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1.
Catalytic Reduction of CN−, CO,and CO2 by Nitrogenase Cofactors in Lanthanide‐Driven Reactions 下载免费PDF全文
Dr. Chi Chung Lee Prof. Dr. Yilin Hu Prof. Dr. Markus W. Ribbe 《Angewandte Chemie (International ed. in English)》2015,54(4):1219-1222
Nitrogenase cofactors can be extracted into an organic solvent to catalyze the reduction of cyanide (CN?), carbon monoxide (CO), and carbon dioxide (CO2) without using adenosine triphosphate (ATP), when samarium(II) iodide (SmI2) and 2,6‐lutidinium triflate (Lut‐H) are employed as a reductant and a proton source, respectively. Driven by SmI2, the cofactors catalytically reduce CN? or CO to C1–C4 hydrocarbons, and CO2 to CO and C1–C3 hydrocarbons. The C? C coupling from CO2 indicates a unique Fischer–Tropsch‐like reaction with an atypical carbonaceous substrate, whereas the catalytic turnover of CN?, CO, and CO2 by isolated cofactors suggests the possibility to develop nitrogenase‐based electrocatalysts for the production of hydrocarbons from these carbon‐containing compounds. 相似文献
2.
Dr. Amanda Sølvhøj Andreas Ahlburg Prof. Dr. Robert Madsen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(45):16272-16279
A new coupling reaction has been developed in which β‐bromostyrenes react with ethers and tertiary amines to introduce the styryl group in the α‐position. The transformation is mediated by Me2Zn/O2 with 10 % MnCl2 and is believed to proceed by a radical addition–elimination mechanism. The ether and the amine are employed as solvent and the coupling takes place through the most stable α radical for unsymmetrical substrates. The products are obtained in moderate to good yields as the pure E isomers. The coupling can be achieved with a range of smaller cyclic and acyclic ethers/amines as well as various substituted β‐bromostyrenes. 相似文献
3.
The Cross‐Dehydrogenative Coupling of CH Bonds: A Versatile Strategy for CC Bond Formations 下载免费PDF全文
Simon A. Girard Dr. Thomas Knauber Prof. Dr. Chao‐Jun Li 《Angewandte Chemie (International ed. in English)》2014,53(1):74-100
Over the last decade, substantial research has led to the introduction of an impressive number of efficient procedures which allow the selective construction of C? C bonds by directly connecting two different C? H bonds under oxidative conditions. Common to these methodologies is the generation of the reactive intermediates in situ by activation of both C? H bonds. This strategy was introduced by the group of Li as cross‐dehydrogenative coupling (CDC) and discloses waste‐minimized synthetic alternatives to classic coupling procedures which rely on the use of prefunctionalized starting materials. This Review highlights the recent progress in the field of cross‐dehydrogenative C? C formations and provides a comprehensive overview on existing procedures and employed methodologies. 相似文献
4.
Yuki Mizukami Dr. Haijun Li Prof. Dr. Kiyohiko Nakajima Dr. Zhiyi Song Prof. Dr. Tamotsu Takahashi 《Angewandte Chemie (International ed. in English)》2014,53(34):8899-8903
Titanacyclopentadienes, prepared from [Cp2TiBu2] and either two equivalents of an alkyne or a diyne, were treated with PMe3 (3 equiv) at 50 °C for 3 h and then with azobenzene at room temperature for 12 h to give 4,5,6‐trisubstituted indene derivatives with the loss of one substituent in good yields. This reaction contrasts sharply with our previously reported reaction for the formation of 4,5,6,7‐tetrasubstituted indene derivatives without the loss of substituents by the treatment of titanacyclopentadienes with azobenzene without PMe3. 13C NMR spectroscopy of the product derived from a 13C‐enriched complex revealed that the five carbon atoms originating from a Cp ligand were arranged linearly in the trisubstituted indene derivatives, in contrast to the 4,5,6,7‐tetrasubsituted indene derivatives, in which the corresponding five carbon atoms are arranged in a ring. 相似文献
5.
