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1.
Dr. Li Ma Dr. Rizhe Jin Dr. Zheng Bian Dr. Chuanqing Kang Yu Chen Prof. Jingwei Xu Prof. Lianxun Gao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(41):13168-13172
An atropisomeric biaryl molecule with a given absolute configuration could present two opposite helical conformations through the rotation around C? C single bond. To the best of our knowledge, the biaryl system is the simplest helical inversion model apart from stereomutation between two enantiomers. Herein, we first report such true helical inversion phenomena of biaryl compounds. Two [MoVIO2(L)]‐type complexes, in which L is a tridentate dioxoanionic pyridine O,N,O‐ligand, are coalesced on the 2,2′,3,3′‐positions of an (R)‐1,1′‐binaphthyl unit and an intramolecular dioxo bridge is formed by two Mo?O???Mo interactions. Exterior strong donors can coordinate to molybdenum to interrupt this dioxo bridge and inversions from negative to positive chirality are explicitly observed by circular dichroism spectroscopy, consistent with single‐crystal X‐ray diffraction analyses. 相似文献
2.
Two new flavones, 8‐hydroxy‐7,3′,4′,5′‐tetramethoxyflavone and 8,4′‐dihydroxy‐7,3′,5′‐trimethoxyflavone, together with thirteen known compounds have been isolated from the stem bark of Muntingia calabura. The structures of two new compounds were determined through spectral analyses. Among the isolates, 8‐hydroxy‐7,3′,4′,5′‐tetramethoxyflavone, 8,4′‐dihydroxy‐7,3′,5′‐trimethoxyflavone, and 3‐hydroxy‐1‐(3,5‐dimethoxy‐4‐hydroxyphenyl)propan‐1‐one exhibited effective cytotoxicities (ED50 values = 3.56, 3.71, and 3.27 μg/mL, respectively) against the P‐388 cell line in vitro. 相似文献
3.
Dr. Antoine Joosten Dr. Yann Trolez Prof. Valérie Heitz Prof. Jean‐Pierre Sauvage 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(38):12815-12823
A new methodology allowing preparation of a linear “unsaturated” [3]rotaxane consisting of an axis incorporating more coordination sites than threaded rings was developed. It was based on the preliminary synthesis of a “saturated” [5]rotaxane consisting of a four‐chelating site axis threaded through four macrocyclic components, two of them being cleavable rings incorporating a lactone function and the two others being “secure” non‐cleavable rings. The stoppering reaction was based on click chemistry. Subsequently, cleavage and removal of the two lactone‐containing macrocycles from the [5]rotaxane in basic medium afforded the desired “unsaturated” [3]rotaxane in quantitative yield. 相似文献
4.
Prof. Dr. Gerhard Bringmann Guoliang Zhang Tobias Büttner Gabi Bauckmann Dr. Thomas Kupfer Prof. Dr. Holger Braunschweig Prof. Dr. Reto Brun Prof. Dr. Virima Mudogo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(3):916-923
A new dimeric naphthylisoquinoline alkaloid, jozimine A2 ( 2 ), was isolated from the root bark of an Ancistrocladus species from the Democratic Republic of Congo. Its absolute stereostructure was determined by chemical, spectroscopic, and chiroptical methods, and confirmed by X‐ray crystallography. Jozimine A2 ( 2 ) is one of the as yet very rare naphthylisoquinoline dimers whose central biaryl axis is rotationally hindered. Moreover, it is the first natural dimer of a Dioncophyllaceae‐type alkaloid, that is, lacking oxygen functions at C6, and bearing R configurations at C3 in its two isoquinoline portions. Despite this decreased steric hindrance, the outer biaryl axes are chiral, too, so that jozimine A2 ( 2 ) has three consecutive stereogenic axes and, together with the four stereogenic centers, seven elements of chirality and is C2‐symmetric. The new dimer exhibits excellent, and specific, antiplasmodial activity. To further confirm its stereostructure and for likewise testing the bioactivities of its (unnatural) atropo‐diastereomer, compound 2 was prepared by semi‐synthesis from the co‐occurring (and likewise synthetically available) dioncophylline A ( 5 ), along with its atropo‐diastereomer, 3′‐epi‐ 2 . 相似文献
5.
Maria B. García Isabel A. Perillo Liliana R. Orelli 《Journal of heterocyclic chemistry》2001,38(5):1209-1211
In the present communication we describe two examples of a new kind of configurationally stable non‐biaryl atropisomers in which the Ar‐N bond is the chiral axis, namely 1‐(o‐nitrophenyl)‐2‐aryl‐3‐methyl‐1,4,5,6‐tetrahydropyrimidinium iodides 1. Stereochemical features of such compounds are analyzed on the basis of their 1H and 13C one‐ and two‐dimensional nmr spectra. A comparison is made with the corresponding amidines 2 . 相似文献
6.
