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1.
Benign Approaches for the Microwave‐assisted Synthesis of Five‐membered 1,2‐N,N‐heterocycles
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Navjeet Kaur 《Journal of heterocyclic chemistry》2015,52(4):953-973
The development of new strategies for the synthesis of small‐sized heterocycles has remained a highly attractive but challenging proposition. An overview of the application of microwave irradiation in the synthesis of two nitrogen atoms containing five‐membered heterocyclic compounds is presented, focusing on the developments in the last 5–10 years. This contribution covers the literature concerning the total synthesis of five‐membered 1,2‐N,N‐heterocycles. 相似文献
2.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2018,130(6):1612-1616
We report herein the first enantioselective cycloaddition of vinyl oxetanes, the reaction of which with azadienes provided unprecedented access to ten‐membered heterocycles through a [6+4] cycloaddition. By using a commercially available chiral Pd‐SIPHOX catalyst, a wide range of benzofuran‐ as well as indole‐fused heterocycles could be accessed in excellent yield and enantioselectivity. A unique Lewis acid induced fragmentation of these ten‐membered heterocycles was also discovered. 相似文献
3.
Paving the Way to Novel Phosphorus‐Based Architectures: A Noncatalyzed Protocol to Access Six‐Membered Heterocycles
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Dr. Carlos Romero‐Nieto Alicia López‐Andarias Dr. Carolina Egler‐Lucas Florian Gebert Jens‐Peter Neus Oliver Pilgram 《Angewandte Chemie (International ed. in English)》2015,54(52):15872-15875
Phosphorus‐based heterocycles provide access to materials with properties that are inaccessible from all‐carbon architectures. The unique hybridization of phosphorus gives rise to electron‐accepting capacities, a large variety of coordination reactions, and the possibility of controlling the electronic properties through phosphorus postfunctionalization. Herein, we describe a new noncatalyzed synthetic protocol to prepare fused six‐membered phosphorus heterocycles. In particular, we report the synthesis of novel phosphaphenalenes. These fused systems exhibit the benefits of both five‐ and six‐membered phosphorus heterocycles and enable a series of versatile postfunctionalization reactions. This work thus opens up new horizons in the field of conjugated materials. 相似文献
4.
Carbaborane‐Substituted 1,2,3‐Triphospholanes and 1‐Aza‐2,5‐diphospholane: New Synthetic Approaches
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Dr. Anika Kreienbrink Sarah Heinicke Thi Thuy Duong Pham Dr. René Frank Dr. Peter Lönnecke Prof. Dr. Evamarie Hey‐Hawkins 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(5):1434-1439
New phosphorus‐containing, five‐membered P,P,P and P,N,P heterocycles were synthesized and fully characterized. The P,P,P heterocycles, 1,2,3‐triphospholanes, can be synthesized by two different facile pathways, whereas the P,N,P compound, a 1‐aza‐2,5‐diphospholane, can only be obtained with silylamine. 相似文献
5.
Dr. Pilar Ventosa‐Andrés Dr. Agustina La‐Venia Dr. Carlos Alfonso Barea Ripoll Dr. Ludmila Hradilová Dr. Viktor Krchňák 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(37):13112-13119
Herein, we describe the synthesis of molecular scaffolds consisting of medium‐sized fused heterocycles using amino acids, which are some of the most useful building blocks used by nature as well as chemists to create structural diversity. The acyclic precursors were assembled by using traditional Merrifield solid‐phase peptide synthesis, and cyclization was carried out through acid‐mediated tandem endocyclic N‐acyliminium ion formation, followed by nucleophilic addition with internal nucleophiles. The synthesis of molecular scaffolds consisting of seven‐, eight‐, and nine‐membered rings proceeded with full stereocontrol of the newly generated stereogenic center in most cases. 相似文献
6.
Chong Huang Xiang‐Yang Qian Hai‐Chao Xu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(20):6722-6725
Reported herein is the synthesis of benzofused six‐membered S‐heterocycles by intramolecular dehydrogenative C?S coupling using a modular flow electrolysis cell. The continuous‐flow electrosynthesis not only ensures efficient product formation, but also obviates the need for transition‐metal catalysts, oxidizing reagents, and supporting electrolytes. Reaction scale‐up is conveniently achieved through extended electrolysis without changing the reaction conditions and equipment. 相似文献
7.
Synthesis of Organofluoro Compounds Using Methyl Perfluoroalk‐2‐ynoates as Building Blocks
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This review provides an overview of several synthetic applications of methyl perfluoroalk‐2‐ynoates, leading to convenient preparation of many perfluoroalkylated compounds. The use of these important substrates in the synthesis of various five‐, six‐, and seven‐membered heterocycles, cyclopentadienes, and biphenyls is described, alongside a discussion of the mechanistic aspects of these reactions. 相似文献
8.
