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1.
Tobias Gylling Frihed Christian Marcus Pedersen Mikael Bols 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(50):14109-14113
The synthesis of all eight rare, but biologically important L ‐hexoses as the according thioglycosyl donors was achieved through a procedure involving the C H activation of their corresponding 6‐deoxy‐L ‐hexoses. The key steps of the procedure were the silylation of the OH group at C4 followed by an intramolecular C H activation of the methyl group in γ‐position; both steps were catalyzed by iridium. The following Fleming–Tamao oxidation and acetylation gave the suitably protected L ‐hexoses. This is the first general method for the preparation of all eight L ‐hexoses as their thioglycosyl donors ready for glycosylation and the first example of an iridium‐catalyzed C(sp3) H activation on sulfide‐containing compounds. 相似文献
2.
A novel route with L ‐ascorbic acid as a single common starting material to asymmetric synthesis of all eight diastereomers of L ‐hexoses is described. Assessment of this new approach is demonstrated by the expedient synthesis of L ‐galactopyranose and L ‐talopyranose derivatives. Key steps involve stereoselective preparation of chiral (E)‐ and (Z)‐γ‐hydroxy‐α,β‐unsaturated esters and their stereo‐controlled dihydroxylation by OsO4. 相似文献
3.
Iridium‐Catalyzed Synthesis of Diaryl Ethers by Means of Chemoselective CF Bond Activation and the Formation of BF Bonds
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Jianping Chen Keyan Zhao Bingyang Ge Chongying Xu Dr. Dawei Wang Prof. Yuqiang Ding 《化学:亚洲杂志》2015,10(2):468-473
Transition‐metal‐catalyzed C? F activation, in comparison with C? H activation, is more difficult to achieve and therefore less fully understood, mainly because carbon–fluorine bonds are the strongest known single bonds to carbon and have been very difficult to cleave. Transition‐metal complexes are often more effective at cleaving stronger bonds, such as C(sp2)? X versus C(sp3)? X. Here, the iridium‐catalyzed C? F activation of fluorarenes was achieved through the use of bis(pinacolato)diboron with the formation of the B? F bond and self‐coupling. This strategy provides a convenient method with which to convert fluoride aromatic compounds into symmetrical diaryl ether compounds. Moreover, the chemoselective products of the C? F bond cleavage were obtained at high yields with the C? Br and C? Cl bonds remaining. 相似文献
4.
Carboxylate‐Assisted Iridium‐Catalyzed C−H Amination of Arenes with Biologically Relevant Alkyl Azides
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Tao Zhang Xuejiao Hu Zhen Wang Tiantian Yang Hao Sun Prof. Guigen Li Prof. Hongjian Lu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(9):2920-2924
An iridium‐catalyzed C?H amination of arenes with a wide substrate scope is reported. Benzamides with electron‐donating and ‐withdrawing groups and linear, branched, and cyclic alkyl azides are all applicable. Cesium carboxylate is crucial for both reactivity and regioselectivity of the reactions. Many biologically relevant molecules, such as amino acid, peptide, steroid, sugar, and thymidine derivatives can be introduced to arenes with high yields and 100 % chiral retention. 相似文献
5.
Iridium‐Catalyzed Intermolecular Dehydrogenative Silylation of Polycyclic Aromatic Compounds without Directing Groups
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Dr. Masahito Murai Keishi Takami Prof. Dr. Kazuhiko Takai 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(12):4566-4570
This study describes the iridium‐catalyzed intermolecular dehydrogenative silylation of C(sp2)?H bonds of polycyclic aromatic compounds without directing groups. The reaction produced various arylsilanes through both Si?H and C?H bond activation, with hydrogen as the sole byproduct. Reactivity was affected by the electronic nature of the aromatic compounds, and silylation of electron‐deficient and polycyclic aromatic compounds proceeded efficiently. Site‐selectivity was controlled predominantly by steric factors. Therefore, the current functionalization proceeded with opposite chemo‐ and site‐selectivity compared to that observed for general electrophilic functionalization of aromatic compounds. 相似文献
6.
Total Synthesis of Cryptocaryol A by Enantioselective Iridium‐Catalyzed Alcohol C−H Allylation
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Dr. Felix Perez Andrew R. Waldeck Prof. Michael J. Krische 《Angewandte Chemie (International ed. in English)》2016,55(16):5049-5052
The polyketide natural product cryptocaryol A is prepared in 8 steps via iridium catalyzed enantioselective diol double C?H allylation, which directly generates an acetate‐based triketide stereodiad. In 4 previously reported total syntheses, 17–28 steps were required. 相似文献
7.
