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An intramolecular, organocatalyzed Michael addition has been developed to obtain biologically important 2,3‐disubstituted cis‐2,3‐dihydrobenzofurans. By using mandelic acid salts of primary aminocatalysts, derived from cinchona alkaloids, the intramolecular cyclization reaction has been developed to proceed in high yield, with moderate to good diastereoselectivity, and up to 99 % ee. Based on the absolute configuration of the formed 2,3‐disubstituted‐cis‐2,3‐dihydrobenzofurans and by considering the observed substrate scope restrictions, a mechanistic rationalization has been presented. 相似文献
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The efficient, regioselective synthesis of functionalized/annulated quinolines was achieved by the coupling of 2‐aminoaryl ketones with alkynes/active methylenes/α‐oxoketene dithioacetals promoted by InCl3 in refluxing acetonitrile as well as under solvent‐free conditions in excellent yields. This transformation presumably proceeded through the hydroamination–hydroarylation of alkynes, and the Friedländer annulation of active methylene compounds and α‐oxoketene dithioacetals with 2‐aminoarylketones. In addition, simple reductive and oxidative cyclization of 2‐nitrobenzaldehyde and 2‐aminobenzylalcohol, respectively, afforded substituted quinolines. Systematic optimization of the reaction parameters allowed us to identify two‐component coupling (2CC) conditions that were tolerant of a wide range of functional groups, thereby providing densely functionalized/annulated quinolines. This approach tolerates the synthesis of various bioactive quinoline frameworks from the same 2‐aminoarylketones under mild conditions, thus making this strategy highly useful in diversity‐oriented synthesis (DOS). The scope and limitations of the alkyne‐, activated methylene‐, and α‐oxoketene dithioacetal components on the reaction were also investigated. 相似文献
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Efficient 1,2‐carboboration reactions to the C=N bond of carbodiimides with 9‐borafluorenes, which give rise to cyclic borane‐amidine conjugates with a seven‐membered BNC5 ring, are reported. The resulting cyclic borane‐amidine conjugates can be hydrolyzed into an acyclic bifunctional biaryl compound carrying both boronic acid and amidine groups, rendering the utility of the two‐step protocol for the synthesis of multi‐functionalized molecular systems with a potential as a supramolecular building block. Furthermore, the conjugated structure of the cyclic boron‐amidine compounds can be changed upon alkylation of the boron atom that increases the coordination number of boron. The combination of Lewis acid (borane) and conjugated base (amidine) provides rich structural diversity of heteroatom‐containing π‐conjugated systems. 相似文献
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Prof. Dr. Santos Fustero Lidia Herrera Ruben Lázaro Elsa Rodríguez Dr. Miguel A. Maestro Dr. Natalia Mateu Pablo Barrio 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(35):11776-11785
The nucleophilic addition (AN) / intramolecular aza‐Michael reaction (IMAMR) process on Ellman’s tert‐butylsulfinyl imines, bearing a Michael acceptor in the ortho position, is studied. This reaction affords 1,3‐disubstituted isoindolines with a wide range of substituents in good yields and diastereoselectivities. Interestingly, careful choice of the base for the aza‐Michael step allows either the cis or the trans diastereoisomers to be exclusively obtained. This stereodivergent cyclization has enabled the synthesis of C2‐symmetric bisacetate‐substituted isoindolines. In addition, bisacetate isoindolines bearing two well‐differentiated ester moieties are also noteworthy because they may allow for the orthogonal synthesis of β,β′‐dipeptides using a single nitrogen atom as a linchpin. 相似文献
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Christian Gnamm Dipl.‐Chem. Caroline M. Krauter Kerstin Brödner Günter Helmchen Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(9):2050-2054
Pressing the configurational switch : Use of enantiomeric Ir catalysts allows the vinylpiperidine building blocks 2 a and 2 b to be synthesized with high selectivity. Total syntheses of the dendrobate alkaloid (+)‐241 D, its C6‐epimer, and a spruce alkaloid are presented as applications.
