共查询到20条相似文献,搜索用时 15 毫秒
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Masashi Shigenobu Kazuhiro Takenaka Hiroaki Sasai 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(33):9708-9712
A palladium‐catalyzed direct arylation of isoxazoles with aryl iodides has been achieved. The C H bond at the 5‐position is activated selectively to give coupling products in moderate to good yields. This direct arylation was applied to the synthesis of a spiro‐type chiral ligand, which proved to be most effective to the palladium‐catalyzed tandem cyclization of a dialkenyl alcohol. 相似文献
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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
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Hai Zhou Yun‐He Xu Wan‐Jun Chung Teck‐Peng Loh Prof. 《Angewandte Chemie (International ed. in English)》2009,48(29):5355-5357
It does get in! A fluoride‐assisted direct cross‐coupling of cyclic enamides with trialkoxy aryl silanes by a palladium‐catalyzed C? H activation leads to a wide range of enamides in yields of up to 95 %.
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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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Prof. Dr. Hiroaki Ohno Mutsumi Iuchi Dr. Naoto Kojima Prof. Dr. Takehiko Yoshimitsu Prof. Dr. Nobutaka Fujii Prof. Dr. Tetsuaki Tanaka 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(17):5352-5360
Palladium‐catalyzed cascade C? H alkenylation and arylation provides convenient access to polycyclic aromatic compounds. Treatment of 3‐bromoaniline derivatives bearing a bromocinnamyl group on the nitrogen atom with a catalytic amount of [Pd(OAc)2] and PCy3?HBF4 in the presence of Cs2CO3 in dioxane affords naphthalene‐fused indole derivatives in good yields. This double cyclization reaction is also applicable to heterocyclic substrates, giving fused indoles containing a heteroaromatic ring such as dibenzofuran, dibenzothiophene, carbazole, indole, or benzofuran through heterocyclic C? H arylation. When using a 2,6‐unsubstituted aniline derivative, the first C? H arylation preferentially proceeds at the more hindered position of the aniline ring. 相似文献
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Lutz Ackermann Prof. Dr. Rubén Vicente Dr. Anant R. Kapdi Dr. 《Angewandte Chemie (International ed. in English)》2009,48(52):9792-9826
The area of transition‐metal‐catalyzed direct arylation through cleavage of C? H bonds has undergone rapid development in recent years, and is becoming an increasingly viable alternative to traditional cross‐coupling reactions with organometallic reagents. In particular, palladium and ruthenium catalysts have been described that enable the direct arylation of (hetero)arenes with challenging coupling partners—including electrophilic aryl chlorides and tosylates as well as simple arenes in cross‐dehydrogenative arylations. Furthermore, less expensive copper, iron, and nickel complexes were recently shown to be effective for economically attractive direct arylations. 相似文献
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Xiang Gao Bo Wu Wen‐Xue Huang Mu‐Wang Chen Yong‐Gui Zhou 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(41):12124-12128
A palladium‐catalyzed enantioselective C H functionalization of indoles was achieved with an axially chiral 2,2′‐bipyridine ligand, thus providing the desired indol‐3‐acetate derivatives with up to 98 % ee. Moreover, the reaction protocol was also effective for asymmetric O H insertion reaction of phenols using α‐aryl‐α‐diazoacetates. This represents the first successful application of bipyridine ligands with axial chirality in palladium‐catalyzed carbene migratory insertion reactions. 相似文献
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Xiang Gao Bo Wu Wen‐Xue Huang Mu‐Wang Chen Yong‐Gui Zhou 《Angewandte Chemie (International ed. in English)》2015,54(41):11956-11960
A palladium‐catalyzed enantioselective C H functionalization of indoles was achieved with an axially chiral 2,2′‐bipyridine ligand, thus providing the desired indol‐3‐acetate derivatives with up to 98 % ee. Moreover, the reaction protocol was also effective for asymmetric O H insertion reaction of phenols using α‐aryl‐α‐diazoacetates. This represents the first successful application of bipyridine ligands with axial chirality in palladium‐catalyzed carbene migratory insertion reactions. 相似文献
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Toshiki Kurokawa Dr. Mihyong Kim Dr. J. Du Bois Prof. 《Angewandte Chemie (International ed. in English)》2009,48(15):2777-2779
A grand opening : N‐Boc‐N‐alkylsulfamides are effective substrates for the title transformation. Oxidative cyclization is highly chemoselective as well as being both stereospecific and diastereoselective. With the advent of new protocols that facilitate ring opening of the six‐membered‐ring heterocyclic products, access to differentially protected 1,3‐diamines has been made possible (see scheme).
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Toshiki Kurokawa Mihyong Kim J. DuBois 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2009,121(15):2815-2817
Schließen und öffnen : N‐Boc‐N‐alkylsulfamide sind geeignete Substrate für die Titelreaktion. Die oxidative Cyclisierung im ersten Schritt ist hoch chemoselektiv sowie stereospezifisch und diastereoselektiv. Mit neuen Verfahren zur Öffnung der dabei erhaltenen Sechsringheterocyclen werden unterschiedlich geschützte 1,3‐Diamine zugänglich (siehe Schema).
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Chris E. Houlden Marc Hutchby Chris D. Bailey J. Gair Ford Dr. Simon N. G. Tyler Dr. Michel R. Gagné Prof. Dr. Guy C. Lloyd‐Jones Prof. Dr. Kevin I. Booker‐Milburn Prof. Dr. 《Angewandte Chemie (International ed. in English)》2009,48(10):1830-1833
Pd and CO—ureally got me! The title reaction proceeds efficiently at 18 °C under CO (1 atm) with 5 % [Pd(OTs)2(MeCN)2] as precatalyst. Depending on the solvents used, either anthranilates or cyclic imides can be obtained in high yields (see picture, BQ=benzoquinone, Ts=4‐toluenesulfonyl).
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Shuai Xu Guojiao Wu Fei Ye Xi Wang Huan Li Xia Zhao Yan Zhang Jianbo Wang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(15):4752-4755
The copper(I)‐catalyzed alkylation of electron‐deficient polyfluoroarenes with N‐tosylhydrazones and diazo compounds has been developed. This reaction uses readily available starting materials and is operationally simple, thus representing a practical method for the construction of C(sp2) C(sp3) bonds with polyfluoroarenes through direct C H bond functionalization. Mechanistically, copper(I) carbene formation and subsequent migratory insertion are proposed as the key steps in the reaction pathway. 相似文献
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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