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1.
Eosin Y as a Direct Hydrogen‐Atom Transfer Photocatalyst for the Functionalization of C−H Bonds 下载免费PDF全文
Xuan‐Zi Fan Dr. Jia‐Wei Rong Hao‐Lin Wu Quan Zhou Dr. Hong‐Ping Deng Jin Da Tan Cheng‐Wen Xue Dr. Li‐Zhu Wu Dr. Hai‐Rong Tao Dr. Jie Wu 《Angewandte Chemie (International ed. in English)》2018,57(28):8514-8518
Eosin Y, a well‐known economical alternative to metal catalysts in visible‐light‐driven single‐electron transfer‐based organic transformations, can behave as an effective direct hydrogen‐atom transfer catalyst for C?H activation. Using the alkylation of C?H bonds with electron‐deficient alkenes as a model study revealed an extremely broad substrate scope, enabling easy access to a variety of important synthons. This eosin Y‐based photocatalytic hydrogen‐atom transfer strategy is promising for diverse functionalization of a wide range of native C?H bonds in a green and sustainable manner. 相似文献
2.
Tertiary‐Alcohol‐Directed Functionalization of Remote C(sp3)−H Bonds by Sequential Hydrogen Atom and Heteroaryl Migrations 下载免费PDF全文
Xinxin Wu Mingyang Wang Leitao Huan Dongping Wang Jinwei Wang Prof. Dr. Chen Zhu 《Angewandte Chemie (International ed. in English)》2018,57(6):1640-1644
Reported for the first time is a tertiary‐alcohol‐guided heteroarylation of remote C(sp3)?H bonds. The mild and direct generation of alkoxyl radicals from alcohols is enabled by visible‐light photocatalysis. A remote hydrogen atom and heteroaryl migration sequence are involved in the reaction. Many sensitive groups remain intact in the reaction, thus illustrating wide functional‐group compatibility. This protocol provides a practical strategy for the late‐stage modification of alkyl ketones. 相似文献
3.
Ligand‐Enabled Enantioselective C
–H Activation of Tetrahydroquinolines and Saturated Aza‐Heterocycles by RhI 下载免费PDF全文
《Angewandte Chemie (International ed. in English)》2018,57(31):9950-9954
The first rhodium(I)‐catalyzed enantioselective intermolecular C –H activation of various saturated aza‐heterocycles including tetrahydroquinolines, piperidines, piperazines, azetidines, pyrrolidines, and azepanes is presented. The combination of a rhodium(I) precatalyst and a chiral monodentate phosphonite ligand is shown to be a powerful catalytic system to access a variety of important enantio‐enriched heterocycles from simple starting materials. Notably, the C –H activation of tetrahydroquinolines is especially challenging due to the adjacent C −H bond. This redox‐neutral methodology provides a new synthetic route to α‐N‐arylated heterocycles with high chemoselectivity and enantioselectivity up to 97 % ee. 相似文献
4.
Microtubing‐Reactor‐Assisted Aliphatic C−H Functionalization with HCl as a Hydrogen‐Atom‐Transfer Catalyst Precursor in Conjunction with an Organic Photoredox Catalyst 下载免费PDF全文
Dr. Hong‐Ping Deng Quan Zhou Dr. Jie Wu 《Angewandte Chemie (International ed. in English)》2018,57(39):12661-12665
Chlorine radical, which is classically generated by the homolysis of Cl2 under UV irradiation, can abstract a hydrogen atom from an unactivated C(sp3)?H bond. We herein demonstrate the use of HCl as an effective hydrogen‐atom‐transfer catalyst precursor activated by an organic acridinium photoredox catalyst under visible‐light irradiation for C?H alkylation and allylation. The key to success relied on the utilization of microtubing reactors to maintain the volatile HCl catalyst. This photomediated chlorine‐based C?H activation protocol is effective for a variety of unactivated C(sp3)?H bond patterns, even with primary C(sp3)?H bonds, as in ethane. The merit of this strategy is illustrated by rapid access to several pharmaceutical drugs from abundant unfunctionalized alkane feedstocks. 相似文献
5.