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Mehdi Khoobi Ali Ramazani Alireza Foroumadi Saeed Emami Farnaz Jafarpour Amir Mahyari Katarzyna Ślepokura Tadeusz Lis Abbas Shafiee 《Helvetica chimica acta》2012,95(4):660-671
An efficient and organocatalyzed asymmetric reaction of phenacyl halides with coumarin‐based dihydrobenzothiazoles was developed to afford cis‐2,3‐disubstituted 3,4‐dihydro‐2H‐benzothiazines. This method provides a one‐step and highly diastereoselective route to a wide variety of coumarin‐based 3,4‐dihydro‐2H‐benzothiazines using the cheap and commercially available Cinchona alkaloid quinine hydrochloride. 相似文献
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A Highly cis‐Selective and Enantioselective Metal‐Free Hydrogenation of 2,3‐Disubstituted Quinoxalines 下载免费PDF全文
Zhenhua Zhang Prof. Dr. Haifeng Du 《Angewandte Chemie (International ed. in English)》2015,54(2):623-626
A wide range of 2,3‐disubstituted quinoxalines have been successfully hydrogenated with H2 using borane catalysts to produce the desired tetrahydroquinoxalines in 80–99 % yields with excellent cis selectivity. Significantly, the asymmetric reaction employing chiral borane catalysts generated by the in situ hydroboration of chiral dienes with HB(C6F5)2 under mild reaction conditions has also been achieved with up to 96 % ee, and represents the first catalytic asymmetric system to furnish optically active cis‐2,3‐disubstituted 1,2,3,4‐tetrahydroquinoxalines. 相似文献
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Daniel Sol Josep Bonjoch Silvina García‐Rubio Emma Peidr Joan Bosch 《Angewandte Chemie (International ed. in English)》1999,38(3):395-397
Fifteen steps suffice for an enantioselective total synthesis of (−)‐strychnine ( 1 ) from 1,3‐cyclohexanedione. The key steps are the easy generation of the enantiopure intermediate 2 , the closure of the piperidine ring by a reductive Heck reaction, and the elaboration of the indoline nucleus in an advanced synthetic stage. TBDMS=tert‐butyldimethylsilyl. 相似文献
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Palladium‐Catalyzed Enantioselective Reductive Heck Reactions: Convenient Access to 3,3‐Disubstituted 2,3‐Dihydrobenzofuran 下载免费PDF全文
Zhan‐Ming Zhang Bing Xu Yanyan Qian Lizuo Wu Yuanqi Wu Lujia Zhou Prof. Dr. Yu Liu Prof. Dr. Junliang Zhang 《Angewandte Chemie (International ed. in English)》2018,57(32):10373-10377
The first example of highly enantioselective intramolecular hydroarylation of allyl aryl ethers was realized by palladium‐catalyzed reductive heck reactions utilizing a new chiral sulfinamide phosphine ligand (N‐Me‐ XuPhos ). N‐Me‐ XuPhos can be easily prepared on gram scale from readily available starting materials in a one‐pot synthesis approach. A series of optically active 2,3‐dihydrobenzofurans bearing a quaternary stereocenter were obtained in good yields and with excellent enantioselectivities. The practicality of this reaction was validated in the straightforward synthesis of CB2 receptor agonists. Moreover, deuterium was efficiently incorporated into the products. 相似文献
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Taku Sakaguchi Toyoharu Kobayashi Dr. Sho Hatano Hiroshi Tsuchikawa Dr. Koichi Fukase Prof. Dr. Katsunori Tanaka Dr. Shigeo Katsumura Prof. Dr. 《化学:亚洲杂志》2009,4(10):1573-1577
An efficient one‐pot synthetic procedure for the synthesis of 2,4‐disubstituted pyridines has been successfully established. The method proceeds through a 6π‐azaelectrocyclization‐aromatization sequence. Using this method, a wide variety of pyridine structures substituted at the 2‐position have been rapidly constructed from vinyl stannanes, vinyl iodide, sulfonamide, and a palladium catalyst. The method was further applied to the solid‐phase synthesis wherein the use of a “traceless” sulfonamide linker enabled the rapid preparation of a small library of pyridines with high purity, without any chromatographic separation. 相似文献
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《Journal of heterocyclic chemistry》2017,54(5):2656-2663
A simple and convenient procedure for the preparation of some unknown 2,3‐disubstituted 5‐iodo‐1H‐pyrrolo[2,3‐b ]pyridines from readily available starting materials by Fischer indole cyclization in polyphosphoric acid is described. The present methodology provides an alternative synthetic approach to the synthesis of 5‐iodo‐7‐azaindole scaffold. All synthesized compounds were characterized by IR, MS, 1H and 13C NMR, and elemental analysis. 相似文献
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Yu‐Ping He Hua Wu Qian Wang Jieping Zhu 《Angewandte Chemie (International ed. in English)》2020,59(5):2105-2109
We report herein the first examples of a palladium‐catalyzed enantioselective Cacchi reaction for the synthesis of indoles bearing a chiral C2‐aryl axis. In the presence of a catalytic amount of Pd(OAc)2 and (R,R)‐QuinoxP* ligand, reaction of N‐aryl(alkyl)sulfonyl‐2‐alkynylanilides with arylboronic acids under oxygen atmosphere afforded enantioenriched 2,3‐disubstituted indoles in high yields and enantioselectivity. The indole ring is constructed de novo in this process and a complexation‐induced chirality transfer is proposed to account for the observed enantioselectivity. 相似文献
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Squaramide‐Catalyzed Synthesis of Enantioenriched Spirocyclic Oxindoles via Ketimine Intermediates with Multiple Active Sites 下载免费PDF全文
Qiang‐Sheng Sun Hua Zhu Yong‐Jian Chen Dr. Xiao‐Di Yang Prof. Xing‐Wen Sun Prof. Guo‐Qiang Lin 《Angewandte Chemie (International ed. in English)》2015,54(45):13253-13257
A new method for the construction of five‐membered spirocyclic oxindoles is based on a Michael–Mannich cascade reaction of a ketimine intermediated catalyzed by a bifunctional quinine‐derived squaramide. The desired products were obtained in excellent yields (up to 94 %) and stereoselectivities (up to >20:1 d.r., >99 % ee). A scaled‐up variant also proceeded smoothly showing that the one‐pot reaction might find application in the synthesis of bioactive‐compound libraries. 相似文献
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A series of regioisomers of pyrazolyl-substituted quinolines has been synthesized through the simple condensation reaction between hydrazinylquinolines with aliphatic 1,3-diketones with InCl3 as a catalyst under microwave irradiation. This method produces pure products in good yield in a rapid manner compared to conventional procedures and withneat reaction condition. The approach has the advantages of operational simplicity and increased safety for a shortened synthesis of pyrazolyl-substituted quinolines. 相似文献
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