共查询到20条相似文献,搜索用时 31 毫秒
1.
Fei Wang Shannon S. Stahl 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(19):6451-6456
Direct amination of C(sp3)?H bonds is of broad interest in the realm of C?H functionalization because of the prevalence of nitrogen heterocycles and amines in pharmaceuticals and natural products. Reported here is a combined electrochemical/photochemical method for dehydrogenative C(sp3)?H/N?H coupling that exhibits good reactivity with both sp2 and sp3 N?H bonds. The results show how use of iodide as an electrochemical mediator, in combination with light‐induced cleavage of intermediate N?I bonds, enables the electrochemical process to proceed at low electrode potentials. This approach significantly improves the functional‐group compatibility of electrochemical C?H amination, for example, tolerating electron‐rich aromatic groups that undergo deleterious side reactions in the presence of high electrode potentials. 相似文献
2.
N‐Heterocyclic Carbene Iron(III) Porphyrin‐Catalyzed Intramolecular C(sp3)–H Amination of Alkyl Azides
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Ka‐Pan Shing Dr. Yungen Liu Dr. Bei Cao Dr. Xiao‐Yong Chang Tingjie You Prof. Dr. Chi‐Ming Che 《Angewandte Chemie (International ed. in English)》2018,57(37):11947-11951
Metal‐catalyzed intramolecular C?H amination of alkyl azides constitutes an appealing approach to alicyclic amines; challenges remain in broadening substrate scope, enhancing regioselectivity, and applying the method to natural product synthesis. Herein we report an iron(III) porphyrin bearing axial N‐heterocyclic carbene ligands which catalyzes the intramolecular C(sp3)–H amination of a wide variety of alkyl azides under microwave‐assisted and thermal conditions, resulting in selective amination of tertiary, benzylic, allylic, secondary, and primary C?H bonds with up to 95 % yield. 14 out of 17 substrates were cyclized selectively at C4 to give pyrrolidines. The regioselectivity at C4 or C5 could be tuned by modifying the reactivity of the C5–H bond. Mechanistic studies revealed a concerted or a fast re‐bound mechanism for the amination reaction. The reaction has been applied to the syntheses of tropane, nicotine, cis‐octahydroindole, and leelamine derivatives. 相似文献
3.
Chemoselective Amination of Propargylic C(sp3)H Bonds by Cobalt(II)‐Based Metalloradical Catalysis
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Prof. Dr. Hongjian Lu Dr. Chaoqun Li Dr. Huiling Jiang Christopher L. Lizardi Prof. Dr. X. Peter Zhang 《Angewandte Chemie (International ed. in English)》2014,53(27):7028-7032
Highly chemoselective intramolecular amination of propargylic C(sp3)? H bonds has been demonstrated for N‐bishomopropargylic sulfamoyl azides through cobalt(II)‐based metalloradical catalysis. Supported by D2h‐symmetric amidoporphyrin ligand 3,5‐DitBu‐IbuPhyrin, the cobalt(II)‐catalyzed C? H amination proceeds effectively under neutral and nonoxidative conditions without the need of any additives, and generates N2 as the only byproduct. The metalloradical amination is suitable for both secondary and tertiary propargylic C? H substrates with an unusually high degree of functional‐group tolerance, thus providing a direct method for high‐yielding synthesis of functionalized propargylamine derivatives. 相似文献
4.
Alexander Reckziegel Clemens Pietzonka Florian Kraus C. Gunnar Werncke 《Angewandte Chemie (International ed. in English)》2020,59(22):8527-8531
The 3d‐metal mediated nitrene transfer is under intense scrutiny due to its potential as an atom economic and ecologically benign way for the directed amination of (un)functionalised C?H bonds. Here we present the isolation and characterisation of a rare, trigonal imido cobalt(III) complex, which bears a rather long cobalt–imido bond. It can cleanly cleave strong C?H bonds with a bond dissociation energy of up to 92 kcal mol?1 in an intermolecular fashion, unprecedented for imido cobalt complexes. This resulted in the amido cobalt(II) complex [Co(hmds)2(NHtBu)]?. Kinetic studies on this reaction revealed an H atom transfer mechanism. Remarkably, the cobalt(II) amide itself is capable of mediating H atom abstraction or stepwise proton/electron transfer depending on the substrate. A cobalt‐mediated catalytic application for substrate dehydrogenation using an organo azide is presented. 相似文献
5.