Etienne Brachet Prof. Jean‐Daniel Brion Dr. Mouad Alami Dr. Samir Messaoudi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(45):15276-15280
Unprotected thioglycosides were effective nucleophiles for Ni0‐catalyzed C? S bond‐forming reaction with functionalized (hetero)aryl, alkenyl, and alkynyl halides. The functional‐group tolerance on the electrophilic partner was typically high and the anomeric selectivities of the thioglycosides were high in all cases. The efficiency of this general procedure was well‐demonstrated by the synthesis of 4‐methyl‐7‐thioumbelliferyl‐β‐D ‐cellobioside (MUS‐CB). 相似文献
8.
Jian Wen Dingyi Wang Jiasheng Qian Di Wang Chendan Zhu Yue Zhao Zhuangzhi Shi 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(7):2100-2104
Transition‐metal‐mediated metalation of an aromatic C?H bond that is adjacent to a tertiary phosphine group in arylphosphines via a four‐membered chelate ring was first discovered in 1968. Herein, we overcome a long‐standing problem with the ortho‐C?H activation of arylphosphines in a catalytic fashion. In particular, we developed a rhodium‐catalyzed ortho‐selective C?H borylation of various commercially available arylphosphines with B2pin2 through PIII‐chelation‐assisted C?H activation. This discovery is suggestive of a generic platform that could enable the late‐stage modification of readily accessible arylphosphines. 相似文献
9.
Mechanochemical Iridium(III)‐Catalyzed C−H Bond Amidation of Benzamides with Sulfonyl Azides under Solvent‐Free Conditions in a Ball Mill
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Gary N. Hermann Peter Becker Prof. Dr. Carsten Bolm 《Angewandte Chemie (International ed. in English)》2016,55(11):3781-3784
Mechanochemical conditions have been applied to an iridium(III)‐catalyzed C?H bond amidation process for the first time. In the absence of solvent, the mechanochemical activation enables the formation of an iridium species that catalyzes the ortho‐selective amidation of benzamides with sulfonyl azides as the nitrogen source. As the reaction proceeds in the absence of organic solvents without external heating and yields the desired products in excellent yields within short reaction times, this method constitutes a powerful, fast, and environmentally benign alternative to the common solvent‐based standard approaches. 相似文献
10.
Iridium‐Catalyzed Sequential Silylation and Borylation of Heteroarenes Based on Regioselective C−H Bond Activation
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Dr. Masahito Murai Naoki Nishinaka Prof. Dr. Kazuhiko Takai 《Angewandte Chemie (International ed. in English)》2018,57(20):5843-5847
An iridium‐catalyzed regioselective sequential silylation and borylation of heteroarenes was developed, which represents a rare example of unsymmetrical intermolecular C?H bond difunctionalization through the introduction of two different functionalities during a one‐pot transformation. Although the substrate scope for the dehydrogenative silylation of heteroarenes has been limited mainly to electron‐rich five‐membered rings, the current reaction proceeds with both electron‐rich and electron‐deficient heteroarenes with the aid of heteroatom‐directing C?H bond activation. The regioselectivity of the second borylation was controlled by both steric factors and the electronic effect of the silyl group installed in the first step. In combination with the classic cross‐coupling reaction, this method provides rapid access to multisubstituted heteroarenes. 相似文献
11.
Jian He Heng Jiang Ryosuke Takise Ru‐Yi Zhu Dr. Gang Chen Prof. Dr. Hui‐Xiong Dai Dr. T. G. Murali Dhar Dr. Jun Shi Dr. Hao Zhang Dr. Peter T. W. Cheng Prof. Dr. Jin‐Quan Yu 《Angewandte Chemie (International ed. in English)》2016,55(2):785-789
A quinoline‐based ligand effectively promotes the palladium‐catalyzed borylation of C(sp3)? H bonds. Primary β‐C(sp3)? H bonds in carboxylic acid derivatives as well as secondary C(sp3)? H bonds in a variety of carbocyclic rings, including cyclopropanes, cyclobutanes, cyclopentanes, cyclohexanes, and cycloheptanes, can thus be borylated. This directed borylation method complements existing iridium(I)‐ and rhodium(I)‐catalyzed C? H borylation reactions in terms of scope and operational conditions. 相似文献
12.