Highly Antiplasmodial Non‐Natural Oxidative Products of Dioncophylline A: Synthesis,Absolute Configuration,and Conformational Stability
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Yasmin Hemberger Dr. Guoliang Zhang Prof. Dr. Reto Brun Marcel Kaiser Prof. Dr. Gerhard Bringmann 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(41):14507-14518
Four new compounds, the monomeric dioncotetralones A ( 6 a ) and B ( 6 b ) and the dimeric compounds jozimine A3 ( 7 ) and jozimine A4 ( 9 ), were semi‐synthesized from the natural product dioncophylline A ( 4 ) and its 5′‐O‐demethylated derivative ( 5 ), respectively, under phenol oxidative reaction conditions. Dioncotetralones A ( 6 a ) and B ( 6 b ) possess an unprecedented Z‐configured double bond, in contrast to the classic biaryl axis that is present in the precursor dioncophylline A ( 4 ), and an additional stereogenic center at the C2′ atom was generated due to the dearomatization. The resulting steric repulsion forced the expected planar double bond into a helical distorted conformation. The homocoupling of 5 yielded compounds 7 and 9 , the latter of which is the first sp3–sp2 coupled product of a monomeric naphthylisoquinoline with a reduced one and, thus, contains a newly generated stereogenic center. The full stereostructures of 6 a , 6 b , 7 , and 9 were successfully elucidated by the interplay of spectroscopic methods (1D/2D NMR and electronic circular‐dichroism spectroscopy) in combination with quantum‐chemical calculations. In addition, compounds 6 a and 7 exhibited high antiplasmodial activities with excellent half‐maximal inhibitory concentration values. 相似文献
7.
Chun‐Feng Xie Rong‐Xiu Zhu Jian‐Bo Qu Li‐Ning Wang Dong‐Xiao Guo Wen‐Tao Yu Cheng‐Bu Liu Hong‐Xiang Lou 《Helvetica chimica acta》2011,94(11):2077-2086
7′‐Hydroxyriccardin C ( 1 ) and marchantin E ( 2 ), two macrocyclic bisbibenzyls with a stereogenic center at the ethylene bridge from Chinese liverworts, were investigated stereochemically. Compound 1 was found to be optically active and occurred as a pair of dynamically interchangeable atropisomers at room temperature due to the low barrier of rotation around the biaryl bond, while 2 was a racemic mixture, which was successfully resolved by chiral HPLC into two enantiomers. Their absolute configurations were unequivocally assigned by analysis of temperature‐dependent NMR spectra, X‐ray crystallographic diffraction, and comparison of experimental and calculated ECD data. 相似文献
8.
Lipase‐Catalyzed Dynamic Kinetic Resolution of C1‐ and C2‐Symmetric Racemic Axially Chiral 2,2′‐Dihydroxy‐1,1′‐biaryls
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Dr. Gamal A. I. Moustafa Yasuhiro Oki Prof. Dr. Shuji Akai 《Angewandte Chemie (International ed. in English)》2018,57(32):10278-10282
We have discovered that the racemization of configurationally stable, axially chiral 2,2′‐dihydroxy‐1,1′‐biaryls proceeds with a catalytic amount of a cyclopentadienylruthenium(II) complex at 35–50 °C. Combining this racemization procedure with lipase‐catalyzed kinetic resolution led to the first lipase/metal‐integrated dynamic kinetic resolution of racemic axially chiral biaryl compounds. The method was applied to the synthesis of various enantio‐enriched C1‐ and C2‐symmetric biaryl diols in yields of up to 98 % and enantiomeric excesses of up to 98 %, which paves the way for new developments in the field of asymmetric synthesis. 相似文献
9.
Three copper(II) complexes, [Cu2(OAc)4L2] · 2CH3OH ( 1 ), [CuBr2L′2(CH3OH)] · CH3OH ( 2a ), and [CuBr2L′2(DMSO)] · 0.5CH3OH ( 2b ) {L = N‐(9‐anthracenyl)‐N′‐(3‐pyridyl)urea and L′ = N‐[10‐(10‐methoxy‐anthronyl)]‐N′‐(3‐pyridyl)urea} have been synthesized by the reaction of L with the corresponding copper(II) salts. Complex 1 shows a dinuclear structure with a conventional “paddlewheel” motif, in which four acetate units bridge the two CuII ions. In complexes 2a and 2b , the anthracenyl ligand L has been converted to an anthronyl derivative L′, and the central metal ion exhibits a distorted square pyramidal arrangement, with two pyridyl nitrogen atoms and two bromide ions defining the basal plane and the apical position is occupied by a solvent molecule (CH3OH in 2a and DMSO in 2b ). 相似文献
10.
