共查询到20条相似文献,搜索用时 15 毫秒
1.
Transition metal-catalyzed site- and stereoselective C−H activation of strained (hetero)cycloalkanes remains a formidable challenge. We herein report a carbamate-directed iridium-catalyzed asymmetric β−C(sp3)−H borylation of cyclopropanol derivatives. A variety of densely functionalized cyclopropanols were obtained in good enantioselectivities via desymmetrization and kinetic resolution. In addition, site-selective C(sp3)−H borylation of methine groups furnished α-borylated (hetero)cycloalkanols in moderate to good yields. The synthetic utility of the method was further shown in a gram-scale synthesis and diverse downstream transformations of borylated products. 相似文献
2.
Ling Dai Ying-Ying Chen Prof. Li-Jun Xiao Prof. Qi-Lin Zhou 《Angewandte Chemie (International ed. in English)》2023,62(24):e202304427
Chiral benzylic amines are privileged motifs in pharmacologically active molecules. Intramolecular enantioselective radical C(sp3)−H functionalization by hydrogen-atom transfer has emerged as a straightforward, powerful tool for the synthesis of chiral amines, but methods for intermolecular enantioselective C(sp3)−H amination remain elusive. Herein, we report a cationic copper catalytic system for intermolecular enantioselective benzylic C(sp3)−H amination with peroxide as an oxidant. This mild, straightforward method can be used to transform an array of feedstock alkylarenes and amides into chiral amines with high enantioselectivities, and it has good functional group tolerance and broad substrate scope. More importantly, it can be used to synthesize bioactive molecules, including chiral drugs. Preliminary mechanistic studies indicate that the amination reaction involves benzylic radicals generated by hydrogen-atom transfer. 相似文献
3.
Jie Li Prof. Dr. Shuanglin Qu Prof. Dr. Wanxiang Zhao 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(6):2380-2384
A rhodium-catalyzed remote C(sp3)−H borylation of silyl enol ethers (SEEs, E/Z mixtures) by alkene isomerization and hydroboration is reported. The reaction exhibits mild reaction conditions and excellent functional-group tolerance. This method is compatible with an array of SEEs, including linear and branched SEEs derived from aldehydes and ketones, and provides direct access to a broad range of structurally diverse 1,n-borylethers in excellent regioselectivities and good yields. These compounds are precursors to various valuable chemicals, such as 1,n-diols and aminoalcohols. 相似文献
4.
Dimitris I. Ioannou Prof. Dr. Luca Capaldo Jiri Sanramat Prof. Dr. Joost N. H. Reek Prof. Dr. Timothy Noël 《Angewandte Chemie (International ed. in English)》2023,62(52):e202315881
Electrophotocatalytic transformations are garnering attention in organic synthesis, particularly for accessing reactive intermediates under mild conditions. Moving these methodologies to continuous-flow systems, or flow ElectroPhotoCatalysis (f-EPC), showcases potential for scalable processes due to enhanced irradiation, increased electrode surface, and improved mixing of the reaction mixture. Traditional methods sequentially link photochemical and electrochemical reactions, using flow reactors connected in series, yet struggle to accommodate reactive transient species. In this study, we introduce a new flow reactor concept for electrophotocatalysis (EPC) that simultaneously utilizes photons and electrons. The reactor is designed with a transparent electrode and employs cost-effective materials. We used this technology to develop an efficient process for electrophotocatalytic heteroarylation of C(sp3)−H bonds. Importantly, the same setup can also facilitate purely electrochemical and photochemical transformations. This reactor represents a significant advancement in electrophotocatalysis, providing a framework for its application in flow for complex synthetic transformations. 相似文献
5.
Dr. María J. González Prof. Dr. Bernhard Breit 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(69):15746-15750
A new methodology to form C(sp3)−C(sp2) bonds by visible-light-driven intermolecular reductive ene–yne coupling has been successfully developed. The process relies on the ability of the Hantzsch ester to contribute in both SET and HAT processes through a unified cobalt and iridium catalytic system. This procedure avoids the use of stoichiometric amounts of reducing metallic reagents, which is translated into high functional-group tolerance and atom economy. 相似文献
6.
Site-Selective,Remote sp3 C−H Carboxylation Enabled by the Merger of Photoredox and Nickel Catalysis
Basudev Sahoo Peter Bellotti Francisco Juliá-Hernández Qing-Yuan Meng Dr. Stefano Crespi Prof. Dr. Burkhard König Prof. Ruben Martin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(38):9001-9005
A photoinduced carboxylation of alkyl halides with CO2 at remote sp3 C−H sites enabled by the merger of photoredox and Ni catalysis is described. This protocol features a predictable reactivity and site selectivity that can be modulated by the ligand backbone. Preliminary studies reinforce a rationale based on a dynamic displacement of the catalyst throughout the alkyl side chain. 相似文献
7.