Manganese(I)‐Catalyzed C−H Activation: The Key Role of a 7‐Membered Manganacycle in H‐Transfer and Reductive Elimination
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Dr. Nasiru P. Yahaya Kate M. Appleby Magdalene Teh Conrad Wagner Erik Troschke Joshua T. W. Bray Prof. Simon B. Duckett L. Anders Hammarback Dr. Jonathan S. Ward Jessica Milani Dr. Natalie E. Pridmore Dr. Adrian C. Whitwood Dr. Jason M. Lynam Prof. Ian J. S. Fairlamb 《Angewandte Chemie (International ed. in English)》2016,55(40):12455-12459
Manganese‐catalyzed C?H bond activation chemistry is emerging as a powerful and complementary method for molecular functionalization. A highly reactive seven‐membered MnI intermediate is detected and characterized that is effective for H‐transfer or reductive elimination to deliver alkenylated or pyridinium products, respectively. The two pathways are determined at MnI by judicious choice of an electron‐deficient 2‐pyrone substrate containing a 2‐pyridyl directing group, which undergoes regioselective C?H bond activation, serving as a valuable system for probing the mechanistic features of Mn C?H bond activation chemistry. 相似文献
13.
Shao‐Tao Bai Charles B. Bheeter Joost N. H. Reek 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(37):13173-13177
Reported is an iridium catalyst for ortho‐selective C?H borylation of challenging secondary aromatic amide substrates, and the regioselectivity is controlled by hydrogen‐bond interactions. The BAIPy ‐Ir catalyst forms three hydrogen bonds with the substrate during the crucial activation step, and allows ortho‐C?H borylation with high selectivity. The catalyst displays unprecedented ortho selectivities for a wide variety of substrates that differ in electronic and steric properties, and the catalyst tolerates various functional groups. The regioselective C?H borylation catalyst is readily accessible and converts substrates on gram scale with high selectivity and conversion. 相似文献
14.
Iridium(I)‐Catalyzed Regioselective CH Activation and Hydrogen‐Isotope Exchange of Non‐aromatic Unsaturated Functionality
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Prof. Dr. William J. Kerr Richard J. Mudd Dr. Laura C. Paterson Dr. Jack A. Brown 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(45):14604-14607
Isotopic labelling is a key technology of increasing importance for the investigation of new C?H activation and functionalization techniques, as well as in the construction of labelled molecules for use within both organic synthesis and drug discovery. Herein, we report for the first time selective iridium‐catalyzed C?H activation and hydrogen‐isotope exchange at the β‐position of unsaturated organic compounds. The use of our highly active [Ir(cod)(IMes)(PPh3)][PF6] (cod=1,5‐cyclooctadiene) catalyst, under mild reaction conditions, allows the regioselective β‐activation and labelling of a range of α,β‐unsaturated compounds with differing steric and electronic properties. This new process delivers high levels of isotope incorporation over short reaction times by using low levels of catalyst loading. 相似文献
15.
Stereodivergent Synthesis of Arylcyclopropylamines by Sequential CH Borylation and Suzuki–Miyaura Coupling
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Shin Miyamura Misaho Araki Prof. Dr. Takayoshi Suzuki Prof. Dr. Junichiro Yamaguchi Prof. Dr. Kenichiro Itami 《Angewandte Chemie (International ed. in English)》2015,54(3):846-851
A step‐economical and stereodivergent synthesis of privileged 2‐arylcyclopropylamines (ACPAs) through a C(sp3)? H borylation and Suzuki–Miyaura coupling sequence has been developed. The iridium‐catalyzed C? H borylation of N‐cyclopropylpivalamide proceeds with cis selectivity. The subsequent B‐cyclopropyl Suzuki–Miyaura coupling catalyzed by [PdCl2(dppf)]/Ag2O proceeds with retention of configuration at the carbon center bearing the Bpin group, while epimerization at the nitrogen‐bound carbon atoms of both the starting materials and products is observed under the reaction conditions. This epimerization is, however, suppressed in the presence of O2. The present new ACPA synthesis results in not only a significant reduction in the steps required for making ACPA derivatives, but also the ability to access either isomer (cis or trans) by simply changing the atmosphere (N2 or O2) in the coupling stage. 相似文献
16.