Palladium‐Catalyzed/Norbornene‐Mediated CH Activation/ N‐Tosylhydrazone Insertion Reaction: A Route to Highly Functionalized Vinylarenes 下载免费PDF全文
Dr. Ping‐Xin Zhou Lan Zheng Jun‐Wei Ma Yu‐Ying Ye Xue‐Yuan Liu Prof. Dr. Peng‐Fei Xu Prof. Dr. Yong‐Min Liang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(22):6745-6751
A straightforward method for the synthesis of highly functionalized vinylarenes through palladium‐catalyzed, norbornene‐mediated C?H activation/carbene migratory insertion is described. Extension to a one‐pot procedure is also developed. Furthermore, this method can also be used to generate polysubstituted bicyclic molecules. The reaction proceeds under mild conditions to give the products in satisfactory yields using readily available starting materials. This is a Catellani–Lautens reaction that incorporates different types of coupling partners. Additionally, this reaction is the first to demonstrate the possibility of combining Pd‐catalyzed insertion of diazo compounds and Pd‐catalyzed C?H activation. 相似文献
6.
Johannes G. Rebelein Prof. Dr. Yilin Hu Prof. Dr. Markus W. Ribbe 《Angewandte Chemie (International ed. in English)》2014,53(43):11543-11546
The molybdenum and vanadium nitrogenases are two homologous enzymes with distinct structural and catalytic features. Previously, it was demonstrated that the V nitrogenase was nearly 700 times more active than its Mo counterpart in reducing CO to hydrocarbons. Herein, a similar discrepancy between the two nitrogenases in the reduction of CO2 is reported, with the V nitrogenase being capable of reducing CO2 to CO, CD4, C2D4, and C2D6, and its Mo counterpart only capable of reducing CO2 to CO. Furthermore, it is shown that the V nitrogenase may direct the formation of CD4 in part via CO2‐derived CO, but that it does not catalyze the formation of C2D4 and C2D6 along this route. The exciting observation of a V nitrogenase‐catalyzed C? C coupling with CO2 as the origin of the building blocks adds another interesting reaction to the catalytic repertoire of this unique enzyme system. The differential activities of the V and Mo nitrogenases in CO2 reduction provide an important framework for systematic investigations of this reaction in the future. 相似文献
7.
Unprecedented Transformation of a Directing Group Generated In Situ and Its Application in the One‐Pot Synthesis of 2‐Alkenyl Benzonitriles 下载免费PDF全文
Ravi Kumar Rajesh K. Arigela Dr. Bijoy Kundu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(33):11807-11812
An unprecedented protocol for the transformation of benzoyl azides into benzonitrile derivatives via iminophosphoranes generated in situ is described. The strategy was successfully applied to the de‐novo synthesis of 2‐alkenylated benzonitrile derivatives from benzoyl azides through ortho C?H activation/alkenylation followed by subsequent rearrangement. The salient features of this protocol involve incorporation of two important functionalities through cyanation and olefination in one pot under mild reaction conditions by using a less expensive Ru catalyst. The mechanism was established by isolating and characterising (using 31P NMR) an intermediate with two ortho functionalities, iminophosphorane and olefin, under specific reaction conditions. 相似文献
8.
Corrigendum: Diastereo‐ and Enantioselective Intramolecular C(sp3)H Arylation for the Synthesis of Fused Cyclopentanes 下载免费PDF全文
Dr. Nicolas Martin Cathleen Pierre Dr. Michaël Davi Dr. Rodolphe Jazzar Prof. Dr. Olivier Baudoin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(39):12341-12341
9.
