreased, which might be caused by steric hindrance. the Partner Organisations 2014.
- Xia, Sheng,Yu, Tianhua,Liu, Huihui,Li, Guiying,Hu, Changwei
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p. 3108 - 3119
(2014/08/18)
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- Nitrogen-centered radical-mediated C-H imidation of arenes and heteroarenes via visible light induced photocatalysis
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The C-H imidation of arenes and heteroarenes has been achieved via visible light induced photocatalysis. In the presence of an iridium(iii) photoredox catalyst, the reaction of aromatic substrates with N-chlorophthalimide furnishes the N-aryl products at room temperature through a nitrogen-centered radical mediated aromatic substitution.
- Kim, Hyejin,Kim, Taehoon,Lee, Dong Gil,Roh, Sang Weon,Lee, Chulbom
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supporting information
p. 9273 - 9276
(2014/08/05)
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- Nanoscale Fe2O3-based catalysts for selective hydrogenation of nitroarenes to anilines
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Production of anilines - key intermediates for the fine chemical, agrochemical, and pharmaceutical industries - relies on precious metal catalysts that selectively hydrogenate aryl nitro groups in the presence of other easily reducible functionalities. Herein, we report convenient and stable iron oxide (Fe2O3) - based catalysts as a more earth-abundant alternative for this transformation. Pyrolysis of iron-phenanthroline complexes on carbon furnishes a unique structure in which the active Fe2O 3 particles are surrounded by a nitrogen-doped carbon layer. Highly selective hydrogenation of numerous structurally diverse nitroarenes (more than 80 examples) proceeded in good to excellent yield under industrially viable conditions.
- Jagadeesh, Rajenahally V.,Surkus, Annette-Enrica,Junge, Henrik,Pohl, Marga-Martina,Radnik, Joerg,Rabeah, Jabor,Huan, Heming,Schunemann, Volker,Brueckner, Angelika,Beller, Matthias
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p. 1073 - 1076
(2014/01/06)
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- Bis(tridentate) ruthenium-terpyridine complexes featuring microsecond excited-state lifetimes
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A series of heteroleptic bis(tridentate) ruthenium(II) complexes, each bearing a substituted 2,2′:6′,2″-terpyridine (terpy) ligand, is characterized by room temperature microsecond excited-state lifetimes. This observation is a consequence of the strongly σ-donating and weakly π-accepting tridentate carbene ligand, 2′,6′-bis(1-mesityl-3- methyl-1,2,3-triazol-4-yl-5-idene)pyridine (C^N^C), adjacent to the terpy maintaining a large separation between the ligand field and metal-to-ligand charge transfer (MLCT) states while also preserving a large 3MLCT energy. The observed lifetimes are the highest documented lifetimes for unimolecular ruthenium(II) complexes and are four orders in magnitude higher than that associated with [Ru(terpy)2]2+.
- Brown, Douglas G.,Sanguantrakun, Nawaporn,Schulze, Benjamin,Schubert, Ulrich S.,Berlinguette, Curtis P.
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p. 12354 - 12357
(2012/09/05)
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- Elusive metal-free primary amination of arylboronic acids: Synthetic studies and mechanism by density functional theory
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Herein, we disclose the first metal-free synthesis of primary aromatic amines from arylboronic acids, a reaction that has eluded synthetic chemists for decades. This remarkable transformation affords structurally diverse primary arylamines in good chemical yields, including a variety of halogenated primary anilines that often cannot be prepared via transition-metal-catalyzed amination. The reaction is operationally simple, requires only a slight excess of aminating agent, proceeds under neutral or basic conditions, and, importantly, can be scaled up to provide multigram quantities of primary anilines. Density functional calculations reveal that the most likely mechanism involves a facile 1,2-aryl migration and that the presence of an ortho nitro group in the aminating agent plays a critical role in lowering the free energy barrier of the 1,2-aryl migration step.
- Zhu, Chen,Li, Gongqiang,Ess, Daniel H.,Falck, John R.,Kürti, László
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supporting information
p. 18253 - 18256
(2013/01/15)
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- Recyclable catalysts for palladium-catalyzed aminations of aryl halides
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Aminated and recycled: Palladium/imidazolium phosphane catalysts enable efficient and general aminations of aryl halides, including direct amination with ammonia. Subsequent recycling is possible without any additional heterogenization (see scheme).