A facile and convenient synthesis of the chiral phthalide framework catalyzed by cationic iridium was developed. The method utilized cationic iridium/bisphosphine‐catalyzed asymmetric intramolecular carbonyl hydroacylation of 2‐keto benzaldehydes to furnish the corresponding optically active phthalide products in good to excellent enantioselectivities (up to 98% ee). The mechanistic studies using a deuterium‐labelled substrate suggested that the reaction involved an intramolecular carbonyl insertion mechanism to iridium hydride intermediate. In addition, we investigated the kinetic isotope effect (KIE) of intramolecular hydroacylation with deuterated substrate and determined that the C?H activation step is not included in the turnover‐limiting step. 相似文献
17.
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
18.
Site‐Selective δ‐C(sp3)−H Alkylation of Amino Acids and Peptides with Maleimides via a Six‐Membered Palladacycle
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Bei‐Bei Zhan Ya Li Jing‐Wen Xu Xing‐Liang Nie Dr. Jun Fan Liang Jin Prof. Dr. Bing‐Feng Shi 《Angewandte Chemie (International ed. in English)》2018,57(20):5858-5862
The site‐selective functionalization of unactivated C(sp3)?H bonds remains one of the greatest challenges in organic synthesis. Herein, we report on the site‐selective δ‐C(sp3)?H alkylation of amino acids and peptides with maleimides via a kinetically less favored six‐membered palladacycle in the presence of more accessible γ‐C(sp3)?H bonds. Experimental studies revealed that C?H bond cleavage occurs reversibly and preferentially at γ‐methyl over δ‐methyl C?H bonds while the subsequent alkylation proceeds exclusively at the six‐membered palladacycle that is generated by δ‐C?H activation. The selectivity can be explained by the Curtin–Hammett principle. The exceptional compatibility of this alkylation with various oligopeptides renders this procedure valuable for late‐stage peptide modifications. Notably, this process is also the first palladium(II)‐catalyzed Michael‐type alkylation reaction that proceeds through C(sp3)?H activation. 相似文献
19.
Rhodium(III)‐Catalyzed CC and CO Coupling of Quinoline N‐Oxides with Alkynes: Combination of CH Activation with O‐Atom Transfer
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Xueyun Zhang Zisong Qi Prof. Xingwei Li 《Angewandte Chemie (International ed. in English)》2014,53(40):10794-10798
[Cp*RhIII]‐catalyzed C? H activation of arenes assisted by an oxidizing N? O or N? N directing group has allowed the construction of a number of hetercycles. In contrast, a polar N? O bond is well‐known to undergo O‐atom transfer (OAT) to alkynes. Despite the liability of N? O bonds in both C? H activation and OAT, these two important areas evolved separately. In this report, [Cp*RhIII] catalysts integrate both areas in an efficient redox‐neutral coupling of quinoline N‐oxides with alkynes to afford α‐(8‐quinolyl)acetophenones. In this process the N? O bond acts as both a directing group for C? H activation and as an O‐atom donor. 相似文献
20.
The Mechanism of NO Bond Cleavage in Rhodium‐Catalyzed CH Bond Functionalization of Quinoline N‐oxides with Alkynes: A Computational Study
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Yingzi Li Song Liu Zisong Qi Xiaotian Qi Prof. Dr. Xingwei Li Prof. Dr. Yu Lan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(28):10131-10137
Metal‐catalyzed C?H activation not only offers important strategies to construct new bonds, it also allows the merge of important research areas. When quinoline N‐oxide is used as an arene source in C?H activation studies, the N?O bond can act as a directing group as well as an O‐atom donor. The newly reported density functional theory method, M11L, has been used to elucidate the mechanistic details of the coupling between quinoline N?O bond and alkynes, which results in C?H activation and O‐atom transfer. The computational results indicated that the most favorable pathway involves an electrophilic deprotonation, an insertion of an acetylene group into a Rh?C bond, a reductive elimination to form an oxazinoquinolinium‐coordinated RhI intermediate, an oxidative addition to break the N?O bond, and a protonation reaction to regenerate the active catalyst. The regioselectivity of the reaction has also been studied by using prop‐1‐yn‐1‐ylbenzene as a model unsymmetrical substrate. Theoretical calculations suggested that 1‐phenyl‐2‐quinolinylpropanone would be the major product because of better conjugation between the phenyl group and enolate moiety in the corresponding transition state of the regioselectivity‐determining step. These calculated data are consistent with the experimental observations. 相似文献