共查询到20条相似文献,搜索用时 15 毫秒
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Hui Yu Guoying Zhang Hanmin Huang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(37):11062-11066
A fundamentally novel approach to bioactive quinolizinones is based on the palladium‐catalyzed intramolecular cyclocarbonylation of allylamines. [Pd(Xantphos)I2], which features a very large bite angle, has been found to facilitate the rapid carbonylation of azaarene‐substituted allylamines into bioactive quinolizinones in good to excellent yields. This transformation represents the first dearomative carbonylation and is proposed to proceed by palladium‐catalyzed C N bond activation, dearomatization, CO insertion, and a Heck reaction. 相似文献
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Jimin Xu Guolin Cheng Deyong Su Yantao Liu Xinyan Wang Yuefei Hu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(47):13105-13110
A novel palladium catalyzed direct ortho‐arylation of N‐phenacylpyridinium bromide was developed. The amazing N‐phenacyl group regioselectively activates the C? H bond of pyridine and automatically departs from the arylated products. A kinetic isotope effect study proved that the reaction went through a C? H‐bond activation pathway and 2,6‐diphenylpyridine was produced stepwise from 2‐phenylpyridine. 相似文献
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Wen‐Hao Guo Qiao‐Qiao Min Ji‐Wei Gu Xingang Zhang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(31):9203-9206
An ortho‐selective C F bond borylation between N‐heterocycle‐substituted polyfluoroarenes and Bpin‐Bpin with simple and commercially available [Rh(cod)2]BF4 as a catalyst is now reported. The reaction proceeds under mild reaction conditions with high efficiency and broad substrate scope, even toward monofluoroarene, thus providing a facile access to a wide range of borylated fluoroarenes that are useful for photoelectronic materials. Preliminary mechanistic studies reveal that a RhIII/V catalytic cycle via a key intermediate rhodium(III) hydride complex [(H)RhIIILn(Bpin)] may be involved in the reaction. 相似文献
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Naohiko Yoshikai Arimasa Matsumoto Jakob Norinder Eiichi Nakamura 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2009,121(16):2969-2972
Naheliegende Alternative : Eine eisenkatalysierte Imin‐gesteuerte C‐H‐Aktivierung mit einem Diarylzinkreagens führt eine Arylgruppe in ortho‐Stellung an einem von Acetophenon abgeleiteten Imin ein (siehe Schema); mit einem Palladiumkatalysator tritt dagegen eine gewöhnliche Substitution auf. Die Titelreaktion ist eine milde C‐H‐Aktivierung, die in Gegenwart von 1,2‐Dichlorisobutan mit Arylbromiden, ‐chloriden oder ‐sulfonaten selektiv verläuft.
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Naohiko Yoshikai Dr. Arimasa Matsumoto Jakob Norinder Dr. Eiichi Nakamura Prof. Dr. 《Angewandte Chemie (International ed. in English)》2009,48(16):2925-2928
No Fe‐ar : Iron catalyzes an imine‐directed C? H bond activation to introduce an ortho‐aryl group to an acetophenone‐derived imine using a diarylzinc reagent (see scheme), whereas palladium catalyzes the conventional substitution reaction . The title reaction features mild and selective C? H bond activation in the presence of aryl bromide, chloride, or sulfonate groups, and 1,2‐dichloroisobutane is essential to achieve such selectivity.
