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Directing/Protecting‐Group‐Free Synthesis of Tetraaryl‐Substituted Pyrazoles through Four Direct Arylations on an Unsubstituted Pyrazole Scaffold 下载免费PDF全文
Dr. Shinichiro Fuse Taiki Morita Dr. Kohei Johmoto Dr. Hidehiro Uekusa Dr. Hiroshi Tanaka 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(41):14370-14375
A directing/protecting‐group‐free synthesis of 1,3,4,5‐tetraaryl‐substituted pyrazoles was achieved through four transition metal‐catalyzed direct arylations. Various pyrazoles with four different aryl rings were obtained using readily available reagents from an unsubstituted pyrazole. Two aryl‐substituted pyrazoles showed intense violet fluorescence, high quantum yields (Φf=0.68, 0.64), and large Stokes shifts (19000, 15200 cm?1). 相似文献
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Palladium‐Catalyzed Intramolecular CH Difluoroalkylation: Synthesis of Substituted 3,3‐Difluoro‐2‐oxindoles 下载免费PDF全文
Dr. Shi‐Liang Shi Prof. Dr. Stephen L. Buchwald 《Angewandte Chemie (International ed. in English)》2015,54(5):1646-1650
The synthesis of 3,3‐difluoro‐2‐oxindoles through a robust and efficient palladium‐catalyzed C? H difluoroalkylation is described. This process generates a broad range of difluorooxindoles from readily prepared starting materials. The use of BrettPhos as the ligand was crucial for high efficiency. Preliminary mechanistic studies suggest that oxidative addition is the rate‐determining step for this process. 相似文献
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Inside Cover: Ru‐Catalysed CH Arylation of Indoles and Pyrroles with Boronic Acids: Scope and Mechanistic Studies (Chem. Eur. J. 14/2015) 下载免费PDF全文
Carina Sollert Karthik Devaraj Dr. Andreas Orthaber Dr. Paul J. Gates Dr. Lukasz T. Pilarski 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(14):5258-5258
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Inside Cover: tert‐Butyl Nitrite Mediated Regiospecific Nitration of (E)‐Azoarenes through Palladium‐Catalyzed Directed CH Activation (Chem. Eur. J. 32/2014) 下载免费PDF全文
Biju Majhi Debasish Kundu Dr. Sabir Ahammed Prof. Dr. Brindaban C. Ranu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(32):9818-9818
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Cover Picture: Sequential SNAr Reaction/Suzuki–Miyaura Coupling/C−H Direct Arylations Approach for the Rapid Synthesis of Tetraaryl‐Substituted Pyrazoles (Chem. Asian J. 8/2015) 下载免费PDF全文
Taiki Morita Daisuke Kobayashi Keisuke Matsumura Dr. Kohei Johmoto Dr. Hidehiro Uekusa Dr. Shinichiro Fuse Prof. Dr. Takashi Takahashi 《化学:亚洲杂志》2015,10(8):1589-1589
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Back Cover: Silver‐Catalyzed Coupling of Two CH Groups and One‐Pot Synthesis of Tetrasubstituted Furans,Thiophenes, and Pyrroles (Chem. Eur. J. 32/2015) 下载免费PDF全文
Shuai Mao Xue‐Qing Zhu Ya‐Ru Gao Dong‐Dong Guo Prof. Dr. Yong‐Qiang Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(32):11612-11612
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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
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Back Cover: Reactions of Group 4 Metallocenes with Monosubstituted Acetonitriles: Keteniminate Formation versus CC Coupling (Chem. Eur. J. 8/2015) 下载免费PDF全文
Lisanne Becker Dr. Martin Haehnel Dr. Anke Spannenberg Dr. Perdita Arndt Dr. Uwe Rosenthal 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(8):3504-3504
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Back Cover: Organomagnesium‐Catalyzed Isomerization of Terminal Alkynes to Allenes and Internal Alkynes (Chem. Eur. J. 22/2015) 下载免费PDF全文
Dr. Raphaël Rochat Koji Yamamoto Michael J. Lopez Haruki Nagae Dr. Hayato Tsurugi Prof. Dr. Kazushi Mashima 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(22):8300-8300