《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(1):81-93
Efficient electrochemical syntheses of “homocoenzyme B12” ( 2 , Coβ‐(5′‐deoxy‐5′‐adenosyl‐methyl)‐cob(III )alamin) and “bishomocoenzyme B12” ( 3 , Coβ‐[2‐(5′‐deoxy‐5′‐adenosyl)‐ethyl]‐cob(III )alamin) are reported here. These syntheses have provided crystalline samples of 2 and 3 in 94 and 77 % yield, respectively. In addition, in‐depth investigations of the structures of 2 and 3 in solution were carried out and a high‐resolution crystal structure of 2 was obtained. The two homologues of coenzyme B12 ( 2 and 3 ) are suggested to function as covalent structural mimics of the hypothetical enzyme‐bound “activated” (that is, “stretched” or even homolytically cleaved) states of the B12 cofactor. From crude molecular models, the crucial distances from the corrin‐bound cobalt center to the C5′ atom of the (homo)adenosine moieties in 2 and 3 were estimated to be about 3.0 and 4.4 Å, respectively. These values are roughly the same as those found in the two “activated” forms of coenzyme B12 in the crystal structure of glutamate mutase. Indeed, in the crystal structure of 2 , the cobalt center was observed to be at a distance of 2.99 Å from the C5′ atom of the homoadenosine moiety and the latter was found to be present in the unusual syn conformation. In solution, the organometallic moieties of 2 and 3 were shown to be rather flexible and to be considerably more dynamic than the equivalent group in coenzyme B12. The homoadenosine moiety of 2 was indicated to occur in both the syn and the anti conformations. 相似文献
11.
Adamantane‐Based Wide‐Bandgap Host Material: Blue Electrophosphorescence with High Efficiency and Very High Brightness
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Yu Gu Liping Zhu Yifan Li Ling Yu Kailong Wu Tianheng Chen Manli Huang Feng Wang Dr. Shaolong Gong Prof. Dongge Ma Prof. Jingui Qin Prof. Chuluo Yang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(22):8250-8256
An adamantane‐based host material, namely, 4‐{3‐[4‐(9H‐carbazol‐9‐yl)phenyl]adamantan‐1‐yl}benzonitrile (CzCN‐Ad), was prepared by linking an electron‐donating carbazole unit and an electron‐accepting benzonitrile moiety through an adamantane bridge. In this approach, two functional groups were attached to tetrahedral points of adamantane to construct an “sp3” topological configuration. This design strategy endows the host material with a high triplet energy of 3.03 eV due to the disruption of intramolecular charge transfer. Although CzCN‐Ad has a low molecular weight, the rigid nonconjugated adamantane bridge results in a glass transition temperature of 89 °C. These features make CzCN‐Ad suitable for fabricating blue phosphorescent organic light‐emitting diodes (PhOLEDs). The devices based on sky‐blue phosphor bis[(4,6‐difluorophenyl)pyridinato‐N,C2′](picolinato)iridium(III) (FIrpic) achieved a high maximum external quantum efficiency (EQE) of 24.1 %, which is among the best results for blue PhOLEDs ever reported. Furthermore, blue PhOLEDs with bis(2,4‐difluorophenylpyridinato)‐tetrakis(1‐pyrazolyl)borate iridium(III) (FIr6) as dopant exhibited a maximum EQE of 14.2 % and a maximum luminance of 34 262 cd m?2. To the best of our knowledge, this is the highest luminance ever reported for FIr6‐based PhOLEDs. 相似文献
12.
Xiqing Wang ke Kvick Gavin B. M. Vaughan Yuan Sun Yingcai Long 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(10):1232-1233
The structure of the lactone form of rhodamine B, 3,6‐bis(diethylamino)‐1′,3′‐dihydrospiro[xanthene‐9,3′‐isobenzofuran]‐1′‐one, C28H30N2O3, has been determined at 120 K using synchrotron radiation at a wavelength of 0.496 Å. The structure contains two independent rhodamine B molecules with virtually identical geometry. The xanthene main planes of the molecules are inclined at an angle of 41.6 (2)° to one another. Molecule 2 has a statistically disordered ethyl group, with 71% in one orientation and 29% in a second orientation. The lactone C—O bonds are 1.497 (1) and 1.495 (1) Å. There are no classical hydrogen bonds, but the structure is stabilized by two short C?O interactions. The crystals of the lactone form were produced by a novel hydrothermal reaction. 相似文献
13.
