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1.
α‐Aminoxy‐Acid‐Auxiliary‐Enabled Intermolecular Radical γ‐C(sp3)−H Functionalization of Ketones 下载免费PDF全文
Dr. Heng Jiang Prof. Dr. Armido Studer 《Angewandte Chemie (International ed. in English)》2018,57(6):1692-1696
A method for site‐specific intermolecular γ‐C(sp3)?H functionalization of ketones has been developed using an α‐aminoxy acid auxiliary applying photoredox catalysis. Regioselective activation of an inert C?H bond is achieved by 1,5‐hydrogen atom abstraction by an oxidatively generated iminyl radical. Tertiary and secondary C‐radicals thus formed at the γ‐position of the imine functionality undergo radical conjugate addition to various Michael acceptors to provide, after reduction and imine hydrolysis, the corresponding γ‐functionalized ketones. 相似文献
2.
A Highly Efficient Gold‐Catalyzed Photoredox α‐C(sp3)H Alkynylation of Tertiary Aliphatic Amines with Sunlight 下载免费PDF全文
Dr. Jin Xie Dr. Shuai Shi M. Sc. Tuo Zhang M. Sc. Nina Mehrkens Dr. Matthias Rudolph Prof. Dr. A. Stephen K. Hashmi 《Angewandte Chemie (International ed. in English)》2015,54(20):6046-6050
A new α‐C(sp3)? H alkynylation of unactivated tertiary aliphatic amines with 1‐iodoalkynes as radical alkynylating reagents in the presence of [Au2(μ‐dppm)2]2+ in sunlight provides propargylic amines. Based on mechanistic studies, a C? C coupling of an α‐aminoalkyl radical and an alkynyl radical is proposed for the C(sp3)? C(sp) bond formation. The mild, convenient, efficient, and highly selective C(sp3)? H alkynylation reaction shows excellent regioselectivity and good functional‐group compatibility. A scale‐up to gram quantities is possible with sunlight used as a clean and sustainable energy source. 相似文献
3.
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
4.
Silver‐Mediated Intermolecular 1,2‐Alkylarylation of Styrenes with α‐Carbonyl Alkyl Bromides and Indoles 下载免费PDF全文
Xuan‐Hui Ouyang Dr. Ren‐Jie Song Ming Hu Yuan Yang Prof. Dr. Jin‐Heng Li 《Angewandte Chemie (International ed. in English)》2016,55(9):3187-3191
A new iron‐facilitated silver‐mediated radical 1,2‐alkylarylation of styrenes with α‐carbonyl alkyl bromides and indoles is described, and two new C?C bonds were generated in a single step through a sequence of intermolecular C(sp3)?Br functionalization and C(sp2)?H functionalization across the alkenes. This method provides an efficient access to alkylated indoles with broad substrate scope and excellent selectivity. 相似文献
5.
Shuo Wu Xinxin Wu Dongping Wang Chen Zhu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(5):1513-1517
Regioselective incorporation of a particular functional group into aliphatic sites by direct activation of unreactive C?H bonds is of great synthetic value. Despite advances in radical‐mediated functionalization of C(sp3)?H bonds by a hydrogen‐atom transfer process, the site‐selective vinylation of remote C(sp3)?H bonds still remains underexplored. Reported herein is a new protocol for the regioselective vinylation of unactivated C(sp3)?H bonds. The remote C(sp3)?H activation is promoted by a C‐centered radical instead of the commonly used N and O radicals. The reaction possesses high product diversity and synthetic efficiency, furnishing a plethora of synthetically valuable E alkenes bearing tri‐/di‐/mono‐fluoromethyl and perfluoroalkyl groups. 相似文献
6.
Radical Cation Salt‐initiated Aerobic C−H Phosphorylation of N‐Benzylanilines: Synthesis of α‐Aminophosphonates 下载免费PDF全文
Prof. Xiaodong Jia Xiaofei Liu Prof. Yu Yuan Pengfei Li Wentao Hou Kaixuan He 《化学:亚洲杂志》2018,13(15):1911-1914
A radical cation salt‐initiated phosphorylation of N‐benzylanilines was realized through an aerobic oxidation of the sp3 C?H bond, providing a series of α‐aminophosphonates in high yields. An investigation of the reaction scope revealed that this mild catalyst system is superior in good functional group tolerance and high reaction efficiency. The mechanistic study implied that the cleavage of the sp3 C?H bond was involved in the rate‐determining step. 相似文献
7.
