共查询到20条相似文献,搜索用时 31 毫秒
1.
Yasuhiro Hashimoto Dr. Genki Horiguchi Prof. Dr. Hidehiro Kamiya Prof. Dr. Yohei Okada 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(65):e202202018
The design of photocatalytic processes is important for a sustainable society. Key to these photocatalytic reactions is electron transfer. This article is focused on titanium dioxide photocatalyzed organic synthesis and the design of a new [2+2] cycloaddition reaction based on the electron transfer process. Electron transfer - not only between the substrate and the photocatalyst but also inter- and intramolecularly – is crucial for the reaction design. Radical cations were generated by the photocatalyst and trapped by alkenes. The resultant cyclobutyl radical cations were immediately reduced by the aryl rings via intramolecular electron transfer to obtain cyclobutane rings. The outcome of the reaction was controlled by substitution of the aryl ring and the linker connecting the aryl ring to the enol ether. The carefully designed substrates were highly effective for photocatalytic cycloaddition. 相似文献
2.
Avinash S. Bhat Sven M. Elbert Wen‐Shan Zhang Frank Rominger Michael Dieckmann Rasmus R. Schrder Michael Mastalerz 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(26):8911-8915
In recent years, interest in shape‐persistent organic cage compounds has steadily increased, not least because dynamic covalent bond formation enables such structures to be made in high to excellent yields. One often used type of dynamic bond formation is the generation of an imine bond from an aldehyde and an amine. Although the reversibility of the imine bond formation is advantageous for high yields, it is disadvantageous for the chemical stability of the compounds. Amide bonds are, in contrast to imine bonds much more robust. Shape‐persistent amide cages have so far been made by irreversible amide bond formations in multiple steps, very often accompanied by low yields. Here, we present an approach to shape‐persistent amide cages by exploiting a high‐yielding reversible cage formation in the first step, and a Pinnick oxidation as a key step to access the amide cages in just three steps. These chemically robust amide cages can be further transformed by bromination or nitration to allow post‐functionalization in high yields. The impact of the substituents on the gas sorption behavior was also investigated. 相似文献
3.
Ke Xu Wenchang Li Shaoheng Zhu Tingshun Zhu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(49):17789-17794
Atroposelective arene formation is an efficient method to build axially chiral molecules with multi‐substituted arenes. Reported here is an organocatalyzed atroposelective arene formation reaction by an N‐heterocyclic carbene (NHC) catalyzed formal [4+2] cycloaddition of conjugated dienals and α‐aryl ketones. This study expands the synthetic potential of NHC organocatalysis and provides a competitive pathway for the synthesis of axially chiral ligands, catalysts, and other functional molecules. 相似文献
4.
Twelve kinds of ketene [2+2] cycloadditions have been investigated by ab initio calculations. They are composed of four ketenes
(Y–HC=C=O, Y=H, NH2, Cl, and CN) and three isoelectronic ketenophiles (ethylene, methylenimine, and formaldehyde). All the transition state geometries
obtained here are not different significantly, but the extent of formation of two covalent bonds differs appreciably. The
difference is attributable to the degree of the charge transfer interactions. One is the interaction from the π orbital and/or the lone pair orbital of a ketenophile to the LUMO of a ketene (dominant charge transfer, CT1). The other
is that from the HOMO of the ketene to the π* orbital of the ketenophile (second dominant charge transfer, ct1). CT1 contributes to the formation of only one covalent
bond, and ct1 does to the formation of the other. This independent function is characteristic of ketene [2+2] cycloadditions.
They are not concerned with the orbital phase. We also have examined Fukui's postulate that the deformation of particular
frontier orbitals causes the reaction progress. The role has been verified both by configuration analyses along the intrinsic
reaction coordinate of the ketene-ethylene reaction and by the examination of distortions of frontier-orbital shapes along
the low-frequency vibrational modes.
Received: 25 June 1998 / Accepted: 28 August 1998 / Published online: 11 November 1998 相似文献
5.
Dr. Yi Qin Qing-Hui Ling Yu-Te Wang Dr. Yi-Xiong Hu Prof. Lianrui Hu Prof. Xiaoli Zhao Prof. Dong Wang Prof. Hai-Bo Yang Prof. Lin Xu Prof. Ben Zhong Tang 《Angewandte Chemie (International ed. in English)》2023,62(36):e202308210
A series of covalent organic cages built from fluorophores capable of aggregation-induced emission (AIE) were elegantly prepared through the reduction of preorganized M2(LA)3(LB)2-type metallacages, simultaneously taking advantage of the synthetic accessibility and well-defined shapes and sizes of metallacages, the good chemical stability of the covalent cages as well as the bright emission of AIE fluorophores. Moreover, the covalent cages could be further post-synthetically modified into an amide-functionalized cage with a higher quantum yield. Furthermore, these presented covalent cages proved to be good energy donors and were used to construct light-harvesting systems employing Nile Red as an energy acceptor. These light-harvesting systems displayed efficient energy transfer and relatively high antenna effect, which enabled their use as efficient photocatalysts for a dehalogenation reaction. This research provides a new avenue for the development of luminescent covalent cages for light-harvesting and photocatalysis. 相似文献
6.