Direct Cross‐Coupling of Allylic C(sp3)−H Bonds with Aryl‐ and Vinylbromides by Combined Nickel and Visible‐Light Catalysis 下载免费PDF全文
Dr. Long Huang Prof. Dr. Magnus Rueping 《Angewandte Chemie (International ed. in English)》2018,57(32):10333-10337
An efficient protocol for the direct allylic C(sp3)?H bond activation of unactivated tri‐ and tetrasubstituted alkenes and their functionalization with aryl‐ and vinylbromides by nickel and visible‐light photocatalysis has been developed. The method allows C(sp2)?C(sp3) formation under mild reaction conditions with good functional‐group tolerance and excellent regioselectivity. 相似文献
6.
Alison S. H. Ryder William B. Cunningham George Ballantyne Tom Mules Anna G. Kinsella Jacob Turner‐Dore Catherine M. Alder Lee J. Edwards Blandine S. J. McKay Matthew N. Grayson Alexander J. Cresswell 《Angewandte Chemie (International ed. in English)》2020,59(35):14986-14991
A practical, catalytic entry to α,α,α‐trisubstituted (α‐tertiary) primary amines by C?H functionalisation has long been recognised as a critical gap in the synthetic toolbox. We report a simple and scalable solution to this problem that does not require any in situ protection of the amino group and proceeds with 100 % atom‐economy. Our strategy, which uses an organic photocatalyst in combination with azide ion as a hydrogen atom transfer (HAT) catalyst, provides a direct synthesis of α‐tertiary amines, or their corresponding γ‐lactams. We anticipate that this methodology will inspire new retrosynthetic disconnections for substituted amine derivatives in organic synthesis, and particularly for challenging α‐tertiary primary amines. 相似文献
7.
Geun Seok Lee Joonghee Won Seulhui Choi Mu‐Hyun Baik Soon Hyeok Hong 《Angewandte Chemie (International ed. in English)》2020,59(39):16933-16942
The utilizations of omnipresent, thermodynamically stable amides and aliphatic C(sp3)?H bonds for various functionalizations are ongoing challenges in catalysis. In particular, the direct coupling between the two functional groups has not been realized. Here, we report the synergistic activation of the two challenging bonds, the amide C?N and unactivated aliphatic C(sp3)?H, via metallaphotoredox catalysis to directly acylate aliphatic C?H bonds utilizing amides as stable and readily accessible acyl surrogates. N‐acylsuccinimides served as efficient acyl reagents for the streamlined synthesis of synthetically useful ketones from simple C(sp3)?H substrates. Detailed mechanistic investigations using both computational and experimental mechanistic studies were performed to construct a detailed and complete catalytic cycle. The origin of the superior reactivity of the N‐acylsuccinimides over other more reactive acyl sources such as acyl chlorides was found to be an uncommon reaction pathway which commences with C?H activation prior to oxidative addition of the acyl substrate. 相似文献
8.
Parthasarathy Gandeepan Julian Koeller Korkit Korvorapun Jens Mohr Lutz Ackermann 《Angewandte Chemie (International ed. in English)》2019,58(29):9820-9825
Visible‐light‐induced ruthenium catalysis has enabled remote C?H alkylations with excellent levels of position control under exceedingly mild conditions at room temperature. The metallaphotocatalysis occurred under exogenous‐photosensitizer‐free conditions and features an ample substrate scope. The robust nature of the photo‐induced mild meta‐C?H functionalization is reflected by the broad functional group tolerance, and the reaction can be carried out in an operationally simple manner, setting the stage for challenging secondary and tertiary meta‐C?H alkylations by ruthenaphotoredox catalysis. 相似文献
9.
