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Cover Picture: Source of Selectivity in Oxidative Cross‐Coupling of Aryls by Solvent Effect of 1,1,1,3,3,3‐Hexafluoropropan‐2‐ol (Chem. Eur. J. 35/2015) 下载免费PDF全文
Dr. Bernd Elsler Anton Wiebe Dr. Dieter Schollmeyer Dr. Katrin M. Dyballa Prof. Dr. Robert Franke Prof. Dr. Siegfried R. Waldvogel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(35):12205-12205
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Significant Enhancement in the Efficiency and Selectivity of Iron‐Catalyzed Oxidative Cross‐Coupling of Phenols by Fluoroalcohols 下载免费PDF全文
Eden Gaster Yulia Vainer Almog Regev Dr. Sachin Narute Dr. Kavitha Sudheendran Aviya Werbeloff Hadas Shalit Dr. Doron Pappo 《Angewandte Chemie (International ed. in English)》2015,54(14):4198-4202
Significant enhancement of both the rate and the chemoselectivity of iron‐catalyzed oxidative coupling of phenols can be achieved in fluorinated solvents, such as 1,1,1,3,3,3‐hexafluoropropan‐2‐ol (HFIP), 2,2,2‐trifluoroethanol (TFE), and 1‐phenyl‐2,2,2‐trifluoroethanol. The generality of this effect was examined for the cross‐coupling of phenols with arenes and polycyclic aromatic hydrocarbons (PAHs) and of phenol with β‐dicarbonyl compounds. The new conditions were utilized in the synthesis of 2′′′‐dehydroxycalodenin B in only four synthetic steps. 相似文献
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Metal‐ and Reagent‐Free Dehydrogenative Formal Benzyl–Aryl Cross‐Coupling by Anodic Activation in 1,1,1,3,3,3‐Hexafluoropropan‐2‐ol 下载免费PDF全文
Yasushi Imada Johannes L. Röckl Dr. Anton Wiebe Dr. Tile Gieshoff Dr. Dieter Schollmeyer Prof. Dr. Kazuhiro Chiba Prof. Dr. Robert Franke Prof. Dr. Siegfried R. Waldvogel 《Angewandte Chemie (International ed. in English)》2018,57(37):12136-12140
A selective dehydrogenative electrochemical functionalization of benzylic positions that employs 1,1,1,3,3,3‐hexafluoropropan‐2‐ol (HFIP) has been developed. The electrogenerated products are versatile intermediates for subsequent functionalizations as they act as masked benzylic cations that can be easily activated. Herein, we report a sustainable, scalable, and reagent‐ and metal‐free dehydrogenative formal benzyl–aryl cross‐coupling. Liberation of the benzylic cation was accomplished through the use of acid. Valuable diarylmethanes are accessible in the presence of aromatic nucleophiles. The direct application of electricity enables a safe and environmentally benign chemical transformation as oxidizers are replaced by electrons. A broad variety of different substrates and nucleophiles can be employed. 相似文献
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Dr. Christiane E. I. Knappke Dr. Sabine Grupe Dominik Gärtner Martin Corpet Dr. Corinne Gosmini Prof. Dr. Axel Jacobi von Wangelin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(23):6828-6842
Reductive cross‐electrophile coupling reactions have recently been developed to a versatile and sustainable synthetic tool for selective C?C bond formation. The employment of cheap and abundant electrophiles avoids the pre‐formation and handling of organometallic reagents. In situ reductive coupling is effected in the presence of a transition‐metal catalyst (Ni, Co, Pd, Fe) and a suitable metallic reductant (Mn, Zn, Mg). This Concept article assesses the current state of the art and summarizes recent protocols with various combinations of alkyl, alkenyl, allyl, and aryl reagents and highlights key mechanistic studies. 相似文献
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Guozhu Zhang Yu Peng Dr. Li Cui Dr. Liming Zhang Prof. Dr. 《Angewandte Chemie (International ed. in English)》2009,48(17):3112-3115
Oxidizing gold? A gold(I)/gold(III) catalytic cycle is essential for the first oxidative cross‐coupling reaction in gold catalysis. By using Selectfluor for gold(I) oxidation, this chemistry reveals the synthetic potential of incorporating gold(I)/gold(III) catalytic cycles into contemporary gold chemistry and promises a new area of gold research by merging powerful gold catalysis and oxidative metal‐catalyzed cross‐coupling reactions.