Water‐Promoted Generation of a Diazairida Homobarrelene by CC Coupling Between an Iridacyclic Alkylidene and Acetonitrile 下载免费PDF全文
María F. Espada Prof. Dr. Manuel L. Poveda Prof. Dr. Ernesto Carmona 《Angewandte Chemie (International ed. in English)》2015,54(30):8751-8755
The stable cationic iridacyclopentenylidene [TpMe2Ir(?CHC(Me)?C(Me)C H2(NCMe)]PF6 ( A ; TpMe2=hydrotris(3,5‐dimethylpyrazolyl)borate) has been obtained by α‐hydride abstraction from the iridacyclopent‐2‐ene [TpMe2Ir(CH2C(Me)?C(Me)C H2)(NCMe)]. Complex A exhibits Brønsted–Lowry acidity at the Ir? CH2 and proximal (relative to Ir? CH2) methyl sites. The coordination of an extra molecule of acetonitrile to the iridium center initiates the reversible isomerization of the chelating carbon chain of A to the monodentate butadienyl ligand of complex [TpMe2Ir(CH?C(Me)C(Me)?CH2)(NCMe)2]PF6, which is capable to engage in a water‐promoted C? C coupling with the MeCN co‐ligands. The product is an aesthetically appealing bicyclic structure that resembles the hydrocarbon barrelene. 相似文献
10.
Modular Synthesis of Phenanthro[9,10‐c]thiophenes by a Sequence of CH Activation,Suzuki Cross‐Coupling and Photocyclization Reactions 下载免费PDF全文
Dr. Ingo Schnapperelle Prof. Dr. Thorsten Bach 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(31):9725-9732
A total number of 15 different 3,4‐diarylthiophenes were synthesized, which bear a chlorine atom in ortho‐position of one of the aryl substituents. One aryl group was introduced by an oxidative cross‐coupling reaction, involving a C?H activation at C4(3) of the thiophene core. The other aryl group was in most cases introduced by a Suzuki cross‐coupling reaction, which succeeded the oxidative cross‐coupling step. Photocyclization reactions of the 3,4‐diarylthiophenes were performed in a solvent mixture of benzene and acetonitrile (50:50 v/v) at λ=254 nm and proceeded to the title compounds in yields of 60–82 %. The selectivity of the photocyclization was determined at the ortho‐chloro‐substituted aryl ring by the position of the chlorine substituent. At the other ring, a single regioisomer was observed for phenyl and para‐substituted phenyl groups. For 2‐naphthyl and ortho‐substituted phenyl rings a clear preference was observed in favor of a major regioisomer, while meta‐substitution in the phenyl ring led to a about 1:1 mixture of 5‐ and 7‐substituted phenanthro[9,10‐c]thiophenes. Mechanistically, the photocyclization is likely to occur as a photochemically allowed, conrotatory [(4n+2)π] process accompanied by elimination of HCl. It was shown for two phenanthro[9,10‐c]thiophene products that they can be readily brominated in positions C1 and C3 (74–77 %), which in turn allows for further functionalization at these positions, for example, in the course of halogen–metal exchange and polymerization reactions. 相似文献
11.
Synthesis of Heterodinuclear Hemisalen Complexes on a Hexaarylbenzene Scaffold and their Application for the Cross‐Pinacol Coupling Reaction 下载免费PDF全文
Akihiro Miyasaka Dr. Toru Amaya Prof. Toshikazu Hirao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(6):1615-1621
Intermolecular cross‐pinacol coupling reaction between aliphatic and aromatic aldehydes by using heterodinuclear hemisalen complexes 1 cis with vanadium(V) and titanium(IV) on a hexaarylbenzene scaffold is reported. Our ligand design is based on the individual activation of two aldehydes by vanadium and titanium, which are positioned with a suitable space on the rigid scaffold. Ligands such as 1 cis were synthesized by Diels–Alder addition and decarbonylation reaction, followed by condensation of dialdehyde 3 cis with various aminophenols. The influence of the substituents on the ligands on the pinacol coupling reaction was investigated. As a result, the reductive coupling reaction between aliphatic and aromatic aldehydes by using a catalytic amount of 1 cis in the presence of Me3SiCl and Zn provided the corresponding cross‐coupled 1,2‐diol in good yields with high cross‐selectivity. 相似文献
12.