- Dumrath, Andreas,Luebbe, Christa,Neumann, Helfried,Jackstell, Ralf,Beller, Matthias
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experimental part
p. 9599 - 9604
(2011/10/04)
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- Synthesis of primary aryl amines through a copper-assisted aromatic substitution reaction with sodium azide
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(Figure Presented) A method is presented by which aryl halides and azides are converted to the corresponding primary aryl amines with copper(I) and sodium azide.
- Markiewicz, John T.,Wiest, Olaf,Helquist, Paul
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supporting information; experimental part
p. 4887 - 4890
(2010/10/19)
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- A general palladium-catalyzed animation of aryl halides with ammonia
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A study was conducted to demonstrate palladium(Pd)-catalyzed amination of aryl halides with ammonia. The active catalyst was formed in situ from Pd(OAc)2, along with air- and moisture stable phosphines as pre-catalysts. It was found that the productivity of the catalyst system was similar to that of competitive Pd and phosphine systems. It was demonstrated that the novel electron-rich sterically demanding phosphine ligand was unable to be displaced from the palladium by ammonia to a significant extent, which prevented the deactivation of the catalyst by the ligand. It was also demonstrated that the Pd-catalyzed animation worked at ambient pressure. It was observed that the optimized system showed an excellent substrate scope including deactivated, electron-neutral, and activated halides, o-, m- p-substituted substrates, aryl chlorides, and heterocycles.
- Schulz, Thomas,Torborg, Christian,Enthaler, Stephan,Schaeffner, Benjamin,Dumrath, Andreas,Spannenberg, Anke,Neumann, Helfried,Boerner, Armin,Beller, Matthias
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experimental part
p. 4528 - 4533
(2009/12/24)
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- Easy copper-catalyzed synthesis of primary aromatic amines by coupling aromatic boronic acids with aqueous ammonia at room temperature
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(Chemical Equation Presented) A reaction without the added extras: Aromatic boronic acids have been coupled using inexpensive aqueous ammonia to give primary aromatic amines under copper catalysis. This simple and highly efficient approach can be carried
- Rao, Honghua,Fu, Hua,Jiang, Yuyang,Zhao, Yufen
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supporting information; experimental part
p. 1114 - 1116
(2009/06/20)
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- An efficient copper-catalyzed amination of aryl halides by aqueous ammonia
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The copper(I) bromide/1-(5,6,7,8-tetrahydroquinolin-8-yl)-2-methylpropan-l- one (CuBr-LS) combination catalyzed the cross-coupling reactions between aryl or heteroaryl halides and aqueous ammonia with high yields to produce primary aromatic or heteroaromatic amines at room temperature or under mild conditions.
- Wang, Deping,Cai, Qian,Ding, Ke
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supporting information; experimental part
p. 1722 - 1726
(2011/02/25)
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- Palladium-catalyzed coupling of ammonia with aryl chlorides, bromides, iodides, and sulfonates: A general method for the preparation of primary arylamines
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We report that the complex generated from Pd[P(o-tol)3] 2 and the alkylbisphosphine CyPF-t-Bu is a highly active and selective catalyst for the coupling of ammonia with aryl chlorides, bromides, iodides, and sulfonates. The couplings of ammonia with this catalyst conducted with a solution of ammonia in dioxane form primary arylamines from a variety of aryl electrophiles in high yields. Catalyst loadings as low as 0.1 mol % were sufficient for reactions of many aryl chlorides and bromides. In the presence of this catalyst, aryl sulfonates also coupled with ammonia for the first time in high yields. A comparison of reactions in the presence of this catalyst versus those in the presence of existing copper and palladium systems revealed a complementary, if not broader, substrate scope. The utility of this method to generate amides, imides, and carbamates is illustrated by a one-pot synthesis of a small library of these carbonyl compounds from aryl bromides and chlorides, ammonia, and acid chlorides or anhydrides. Mechanistic studies show that reactions conducted with the combination of Pd[P(o-tol)3]2 and CyPF-t-Bu as catalyst occur with faster rates and higher yields than those conducted with CyPF-t-Bu and palladiun(II) as catalyst precursors because of the low concentration of active catalyst that is generated from the combination of palladium(II), ammonia, and base.