van Leeuwen FW Beijleveld H Velders AH Huskens J Verboom W Reinhoudt DN 《Organic & biomolecular chemistry》2005,3(10):1993-2001
The synthesis and NOE-based structural characterization is described of thiacalix[4]arene tricarboxylic acid (7), thiacalix[4]crown-5 and -6 monocarboxylic acids (2 and 5), and the bis(N-methylsulfonyl)thiacalix[4]crowns-5 and -6 (4a,b). The 226Ra2+ selectivity coefficients, log(K(Ra)ex/K(M)ex), of the new thiacalix[4]arene derivatives are compared directly with those of thiacalix[4]crown-5 and -6 (1a,b), thiacalix[4]crown-5 and -6 dicarboxylic acids (3a,b), and thiacalix[4]arene di- and tetracarboxylic acids (6 and 8). Thiacalix[4]arene dicarboxylic acid (6) already exhibits a high 226Ra2+ selectivity, but this is significantly improved in the case of 3b, having an additional crown-(6-)ether bridge. The covalent combination of a crown ether and carboxylic acid substituents as in the thiacalix[4]arenes 2,3a,b,4a,b, and 5 gives a better 226Ra2+ selectivity in the presence of Sr2+ or Ba2+ than mixtures of dibenzo-21-crown-7 and thiacalix[4]arene dicarboxylic acid (6) or of pentadecanoic acid and thiacalix[4]crown-6 (1b). 相似文献
7.
8.
Mathias Schäfer Frank Dreiocker Herbert Budzikiewicz 《Journal of mass spectrometry : JMS》2009,44(2):278-284
The loss of AgH from [M + Ag]+ precursor ions of tertiary amines, aminocarboxylic acids and aryl alkyl ethers is examined by deuterium labeling combined with collision activation (CA) dissociation experiments. It was possible to demonstrate that the AgH loss process is highly selective toward the hydride abstraction. For tertiary amines and aminocarboxylic acids, hydrogen originates from the α‐methylene group carrying the nitrogen function (formation of an immonium ion). In all cases examined, the most stable, i.e. the thermodynamically favored product ion is formed. In the AgH loss process, a large isotope effect operates discriminating against the loss of D. The [M + Ag]+ ion of benzyl methyl ether loses a hydride ion exclusively from the benzylic methylene group supporting the experimental finding that the AgH loss reaction selectively cleaves the weakest C? H bond available. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
9.
Tobias H. G. Schick Jochen C. Lauer Frank Rominger Michael Mastalerz 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(6):1782-1787
In contrast to organic cages which are formed by exploiting dynamic covalent chemistry, such as boronic ester cages, imine cages, or disulfide cages, those with a fully carbonaceous backbone are rarer. With the exception of alkyne metathesis based approaches, the vast majority of hydrocarbon cages need to be synthesized by kinetically controlled bond formation. This strategy implies a multiple step synthesis and no correction mechanism in the final macrocyclization step, both of which are responsible for low overall yields. Whereas for smaller cages the intrinsic drawbacks are not always obvious, larger cages are seldom synthesized in yields beyond a few tenths of a percent. Presented herein is a three‐step method to convert imine cages into hydrocarbon cages. The method has been successfully applied to even larger structures such as derivatives of C72H72 , an unknown cage suggested by Fritz Vögtle more than 20 years ago. 相似文献
10.
Dr. Saibal Bera Dr. Satyajit Das Prof. Dr. Manuel Melle-Franco Prof. Dr. Aurelio Mateo-Alonso 《Angewandte Chemie (International ed. in English)》2023,62(5):e202216540
Organic cages have gained increasing attention in recent years as molecular hosts and porous materials. Among these, barrel-shaped cages or molecular nanobarrels are promising systems to encapsulate large hosts as they possess windows of the same size as their internal cavity. However, these systems have received little attention and remain practically unexplored despite their potential. Herein, we report the design and synthesis of a new trigonal prismatic organic nanobarrel with two large triangular windows with a diameter of 12.7 Å optimal for the encapsulation of C60. Remarkably, this organic nanobarrel shows a high affinity for C60 in solvents in which C60 is virtually insoluble, providing stable solutions of C60. 相似文献
11.