Easily Accessible Auxiliary for Palladium‐Catalyzed Intramolecular Amination of C(sp2)H and C(sp3)H Bonds at δ‐ and ε‐Positions
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Chao Wang Changpeng Chen Jingyu Zhang Jian Han Qian Wang Kun Guo Pei Liu Mingyu Guan Dr. Yingming Yao Prof. Dr. Yingsheng Zhao 《Angewandte Chemie (International ed. in English)》2014,53(37):9884-9888
An easily synthesized and accessible N,O‐bidentate auxiliary has been developed for selective C? H activation under palladium catalysis. The novel auxiliary showed its first powerful application in C? H functionalization of remote positions. Both C(sp2)? H and C(sp3)? H bonds at δ‐ and ε‐positions were effectively activated, thus giving tetrahydroquinolines, benzomorpholines, pyrrolidines, and indolines in moderate to excellent yields by palladium‐catalyzed intramolecular C? H amination. 相似文献
6.
Quan Gou Gang Liu Zi‐Ning Liu Prof. Dr. Jun Qin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(44):15491-15495
PdII‐catalyzed intermolecular amination of unactivated C(sp3)?H bonds has been successfully developed for the first time. This method provides a new way to achieve the challenging intermolecular amination of unactivated C(sp3)?H bonds, producing a variety of unnatural β2‐amino carboxylic acid analogues. This C(sp3)?H amination protocol is demonstrated with a broad substrate scope, good functional‐group tolerance, and chemoselectivity. It is operated without use of phosphine ligand or external oxidant. 相似文献
7.
Dr. Yoshihiro Miyake Kazunari Nakajima Assoc. Prof. Dr. Yoshiaki Nishibayashi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(51):16473-16477
Visible‐light‐mediated direct sp3 C? H amination of benzocyclic amines via α‐aminoalkyl radicals by using photoredox catalysts is described here. The obtained N,N‐acetals were also successfully applied for carbon–carbon bond forming reactions with carbon nucleophiles. The procedure is suitable for a late‐stage modification of C? H bonds to C? C bonds. 相似文献
8.
Dr. Yungen Liu Prof. Dr. Chi‐Ming Che 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(34):10494-10501
[FeIII(F20‐tpp)Cl] (F20‐tpp=meso‐tetrakis(pentafluorophenyl)porphyrinato dianion) is an effective catalyst for imido/nitrene insertion reactions using sulfonyl and aryl azides as nitrogen source. Under thermal conditions, aziridination of aryl and alkyl alkenes (16 examples, 60–95 % yields), sulfimidation of sulfides (11 examples, 76–96 % yields), allylic amidation/amination of α‐methylstyrenes (15 examples, 68–83 % yields), and amination of saturated C? H bonds including that of cycloalkanes and adamantane (eight examples, 64–80 % yields) can be accomplished by using 2 mol % [FeIII(F20‐tpp)Cl] as catalyst. Under microwave irradiation conditions, the reaction time of aziridination (four examples), allylic amination (five examples), sulfimidation (two examples), and amination of saturated C? H bonds (three examples) can be reduced by up to 16‐fold (24–48 versus 1.5–6 h) without significantly affecting the product yield and substrate conversion. 相似文献
9.
Iron(II)‐Catalyzed Site‐Selective Functionalization of Unactivated C(sp3)−H Bonds Guided by Alkoxyl Radicals
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Honghao Guan Shutao Sun Ying Mao Lei Chen Ran Lu Jiancheng Huang Prof. Dr. Lei Liu 《Angewandte Chemie (International ed. in English)》2018,57(35):11413-11417
An alkoxyl radical guided strategy for site‐selective functionalization of unactivated methylene and methine C?H bonds enabled by an FeII‐catalyzed redox process is described. The mild, expeditious, and modular protocol allows efficient remote aliphatic fluorination, chlorination, amination, and alkynylation of structurally and electronically varied primary, secondary, and tertiary hydroperoxides with excellent functional‐group tolerance. The application for one‐pot 1,4‐hydroxyl functionalization of non‐oxygenated alkane substrates initiated by aerobic C?H oxygenation is also demonstrated. 相似文献
10.
Ethan A. Wappes Stacy C. Fosu Trevor C. Chopko Prof. Dr. David A. Nagib 《Angewandte Chemie (International ed. in English)》2016,55(34):9974-9978
The Cδ?H amination of unactivated, secondary C?H bonds to form a broad range of functionalized pyrrolidines has been developed by a triiodide (I3?)‐mediated strategy. By in situ 1) oxidation of sodium iodide and 2) sequestration of the transiently generated iodine (I2) as I3?, this approach precludes undesired I2‐mediated decomposition which can otherwise limit synthetic utility to only weak C(sp3)?H bonds. The mechanism of this triiodide‐mediated cyclization of unbiased, secondary C(sp3)?H bonds, by either thermal or photolytic initiation, is supported by NMR and UV/Vis data, as well as intercepted intermediates. 相似文献
11.