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Palladium‐Catalysed Direct Cross‐Coupling of Organolithium Reagents with Aryl and Vinyl Triflates 下载免费PDF全文
Dr. Carlos Vila Dr. Valentín Hornillos Massimo Giannerini Dr. Martín Fañanás‐Mastral Prof. Dr. Ben L. Feringa 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(41):13078-13083
A palladium‐catalysed cross‐coupling of organolithium reagents with aryl and vinyl triflates is presented. The reaction proceeds at 50 or 70 °C with short reaction times, and the corresponding products are obtained with moderate to high yields, with a variety of alkyl and (hetero)aryl lithium reagents. 相似文献
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tBuLi‐Mediated One‐Pot Direct Highly Selective Cross‐Coupling of Two Distinct Aryl Bromides 下载免费PDF全文
Dr. Carlos Vila Sara Cembellín Dr. Valentín Hornillos Massimo Giannerini Dr. Martín Fañanás‐Mastral Prof. Dr. Ben L. Feringa 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(44):15520-15524
A Pd‐catalyzed direct cross‐coupling of two distinct aryl bromides mediated by tBuLi is described. The use of [Pd‐PEPPSI‐IPr] or [Pd‐PEPPSI‐IPent] as catalyst allows for the efficient one‐pot synthesis of unsymmetrical biaryls at room temperature. The key for this selective cross‐coupling is the use of an ortho‐substituted bromide that undergoes lithium–halogen exchange preferentially. 相似文献
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Yi‐Hung Chen Mai Sun Paul Knochel 《Angewandte Chemie (International ed. in English)》2009,48(12):2236-2239
Sensitive functional groups such as COR, CHO, or CH2OH can be present in benzylic indium reagents prepared by the direct insertion of indium in the presence of LiCl. These reagents undergo palladium‐catalyzed cross‐coupling reactions in the presence of a protic cosolvent after activation with iPrMgCl⋅LiCl (see scheme). Remarkable chemoselectivities are achieved by using various electrophiles containing NH or OH groups.
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Transition‐Metal‐Free BF3‐Mediated Oxidative and Non‐Oxidative Cross‐Coupling of Pyridines 下载免费PDF全文
Dipl.‐Chem. Quan Chen Dr. Thierry León Prof. Dr. Paul Knochel 《Angewandte Chemie (International ed. in English)》2014,53(33):8746-8750
We report a BF3‐mediated direct alkynylation of pyridines at C(2) by using a variety of alkynyllithium reagents (oxidative cross‐coupling). Moreover, we have developed a novel transition‐metal‐free cross‐coupling method between alkylmagnesium reagents and 4‐substituted pyridines, such as isonicotinonitrile and 4‐chloropyridine, by employing BF3?OEt2 as a promoter. The combination of these methods enabled us to efficiently prepare a range of di‐, tri‐, and tetrasubstituted pyridines. 相似文献
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Michael G. Organ Prof. Selçuk Çalimsiz Dr. Mahmoud Sayah Ka Hou Hoi Alan J. Lough Dr. 《Angewandte Chemie (International ed. in English)》2009,48(13):2383-2387
Incredible Bulk : A series of N‐heterocyclic carbene catalysts (see picture) were prepared and evaluated in the Suzuki–Miyaura reaction. A variety of sterically encumbered tetra‐ortho‐substituted biaryl products were formed from unreactive aryl chlorides using the isopentyl‐substituted catalyst at temperatures ranging from 65 °C to room temperature. The cyclopentyl‐substituted catalyst was virtually inactive, demonstrating that “flexible bulk” is essential to promote these transformations.
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Intramolecular Hydrogen Bond Reverting the Solvent Effect on Phosphorus Hyperfine Coupling Constants of β‐Phosphorylated Nitroxides 下载免费PDF全文
Prof. Gérard Audran Dr. Lionel Bosco Dr. Paul Brémond Teddy Butscher Prof. Sylvain R. A. Marque Prof. Stéphane Viel 《Chemphyschem》2016,17(23):3954-3963
Recently, we reported a dramatic solvent effect on the phosphorus hyperfine coupling constant aP of β‐phosphorylated six‐membered ring nitroxides, that is, approximately 25 G of difference in aP from n‐hexane to water (Org. Biomol. Chem. 2016 , 14, —1228‐1292). In this article, we report on the effect of intramolecular hydrogen bonding (IHB) in three nitroxides exhibiting IHB between the hydroxyl and diethylphosphoryl groups and one exhibiting IHB between the hydroxyl group and the nitroxyl moiety. It is observed that for the first three nitroxides, aP increases with increasing polarity/polarizability and hydrogen bond donor (HBD) properties of the solvent (π* and α, respectively)—in sharp contrast to the data reported in the literature—and for the last nitroxide, aP decreases with π* and α. In fact, the occurrence of IHB induces a large strain, its suppression by hydrogen bond acceptor (HBA) solvents affords an increase in aP. 相似文献
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