Three aza‐aromatic base adducts of cadmium(II) furoyltrifluoroacetonate, [Cd(4,4′‐bpy)(ftfa)2]n ( 1 ), [Cd(2,2′‐bpy)(ftfa)2] ( 2 ) and [Cd(dmp)(ftfa)2] ( 3 ) (“4,4′‐bpy”, “2,2′‐bpy”, “dmp” and “ftfa” are the abbreviations of 4,4′‐bipyridine, 2,2′‐bipyridine, 2,9‐dimethyl‐1,10‐phenanthroline and furoyltrifluoroacetonate, respectively) have been synthesized and characterized by elemental analysis and IR, 1H NMR and 13C NMR spectroscopy and studied by thermal as well as X‐ray crystallography. The single‐crystal structure of these complexes shows that the coordination number of the CdII ions are six with two N‐donor atoms from aza‐aromatic base ligands and four O‐donors from two the furoyltrifluoroacetonates. The supramolecular features in these complexes are guided/controlled by weak directional intermolecular interactions. 相似文献
14.
One‐pot Annulation for Biaryl‐fused Monocarba‐closo‐dodecaborate through Aromatic B−H Bond Disconnection
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Gaku Akimoto Mai Otsuka Dr. Kazunori Miyamoto Dr. Atsuya Muranaka Dr. Daisuke Hashizume Dr. Ryo Takita Prof. Dr. Masanobu Uchiyama 《化学:亚洲杂志》2018,13(8):913-917
We have developed a one‐pot annulation reaction of monocarba‐closo‐dodecaborate with cyclic diaryliodonium salts to afford biaryl‐fused derivatives. Aryl functionalities are introduced at both the 1‐carbon and unreactive ortho‐boron vertices of the “σ‐aromatic” carborane cage without the need for pre‐functionalization. DFT calculations revealed that the palladium‐catalyzed C?B bond‐formation step in this process proceeds through a concerted metalation–deprotonation (CMD)‐type pathway for the B?H bond disconnection on the aromatic cage, though such bonds are generally regarded as hydridic. 相似文献
15.
Dr. Omrane Fadhel Dr. Zoltán Benkö Michael Gras Valérie Deborde Damien Joly Christophe Lescop Prof. László Nyulászi Prof. Muriel Hissler Prof. Régis Réau 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(37):11340-11356
Conjugated systems based on phospholes and 1,1′‐biphospholes bearing 3,4‐ethylenedithia bridges have been prepared using the Fagan–Nugent route. The mechanism of this organometallic route leading to intermediate zirconacyclopentadienes has been investigated by using theoretical calculations. This study revealed that the oxidative coupling leading to zirconacyclopentadienes is favored over oxidative addition within the S? C≡C bond both thermodynamically and kinetically. The impact of the presence of the S atoms on the optical and electrochemical behavior of the phospholes and 1,1′‐biphospholes has been systematically evaluated both experimentally and theoretically. A comparison with their “all‐carbon” analogues is provided. Of particular interest, this comparative study revealed that the introduction of S atoms has an impact on the electronic properties of phosphole‐based conjugated systems. A decrease of the HOMO–LUMO separation and a stabilization of the LUMO level were observed. These general trends are also observed with 1,1′‐biphospholes exhibiting σ–π conjugation. The P atom of the 3,4‐ethylenedithiaphospholes can be selectively oxidized by S8 or O2. These P modifications result in a lowering of the HOMO–LUMO separation as well as an increase of the reduction and oxidation potentials. The S atoms of the 3,4‐ethylenedithia bridge of the 2,5‐phosphole have been oxidized using m‐chloroperoxybenzoic acid. The resulting 3,4‐ethylenesulfoxide oxophosphole was characterized by an X‐ray diffraction study. Experimental and theoretical studies show that this novel chemical manipulation results in an increase of the HOMO–LUMO separation and an important decrease of the LUMO level. The electropolymerization of 2‐thienyl‐capped 3,4‐ethylenedithiathioxophosphole and 1,1′‐biphosphole is reported. The impact of the S substituents on the polymer properties is discussed. 相似文献
16.