Dehydrogenative Carbon–Carbon Bond Formation Using Alkynyloxy Moieties as Hydrogen‐Accepting Directing Groups 下载免费PDF全文
Dr. Yasunori Minami Tatsuro Kodama Prof. Dr. Tamejiro Hiyama 《Angewandte Chemie (International ed. in English)》2015,54(40):11813-11816
In the presence of a catalyst system consisting of Pd(OAc)2, PCy3, and Zn(OAc)2, the reaction of alkynyl aryl ethers with bicycloalkenes, α,ß‐unsaturated esters, or heteroarenes results in the site‐selective cleavage of two C? H bonds followed by the formation of C? C bonds. In all cases, the alkynyloxy group acts as a directing group for the activation of an ortho C? H bond and as a hydrogen acceptor, thus rendering the use of additives such as an oxidant or base unnecessary. 相似文献
13.
Visible‐Light‐Induced Decarboxylative Functionalization of Carboxylic Acids and Their Derivatives 下载免费PDF全文
Dr. Jun Xuan Prof. Dr. Zhao‐Guo Zhang Prof. Dr. Wen‐Jing Xiao 《Angewandte Chemie (International ed. in English)》2015,54(52):15632-15641
Visible‐light‐induced radical decarboxylative functionalization of carboxylic acids and their derivatives has recently received considerable attention as a novel and efficient method to create C? C and C? X bonds. Generally, this visible‐light‐promoted decarboxylation process can smoothly occur under mild reaction conditions with a broad range of substrates and an excellent functional‐group tolerance. The radical species formed from the decarboxylation step can participate in not only single photocatalytic transformations, but also dual‐catalytic cross‐coupling reactions by combining photoredox catalysis with other catalytic processes. Recent advances in this research area are discussed herein. 相似文献
14.
Rhodium‐Catalyzed Annulative Coupling of 3‐Phenylthiophenes with Alkynes Involving Double C‐H Bond Cleavages 下载免费PDF全文
Tomonori Iitsuka Dr. Koji Hirano Prof. Dr. Tetsuya Satoh Prof. Dr. Masahiro Miura 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(2):385-389
Double C?H bond activation took place efficiently upon treatment of 3‐phenylthiophenes with alkynes in the presence of a rhodium catalyst and a copper salt oxidant to form the corresponding naphthothiophene derivatives. Dehydrogenative coupling with alkenes was also found to occur on the phenyl moiety rather than the thiophene ring. These reactions provide straightforward synthetic methods for π‐conjugated molecules involving a thiophene unit from readily available, simple building blocks. 相似文献
15.
Dr. Dhananjayan Vasu Prof. Dr. Hideki Yorimitsu Prof. Dr. Atsuhiro Osuka 《Angewandte Chemie (International ed. in English)》2015,54(24):7162-7166
Two new palladium‐catalyzed reactions of aromatic sulfur compounds enabled the conversion of dibenzothiophenes into triphenylenes in four steps. This transformation of one aromatic framework into another consists of 1) 4‐chlorobutylation of the dibenzothiophene to form the corresponding sulfonium salt, 2) palladium‐catalyzed arylative ring opening of the sulfonium salt with a sodium tetraarylborate, 3) an intramolecular SN2 reaction to form a teraryl sulfonium salt, and 4) palladium‐catalyzed intramolecular C? S/C? H coupling through electrophilic palladation. Symmetrical as well as unsymmetrical triphenylenes of interest were synthesized in a tailor‐made fashion in satisfactory overall yields. 相似文献
16.
