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1.
Keita Fukuzumi Dr. Yuji Nishii Prof. Dr. Masahiro Miura 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(41):12920-12924
Arene‐fused cyclooctatetraenes (COTs) possess unique structural and electronic properties that originate from their saddle‐shaped π‐conjugated architectures. Considerable attention has been paid to the transition‐metal‐mediated synthesis of these cyclic compounds; however, there have been limited achievements to date in the efficient construction of heteroarene‐fused COTs. In this contribution, we report a novel Pd‐catalyzed dehydrogenative cyclodimerization of biheteroarenes through four‐fold C−H activation toward the synthesis of a series of heteroarene‐fused COTs. A set of mechanistic investigations indicated the involvement of high‐valent Pd species prior to the dimerization event in the catalytic cycle. The redox behavior of the obtained COTs is also described briefly. 相似文献
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Thomas Hensel Denis Trpcevski Christopher Lind Rémi Grosjean Dr. Peter Hammershøj Dr. Christian B. Nielsen Dr. Theis Brock‐Nannestad Bjarne E. Nielsen Magnus Schau‐Magnussen Prof. Boris Minaev Gleb V. Baryshnikov Dr. Michael Pittelkow 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(50):17097-17102
In this paper we describe a new class of antiaromatic planar cyclooctatetraenes: the diazadioxa[8]circulenes. The synthesis was achieved by means of a new acid‐mediated oxidative dimerization of 3,6‐dihydroxycarbazoles to yield the diazadioxa[8]circulenes in high yields. The synthetic protocol appears to be general, and is a one‐pot transformation in which two C? C bonds and two C? O bonds are formed with the loss of two molecules of water. We also present a detailed characterization of the optical and electrochemical properties of this new class of stable planar cyclooctatetraenes. The properties of the diazadioxa[8]circulenes are compared with the properties of isoelectronic tetraoxa[8]circulenes and azatrioxa[8]circulenes. We discuss the antiaromatic nature of the planar central cyclooctatetraene moiety. The antiaromatic nature of the planar cyclooctatetraenes was studied by using computational methods (NICS calculations), and these calculations reveal that the central eight‐membered ring has antiaromatic character. 相似文献
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Rebecca L. Grange Dr. Michael J. Gallen Dr. Heiko Schill Dr. Jenny P. Johns Lin Dong Dr. Peter G. Parsons Dr. Paul W. Reddell Dr. Victoria A. Gordon Dr. Paul V. Bernhardt Dr. Craig M. Williams Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(29):8894-8903
A detailed examination of [4+2] cycloaddition reactions between 1,8‐disubstituted cyclooctatetraenes and diazo compounds revealed that 4‐phenyl‐1,2,4‐triazole‐3,5‐dione (PTAD) reacts to form either 2,3‐ or 3,4‐disubstituted adducts. The product distribution can be controlled by modulating the electron density of the cyclooctatetraene. Unprecedented [4+2] cycloadditions between diisopropyl azodicarboxylate (DIAD) and 1,8‐disubstituted cyclooctatetraenes are also described and further manipulation of a resulting cycloadduct uncovered a new pathway to the synthetically challenging bicyclo[4.2.0]octa‐2,4‐diene family. Variation of the substituents resulted in a range of compounds displaying selective action against different human tumour cell types. 相似文献
4.