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Chun‐I Lee Wei‐Chun Shih Jia Zhou Joseph H. Reibenspies Oleg V. Ozerov 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(47):14209-14213
A two‐step reaction to convert terminal alkynes into triborylalkenes is reported. In the first step, the terminal alkyne and pinacolborane (HBpin) are converted into an alkynylboronate, which is catalyzed by an iridium complex supported by a SiNN pincer ligand. In the second step, treatment of the reaction mixture with CO generates a new catalyst which mediates dehydrogenative diboration of alkynylboronate with pinacolborane. The mechanism of the diboration remains unclear but it does not proceed via intermediacy of hydroboration products or via B2pin2. 相似文献
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The transformation of C? H bonds into other chemical bonds is of great significance in synthetic chemistry. C? H bond‐activation processes provide a straightforward and atom‐economic strategy for the construction of complex structures; as such, they have attracted widespread interest over the past decade. As a prevalent directing group in the field of C? H activation, the amide group not only offers excellent regiodirecting ability, but is also a potential C? N bond precursor. As a consequence, a variety of nitrogen‐containing heterocycles have been obtained by using these reactions. This Focus Review addresses the recent research into the amide‐directed tandem C? C/C? N bond‐formation process through C? H activation. The large body of research in this field over the past three years has established it as one of the most‐important topics in organic chemistry. 相似文献
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Xueyun Zhang Zisong Qi Xingwei Li 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(40):10970-10974
[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
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Meghan E. Doster Samuel A. Johnson Prof. Dr. 《Angewandte Chemie (International ed. in English)》2009,48(12):2185-2187
N, not NHC : A neutral, basic, strong σ‐donor nitrogen ancillary ligand with properties analogous to those of N‐heterocyclic carbenes (NHCs) was developed to aid in the oxidative additions of challenging substrates to late transition metals. Selective, room‐temperature C? F bond activation was observed with hexa‐, penta‐, and all three isomers of tetrafluorobenzene using a nickel(0) source in the presence of this donor.
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Dr. Benudhar Punji Weifeng Song Grigory A. Shevchenko Prof. Dr. Lutz Ackermann 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(32):10605-10610
Inexpensive cobalt catalysts derived from N‐heterocylic carbenes (NHC) allowed efficient catalytic C? H bond arylations on heteroaryl‐substituted arenes with widely available aryl chlorides, which set the stage for the preparation of sterically hindered tri‐ortho‐substituted biaryls. Likewise, challenging direct alkylations with β‐hydrogen‐containing primary and even secondary alkyl chlorides proceeded on pyridyl‐ and pyrimidyl‐substituted arenes and heteroarenes. The cobalt‐catalyzed C? H bond functionalizations occurred efficiently at ambient reaction temperature with excellent levels of site‐selectivities and ample scope. Mechanistic studies highlighted that electron‐deficient aryl chlorides reacted preferentially, while the arenes kinetic C? H bond acidity was found to largely govern their reactivity. 相似文献
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Hang Zhang Kang Wang Bo Wang Heng Yi Fangdong Hu Changkun Li Yan Zhang Jianbo Wang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(48):13450-13454
An efficient rhodium(III)‐catalyzed synthesis of 2H‐chromene from N‐phenoxyacetamides and cyclopropenes has been developed. The reaction represents the first example of using cyclopropenes as a three‐carbon unit in rhodium(III)‐catalyzed C(sp2) H activations. 相似文献
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Christian Winter Norbert Krause 《Angewandte Chemie (International ed. in English)》2009,48(14):2460-2462
Relieving the strain : The rhodium(I)‐catalyzed activation of C C bonds in functionalized cyclobutanes opens a novel route to highly substituted carbo‐ and heterocycles. Particularly intriguing is the differentiation of enantiotopic C C bonds, which leads to the formation of highly enantiomerically enriched lactones, cyclopentanones, and cyclohexenones (see scheme).
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Sasa Duric Fanni D. Sypaseuth Santina Hoof Emma Svensson Prof. Dr. C. Christoph Tzschucke 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(51):17456-17463
The synthesis of asymmetrically substituted 2,2′:6′,2′′‐terpyridines is reported. First, palladium‐catalyzed C? H arylation of pyridine N‐oxides with substituted bromopyridines gave 2,2′‐bipyridine N‐oxides, which were further arylated in a second step to form 2,2′:6′,2′′‐terpyridine N‐oxides. Yields of up to 77 % were obtained with N‐oxides bearing an electron‐withdrawing ethoxycarbonyl substituent in the 4‐position. Pd(OAc)2 with either P(tBu)3 or P(o‐tolyl)3 was used as the catalyst. Cyclometalated complexes derived from Pd(OAc)2 and these phosphines were also effective. K3PO4 as the base gave better results than K2CO3. Subsequent deoxygenation with H2 and Pd/C as the catalyst gave the asymmetrically substituted 2,2′:6′,2′′‐terpyridines in near quantitative yield. This reaction sequence significantly reduces the number of steps required in comparison with known cross‐coupling methods and therefore allows convenient and scalable access to substituted terpyridines. 相似文献