Dr. Enquan Jin Keyu Geng Ka Hung Lee Weiming Jiang Juan Li Qiuhong Jiang Prof. Dr. Stephan Irle Prof. Dr. Donglin Jiang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(29):12260-12267
A strategy is presented for the synthesis of crystalline porous covalent organic frameworks via topology-templated polymerization. The template is based on imine-linked frameworks and their (001) facets seed the C=C bond formation reaction to constitute 2D sp2 carbon-conjugated frameworks. This strategy is applicable to templates with different topologies, enables designed synthesis of frameworks that cannot be prepared via direct polymerization, and creates a series of sp2 carbon frameworks with tetragonal, hexagonal, and kagome topologies. The sp2 carbon frameworks are highly luminescent even in the solid state and exhibit topology-dependent π transmission and exciton migration; these key fundamental π functions are unique to sp2 carbon-conjugated frameworks and cannot be accessible by imine-linked frameworks, amorphous analogues, and 1D conjugated polymers. These results demonstrate an unprecedented strategy for structural and functional designs of covalent organic frameworks. 相似文献
12.
Masataka Nakahara Prof. Kengo Hanaya Prof. Takeshi Sugai Prof. Shuhei Higashibayashi 《ChemistryOpen》2021,10(6):627-629
Dearomative heterocyclic [4+2] cycloaddition between the N-(2,4-dinitrophenyl)pyridinium ion of nicotinamide and an enol ether was analyzed by Density Functional Theory (DFT) calculations. The calculation revealed that the reaction undergoes stepwise bond formation rather than occurring in a concerted manner. The experimental products were found to be both kinetically and thermodynamically favored. The calculated transition states and intermediate suggested that the high diastereoselectivity is derived from the electrostatic interaction between the 2-nitro group of the pyridinium ion and the hydrogen of the enol ether. 相似文献
13.
14.
Yukimasa Aida Dr. Yu Shibata Prof. Dr. Ken Tanaka 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(14):3004-3009
The enantioselective synthesis of distorted π-extended chiral triptycenes, consisting of three distinct aromatic rings, has been achieved with high ee value of 87 % by the cationic rhodium(I)/segphos complex-catalyzed enantioselective [2+2+2] cycloaddition of 2,2′-di(prop-1-yn-1-yl)-5,5′-bis(trifluoromethyl)-1,1′-biphenyl with 6-methoxy-1,2-dihydronaphthalene followed by the diastereoselective Diels–Alder reaction and aromatization. Demethoxy derivatives were also synthesized by the C−O bond cleavage. In this synthesis, the use of the electron-deficient diyne and the electron-rich alkene is crucial to suppress the undesired strain-relieving carbocation rearrangement and stabilize the distorted triptycene structure. 相似文献
15.
Qi Wang Chenxi Zhang Dr. Bruce C. Noll Dr. Hai Long Dr. Yinghua Jin Prof. Dr. Wei Zhang 《Angewandte Chemie (International ed. in English)》2014,53(40):10663-10667
Shape‐persistent covalent organic polyhedrons (COPs) with ethynylene linkers are usually prepared through kinetically controlled cross‐coupling reactions. The high‐yielding synthesis of ethynylene‐linked rigid tetrameric cages via one‐step alkyne metathesis from readily accessible triyne precursors is presented. The tetrameric cage contains two macrocyclic panels and exhibits D2h symmetry. The assembly of such a COP is a thermodynamically controlled process, which involves the initial formation of macrocycles as key intermediates followed by the connection of two macrocycles with ethynylene linkages. With a large internal cavity, the cage exhibits a high binding selectivity toward C70 (K=3.9×103 L mol?1) over C60 (no noticeable binding). 相似文献
16.
Koushik Acharyya Prof. Dr. Partha Sarathi Mukherjee 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(6):1646-1657
A supramolecular approach that uses hydrogen‐bonding interaction as a driving force to accomplish exceptional self‐sorting in the formation of imine‐based covalent organic cages is discussed. Utilizing the dynamic covalent chemistry approach from three geometrically similar dialdehydes ( A , B , and D ) and the flexible triamine tris(2‐aminoethyl)amine ( X ), three new [3+2] self‐assembled nanoscopic organic cages have been synthesized and fully characterized by various techniques. When a complex mixture of the dialdehydes and triamine X was subjected to reaction, it was found that only dialdehyde B (which has OH groups for H‐bonding) reacted to form the corresponding cage B3X2 selectively. Surprisingly, the same reaction in the absence of aldehyde B yielded a mixture of products. Theoretical and experimental investigations are in complete agreement that the presence of the hydroxyl moiety adjacent to the aldehyde functionality in B is responsible for the selective formation of cage B3X2 from a complex reaction mixture. This spectacular selection was further analyzed by transforming a nonpreferred (non‐hydroxy) cage into a preferred (hydroxy) cage B3X2 by treating the former with aldehyde B . The role of the H‐bond in partner selection in a mixture of two dialdehydes and two amines has also been established. Moreover, an example of unconventional imine bond metathesis in organic cage‐to‐cage transformation is reported. 相似文献
17.