Dr. Yong‐Qiang Zhang Dr. Verena Jakoby Katharina Stainer Alexander Schmer Sven Klare Mirko Bauer Prof. Dr. Stefan Grimme Prof. Dr. Juan Manuel Cuerva Prof. Dr. Andreas Gansäuer 《Angewandte Chemie (International ed. in English)》2016,55(4):1523-1526
Two new catalytic systems for hydrogen‐atom transfer (HAT) catalysis involving the N?H bonds of titanocene(III) complexes with pendant amide ligands are reported. In a monometallic system, a bifunctional catalyst for radical generation and reduction through HAT catalysis depending on the coordination of the amide ligand is employed. The pendant amide ligand is used to activate Crabtree's catalyst to yield an efficient bimetallic system for radical generation and HAT catalysis. 相似文献
10.
Catalytic Asymmetric C
−H Functionalization under Photoredox Conditions by Radical Translocation and Stereocontrolled Alkene Addition 下载免费PDF全文
Chuanyong Wang Dr. Klaus Harms Prof. Dr. Eric Meggers 《Angewandte Chemie (International ed. in English)》2016,55(43):13495-13498
This work demonstrates how photoredox‐mediated C(sp3)?H activation through radical translocation can be combined with asymmetric catalysis. Upon irradiation with visible light, α,β‐unsaturated N‐acylpyrazoles react with N‐alkoxyphthalimides in the presence of a rhodium‐based chiral Lewis acid catalyst and the photosensitizer fac‐[Ir(ppy)3] to provide a C?C bond‐formation product with high enantioselectivity (up to 97 % ee) and, where applicable, with some diastereoselectivity (3.0:1 d.r.). Mechanistically, the synthetic strategy exploits a radical translocation (1,5‐hydrogen transfer) from an oxygen‐centered to a carbon‐centered radical with a subsequent stereocontrolled radical alkene addition. 相似文献
11.
Dr. Candice L. Joe Prof. Abigail G. Doyle 《Angewandte Chemie (International ed. in English)》2016,55(12):4040-4043
Using nickel and photoredox catalysis, the direct functionalization of C(sp3)?H bonds of N‐aryl amines by acyl electrophiles is described. The method affords a diverse range of α‐amino ketones at room temperature and is amenable to late‐stage coupling of complex and biologically relevant groups. C(sp3)?H activation occurs by photoredox‐mediated oxidation to generate α‐amino radicals which are intercepted by nickel in catalytic C(sp3)?C coupling. The merger of these two modes of catalysis leverages nickel's unique properties in alkyl cross‐coupling while avoiding limitations commonly associated with transition‐metal‐mediated C(sp3)?H activation, including requirements for chelating directing groups and high reaction temperatures. 相似文献
12.
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
13.
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
14.
Palladium‐Catalyzed Atom‐Transfer Radical Cyclization at Remote Unactivated C(sp3)−H Sites: Hydrogen‐Atom Transfer of Hybrid Vinyl Palladium Radical Intermediates 下载免费PDF全文
Maxim Ratushnyy Marvin Parasram Yang Wang Prof. Dr. Vladimir Gevorgyan 《Angewandte Chemie (International ed. in English)》2018,57(10):2712-2715
A novel mild, visible‐light‐induced palladium‐catalyzed hydrogen atom translocation/atom‐transfer radical cyclization (HAT/ATRC) cascade has been developed. This protocol involves a 1,5‐HAT process of previously unknown hybrid vinyl palladium radical intermediates, thus leading to iodomethyl carbo‐ and heterocyclic structures. 相似文献
15.
Benedikt S. Schreib Marlene Fadel Erick M. Carreira 《Angewandte Chemie (International ed. in English)》2020,59(20):7818-7822
Palladium‐catalyzed regio‐ and diastereoselective C?H functionalization with bromoalkynes and electronically unbiased olefins is reported. The picolinamide directing group enables the formation of putative 5 and 6‐exo‐metallacycles as intermediates to afford monoalkynylated products in up to 91 % yield in a stereospecific fashion. The systematic study reveals that substrates with a wide range of substituents on the olefin and bromoalkyne coupling partners are tolerated. Chemoselective transformations were demonstrated for the obtained amides, olefins, and alkynes. 相似文献
16.