Abolghasem Bakhoda Quan Jiang Yosra M. Badiei Jeffery A. Bertke Thomas R. Cundari Timothy H. Warren 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(11):3459-3463
Undirected C(sp3)?H functionalization reactions often follow site‐selectivity patterns that mirror the corresponding C?H bond dissociation energies (BDEs). This often results in the functionalization of weaker tertiary C?H bonds in the presence of stronger secondary and primary bonds. An important, contemporary challenge is the development of catalyst systems capable of selectively functionalizing stronger primary and secondary C?H bonds over tertiary and benzylic C?H sites. Herein, we report a Cu catalyst that exhibits a high degree of primary and secondary over tertiary C?H bond selectivity in the amidation of linear and cyclic hydrocarbons with aroyl azides ArC(O)N3. Mechanistic and DFT studies indicate that C?H amidation involves H‐atom abstraction from R‐H substrates by nitrene intermediates [Cu](κ2‐N,O‐NC(O)Ar) to provide carbon‐based radicals R. and copper(II)amide intermediates [CuII]‐NHC(O)Ar that subsequently capture radicals R. to form products R‐NHC(O)Ar. These studies reveal important catalyst features required to achieve primary and secondary C?H amidation selectivity in the absence of directing groups. 相似文献
12.
Dr. Zhen Guo Dr. Xiangguo Guan Dr. Jie‐Sheng Huang Dr. Wai‐Man Tsui Prof. Dr. Zhenyang Lin Prof. Dr. Chi‐Ming Che 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(34):11320-11331
The X‐ray crystal structure of [RuVI(NMs)2(tmp)] (Ms=SO2‐ p‐MeOC6H4; tmp=5,10,15,20‐tetramesitylporphyrinato(2?)), a metal sulfonylimide complex that can undergo alkene aziridination and C? H bond amination reactions, shows a Ru?N distance of 1.79(3) Å and Ru‐N‐S angle of 162.5(3)°. Density functional theory (DFT) calculations on the electronic structures of [RuVI(NMs)2(tmp)] and model complex [RuVI(NMs)2(por0)] (por0=unsubstituted porphyrinato(2?)) using the M06L functional gave results in agreement with experimental observations. For the amination of ethylbenzene by the singlet ground state of [RuVI(NMs)2(por0)], DFT calculations using the M06L functional revealed an effectively concerted pathway involving rate‐limiting hydrogen atom abstraction without a distinct radical rebound step. The substituent effect on the amination reactivity of ethylbenzene by [RuVI(NX)2(por0)] (X=SO2‐p‐YC6H4 with Y=MeO, Me, H, Cl, NO2) was examined. Electron‐withdrawing Y groups lower the energy of the LUMOs of [RuVI(NX)2(por0)], thus facilitating their interaction with the low‐lying HOMO of the ethylbenzene C? H bond and hence increasing the reactivity of [RuVI(NX)2(por0)]. DFT calculations on the amination/aziridination reactions of [RuVI(NSO2C6H5)2(por0)] with pent‐4‐enal, an aldehyde substrate bearing acyl, homoallylic, and allylic C? H bonds and a C?C bond, revealed a lower reaction barrier for the amination of the acyl C? H bond than for both the amination of the other C? H bonds and aziridination of the C?C bond in this substrate. 相似文献
13.
Anthranil: An Aminating Reagent Leading to Bifunctionality for Both C(sp3)−H and C(sp2)−H under Rhodium(III) Catalysis
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Dr. Songjie Yu Guodong Tang Yingzi Li Xukai Zhou Prof. Yu Lan Prof. Xingwei Li 《Angewandte Chemie (International ed. in English)》2016,55(30):8696-8700
Previous direct C?H nitrogenation suffered from simple amidation/amination with limited atom‐economy and is mostly limited to C(sp2)?H substrates. In this work, anthranil was designed as a novel bifunctional aminating reagent for both C(sp2)?H and C(sp3)?H bonds under rhodium(III) catalysis, thus affording a nucleophilic aniline tethered to an electrophilic carbonyl. A tridendate rhodium(III) complex has been isolated as the resting state of the catalyst, and DFT studies established the intermediacy of a nitrene species. 相似文献
14.
Alexandra E. Bosnidou Kilian Muiz 《Angewandte Chemie (International ed. in English)》2019,58(22):7485-7489
The direct amination of aliphatic C?H bonds has remained one of the most tantalizing transformations in organic chemistry. Herein, we report on a unique catalyst system, which enables the elusive intermolecular C(sp3)?H amination. This practical synthetic strategy provides access to aminated building blocks and fosters innovative multiple C?H amination within a new approach to aminated heterocycles. The synthetic utility is demonstrated by the synthesis of four relevant pharmaceuticals. 相似文献
15.
