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1.
Jiawei Chen Didier A. MurilloParra Roger A. Lalancette Frieder Jkle 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(35):10340-10343
A new class of Janus‐like ambiphilic ligands is introduced. The rigid diferrocene backbone in heterocycles 4‐SnP and 4‐BP creates an unprecedented chiral environment as demonstrated by multinuclear NMR and single‐crystal X‐ray studies. In addition, the ligands are redox‐responsive and the Lewis acidic borane moiety in 4‐BP can be exploited to further tune the properties: a clear decrease in the CO stretching frequency of a Vaska‐type RhI complex 5‐BP is observed upon addition of fluoride ions. Thus, the Lewis acid and Lewis base sites influence each other and their strength can be modulated by redox chemistry and anion binding. 相似文献
2.
Diferrocenophosphaborin: A Planar‐Chiral,Redox‐Active and Anion‐Responsive Ambiphilic Ligand
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Dr. Jiawei Chen Didier A. Murillo Parra Prof. Dr. Roger A. Lalancette Prof. Dr. Frieder Jäkle 《Angewandte Chemie (International ed. in English)》2015,54(35):10202-10205
A new class of Janus‐like ambiphilic ligands is introduced. The rigid diferrocene backbone in heterocycles 4‐SnP and 4‐BP creates an unprecedented chiral environment as demonstrated by multinuclear NMR and single‐crystal X‐ray studies. In addition, the ligands are redox‐responsive and the Lewis acidic borane moiety in 4‐BP can be exploited to further tune the properties: a clear decrease in the CO stretching frequency of a Vaska‐type RhI complex 5‐BP is observed upon addition of fluoride ions. Thus, the Lewis acid and Lewis base sites influence each other and their strength can be modulated by redox chemistry and anion binding. 相似文献
3.
Stereoelectronic Basis for the Kinetic Resolution of N‐Heterocycles with Chiral Acylating Reagents
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Sheng‐Ying Hsieh Benedikt Wanner Dr. Philip Wheeler Prof. Dr. André M. Beauchemin Prof. Dr. Tomislav Rovis Prof. Dr. Jeffrey W. Bode 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(24):7228-7231
The kinetic resolution of N‐heterocycles with chiral acylating agents reveals a previously unrecognized stereoelectronic effect in amine acylation. Combined with a new achiral hydroxamate, this effect makes possible the resolution of various N‐heterocycles by using easily prepared reagents. A transition‐state model to rationalize the stereochemical outcome of this kinetic resolution is also proposed. 相似文献
4.
Jin‐Shun Lin Tao‐Tao Li Guan‐Yuan Jiao Qiang‐Shuai Gu Jiang‐Tao Cheng Ling Lv Xin‐Yuan Liu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(21):7166-7170
The first highly efficient and practical chiral Brønsted acid catalyzed dynamic kinetic asymmetric hydroamination (DyKAH) of racemic allenes and asymmetric hydroamination of unactivated dienes with both high E/Z selectivity and enantioselectivity are described herein. The transformation proceeds through a new catalytic asymmetric model involving a highly reactive π‐allylic carbocationic intermediate, generated from racemic allenes or dienes through a proton transfer mediated by an activating/directing thiourea group. This method affords expedient access to structurally diverse enantioenriched, potentially bioactive alkenyl‐containing aza‐heterocycles and bicyclic aza‐heterocycles. 相似文献
5.
The bisphosphine-catalyzed double-Michael addition of dinucleophiles to electron-deficient acetylenes is an efficient process for the synthesis of many nitrogen-containing heterocycles. Because the resulting heterocycles contain at least one stereogenic center, this double-Michael reaction would be even more useful if an asymmetric variant of the reaction were to be developed. Aminophosphines can also facilitate the double-Michael reaction and chiral amines are more readily available in Nature and synthetically; therefore, in this study we prepared several new chiral aminophosphines. When employed in the asymmetric double-Michael reaction between ortho-tosylamidophenyl malonate and 3-butyn-2-one, the chiral aminophosphines produced indolines in excellent yields with moderate asymmetric induction. 相似文献
6.