Metal‐Free Hydrogen Atom Transfer from Water: Expeditious Hydrogenation of N‐Heterocycles Mediated by Diboronic Acid
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Yun‐Tao Xia Xiao‐Tao Sun Ling Zhang Kai Luo Prof. Dr. Lei Wu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(48):17151-17155
A hydrogenation of N‐heterocycles mediated by diboronic acid with water as the hydrogen atom source is reported. A variety of N‐heterocycles can be hydrogenated with medium to excellent yields within 10 min. Complete deuterium incorporation from stoichiometric D2O onto substrates further exemplifies the H/D atom sources. Mechanism studies reveal that the reduction proceeds with initial 1,2‐addition, in which diboronic acid synergistically activates substrates and water via a six‐membered ring transition state. 相似文献
9.
Palladium‐Catalyzed Carbonylative Reactions of 1‐Bromo‐2‐fluorobenzenes with Various Nucleophiles: Effective Combination of Carbonylation and Nucleophilic Substitution
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Jianbin Chen Dr. Kishore Natte Dr. Helfried Neumann Prof. Xiao‐Feng Wu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(49):16107-16110
A systematic study on the carbonylative transformation of 1‐bromo‐2‐fluorobenzenes with various nucleophiles has been performed. Different types of double nucleophiles, such as N?N, N?C, O?C, and N?S, can be effectively applied as coupling partners. The corresponding six‐membered heterocycles were isolated in moderate to good yields. 相似文献
10.
Julio Hernndez‐Díaz Angelina Flores‐Parra Rosalinda Contreras 《Heteroatom Chemistry》2004,15(4):307-320
Sixteen different P(III) and P(V) heterocycles derived from 2‐(2‐hydroxyphenyl)‐1H‐benzimidazole ( 1 ) are reported. In these heterocycles the phosphorus atom is part of a six‐membered unsaturated ring. They were mainly studied by multinuclear NMR. The X‐ray diffraction of 3,4‐ benzimidazole‐5,6‐benzo‐2‐dimethylamino‐2‐seleno‐ 1,3,2‐oxazaphosphorinane is reported. Phosphoranes derived from 1 and 3,5‐di‐tert‐butylcatechol, and bearing Cl, NMe2, or phenyl as substituent at phosphorus are presented. © 2004 Wiley Periodicals, Inc. Heteroatom Chem 15:307–320, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20021 相似文献
11.
Navjeet Kaur 《Journal of heterocyclic chemistry》2019,56(4):1141-1167
Some transformations are not possible with ground‐state reactions even in the presence of a catalyst; hence, they are performed under photochemical conditions. Electron transfer occurred even with the photochemical excitement of one molecule where redox reaction is not possible at the ground state. The side products were obtained from ground‐state reactions. For C─C bond formation during photochemical reactions, there was no requirement of any chemical activation of the substrates. Therefore, these reactions are presented here for the synthesis of three‐membered and four‐membered heterocycles in the context of sustainable processes. 相似文献
12.
The versatility and potential of oxidative cyclization in the synthesis of 5‐ and 6‐membered N‐ and/or O‐heterocycles is presented through judiciously selected examples.© 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:642–670, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10200 相似文献
13.
Highly Enantioselective Nucleophilic Dearomatization of Pyridines by Anion‐Binding Catalysis
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Prof. Dr. Olga García Mancheño Sören Asmus Mercedes Zurro Theresa Fischer 《Angewandte Chemie (International ed. in English)》2015,54(30):8823-8827
The asymmetric dearomatization of N‐heterocycles is an important synthetic method to gain bioactive and synthetically valuable chiral heterocycles. However, the catalytic enantio‐ and regioselective dearomatization of the simplest six‐membered‐ring N‐heteroarenes, the pyridines, is still very challenging. The first anion‐binding‐catalyzed, highly enantioselective nucleophilic dearomatization of pyridines with triazole‐based H‐bond donor catalysts is presented. Contrary to other more common NH‐based H‐bond donors, this type of organocatalyst shows a prominent higher C2‐regioselectivity and is able to promote high enantioinductions via formation of a close chiral anion‐pair complex with a preformed N‐acyl pyridinium ionic intermediate. This method offers a straightforward and useful synthetic approach to chiral N‐heterocycles from abundant and readily available pyridines. 相似文献
14.
Light‐Induced Ruthenium‐Catalyzed Nitrene Transfer Reactions: A Photochemical Approach towards N‐Acyl Sulfimides and Sulfoximines
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Dr. Vincent Bizet Laura Buglioni Prof. Dr. Carsten Bolm 《Angewandte Chemie (International ed. in English)》2014,53(22):5639-5642
1,4,2‐Dioxazol‐5‐ones are five‐membered heterocycles known to decarboxylate under thermal or photochemical conditions, thus yielding N‐acyl nitrenes. Described herein is a light‐induced ruthenium‐catalyzed N‐acyl nitrene transfer to sulfides and sulfoxides by decarboxylation of 1,4,2‐dioxazol‐5‐ones at room temperature, thus providing direct access to N‐acyl sulfimides and sulfoximines under mild reaction conditions. In addition, a one‐pot sulfur imidation/oxidation sequence catalyzed by a single ruthenium complex is reported. 相似文献
15.