Copper‐Catalyzed Radical/Radical CH/PH Cross‐Coupling: α‐Phosphorylation of Aryl Ketone O‐Acetyloximes 下载免费PDF全文
Jie Ke Yuliang Tang Hong Yi Yali Li Yongde Cheng Chao Liu Prof. Aiwen Lei 《Angewandte Chemie (International ed. in English)》2015,54(22):6604-6607
The selective radical/radical cross‐coupling of two different organic radicals is a great challenge due to the inherent activity of radicals. In this paper, a copper‐catalyzed radical/radical C? H/P? H cross‐coupling has been developed. It provides a radical/radical cross‐coupling in a selective manner. This work offers a simple way toward β‐ketophosphonates by oxidative coupling of aryl ketone o‐acetyloximes with phosphine oxides using CuCl as catalyst and PCy3 as ligand in dioxane under N2 atmosphere at 130 °C for 5 h, and yields ranging from 47 % to 86 %. The preliminary mechanistic studies by electron paramagnetic resonance (EPR) showed that, 1) the reduction of ketone o‐acetyloximes generates iminium radicals, which could isomerize to α‐sp3‐carbon radical species; 2) phosphorus radicals were generated from the oxidation of phosphine oxides. Various aryl ketone o‐acetyloximes and phosphine oxides were suitable for this transformation. 相似文献
8.
Xiao‐Long Su Liu Ye Ji‐Jun Chen Xiao‐Dong Liu Sheng‐Peng Jiang Fu‐Li Wang Lin Liu Chang‐Jiang Yang Xiao‐Yong Chang Zhong‐Liang Li Qiang‐Shuai Gu Xin‐Yuan Liu 《Angewandte Chemie (International ed. in English)》2021,60(1):380-384
The development of enantioconvergent cross‐coupling of racemic alkyl halides directly with heteroarene C(sp2)?H bonds has been impeded by the use of a base at elevated temperature that leads to racemization. We herein report a copper(I)/cinchona‐alkaloid‐derived N,N,P‐ligand catalytic system that enables oxidative addition with racemic alkyl bromides under mild conditions. Thus, coupling with azole C(sp2)?H bonds has been achieved in high enantioselectivity, affording a number of potentially useful α‐chiral alkylated azoles, such as 1,3,4‐oxadiazoles, oxazoles, and benzo[d]oxazoles as well as 1,3,4‐triazoles, for drug discovery. Mechanistic experiments indicated facile deprotonation of an azole C(sp2)?H bond and the involvement of alkyl radical species under the reaction conditions. 相似文献
9.
Dual C(sp3)−H Bond Functionalization of N‐Heterocycles through Sequential Visible‐Light Photocatalyzed Dehydrogenation/[2+2] Cycloaddition Reactions 下载免费PDF全文
Dr. Guo‐Qiang Xu Ji‐Tao Xu Zhi‐Tao Feng Hui Liang Prof. Dr. Zhu‐Yin Wang Prof. Dr. Yong Qin Prof. Dr. Peng‐Fei Xu 《Angewandte Chemie (International ed. in English)》2018,57(18):5110-5114
Herein we describe a mild method for the dual C(sp3)?H bond functionalization of saturated nitrogen‐containing heterocycles through a sequential visible‐light photocatalyzed dehydrogenation/[2+2] cycloaddition procedure. As a complementary approach to the well‐established use of iminium ion and α‐amino radical intermediates, the elusive cyclic enamine intermediates were effectively generated by photoredox catalysis under mild conditions and efficiently captured by acetylene esters to form a wide array of bicyclic amino acid derivatives, thus enabling the simultaneous functionalization of two vicinal C(sp3)?H bonds. 相似文献
10.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(7):1899-1902
The palladium(II)‐catalyzed β‐ and γ‐alkynylation of amide C(sp3)−H bonds is enabled by pyridine‐based ligands. This alkynylation reaction is compatible with substrates containing α‐tertiary or α‐quaternary carbon centers. The β‐methylene C(sp3)−H bonds of various carbocyclic rings were also successfully alkynylated. 相似文献
11.