Catalytic Enantioselective Synthesis of α‐Chiral Azaheteroaryl Ethylamines by Asymmetric Protonation
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Dr. Chao Xu Calum W. Muir Dr. Andrew G. Leach Dr. Alan R. Kennedy Dr. Allan J. B. Watson 《Angewandte Chemie (International ed. in English)》2018,57(35):11374-11377
The direct enantioselective synthesis of chiral azaheteroaryl ethylamines from vinyl‐substituted N‐heterocycles and anilines is reported. A chiral phosphoric acid (CPA) catalyst promotes dearomatizing aza‐Michael addition to give a prochiral exocyclic aryl enamine, which undergoes asymmetric protonation upon rearomatization. The reaction accommodates a broad range of N‐heterocycles, nucleophiles, and substituents on the prochiral centre, generating the products in high enantioselectivity. DFT studies support a facile nucleophilic addition based on catalyst‐induced LUMO lowering, with site‐selective, rate‐limiting, intramolecular asymmetric proton transfer from the ion‐paired prochiral intermediate. 相似文献
7.
Jiawei Chen Krishnan Venkatasubbaiah Dr. Thilagar Pakkirisamy Dr. Ami Doshi Dr. Andrej Yusupov Yesha Patel Roger A. Lalancette Prof. Dr. Frieder Jäkle Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(29):8861-8867
Enantiomerically pure metalated 2‐(1‐naphthyl)ferrocene (NpFc) derivatives NpFcM (M=SnMe3, HgCl) were prepared and characterized by multinuclear NMR and UV/Vis spectroscopy, cyclic voltammetry, and elemental analysis. Optical rotation measurements were performed and the absolute configuration of the new planar chiral ferrocene species was confirmed by single‐crystal X‐ray diffraction analysis. The mercuriated species NpFcHgCl proved suitable as a reagent for the preparation of the chiral organoborane Lewis acid NpFcBCl2, which can in turn be converted to other ferrocenylboranes by replacement of Cl with nucleophiles. The highly Lewis acidic perfluoroarylborane derivatives NpFcB(C6F5)Cl and NpFcB(C6F5)2 were successfully prepared by treatment with CuC6F5. The structures were studied by single‐crystal X‐ray diffraction and variable‐temperature 19F NMR spectroscopy, which suggested that π stacking of a C6F5 group on boron with the adjacent naphthyl group is energetically favorable. UV/Vis absorption spectroscopy and cyclic voltammetry measurements were performed to examine the electronic properties of these novel redox‐active chiral Lewis acids. 相似文献
8.
Yuko Ouchi Yasuhiro Morisaki Dr. Tomoki Ogoshi Dr. Yoshiki Chujo Prof. Dr. 《化学:亚洲杂志》2007,2(3):397-402
A reaction of the P‐chiral compound (S,S)‐1,2‐bis(boranato(tert‐butyl)methylphosphino)ethane with an azobenzene derivative gave stimuli‐responsive polymers with P‐chiral phosphines in the main chain. This is the first example of a stimuli‐responsive P‐chiral polymer. The polymer isomerized from the trans to the cis form upon UV irradiation and reverted to the trans form reversibly. The polymer was able to coordinate to platinum, and the resulting polymer complex exhibited the Cotton effect owing to the chirality of the phosphorus atoms. The structure of the P‐chiral polymer obtained could be changed reversibly by light and thermal stimuli, and the polymer chain was induced to rotate helically when complexed with transition metals through the chiral phosphorus atoms. 相似文献
9.
Photochemical Generation of Chiral N,B,X‐Heterocycles by Heteroaromatic C−X Bond Scission (X=S,O) and Boron Insertion
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Soren K. Mellerup Cally Li Julian Radtke Dr. Xiang Wang Prof. Dr. Quan‐Song Li Prof. Dr. Suning Wang 《Angewandte Chemie (International ed. in English)》2018,57(31):9634-9639
Chiral organoboron compounds with a chelate backbone and mesityl/heterocycle substituents (thienyl, furyl, and derivatives thereof) undergo a quantitative phototransformation that yields rare, chiral N,B,X‐containing heterocycles, such as base‐stabilized 1,2‐thiaborinines and 1,2‐oxaborinines. Boriranes were observed as intermediates in some of these transformations. The oxaborinines display further reactivity, generating 4a,12b‐dihydrobenzo[h][1,2]oxaborinino[4,3‐f]quinolines through a sequential conrotatory electrocyclization and a [1,5]‐H shift. The N,B,X‐containing heterocycles display strong blue‐green to orange‐red emission in the solid state. Combined DFT//CASP2T calculations suggest that a common biradical intermediate is responsible for the formation of these compounds as well as their interconversion. 相似文献
10.