Palladium(II)‐Catalyzed Enantioselective Arylation of Unbiased Methylene C(sp3)−H Bonds Enabled by a 2‐Pyridinylisopropyl Auxiliary and Chiral Phosphoric Acids 下载免费PDF全文
Sheng‐Yi Yan Ye‐Qiang Han Qi‐Jun Yao Xing‐Liang Nie Lei Liu Prof. Dr. Bing‐Feng Shi 《Angewandte Chemie (International ed. in English)》2018,57(29):9093-9097
Enantioselective functionalizations of unbiased methylene C(sp3)?H bonds of linear systems by metal insertion are intrinsically challenging and remain a largely unsolved problem. Herein, we report a palladium(II)‐catalyzed enantioselective arylation of unbiased methylene β‐C(sp3)?H bonds enabled by the combination of a strongly coordinating bidentate PIP auxiliary with a monodentate chiral phosphoric acid (CPA). The synergistic effect between the PIP auxiliary and the non‐C2‐symmetric CPA is crucial for effective stereocontrol. A broad range of aliphatic carboxylic acids and aryl bromides can be used, providing β‐arylated aliphatic carboxylic acid derivatives in high yields (up to 96 %) with good enantioselectivities (up to 95:5 e.r.). Notably, this reaction also represents the first palladium(II)‐catalyzed enantioselective C?H activation with less reactive and cost‐effective aryl bromides as the arylating reagents. Mechanistic studies suggest that a single CPA is involved in the stereodetermining C?H palladation step. 相似文献
17.
Xuesong Liu Linqian Yu Mupeng Luo Prof. Jidong Zhu Prof. Wanguo Wei 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(24):8745-8749
A direct C(sp2)?H alkynylation of aldehyde C(O)?H bonds with hypervalent iodine alkynylation reagents provides ynones under metal‐free conditions. In this method, 1‐[(triisopropylsilyl)ethynyl]‐1,2‐benziodoxol‐3(1H)‐one (TIPS‐EBX) constitutes an efficient alkynylation reagent for the introduction of the triple bond. The substrate scope is extended to a variety of (hetero)aromatic, aliphatic, and α,β‐unsaturated aldehydes. 相似文献
18.
Santhivardhana Reddy Yetra Torben Rogge Svenja Warratz Julia Struwe Wentao Peng Philipp Vana Lutz Ackermann 《Angewandte Chemie (International ed. in English)》2019,58(22):7490-7494
Chemoselective C?H arylations were accomplished through micellar catalysis by a versatile single‐component ruthenium catalyst. The strategy provided expedient access to C?H‐arylated ferrocenes with wide functional‐group tolerance and ample scope through weak chelation assistance. The sustainability of the C?H arylation was demonstrated by outstanding atom‐economy and recycling studies. Detailed computational studies provided support for a facile C?H activation through thioketone assistance. 相似文献
19.
Iron(II)‐Catalyzed Site‐Selective Functionalization of Unactivated C(sp3)−H Bonds Guided by Alkoxyl Radicals 下载免费PDF全文
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
20.
Selective Reductive Elimination at Alkyl Palladium(IV) by Dissociative Ligand Ionization: Catalytic C(sp3)−H Amination to Azetidines 下载免费PDF全文
Manuel Nappi Chuan He William G. Whitehurst Ben G. N. Chappell Prof. Dr. Matthew J. Gaunt 《Angewandte Chemie (International ed. in English)》2018,57(12):3178-3182
A palladium(II)‐catalyzed γ‐C?H amination of cyclic alkyl amines to deliver highly substituted azetidines is reported. The use of a benziodoxole tosylate oxidant in combination with AgOAc was found to be crucial for controlling a selective reductive elimination pathway to the azetidines. The process is tolerant of a range of functional groups, including structural features derived from chiral α‐amino alcohols, and leads to the diastereoselective formation of enantiopure azetidines. 相似文献