采用Car-Parrinello分子动力学(CPMD)方法分别研究了Be2+在水、甲醇和乙醇中的溶剂结构性质, 并对Be2+的第一溶剂壳结构的实验及理论结果进行了比较. 所得第一溶剂壳结构与已报道的实验和理论结果较为一致. 对径向分布函数、配位数以及角度分布等进行了详细的分析. 结果表明: 在水、甲醇和乙醇中, Be2+第一溶剂壳为稳定理想的四面体结构. 在本文的模拟时间尺度内,没有观察到第一溶剂壳中的分子与第二溶剂壳中的分子进行交换, 进一步证明Be2+第一溶剂壳为稳定的四配位结构. 根据计算得到的空间分布函数, Be2+在溶剂分子的等高面上主要集中分布在溶剂分子接受氢键的方向. 根据氧原子在Be2+周围的分布, 壳层分子主要集中分布在Be2+周围的四个区域, 进一步证实溶剂壳为四面体对称. 相似文献
18.
我们方便地合成了上沿修饰四丹磺酰胺基团的杯[4]芳烃衍生物1,发现该化合物在含50%水的乙腈中显示出对汞离子高选择性和灵敏性的识别作用,竞争实验表明多数金属离子对其检测干扰较小。机理研究结果表明荧光萃灭源于由丹磺酰胺基团到汞离子的光致电子转移过程。另外,通过研究1和1-Hg2+的荧光衰减实验,以及对比双丹磺酰胺杯[4]芳烃2和单丹磺酰胺杯[4]芳烃3对汞离子的识别作用,发现化合物1的四丹磺酰胺基团具有很好的预组织和协同作用。化合物1对汞离子的检测限为3.41×10-6 mol·L-1,这可以使1成为一个潜在的汞离子荧光化学传感器。 相似文献
19.
Yuya Tanikawa Shingo Kanemura Dai Ito Yuxi Lin Motonori Matsusaki Kimiko Kuroki Hiroshi Yamaguchi Katsumi Maenaka Young-Ho Lee Kenji Inaba Masaki Okumura 《Molecules (Basel, Switzerland)》2021,26(10)
ERp57, a member of the protein disulfide isomerase family, is a ubiquitous disulfide catalyst that functions in the oxidative folding of various clients in the mammalian endoplasmic reticulum (ER). In concert with ER lectin-like chaperones calnexin and calreticulin (CNX/CRT), ERp57 functions in virtually all folding stages from co-translation to post-translation, and thus plays a critical role in maintaining protein homeostasis, with direct implication for pathology. Here, we present mechanisms by which Ca2+ regulates the formation of the ERp57-calnexin complex. Biochemical and isothermal titration calorimetry analyses revealed that ERp57 strongly interacts with CNX via a non-covalent bond in the absence of Ca2+. The ERp57-CNX complex not only promoted the oxidative folding of human leukocyte antigen heavy chains, but also inhibited client aggregation. These results suggest that this complex performs both enzymatic and chaperoning functions under abnormal physiological conditions, such as Ca2+ depletion, to effectively guide proper oxidative protein folding. The findings shed light on the molecular mechanisms underpinning crosstalk between the chaperone network and Ca2+. 相似文献
20.
Enquan Jin Keyu Geng Ka Hung Lee Weiming Jiang Juan Li Qiuhong Jiang Stephan Irle Donglin Jiang 《Angewandte Chemie (International ed. in English)》2020,59(29):12162-12169
A strategy is presented for the synthesis of crystalline porous covalent organic frameworks via topology‐templated polymerization. The template is based on imine‐linked frameworks and their (001) facets seed the C=C bond formation reaction to constitute 2D sp2 carbon‐conjugated frameworks. This strategy is applicable to templates with different topologies, enables designed synthesis of frameworks that cannot be prepared via direct polymerization, and creates a series of sp2 carbon frameworks with tetragonal, hexagonal, and kagome topologies. The sp2 carbon frameworks are highly luminescent even in the solid state and exhibit topology‐dependent π transmission and exciton migration; these key fundamental π functions are unique to sp2 carbon‐conjugated frameworks and cannot be accessible by imine‐linked frameworks, amorphous analogues, and 1D conjugated polymers. These results demonstrate an unprecedented strategy for structural and functional designs of covalent organic frameworks. 相似文献