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1.
Guanjun Chang Li Yang Junxiao Yang Yawen Huang Lin Zhang Runxiong Lin 《Journal of polymer science. Part A, Polymer chemistry》2014,52(3):313-320
We present here a novel programmable polymerization route for the synthesis of new indole‐based polymers via a catalyst‐free nucleophilic substitution reaction. The polycondensation of 4‐hydroxyindole with different activated difluoro monomers undergoes in N‐methylpyrrolidinone, affording soluble poly(N‐aryleneindole ether)s (PEINs) with high molecular weights (Mw up to 486,000) in high yields (up to 96%). The structures of the polymers are characterized by means of FT‐IR, 1H NMR spectroscopy and elemental analysis, the results show good agreement with the proposed structures. The resulting polymers are processable and enjoy high glass transition temperatures (Tgs > 180 °C) and thermal stability (Tds > 420 °C). Thin films of PEINs show great mechanical behaviors with high tensile strength up to 104 Mpa, and good optical transparency. In addition, due to the indole moieties in the main chains, all these PEINs are endowed with significantly strong photonic luminescence in chloroform and display highly solvent‐dependent emission bands. Especially, the polymer PEIN‐3 carrying sulfonyl units, shows outstanding blue‐light emission with high quantum yields (45.2%, determined against quinine sulfate). The results obtained by cyclic voltammetry suggest that PEINs possess good electroactivity. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 313–320 相似文献
2.
Yin‐Lin Wang Ling‐Liang Long Jin‐Fang Zhang 《Acta Crystallographica. Section C, Structural Chemistry》2015,71(6):435-439
A two‐dimensional MnII coordination polymer (CP), poly[bis[μ2‐2,6‐bis(imidazol‐1‐yl)pyridine‐κ2N3:N3′]bis(thiocyanato‐κN)manganese] [Mn(NCS)2(C11H9N5)2]n, (I), has been obtained by the self‐assembly reaction of Mn(ClO4)2·6H2O, NH4SCN and bent 2,6‐bis(imidazol‐1‐yl)pyridine (2,6‐bip). CP (I) was characterized by FT–IR spectroscopy, elemental analysis and single‐crystal X‐ray diffraction. The crystal structure features a unique two‐dimensional (4,4) network with one‐dimensional channels. The luminescence and nitrobenzene‐sensing properties were explored in a DMF suspension, revealing that CP (I) shows a strong luminescence emission and is highly sensitive for nitrobenzene detection. 相似文献
3.
Nail M. Shavaleev Dr. Svetlana V. Eliseeva Dr. Rosario Scopelliti Dr. Jean‐Claude G. Bünzli Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(41):10790-10802
A series of tridentate benzimidazole‐substituted pyridine‐2‐carboxylic acids have been prepared with a halogen, methyl or alkoxy group in the 6‐position of the benzimidazole ring, which additionally contains a solubilising N‐alkyl chain. The ligands form neutral homoleptic nine‐coordinate lanthanum, europium and terbium complexes as established from X‐ray crystallographic analysis of eight structures. The coordination polyhedron around the lanthanide ion is close to a tricapped trigonal prism with ligands arranged in an up–up–down fashion. The coordinated ligands serve as light‐harvesting chromophores in the complexes with absorption maxima in the range 321–341 nm (ε=(4.9–6.0)×104 M ?1 cm?1) and triplet‐state energies between 21 300 and 18 800 cm?1; the largest redshifts occur for bromine and electron‐donor alkoxy substituents. The ligands efficiently sensitise europium luminescence with overall quantum yields ( ) and observed lifetimes (τobs) reaching 71 % and 3.00 ms, respectively, in the solid state and 52 % and 2.81 ms, respectively, in CH2Cl2 at room temperature. The radiative lifetimes of the Eu(5D0) level amount to τrad=3.6–4.6 ms and the sensitisation efficiency ηsens= (τrad/τobs) is close to unity for most of the complexes in the solid state and equal to approximately 80 % in solution. The photophysical parameters of the complexes correlate with the triplet energy of the ligands, which in turn is determined by the nature of the benzimidazole substituent. Facile modification of the ligands makes them promising for the development of brightly emissive europium‐containing materials. 相似文献
4.