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Chuanhu Lei Xiaojia Jin Jianrong Zhou 《Angewandte Chemie (International ed. in English)》2015,54(45):13397-13400
Three‐component couplings were achieved from common aryl halides, alkyl halides, and heteroarenes under palladium and norbornene co‐catalysis. The reaction forges hindered aryl–heteroaryl bonds and introduces ortho‐alkyl groups to aryl rings. Various heterocycles such as oxazoles, thiazoles and thiophenes underwent efficient coupling. The heteroarenes were deprotonated in situ by bases without the assistance of palladium catalysts. 相似文献
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Kinetic Studies on the Palladium(II)‐Catalyzed Oxidative Cross‐Coupling of Thiophenes with Arylboron Compounds and Their Mechanistic Implications 下载免费PDF全文
Dr. Ingo Schnapperelle Dr. Stefan Breitenlechner Prof. Dr. Thorsten Bach 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(50):18407-18416
Reaction orders for the key components in the palladium(II)‐catalyzed oxidative cross‐coupling between phenylboronic acid and ethyl thiophen‐3‐yl acetate were obtained by the method of initial rates. It turned out that the reaction rate not only depended on the concentration of palladium trifluoroacetate (reaction order: 0.97) and phenylboronic acid (reaction order: 1.26), but also on the concentration of the thiophene (reaction order: 0.55) and silver oxide (reaction order: ?1.27). NMR spectroscopy titration studies established the existence of 1:1 complexes between the silver salt and both phenylboronic acid and ethyl thiophen‐3‐yl acetate. A low inverse kinetic isotope effect (kH/kD=0.93) was determined upon employing the 4‐deuterated isotopomer of ethyl thiophen‐3‐yl acetate and monitoring its reaction to the 4‐phenyl‐substituted product. A Hammett analysis performed with para‐substituted 2‐phenylthiophenes gave a negative ρ value for oxidative cross‐coupling with phenylboronic acid. Based on the kinetic data and additional evidence, a mechanism is suggested that invokes transfer of the phenyl group from phenylboronic acid to a 1:1 complex of palladium trifluoroacetate and thiophene as the rate‐determining step. Proposals for the structure of relevant intermediates are made and discussed. 相似文献
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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
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Sequential SNAr Reaction/Suzuki–Miyaura Coupling/C−H Direct Arylations Approach for the Rapid Synthesis of Tetraaryl‐Substituted Pyrazoles 下载免费PDF全文
Taiki Morita Daisuke Kobayashi Keisuke Matsumura Dr. Kohei Johmoto Dr. Hidehiro Uekusa Dr. Shinichiro Fuse Prof. Dr. Takashi Takahashi 《化学:亚洲杂志》2015,10(8):1626-1630
A rapid synthesis of 1,3,4,5‐tetraaryl‐substituted pyrazoles has been achieved through a sequence of SNAr reaction/Suzuki–Miyaura coupling/Pd‐catalyzed direct arylations that used 3‐iodo‐1H‐pyrazole as a scaffold. Pyrazoles with four different aryl groups were synthesized in a straightforward manner with no extra synthetic steps, such as protection/deprotection or the introduction of activating/directing groups, using readily available substrates and reagents. The developed synthetic approach enabled the structurally diverse synthesis of multiaryl‐substituted pyrazoles without using a glovebox technique. 相似文献
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Back Cover: Dormant versus Evolving Aminopalladated Intermediates: Toward a Unified Mechanistic Scenario in PdII‐Catalyzed Aminations (Chem. Eur. J. 6/2014) 下载免费PDF全文
Dr. Jamshid Rajabi Mélanie M. Lorion Vu Linh Ly Dr. Frédéric Liron Dr. Julie Oble Prof. Dr. Guillaume Prestat Prof. Dr. Giovanni Poli 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(6):1768-1768