Intermolecular Amination of Unactivated C(sp3)−H Bonds with Cyclic Alkylamines: Formation of C(sp3)−N Bonds through Copper/Oxygen‐Mediated C(sp3)−H/N−H Activation
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Quan Gou Yu‐Wen Yang Zi‐Ning Liu Prof. Jun Qin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(45):16057-16061
The first example of intermolecular amination of unactivated C(sp3)?H bonds by cyclic alkylamines mediated by Cu(OAc)2/O2 is reported. This method avoids the use of benzoyloxyamines as the aminating reagent, which are normally prepared from alkylamines in extra steps. A variety of unnatural β2, 2‐amino acid analogues are synthesized by this simple and efficient procedure. This approach offers a solution to the previous unmet challenge of C(sp3)?H/N?H activation for the formation of C(sp3)?N bonds. 相似文献
16.
The Effect of C4H and C5H on the Microstructure of Aqueous Solutions of 1‐Alkyl‐3‐methylimidazolium Tetrafluoroborate Ionic Liquids
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As is well‐known, the C2?H proton of 1‐ethyl‐3‐methylimidazolium tetrafluoroborate ([Emim]BF4) and 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([Bmim]BF4) has a strong ability to form hydrogen bonds. The purpose of this work is to evaluate the effect of the interactions of the C4?H and C5?H protons on the microstructure of [Emim]BF4 and [Bmim]BF4 with water by using 1H NMR spectroscopy. The differences between the relative 1H NMR chemical shifts of C2?H, C4?H, and C5?H and between the interaction‐energy parameters obtained from these chemical shifts are minor, thus suggesting that the interactions of C4?H and C5?H may have a considerable effect on the microstructure. To confirm this, the viscosities of the systems are estimated by using the interaction‐energy parameters obtained from the 1H NMR chemical shifts of the three studied aromatic protons and water, showing that the interactions of C4?H and C5?H also play an important role in the microstructure. 相似文献
17.
Rhodium‐Catalyzed Direct Amination of Arenes with Nitrosobenzenes: A New Route to Diarylamines
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Dr. Juanjuan Du Dr. Yaxi Yang Huijin Feng Dr. Yuanchao Li Dr. Bing Zhou 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(19):5727-5731
A RhIII‐catalyzed addition of aryl C?H bonds to nitrosobenzenes, followed by cleavage of the resulting hydroxylamines in situ, has been reported. Different directing groups, such as N‐based heterocycles and ketoximes, can be used in this C?H amination process, providing valuable diarylamines in excellent yields. Most importantly, this process provides a new method for attaching arylamine groups to aromatic rings. 相似文献
18.
Palladium(0)/PAr3‐Catalyzed Intermolecular Amination of C(sp3)H Bonds: Synthesis of β‐Amino Acids
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Jian He Toshihiko Shigenari Prof. Dr. Jin‐Quan Yu 《Angewandte Chemie (International ed. in English)》2015,54(22):6545-6549
An intermolecular C(sp3)? H amination using a Pd0/PAr3 catalyst was developed. The reaction begins with oxidative addition of R2N? OBz to a Pd0/PAr3 catalyst and subsequent cleavage of a C(sp3)? H bond by the generated Pd? NR2 intermediate. The catalytic cycle proceeds without the need for external oxidants in a similar manner to the extensively studied palladium(0)‐catalyzed C? H arylation reactions. The electron‐deficient triarylphosphine ligand is crucial for this C(sp3)? H amination reaction to occur. 相似文献
19.
Guan‐Hao Huang Jian‐Min Li Jing‐Jyun Huang Jyun‐Dai Lin Prof. Gary Jing Chuang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(18):5240-5243
The first Co/Pd‐cocatalyzed intramolecular C?H amination and aziridination reactions were developed. Sulfamate esters were converted to oxathiazinanes by using CoPd(OAc)4 as catalyst and PhI(OAc)2 as oxidant. The mutual presence of both Co and Pd is crucial for the catalytic activity. This combination of two metals with simple acetate ligands provides an economical alternative to the Rh‐catalyzed insertion of nitrenoids into C?H bonds. 相似文献
20.
Teruki Sugiyama Jiben Meng Teruo Matsuura 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(4):o242-o246
The crystal structures of the four isomeric organic salts 4‐aminopyridinium 2‐chloro‐4‐nitrobenzoate, (I), 4‐aminopyridinium 2‐chloro‐5‐nitrobenzoate, (II), 4‐aminopyridinium 5‐chloro‐2‐nitrobenzoate, (III), and 4‐aminopyridinium 4‐chloro‐2‐nitrobenzoate, (IV), all C5H7N2+·C7H3ClNO4?, are presented. Compound (I) has one intramolecular hydrogen bond, one intermolecular C—H?O hydrogen bond and π–π‐stacking interactions. Compound (II) has N—H?O, C—H?O and C—H?Cl hydrogen bonds, and Cl?O—C electrostatic interactions. Compound (III) has N—H?O and C—H?O hydrogen bonds. Compound (IV) has a π–π‐stacking interaction, but no C—H?O hydrogen bonds. 相似文献