Guillaume Ernouf Egor Chirkin Lydia Rhyman Ponnadurai Ramasami Jean‐Christophe Cintrat 《Angewandte Chemie (International ed. in English)》2020,59(7):2618-2622
A new photoredox‐catalyzed decarboxylative radical addition approach to functionalized cyclobutanes is described. The reaction involves an unprecedented formal Giese‐type addition of C(sp3)‐centered radicals to highly strained bicyclo[1.1.0]butanes. The mild photoredox conditions, which make use of a readily available and bench stable phenyl sulfonyl bicyclo[1.1.0]butane, proved to be amenable to a diverse range of α‐amino and α‐oxy carboxylic acids, providing a concise route to 1,3‐disubstituted cyclobutanes. Furthermore, kinetic studies and DFT calculations unveiled mechanistic details on bicyclo[1.1.0]butane reactivity relative to the corresponding olefin system. 相似文献
12.
Melanie A. Short J. Miles Blackburn Prof. Dr. Jennifer L. Roizen 《Angewandte Chemie (International ed. in English)》2018,57(1):296-299
Masked alcohols are particularly appealing as directing groups because of the ubiquity of hydroxy groups in organic small molecules. Herein, we disclose a general strategy for aliphatic γ‐C(sp3)?H functionalization guided by a masked alcohol. Specifically, we determine that sulfamate ester derived nitrogen‐centered radicals mediate 1,6‐hydrogen‐atom transfer (HAT) processes to guide γ‐C(sp3)?H chlorination. This reaction proceeds through a light‐initiated radical chain‐propagation process and is capable of installing chlorine atoms at primary, secondary, and tertiary centers. 相似文献
13.
Generation of Alkoxyl Radicals by Photoredox Catalysis Enables Selective C(sp3)−H Functionalization under Mild Reaction Conditions 下载免费PDF全文
Jing Zhang Yang Li Fuyuan Zhang Chenchen Hu Prof. Dr. Yiyun Chen 《Angewandte Chemie (International ed. in English)》2016,55(5):1872-1875
Reported herein is the first visible‐light‐induced formation of alkoxyl radicals from N‐alkoxyphthalimides, and the Hantzsch ester as the reductant is crucial for the reaction. The selective hydrogen atom abstraction by the alkoxyl radical enables C(sp3)?H allylation and alkenylation reactions under mild reaction conditions at room temperature. Broad substrate variations, including a structurally complexed steroid, undergo the C(sp3)?H functionalization reaction effectively with high regio‐ and chemoselectivity. 相似文献
14.
2,4‐Dinitrophenol‐Catalyzed α‐C(sp3)−H and C(sp)−H Bond Functionalization of Cyclic Amines and Alkynes: Highly Regio‐/Diastereoselective Synthesis of α‐Alkynyl‐3‐Amino‐2‐Oxindoles 下载免费PDF全文
Dr. Mukesh Kumar Banni P. Kaur Prof. Swapandeep S Chimni 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(29):9948-9952
A transition‐metal‐ and oxidant‐free DNP (2,4‐dinitrophenol)‐catalyzed atom‐economical regio‐ and diastereoselective synthesis of monofunctionalized α‐alkynyl‐3‐amino‐2‐oxindole derivatives by C?H bond functionalization of cyclic amines and alkynes with indoline‐2,3‐diones has been developed. This cascade event sequentially involves the reductive amination of indoline‐2,3‐dione by imine formation and cross coupling between C(sp3)?H and C(sp)?H of the cyclic amines and alkynes. This reaction offers an efficient and attractive pathway to different types of α‐alkynyl‐3‐amino‐2‐oxindole derivatives in good yields with a wide tolerance of functional groups. The salient feature of this methodology is that it completely suppresses the homocoupling of alkynes. To the best of our knowledge, this is the first example of a DNP‐catalyzed metal‐free direct C(sp3)?H and C(sp)?H bond functionalization providing biologically active α‐alkynyl‐3‐amino‐2‐oxindole scaffolds. 相似文献
15.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(6):1528-1531
Herein we report acid‐directed β‐C(sp3)‐H arylation of α‐amino acids enabled by pyridine‐type ligands. This reaction does not require the installation of an exogenous directing group, is scalable, and enables the preparation of Fmoc‐protected unnatural amino acids in three steps. The pyridine‐type ligands are crucial for the development of this new C(sp3)‐H arylation. 相似文献
16.