Dr. Sabin Llona‐Minguez Dr. Matthieu Desroses Artin Ghassemian Dr. Sylvain A. Jacques Dr. Lars Eriksson Rebecka Isacksson Tobias Koolmeister Dr. Pål Stenmark Dr. Martin Scobie Prof. Thomas Helleday 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(20):7394-7398
A two‐step synthesis of structurally diverse pyrrole‐containing bicyclic systems is reported. ortho‐Nitro‐haloarenes coupled with vinylic N‐methyliminodiacetic acid (MIDA) boronates generate ortho‐vinyl‐nitroarenes, which undergo a “metal‐free” nitrene insertion, resulting in a new pyrrole ring. This novel synthetic approach has a wide substrate tolerance and it is applicable in the preparation of more complex “drug‐like” molecules. Interestingly, an ortho‐nitro‐allylarene derivative furnished a cyclic β‐aminophosphonate motif. 相似文献
17.
A new compound, Cochinchin (1), together with 7,4‘-dihydroxyflavone (2), 7-hydroxy-4‘-methoxyflavane (3),7-hydroxy-3-(4-hydroxybenzyl)chroman (4), 4‘-hydroxy-2,4-dirnethoxydihydrochalcone (5) and 4‘-hydroxy-2,4,6-trimethoxydihydrochalcone (6) was isolated from the resin (trivial name, “dragon‘s blood“) of Dracaena cochinchinensis (Lour.) S. C. Chert. The structure of 1 was elucidated on the basis of spectroscopic data as (2,3-trans)-6-allyl-2-(3,5-dimethoxyphenyl)-3-(4-hydroxyphenyl)-2,3-dihydrobenzo[1,4]dioxin which is a natural product possessing a new framework. 相似文献
18.
Jeffrey Buter Dorus Heijnen Carlos Vila Valentín Hornillos Edwin Otten Massimo Giannerini Adriaan J. Minnaard Ben L. Feringa 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2016,128(11):3684-3688
A palladium‐catalyzed direct synthesis of symmetric biaryl compounds from aryl halides in the presence of tBuLi is described. In situ lithium–halogen exchange generates the corresponding aryl lithium reagent, which undergoes a homocoupling reaction with a second molecule of the aryl halide in the presence of the palladium catalyst (1 mol %). The reaction takes place at room temperature, is fast (1 h), and affords the corresponding biaryl compounds in good to excellent yields. The application of the method is demonstrated in an efficient asymmetric total synthesis of mastigophorene A. The chiral biaryl axis is constructed with an atropselectivity of 9:1 owing to catalyst‐induced remote point‐to‐axial chirality transfer. 相似文献
19.
Palladium‐Catalyzed,tert‐Butyllithium‐Mediated Dimerization of Aryl Halides and Its Application in the Atropselective Total Synthesis of Mastigophorene A
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Jeffrey Buter Dorus Heijnen Dr. Carlos Vila Dr. Valentín Hornillos Dr. Edwin Otten Dr. Massimo Giannerini Prof. Dr. Adriaan J. Minnaard Prof. Dr. Ben L. Feringa 《Angewandte Chemie (International ed. in English)》2016,55(11):3620-3624
A palladium‐catalyzed direct synthesis of symmetric biaryl compounds from aryl halides in the presence of tBuLi is described. In situ lithium–halogen exchange generates the corresponding aryl lithium reagent, which undergoes a homocoupling reaction with a second molecule of the aryl halide in the presence of the palladium catalyst (1 mol %). The reaction takes place at room temperature, is fast (1 h), and affords the corresponding biaryl compounds in good to excellent yields. The application of the method is demonstrated in an efficient asymmetric total synthesis of mastigophorene A. The chiral biaryl axis is constructed with an atropselectivity of 9:1 owing to catalyst‐induced remote point‐to‐axial chirality transfer. 相似文献
20.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(2):564-568
We describe iron‐catalyzed intermolecular oxidative coupling reactions of diarylamines to form substituted 2,2′‐bis(arylamino)biaryl compounds, tetraarylhydrazines, and 5,6‐dihydrobenzo[c ]cinnolines with the same hexadecafluorinated iron–phthalocyanine catalyst. The mild formation of C−C or N−N bonds was controlled by the use of acidic or basic additives. In contrast to most iron‐catalyzed dehydrogenative coupling reactions, ambient air could be used as the sole oxidant. Moreover, iron(III) chloride hexahydrate promoted a one‐pot coupling and subsequent intramolecular dearomative coupling to give 10H ‐spiro[acridine‐9,1′‐cyclohexa‐2′,5′‐dien‐4′‐ones]. 相似文献