- Vo, Giang D.,Hartwig, John F.
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supporting information; experimental part
p. 11049 - 11061
(2009/12/05)
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- Alumina-, niobia-, and niobia/alumina-supported NiMoS catalysts: Surface properties and activities in the hydrodesulfurization of thiophene and hydrodenitrogenation of 2,6-dimethylaniline
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The activity of NiMoS catalysts supported on niobia, alumina, and niobia/alumina was compared for the thiophene hydrodesulfurization (HDS) and 2,6-dimethylaniline (2,6-DMA) hydrodenitrogenation (HDN) reactions. To evaluate the acidity of the supports and identify the nature of the sulfide sites, adsorption of 2,6-dimethylpyridine, pyridine, and CO was performed and followed by IR spectroscopy. This study has shown that with niobia as a support, the activity of NiMoS catalysts in thiophene HDS and in HDN of 2,6-DMA was no longer promoted by the synergy between Ni and Mo. The absence of synergy between molybdenum and nickel on niobia can be explained by the strong interaction of each metal with niobia at the expense of interaction with each other. Moreover, it has been shown that on a niobia/alumina support, the formation of the NiMoS phase can be directly linked to the presence of alumina not covered by niobia. However, niobia is an interesting support for the HDN of 2,6-DMA, because it favors the formation of xylene through direct ammonia elimination involving low H2 consumption. The activity for xylene formation on niobia is linked to the electron-deficient nature of the Mo sulfide site, as demonstrated by CO adsorption followed by IR.
- Rocha, Angela S.,Faro Jr., Arnaldo C.,Oliviero, Laetitia,Van Gestel, Jacob,Mauge, Francoise
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p. 321 - 334
(2008/09/18)
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- Conversion of azobenzenes into N,N′-diarylhydrazines by sodium dithionite
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A number of chloro-, methyl- and methoxy-substituted azobenzenes have been reduced to the corresponding hydrazines by using an aqueous solution of Na 2S2O4. The yield is generally excellent, but two compounds, viz. 4,4-dimethoxyazobenzene and 2,2,4,4,6,6- hexamethylazobenzene, gave no hydrazine at all. Georg Thieme Verlag Stuttgart.
- Sydnes, Leiv K.,Elmi, Shire,Heggen, Per,Holmelid, Bjarte,Malthe-S?rensen, Didrik
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p. 1695 - 1698
(2007/12/28)
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- Oxidative dearomatization of phenols and anilines via λ3 - and λ5-iodane-mediated phenylation and oxygenation
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Treatment of 2-methylphenols with chloro(diphenyl)-λ3- iodane led to their regioselective dearomatizing 2-phenylation into cyclohexa-2,4-dienone derivatives via a proposed ligand coupling reaction. In the same vein of investigation, treatment of 2-methylanilines with the λ5-iodane 2-iodoxybenzoic acid IBX reagent led to their regioselective dearomatization into previously undescribed ortho-quinol imines.
- Quideau, Stephane,Pouysegu, Laurent,Ozanne, Aurelie,Gagnepain, Julien
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p. 201 - 216
(2007/10/03)
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- Electrophilic Amination of Methylbenzenes with the System NaN 3-AlCl3-HCl. Effects of the Solvent, Crown Ether, and Substrate Structure
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Using mesitylene and o-xylene as examples, it was shown that the solvent nature strongly affects the conversion of methylbenzenes in electrophilic amination with the system NaN3-AlCl3-HCl. Two-parameter correlations were found between the substrate conversion, on the one hand, and dielectric constant and number of heavy atoms in the solvent, on the other. A considerable solvent effect on the regioselectivity of amination of o-xylene was observed. The presence of 18-crown-6 weakly affects the ratio of isomeric amines, but the conversion of o-xylene sharply decreases. Solid aromatic substrates, such as durene and pentamethylbenzene can also be involved in electrophilic amination with the system NaN3-AlCl3-HCl. On the basis of the experimental data and the results of quantum-chemical calculations, participation of a nitrenium intermediate in this reaction was postulated.