Hong Yi Wenbin Mao Martin Oestreich 《Angewandte Chemie (International ed. in English)》2019,58(11):3575-3578
An enantioselective C(sp3)?C(sp3) cross‐coupling of racemic α‐silylated alkyl iodides and alkylzinc reagents is reported. The reaction is catalyzed by NiCl2/(S,S)‐Bn‐Pybox and yields α‐chiral silanes with high enantiocontrol. The catalyst system does not promote the cross‐coupling of the corresponding carbon analogue, corroborating the stabilizing effect of the silyl group on the alkyl radical intermediate (α‐silicon effect). Both coupling partners can be, but do not need to be, functionalized, and hence, even α‐chiral silanes with no functional group in direct proximity of the asymmetrically substituted carbon atom become accessible. This distinguishes the new method from established approaches for the synthesis of α‐chiral silanes. 相似文献
17.
《Angewandte Chemie (International ed. in English)》2017,56(38):11649-11652
A decarboxylative silylation of aliphatic N ‐hydroxyphthalimide (NHPI) esters using Si−B reagents as silicon pronucleophiles is reported. This C(sp3)−Si cross‐coupling is catalyzed by copper(I) and follows a radical mechanism, even with exclusion of light. Both primary and secondary alkyl groups couple effectively, whereas tertiary alkyl groups are probably too sterically hindered. The functional‐group tolerance is generally excellent, and α‐heteroatom‐substituted substrates also participate well. This enables, for example, the synthesis of α‐silylated amines starting from NHPI esters derived from α‐amino acids. The new method extends the still limited number of C(sp3)−Si cross‐couplings of unactivated alkyl electrophiles. 相似文献
18.
Hojoon Park Yang Li Jin‐Quan Yu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(33):11546-11550
PdII‐catalyzed C(sp3)?H olefination of weakly coordinating native amides is reported. Three major drawbacks of previous C(sp3)?H olefination protocols, 1) in situ cyclization of products, 2) incompatibility with α‐H‐containing substrates, and 3) installation of exogenous directing groups, are addressed by harnessing the carbonyl coordination ability of amides to direct C(sp3)?H activation. The method enables direct C(sp3)?H functionalization of a wide range of native amide substrates, including secondary, tertiary, and cyclic amides, for the first time. The utility of this process is demonstrated by diverse transformations of the olefination products. 相似文献
19.
《化学:亚洲杂志》2017,12(9):978-981
Although numerous reports exist on strained C−C bond cleavage reactions in aryl substitutions, the cleavage methodology for unstrained C−C bonds in alkylation reactions has not yet been established. We found that unstrained allylic C−C bonds can be cleaved using α‐radicals to form C(sp3)−C(sp3) bonds in the presence of a copper catalyst. In this reaction, the property of leaving and loading radicals is very important for radical fragmentations. In this paper, we investigated the effects of these properties in cleavage reactions for unstrained C−C bonds. 相似文献
20.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(7):1907-1910
A redox‐neutral, light‐mediated functionalization of unactivated C(sp3)−H bonds via iminyl radicals is presented here. A 1,5‐H transfer followed by the functionalization of a C(sp2)−H bond takes place in aqueous media producing a variety of elaborated fused ketones. Mechanistic investigations have revealed 1,5‐H transfer as the reversible, rate‐determining step in this transformation. Divergent scaffolds are also accessible via C(sp3)−N bond formation upon a careful choice of the reaction additives. 相似文献