Dr. Rishikesh Narayan Dr. Kiran Matcha Dr. Andrey P. Antonchick 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(42):14678-14693
The formation of C?C bonds embodies the core of organic chemistry because of its fundamental application in generation of molecular diversity and complexity. C?C bond‐forming reactions are well‐known challenges. To achieve this goal through direct functionalization of C?H bonds in both of the coupling partners represents the state‐of‐the‐art in organic synthesis. Oxidative C?C bond formation obviates the need for prefunctionalization of both substrates. This Minireview is dedicated to the field of C?C bond‐forming reactions through direct C?H bond functionalization under completely metal‐free oxidative conditions. Selected important developments in this area have been summarized with representative examples and discussions on their reaction mechanisms. 相似文献
17.
Xiaoge Yang Zhuqing Liu Prof. Chenglin Sun Prof. Dr. Jiping Chen Prof. Dr. Zhengkun Yu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(40):14085-14094
Efficient palladium‐catalyzed cross‐coupling reactions of the internal olefins α‐cyanoketene dithioacetals with a variety of olefins were achieved in dioxane/HOAc/DMSO (9:3:1 v/v/v) under air atmosphere or by means of AgOAc as the terminal oxidant. Electron‐deficient terminal olefins reacted to form the linear diene derivatives with air as the oxidant. Styrenes underwent the cross‐coupling to give both the linear and branched dienes when using AgOAc as the oxidant. Unactivated cyclic and linear internal olefin substrates both reacted in the presence of a catalytic amount of benzoquinone in air to produce skipped dienes. The typical products were structurally confirmed by X‐ray crystallography. 相似文献
18.
Ln[N(SiMe3)2]3‐Catalyzed Cross‐Diinsertion of CN/CC into an NH Bond: Facile Synthesis of 1,2,4‐Trisubstituted Imidazoles from Propargylamines and Nitriles 下载免费PDF全文
Longcheng Hong Yinlin Shao Lixin Zhang Prof. Dr. Xigeng Zhou 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(28):8551-8555
A lanthanide‐catalyzed sequential insertion of C?N and C?C into an N?H bond is presented. The convenient reaction, which proceeds under mild conditions, is an efficient method for preparing 1,2,4‐trisubstituted imidazoles directly from readily available propargylamines and nitriles. 相似文献
19.
Highly Selective Allylborations of Aldehydes Using α,α‐Disubstituted Allylic Pinacol Boronic Esters 下载免费PDF全文
Dr. Matthew J. Hesse Dr. Stéphanie Essafi Charlotte G. Watson Prof. Dr. Jeremy N. Harvey Dr. David Hirst Prof. Dr. Christine L. Willis Prof. Dr. Varinder K. Aggarwal 《Angewandte Chemie (International ed. in English)》2014,53(24):6145-6149
α,α‐Disubstituted allylic pinacol boronic esters undergo highly selective allylborations of aldehydes to give tetrasubstituted homoallylic alcohols with exceptional levels of anti‐Z‐selectivity (>20:1). The scope of the reaction includes both acyclic and cyclic allylic boronic esters which lead to acyclic and exocyclic tetrasubstituted homoallylic alcohols. The use of β‐borylated allylic boronic esters gave fully substituted alkenes bearing a boronic ester which underwent further cross‐coupling enabling a highly modular and stereoselective approach to the synthesis of diaryl tetrasubstituted alkenes. Computational analysis revealed the origin of the remarkable selectivity observed. 相似文献
20.
Regioselective Acceptorless Dehydrogenative Coupling of N‐Heterocycles toward Functionalized Quinolines,Phenanthrolines, and Indoles 下载免费PDF全文
Dinesh Talwar Angela Gonzalez‐de‐Castro Dr. Ho Yin Li Prof. Jianliang Xiao 《Angewandte Chemie (International ed. in English)》2015,54(17):5223-5227
A new strategy has been developed for the oxidant‐ and base‐free dehydrogenative coupling of N‐heterocycles at mild conditions. Under the action of an iridium catalyst, N‐heterocycles undergo multiple sp3 C? H activation steps, generating a nucleophilic enamine that reacts in situ with various electrophiles to give highly functionalized products. The dehydrogenative coupling can be cascaded with Friedel–Crafts addition, resulting in a double functionalization of the N‐heterocycles. 相似文献