由于独特的结构和广泛的应用,多取代环辛四烯及其苯并稠环衍生物的合成方法研究具有重要意义.本文报道了一种钯催化烯基溴化物与芳基溴化物的偶联反应.利用此钯催化的环化自偶联反应,以中等至较好的收率高选择性地从双溴代芳基或烯基化合物合成了多种二苯并[a,e]环辛四烯衍生物. 相似文献
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Ab initio and hybrid density functional quantum mechanical computation are applied to the structure and energetics of a series of annelated cyclooctatetraenes. Tetrakis-cyclobuteno, perfluorocyclobuteno or bicyclo[2.1.1]hexeno annelations result in planar structures with distinct exo and endo valence tautomers of the double bonded cycle. The contribution of each basic annelation to the exo/endo relative energy is estimated. An additivity scheme for approximating the energy of a mixed system is developed and compared to the quantum mechanical prediction. Bis bicyclic annelation to the a and d positions creates "valence tautomeric frustration" and strongly perturbs the molecular structure. This phenomenon leads to a general design for a planar cyclooctatetraenes where the "delocalized" diradicaloid state is the minimum energy form. These compounds are seen as excellent targets for chemical synthesis. 相似文献
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Ruixian Deng Shuming Zhan Chunyu Li Zhenhua Gu 《Angewandte Chemie (International ed. in English)》2020,59(8):3093-3098
A transition‐metal‐free synthesis of spiro compounds from 9H‐fluoren‐9‐ols mediated by hypervalent iodine is reported. In this reaction, an unprecedented β‐carbon elimination of tertiary alkoxyliodine(III) to form new diaryliodonium salts is proposed. The obtained phenol intermediates undergo oxidative dearomatization to furnish a class of oxo‐spiro compounds. This domino reaction significantly increases the complexity of these molecules and shows excellent regio‐ and stereoselectivity. 相似文献
7.
Joyce Wei Wei Chang Thi My Uyen Ton Philip Wai Hong Chan 《Chemical record (New York, N.Y.)》2011,11(6):331-357
Catalytic insertion or addition of a metal‐imido/nitrene species, generated from reaction of a transition‐metal catalyst with iminoiodanes, to C? H and C?C bonds offers a convenient and atom economical method for the synthesis of nitrogen‐containing compounds. Following this groundbreaking discovery during the second half of the last century, the field has received an immense amount of attention with a myriad of impressive metal‐mediated methods for the synthesis of amines and aziridines having been developed. This review will cover the significant progress made in improving the efficiency, versatility and stereocontrol of this important reaction. This will include the various iminoiodanes, their in situ formation, and metal catalysts that could be employed and new ligands, both chiral and non‐chiral, which have been designed, as well as the application of this functional group transformation to natural product synthesis and the preparation of bioactive compounds of current therapeutic interest. DOI 10.1002/tcr.201100018 相似文献
8.
This review article describes the chemistry of transition‐metal complexes containing heavier group 14 elements (Si, Ge, and Sn) as the σ‐electron‐acceptor (Z‐type) ligands and discusses the characteristics of bonds between the transition metal and Z‐type ligand. Moreover, we review the iridium hydride mediated cleavage of E–X bonds (E=Si, Ge; X=F, Cl), where the key intermediates are pentacoordinate silicon or germanium compounds bearing a dative M→E bond. 相似文献
9.
Transition‐metal‐catalyzed Chelation‐assisted C–H Functionalization of Aromatic Substrates
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In the past decade, transition‐metal‐catalyzed C–H activations have been very popular in the research field of organometallic chemistry, and have been considered as efficient and convenient strategies to afford complex natural products, functional advanced materials, fluorescent compounds, and pharmaceutical compounds. In this account, we begin with a brief introduction to the development of transition‐metal‐catalyzed C–H activation, especially the development of transition‐metal‐catalyzed chelation‐assisted C–H activation. Then, a more detailed discussion is directed towards our recent studies on the transition‐metal‐catalyzed chelation‐assisted oxidative C–H/C–H functionalization of aromatic substrates bearing directing functional groups. 相似文献
10.
Transition metal alkyls and hydrides isolated from Ziegler-type catalyst mixtures serve as appropriate models for coordination polymerization. These transition metal complexes initiate the polymerization of some vinyl compounds and aldehydes. In some cases the monomer-coordinated complexes may be isolated and the interaction of the monomer with the transition metal complexes may be studied. Comparison of the polymerization kinetics of the vinyl compounds with the decay kinetics of the initial transition metal complexes on interaction with the monomer provided important information with respect to the mechanism of coordination polymerization by these complexes. The effect of organoaluminum compounds on the reactivity of the transition metal complexes has been also studied. These transition metal alkyls initiate the polymerization of acetaldehyde to give a polyether-type polymer at -78°C and a polymer with OH groups at room temperature. 相似文献
11.