Geun Seok Lee Joonghee Won Seulhui Choi Prof. Mu-Hyun Baik Prof. Soon Hyeok Hong 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(39):17081-17090
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.
Baptiste Neil Lamine Saadi Prof. Dr. Louis Fensterbank Dr. Clément Chauvier 《Angewandte Chemie (International ed. in English)》2023,62(31):e202306115
Benzylsilanes have found increasing applications in organic synthesis as bench-stable synthetic intermediates, yet are mostly produced by stoichiometric procedures. Catalytic alternatives based on the atom-economical silylation of benzylic C(sp3)−H bonds remain scarcely available as specialized directing groups and catalytic systems are needed to outcompete the kinetically-favored silylation of C(sp2)−H bonds. Herein, we describe the first general and catalytic-in-metal undirected silylation of benzylic C(sp3)−H bonds under ambient, transition metal-free conditions using stable tert-butyl-substituted silyldiazenes (tBu−N=N−SiR3) as silicon source. The high activity and selectivity of the catalytic system, exemplified by the preparation of various mono- or gem-bis benzyl(di)silanes, originates from the facile generation of organopotassium reagents, including tert-butylpotassium. 相似文献
9.
Jeremy Brals Dr. Thomas M. McGuire Prof. Dr. Allan J. B. Watson 《Angewandte Chemie (International ed. in English)》2023,62(42):e202310462
We report the development of a C(sp3)−C(sp2) coupling reaction using styrene boronic acids and redox-active esters under photoredox catalysis. The reaction proceeds through an unusual polarity-mismatched radical addition mechanism that is orthogonal to established processes. Synergistic activation of the radical precursor and organoboron are critical mechanistic events. Activation of an N-hydroxyphthalimide (NHPI) ester by coordination to boron enables electron transfer, with decomposition leading to a nucleofuge rebound, activating the organoboron to radical addition. The unique mechanism enables chemoselective coupling of styrene boronic acids in the presence of other alkene radical acceptors. The scope and limitations of the reaction, and a detailed mechanistic investigation are presented. 相似文献
10.
Gouranga Naskar Dr. Masilamani Jeganmohan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(39):e202200778
A palladium-catalyzed [3+2] annulation of substituted benzoic acids with maleimides leading to tricyclic heterocyclic molecules having a free carboxylic group in a high atom- and step-economical manner is described. The reaction proceeds via a dual C−H bond activation such as C(sp3)−H at the benzylic position and C(sp2)−H bond activation at the meta position of substituted aromatics. An external ligand (MPAA) is crucial for the success of present protocol. Further, the decarboxylation and esterification of the free carboxylic acid group of observed products were carried out. 相似文献
11.
Anton Kudashev Prof. Dr. Olivier Baudoin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(70):17688-17694
A ligand-controlled site-selective C(sp3)−H arylation of heteroaromatic ketones has been developed using Pd catalysis. The reaction occurred selectively at the α- or β-position of the ketone side-chain. The switch from α- to β-arylation was realized by addition of a pyridone ligand. The α-arylation process showed broad scope and high site- and chemoselectivity, whereas the β-arylation was more limited. Mechanistic investigations suggested that α-arylation occurs through C−H activation/oxidative addition/reductive elimination whereas β-arylation involves desaturation and aryl insertion. 相似文献
12.
Yimin Hu Wangyu Shi Bing Zheng Jianning Liao Wei Wang Yongjun Wu Prof. Dr. Hongchao Guo 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(45):19992-19996
Herein we describe the first organocatalytic asymmetric C(sp2)−H allylation of racemic trisubstituted allenoates with Morita–Baylis–Hillman (MBH) carbonates to access axially chiral tetrasubstituted allenoates. Various trisubstituted allenoates and MBH carbonates were well tolerated under mild reaction conditions, providing novel chiral tetrasubstituted allenoates with adjacent axial chirality and tertiary carbon stereocenters in high yields with good to excellent diastereoselectivities and enantioselectivities. 相似文献
13.
Daisuke Yamauchi Dr. Takahiro Nishimura Prof. Dr. Hideki Yorimitsu 《Angewandte Chemie (International ed. in English)》2017,56(25):7200-7204
Direct alkylation of a methyl group, on di- and trisubstituted ureas, with terminal alkenes by C(sp3)−H bond activation proceeded in the presence of a hydroxoiridium/bisphosphine catalyst to give high yields of the corresponding addition products. The hydroxoiridium/bisphosphine complex generates an amidoiridium intermediate by reaction with ureas having an N−H bond. 相似文献
14.