- Borodkin,Elanov,Popov,Pokrovskii,Shubin
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p. 672 - 679
(2007/10/03)
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- CRF receptor antagonists and methods relating thereto
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CRF receptor antagonists are disclosed which have utility in the treatment of a variety of disorders, including the treatment of disorders manifesting hypersecretion of CRF in a warm-blooded animals, such as stroke. The CRF receptor antagonists of this invention have the following structure: including stereoisomers and pharmaceutically acceptable salts thereof, wherein n, m, A, B, C, R, R1, R2and Ar are as defined herein. Compositions containing a CRF receptor antagonist in combination with a pharmaceutically acceptable carrier are also disclosed, as well as methods for use of the same
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- CRF receptor antagonists and methods relating thereto
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CRF receptor antagonists are disclosed which have utility in the treatment of a variety of disorders, including the treatment of disorders manifesting hypersecretion of CRF in a warm-blooded animals, such as stroke. The CRF receptor antagonists of this invention have the following structure: including stereoisomers and pharmaceutically acceptable salts thereof, wherein n, m, A, B, C, R, R1, R2and Ar are as defined herein. Compositions containing a CRF receptor antagonist in combination with a pharmaceutically acceptable carrier are also disclosed, as well as methods for use of the same
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- Amination reactions of aryl halides with nitrogen-containing reagents mediated by palladium/imidazolium salt systems
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Nucleophilic N-heterocyclic carbenes have been conveniently used as catalyst modifiers in amination reactions involving aryl chlorides, aryl bromides, and aryl iodides with various nitrogen-containing substrates. The scope of a coupling process using a Pd(0) or Pd(II) source and an imidazolium salt in the presence of a base, KOtBu or NaOH, was tested using various substrates. The Pd2(dba)3/IPr·HCl (1, IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) system presents the highest activity with respect to electron-neutral and electron-rich aryl chlorides. The ligand is also effective for the synthesis of benzophenone imines, which can be easily converted to the corresponding primary amines by acid hydrolysis. Less reactive indoles were converted to N-aryl-substituted indoles using as supporting ligand the more donating SIPr·HCl (5, SIPr = 1,3-bis(2,6-diisopropylphenyl)-4,5-dihydroimidazol-2-ylidene). The Pd(OAc)2/SIPr·HCl/NaOH system is efficient for the N-arylation of diverse indoles with aryl bromides. The general protocol developed has been applied successfully to the synthesis of a key intermediate in the synthesis of an important new antibiotic. Mechanistically, palladium-to-ligand ratio studies strongly support an active species bearing one nucleophilic carbene ligand.
- Grasa,Viciu,Huang,Nolan
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p. 7729 - 7737
(2007/10/03)
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- Photochemical Reactions of Mesityl Azide with Tetracyanoethylene: Competitive Trapping of Singlet Nitrene and Didehydroazepine
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Irradiation of the title azide 4 in the presence of TCNE gives a mixture of two stable adducts. One of them is identified as the azomethine ylide 5, the structure of which is strictly determined by X-ray crystallography. The other is spectroscopically assigned to the spiroazepine 6. The effect of wavelength of the light employed in the photolysis reveals that the TCNE-4 charge-transfer complex (λmax 454 and 550 nm in dichloromethane) does not participate in the adduct formation. The ratio of the adducts obtained in the photolysis is dependent linearly upon the initial concentration of TCNE, which strongly suggests that the adducts 5 and 6 are produced by competitive trapping of singlet mesitylnitrene (8S) and trimethyldidehydroazepine (9), respectively. The rate constant for the reaction of 8S with TCNE is estimated to be on the order of 109 M-1 s-1 or greater. The PM3 calculation indicates that the azomethine ylide 5 is thermodynamically more stable than the aziridine 7, which is thought to be initially formed by the reaction of 8S with TCNE. Thus, we propose that these findings make the first example of competitive trapping of singlet arylnitrene and its ring-expanded isomer with an alkene, which definitely reveals the intervention of singlet nitrene in the photolysis of an aryl azide.
- Murata, Shigeru,Abe, Shizue,Tomioka, Hideo
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p. 3055 - 3061
(2007/10/03)
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