Bradley J. Holliday Chad A. Mirkin 《Angewandte Chemie (International ed. in English)》2001,40(11):1983-1983
The cover picture shows a swirling mixture of transition metal fragments and simple organic ligands that assemble into supramolecular coordination compounds, depicted on the perphery of the vortex. The synthesis of such large structures requires strategies that take into account the entropic costs of not forming higher ordered oligomers and polymers. The use of transition metal ions as building blocks for supramolecular compounds has become a widely practiced strategy for making such structures. Within this quickly growing field there have emerged three general synthetic approaches for the metal‐directed formation of supramolecular coordination compounds. These are described by B. J. Holliday and C. A. Mirkin on p. 2022 ff. 相似文献
12.
Interaction studies between photochromic spiropyrans and transition metal cations: the curious case of copper 总被引:1,自引:0,他引:1
A series of four spiropyrans bearing different substituents on the indolic nitrogen were synthesized and their capability of binding mono and bivalent transition metal cations in solution was assessed via UV-visible absorption spectroscopy. All the compounds responded selectively to the presence of Cu(ii) ions producing intense absorption bands in the visible region of their spectra. Bidimensional (1)H-NMR and MALDI-TOF MS spectroscopies revealed the formation of SP dimers mediated by Cu(ii). This is the first example of cross-coupling mediated by copper(ii) in mild conditions causing the symmetric dimerization of spiropyran dyes. 相似文献
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Low-valent N-coordinated cations and dications of heavier group 14 elements are of great interest in recent years. Their unique electronic structure gives them an ambiphilic character, as they contain both a lone electron pair and an empty p-orbital on the central metal atom. Thanks to their nucleophilic character, these compounds can act as ligands in transition metal chemistry, and conversely, their electrophilic character allows them to interact with a wide range of organic substrates and thus replace catalysts based on transition metal complexes in many chemical transformations. The aim of this article is to summarize the synthesis of N-coordinated ionic compounds of heavier group 14 elements with their subsequent reactivity towards various nucleophiles and electrophiles. 相似文献
17.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(12):3244-3248
Trifluoromethylthiolation by sulfuration of difluorocarbene with elemental sulfur is described for the first time, which overrides long‐standing trifluoromethyl anion‐based theory. Mechanistic elucidation reveals an unprecedented chemical process for the formation of thiocarbonyl fluoride and also enables transition‐metal‐mediated trifluoromethylthiolation and [18F]trifluoromethylthiolation of α‐bromo carbonyl compounds with broad substrate scope and compatibility. 相似文献
18.
Johannes Beck 《Angewandte Chemie (International ed. in English)》1994,33(2):163-172
Metal chalcogenides and metal chalcogenide halides are distinguished by their structural diversity and by their very different physical properties. Therefore, the synthesis of novel compounds from this class is always a rewarding goal for the preparatively oriented solid-state chemist. Over the past few years, many syntheses and structural investigations have stimulated the field. The emphasis of the research has been placed on selenium-rich and tellurium-rich compounds, which are characterized by directed covalent bonds between the chalcogen atoms. Compounds with novel chalcogen polycations have also become accessible during the past few years by reacting the chalcogen elements with transition metal halides, or from chemical vapor deposition in the sense of chemical transport reactions. In these compounds, tellurium differs from its lighter homologues by a pronounced tendency towards greater covalence. This article attmepts to provide an overview of new developments in the field of compounds with chalcogen polycations and of metal chalcogenide halides, with an emphasis on compounds containing molybdenum and tungsten as the transition metals and tellurium as the chalcogen. 相似文献
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Ronald N. Warrener Ian W. McCay Richard Y.S. Tan Richard A. Russell 《Tetrahedron letters》1979,20(34):3183-3186
Two new crystalline bicyclo[4.2.0]octa-2,4,7-trienes have been prepared by photodecarbonylation of the appropriate tricyclo[4.2.1.02,5]nona-3,7-dien-9-ones and their structures confirmed by 13C-n.m.r. The title compounds all undergo thermal ring opening to cyclooctatetraenes, but photolysis is substituent dependent. 相似文献