Three new chiral heterocalix [4] crowns containing aza thio atoms bearing two chiral sites provided by (R)‐cysteine ester were synthesized. All new compounds were characterized by 1H NMR, MS and elemental analysis. 相似文献
11.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2018,130(31):9782-9787
Chiral organoboron compounds with a chelate backbone and mesityl/heterocycle substituents (thienyl, furyl, and derivatives thereof) undergo a quantitative phototransformation that yields rare, chiral N,B,X‐containing heterocycles, such as base‐stabilized 1,2‐thiaborinines and 1,2‐oxaborinines. Boriranes were observed as intermediates in some of these transformations. The oxaborinines display further reactivity, generating 4a,12b‐dihydrobenzo[h][1,2]oxaborinino[4,3‐f]quinolines through a sequential conrotatory electrocyclization and a [1,5]‐H shift. The N,B,X‐containing heterocycles display strong blue‐green to orange‐red emission in the solid state. Combined DFT//CASP2T calculations suggest that a common biradical intermediate is responsible for the formation of these compounds as well as their interconversion. 相似文献
12.
Qingxiang Cao Jie Luo Xiaodan Zhao 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(5):1329-1333
An unprecendented chiral sulfide catalyzed desymmetrizing enantioselective chlorination is disclosed. Various aryl‐tethered diolefins and diaryl‐tethered olefins afforded teralins and tricyclic hexahydrophenalene derivatives, respectively, bearing multiple stereogenic centers in high yields with excellent enantio‐ and diastereoselectivities. In contrast, the tertiary amine catalyst (DHQD)2PHAL led to a diastereomeric product. The products could be transformed into a variety of compounds, such as spiro‐N‐heterocycles. 相似文献
13.
Subramani Rajkumar Mengyao Tang Xiaoyu Yang 《Angewandte Chemie (International ed. in English)》2020,59(6):2333-2337
An efficient method for the asymmetric synthesis of 4H‐3,1‐benzoxazines was developed by kinetic resolution of 2‐amido benzyl alcohols using chiral phosphoric acid catalyzed intramolecular cyclizations. A broad range of benzyl alcohols (both secondary and tertiary alcohols) were kinetically resolved with high selectivities, with an s factor of up to 94. Mechanistic studies were performed to elucidate the mechanism of these reactions, wherein the amide moieties reacted as the electrophiles. Gram‐scale reaction and facile transformations of the chiral products demonstrate the potential of this method in asymmetric synthesis of biologically active chiral heterocycles. 相似文献
14.
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
15.
Two new chiral calix[4] arenes bearing chiral pendants,which were from by-product of the antibiotic industry,were synthesized and characterized by ^1H NMR.MS-FAB and elemental analysis,Studies of ^1H NMR of the two calix[4] arene derivatives indicate that they exist in cone conformation in solution.Results of chiral recognition of the two chiral ligands 2a and 2b towards the tartaric acid derivative 3 show that ligand 2a exhibited good chiral recognition abilities compared to ligand 2b. 相似文献
16.
Design of Selenium‐Based Chiral Chemical Probes for Simultaneous Enantio‐ and Chemosensing of Chiral Carboxylic Acids with Remote Stereogenic Centers by NMR Spectroscopy
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Sergey A. Shyshkanov Dr. Nikolai V. Orlov 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(43):15458-15467
Selenium‐based enantiopure chiral chemical probes have been designed in a modular way starting from available amino alcohols. The probes developed were found to be efficient in chemoselective interaction with carboxylic functions of chiral substrates leading to diastereomeric amide formation and in sensing α‐, β‐, and remote (up to seven bonds away from the carboxylic group) chiral centers by using 77Se NMR spectroscopy. As a result, it was possible to determine the enantiomeric ratio of structurally diverse individual chiral acids including polyfunctional compounds and drugs with high accuracy. An approach to analyzing the crude reaction mixtures has been successfully developed by using bifunctional selenium‐ and fluorine‐containing chiral probes. More importantly, it was revealed that, based on the 77Se NMR data obtained, it is possible to obtain primary information about the location and nature of the substituents at the chiral center (chemo‐ and enantiosensing), which can simplify the structural elucidation of complex compounds. The derivatization procedure takes as little as 5 min and can be performed directly in an NMR tube followed by NMR measurements without any isolation and purification steps. 相似文献
17.