Old Selenium Heterocycles Revisited: Synthesis,Spectroscopic, and Structural Characterization of N‐Acyl‐1,3‐selenazol‐2(3H)‐imines and 5‐Acyl‐1,3‐selenazol‐2‐amines from Acylselenourea Derivatives
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Fabian Mohr 《Journal of heterocyclic chemistry》2014,51(5):1435-1441
A series of five‐membered selenium heterocycles was prepared from the reaction of various selenoureas and phenacyl bromides. In the case of 1‐acyl‐3‐arylselenoureas N‐acyl‐1,3‐selenazol‐2(3H)‐imines are formed, whereas the analogous reaction with 3,3‐disubstituted 1‐acylselenoureas affords 5‐acyl‐1,3‐selenazol‐2‐amines. The compounds were characterized by NMR spectroscopy and mass spectrometry. In addition, the proposed structures were unambiguously confirmed by X‐ray diffraction studies. 相似文献
16.
Gyrgy Keglevich 《Journal of heterocyclic chemistry》2005,42(3):451-462
In our laboratory, we have been dealing with the synthesis and utilization of P‐heterocycles for almost two decades. In this paper, our recent results are summarised. In the first part, the synthesis and properties of phospholes with sterically demanding substituent on the phosphorus atom and the fragmentation‐related properties of phosphole oxide‐related 7‐phosphanorbornenes are discussed. Then, new families of 6‐membered P‐heterocycles are introduced available by a ring enlargement method and subsequent modifications. In the next part, I show how bridged P‐heterocycles were prepared and how they were utilised in fragmentation‐related phosphorylations. Finally a novel reaction providing heterocyclic phosphoranes/ylides is discussed. 相似文献
17.
Ring Enlargement of Three‐Membered Boron Heterocycles upon Reaction with Organic π Systems: Implications for the Trapping of Borylenes
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M. Sc. Małgorzata Krasowska Prof. Holger F. Bettinger 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(30):10661-10670
New low‐energy pathways for the reaction between substituted boriranes and borirenes with unsaturated hydrocarbons (ethyne or ethene) were discovered using density functional and coupled cluster theory. The interaction between the π bond of the hydrocarbon and the empty p orbital of the boron center leads to ring expansion of the three‐membered to a five‐membered boron heterocycle. The reactions are strongly exothermic and have low or even no barriers. They involve intermediates with a pentacoordinate boron center with two hydrocarbon molecules coordinating to boron akin to metal‐olefin complexes. These borylene complexes are shallow minima on the potential energy surfaces. But significantly higher barriers for ring formation are computed for 1,5‐cyclooctadiene and dibenzocyclooctatetraene complexes of borylenes, making these complexes likely detectable under appropriate experimental conditions. Our computational findings have implications for the interpretation of trapping experiments of thermally generated small borylenes with excess of small π systems. Because of very low barriers for reactions of three‐membered boron heterocycles with π systems and the at least locally large excess of the latter under such conditions, formation of five‐membered boron heterocycles should be considered. 相似文献
18.
Eric Cuthbertson Christopher S. Frampton David D. MacNicol 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(4):431-432
The structures of the highly substituted title heterocycles, C20H22N2S and C20H22N2O2S, have been determined at 123 (1) K. Both molecules possess exact C2 symmetry and the seven‐membered rings have very similar twist‐boat conformations. The magnitudes of the C—S—C bond angles, 107.13 (6) and 108.27 (7)°, respectively, are influenced significantly by the four substituent methyl groups on the seven‐membered rings. 相似文献
19.
Lawrence L. W. Cheung Andrei K. Yudin Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(13):4100-4109
In this contribution, aminocyclobutanes, as well as eight‐membered enamide rings, have been made from N‐vinyl β‐lactams. The eight‐membered products have been formed by a [3,3]‐sigmatropic rearrangement, whereas the aminocyclobutanes have been derived from a domino [3,3]‐rearrangement/6π‐electrocyclisation process. The aminocyclobutanes have been obtained in a highly diastereoselective fashion. The cyclobutane ring system tolerates fusion even if adjacent quaternary centres are present. Systems containing up to four fused rings are readily accessible. The reaction profile has been investigated by using Gaussian 03. This study suggests that two reaction pathways for aminocyclobutane formation are possible. In one pathway the [3,3]‐sigmatropic rearrangement is the rate‐limiting step and in the second pathway the electrocyclisation is rate limiting. Taken together, these reactions should facilitate the construction of fused heterocycles. 相似文献
20.
First described in the late 1960s, N‐alkylsulfonylimines are heterocumulenes that participate in reactions with a range of 1,3‐dipoles to afford interesting 3‐, 4‐, 5‐, and 6‐membered heterocycles. The distribution of adducts obtained suggests that multistage, stepwise mechanistic pathways rather than a concerted process are in operation. 相似文献