Dr. Jian Wen Dr. Ben Dong Jinjun Zhu Dr. Yue Zhao Prof. Dr. Zhuangzhi Shi 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(27):11001-11004
The first aromatic C−H silylation between arylphosphines and hydrosilanes enabled by a ruthenium complex has been developed. The excellent ortho-selectivity results from a four-membered metallacyclic intermediate involving phosphorus chelation. The developed system can be extended to the benzylic C−H silylation of arylphosphines. Diverse silylated arylphosphines are produced, exhibiting broad functional group compatibility. Further functionalization of the products under mild conditions renders the formed compounds useful building blocks. 相似文献
15.
David Dailler Ronan Rocaboy Prof. Dr. Olivier Baudoin 《Angewandte Chemie (International ed. in English)》2017,56(25):7218-7222
A general and user-friendly synthesis of β-lactams is reported that makes use of Pd0-catalyzed carbamoylation of C(sp3)−H bonds, and operates under stoichiometric carbon monoxide in a two-chamber reactor. This reaction is compatible with a range of primary, secondary and activated tertiary C−H bonds, in contrast to previous methods based on C(sp3)−H activation. In addition, the feasibility of an enantioselective version using a chiral phosphonite ligand is demonstrated. Finally, this method can be employed to synthesize valuable enantiopure free β-lactams and β-amino acids. 相似文献
16.
Xiang Yin Giuseppe Zuccarello Cristina García-Morales Prof. Dr. Antonio M. Echavarren 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(40):9485-9490
A novel synthesis of indanes and dihydronaphtalenes based on the intramolecular insertion into C(sp3)−H bonds of gold(I) carbenes generated by retro-Buchner reaction (decarbenation) has been developed. Deuterium-labeling and kinetic isotope effect experiments, DFT calculations, and generation of the proposed carbene intermediate from a well-characterized gold(I) carbenoid support the involvement of a three-center concerted mechanism for the C(sp3)−H functionalization process. 相似文献
17.
Dr. Hai-Xu Wang Yann Richard Dr. Qingyun Wan Prof. Dr. Cong-Ying Zhou Prof. Dr. Chi-Ming Che 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(5):1861-1866
Described herein is an IrIII/porphyrin-catalyzed intermolecular C(sp3)−H insertion reaction of a quinoid carbene (QC). The reaction was designed by harnessing the hydrogen-atom transfer (HAT) reactivity of a metal-QC species with aliphatic substrates followed by a radical rebound process to afford C−H arylation products. This methodology is efficient for the arylation of activated hydrocarbons such as 1,4-cyclohexadienes (down to 40 min reaction time, up to 99 % yield, up to 1.0 g scale). It features unique regioselectivity, which is mainly governed by steric effects, as the insertion into primary C−H bonds is favored over secondary and/or tertiary C−H bonds in the substituted cyclohexene substrates. Mechanistic studies revealed a radical mechanism for the reaction. 相似文献
18.
Maximilian Stangier Alexej Scheremetjew Prof. Dr. Lutz Ackermann 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(60):e202201654
Electrochemical fluorinations of C(sp3)−H bonds with a nucleophilic fluoride source have been accomplished in a chemo- and site-selective fashion, avoiding the use of electrophilic F+ sources and stoichiometric oxidants. The introduced metal-free strategy exhibits high functional group tolerance, setting the stage for late-stage fluorinations of biorelevant motifs. The synthetic utility of the C(sp3)−H fluorination was reflected by subsequent one-pot arylation of the generated benzylic fluorides. 相似文献
19.
Dr. Matteo Virelli Wei Wang Dr. Rositha Kuniyil Jun Wu Prof. Dr. Giuseppe Zanoni Dr. Antonio Fernandez Jamie Scott Dr. Marc Vendrell Prof. Dr. Lutz Ackermann 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(55):12712-12718
Arylated cyclobutanes were accessed by a versatile palladium-catalyzed secondary C(sp3)−H activation, exploiting chelation assistance by modular triazoles. The C−H arylation led to cyclobutane natural product derivatives in a highly regioselective fashion, setting the stage for the easy access to novel fluorogenic boron-dipyrrin (BODIPY)-labeled probes for live-cell imaging. 相似文献
20.
Yadong Pang Prof. Dr. Tatsuo Ishiyama Prof. Dr. Koji Kubota Prof. Dr. Hajime Ito 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(18):4654-4659
Mechanochemistry has been applied for the first time to an iridium(I)-catalyzed C−H borylation reaction. By using either none or just a catalytic amount of a liquid, the mechanochemical C−H borylation of a series of heteroaromatic compounds proceeded in air to afford the corresponding arylboronates in good-to-excellent yields. A one-pot mechanochemical C−H borylation/Suzuki–Miyaura cross-coupling sequence for the direct synthesis of 2-aryl indole derivatives is also described. The present study constitutes an important milestone towards the development of industrially attractive solvent-free C−H bond functionalization processes in air. 相似文献