Agnieszka Szumna 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(45):12381-12388
The complexation of chiral guests in the cavity of dimeric self‐assembled chiral capsule 1 2 was studied by using NMR spectroscopy and X‐ray crystallography. Capsule 1 2 has walls composed of amino acid backbones forming numerous directional binding sites that are arranged in a chiral manner. The polar character of the interior dictates the encapsulation preferences towards hydrophilic guests and the ability of the capsule to extract guests from water into an organic phase. Chiral discrimination towards hydroxy acids was evaluated by using association constants and competition experiments, and moderate de values were observed (up to 59 %). Complexes with one or two guest molecules in the cavity were formed. For 1:1 complexes, solvent molecules are coencapsulated; this influences guest dynamics and makes the chiral recognition solvent dependent. Reversal of the preferences can be induced by coencapsulation of a nonchiral solvent in the chiral internal environment. For complexes with two guests, filling of the capsule’s internal space can be very effective and packing coefficients of up to 70 % can be reached. The X‐ray crystal structure of complex 1 2?((S) ‐6 )2 with well‐resolved guest molecules reveals a recognition motif that is based on an extensive system of hydrogen bonds. The optimal arrangement of interactions with the alternating positively and negatively charged groups of the capsule’s walls is fulfilled by the guest carboxylic groups acting simultaneously as hydrogen‐bond donors and acceptors. An additional guest molecule interacting externally with the capsule reveals a possible entrance mechanism involving a polar gate. In solution, the structural features and dynamic behavior of the D4‐symmetric homochiral capsule were analyzed by variable‐temperature NMR spectroscopy and the results were compared with those for the S8‐symmetric heterochiral capsule. 相似文献
18.
Connor J. Thomson David M. Barber Darren J. Dixon 《Angewandte Chemie (International ed. in English)》2020,59(13):5359-5364
The catalytic enantioselective synthesis of α‐fluorinated chiral tertiary alcohols from (hetero)aryl methyl ketones is described. The use of a bifunctional iminophosphorane (BIMP) superbase was found to facilitate direct aldol addition by providing the strong Brønsted basicity required for rapid aryl enolate formation. The new synthetic protocol is easy to perform and tolerates a broad range of functionalities and heterocycles with high enantioselectivity (up to >99:1 e.r.). Multi‐gram scalability has been demonstrated along with catalyst recovery and recycling. 1H NMR studies identified a 1400‐fold rate enhancement under BIMP catalysis, compared to the prior state‐of‐the‐art catalytic system. The utility of the aldol products has been highlighted with the synthesis of various enantioenriched building blocks and heterocycles, including 1,3‐aminoalcohol, 1,3‐diol, oxetane, and isoxazoline derivatives. 相似文献
19.
Hagay Moshe Maarten Vanbel Dr. Ventsislav Kolev Valev Prof. Thierry Verbiest Dr. David Dressler Prof. Yitzhak Mastai 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(31):10295-10301
In this paper, we describe for the first time the synthesis of new chiral nanosized metal oxide surfaces based on chiral self‐assembled monolayers (SAMs) coated with metal oxide (TiO2) nanolayers. In this new type of nanosize chiral surface, the metal oxide nanolayers enable the protection of the chiral self‐assembled monolayers while preserving their enantioselective nature. The chiral nature of the SAM/TiO2 films was characterized by variety of unique techniques, such as second‐harmonic generation circular dichroism (SHG‐CD), quartz crystal microbalance, and chiral adsorption measurements with circular dichroism spectroscopy. The chiral resolution abilities of the SAMs coated with metal oxide (TiO2) nanolayers were investigated in the crystallization of a racemic mixture of threonine and glutamic acid. Our proposed methodology for the preparation of nanoscale chiral surfaces described in this article could open up opportunities in other fields of chemistry, such as chiral catalysis. 相似文献
20.
Dr. Ruth K. Schmidt Dr. Hendrik F. T. Klare Prof. Dr. Martin Oestreich 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(15):5376-5383
The preparation of a series of planar chiral, ferrocenyl‐substituted hydrosilanes as precursors of ferrocene‐stabilized silicon cations is described. These molecules also feature stereogenicity at the silicon atom. The generation and 29Si NMR spectroscopic characterization of the corresponding silicon cations is reported, and problems arising from interactions of the electron‐deficient silicon atom and adjacent C(sp3)?H bonds or aromatic π donors are discussed. These issues are overcome by tethering another substituent at the silicon atom to the ferrocene backbone. The resulting annulation also imparts conformational rigidity and steric hindrance in such a way that the central chirality at the silicon atom is set with complete diastereocontrol. These chiral Lewis acid catalysts were then tested in difficult Diels–Alder reactions, but no enantioinduction was seen. 相似文献