Circularly Polarized Luminescence from Helically Chiral N,N,O,O‐Boron‐Chelated Dipyrromethenes
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Rua B. Alnoman Dr. Sandra Rihn Daniel C. O'Connor Fiona A. Black Dr. Bernard Costello Dr. Paul G. Waddell Prof. William Clegg Prof. Robert D. Peacock Prof. Wouter Herrebout Dr. Julian G. Knight Dr. Michael J. Hall 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(1):93-96
Helically chiral N,N,O,O‐boron chelated dipyrromethenes showed solution‐phase circularly polarized luminescence (CPL) in the red region of the visible spectrum (λem(max) from 621 to 663 nm). The parent dipyrromethene is desymmetrised through O chelation of boron by the 3,5‐ortho‐phenolic substituents, inducing a helical chirality in the fluorophore. The combination of high luminescence dissymmetry factors (|glum| up to 4.7 ×10?3) and fluorescence quantum yields (ΦF up to 0.73) gave exceptionally efficient circularly polarized red emission from these simple small organic fluorophores, enabling future application in CPL‐based bioimaging. 相似文献
5.
Jean-Claude G. Bünzli Anne-Sophie Chauvin Hwan Kyu Kim Emmanuel Deiters Svetlana V. Eliseeva 《Coordination chemistry reviews》2010,254(21-22):2623-2633
The photophysical parameters for the sensitization of metal-centred luminescence are analyzed in two series of complexes with tridentate and hexadentate ligands having NxOy chelating units. In particular, the radiative lifetime τrad is experimentally estimated for 29 nine-coordinate EuIII complexes and 10 eight- and nine-coordinate YbIII complexes. The known dependence of τrad on refractive index is substantiated by comparing data for solid-state samples and solutions. Moreover, a clear dependence of τrad with the coordination environment is evidenced and in the case of EuIII, a comparison between τrad and the nephelauxetic effect generated by the ligands is attempted. Altogether, this extensive analysis points to the importance of having a handle on τrad when designing ligands for highly luminescent lanthanide-containing molecular edifices. This, in turn, should stimulate initiating theoretical considerations to unravel a reliable relationship between τrad and the electronic structure of the ligands. 相似文献
6.
Functionalized aminophosphine of the type Ph2PNR2 ( 1,2 ) have been synthesized by treating Ph2PCl with N‐phenylpiperazine or N‐ethylpiperazine. Oxidation of these ligands with aqueous hydrogen peroxide, elemental sulfur or selenium afforded the corresponding phosphine oxides 3,4 , sulfides 5,6 , and selenides 7,8 in good yields. The molybdenum complexes of the aminophosphines have been obtained. All new compounds were fully characterized by IR, NMR, and microanalysis, and the molecular structures of two representative compounds were determined by single‐crystal X‐ray crystallography. © 2011 Wiley Periodicals, Inc. Heteroatom Chem 22:679–686, 2011; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20733 相似文献
7.
Lanthanoid/Alkali Metal β‐Triketonate Assemblies: A Robust Platform for Efficient NIR Emitters
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Brodie L. Reid Dr. Stefano Stagni Dr. Joanna M. Malicka Dr. Massimo Cocchi Dr. Alexandre N. Sobolev Prof. Brian W. Skelton Dr. Evan G. Moore Prof. Garry S. Hanan Prof. Mark I. Ogden Dr. Massimiliano Massi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(50):18354-18363
The reaction of hydrated lanthanoid chlorides with tribenzoylmethane and an alkali metal hydroxide consistently resulted in the crystallization of neutral tetranuclear assemblies with the general formula [Ln(Ae ? HOEt)( L )4]2 (Ln=Eu3+, Er3+, Yb3+; Ae=Na+, K+, Rb+). Analysis of the crystal structures of these species revealed a coordination geometry that varied from a slightly distorted square antiprism to a slightly distorted triangular dodecahedron, with the specific geometrical shape being dependent on the degree of lattice solvation and identity of the alkali metal. The near‐infrared (NIR)‐emitting assemblies of Yb3+ and Er3+ showed remarkably efficient emission, characterized by significantly longer excited‐state lifetimes (τobs≈37–47 μs for Yb3+ and τobs≈4–6 μs for Er3+) when compared with the broader family of lanthanoid β‐diketonate species, even in the case of perfluorination of the ligands. The Eu3+ assemblies show bright red emission and a luminescence performance (τobs≈0.5 ms, ${{\Phi}{{{\rm L}\hfill \atop {\rm Ln}\hfill}}}$ ≈35–37 %, ηsens≈68–70 %) more akin to the β‐diketonate species. The results highlight that the β‐triketonate ligand offers a tunable and facile system for the preparation of efficient NIR emitters without the need for more complicated perfluorination or deuteration synthetic strategies. 相似文献
8.
Bin Xu Fuming Luo Guodong Tang Jinfang Zhang 《Acta Crystallographica. Section C, Structural Chemistry》2019,75(5):508-513
The title coordination polymer, poly[bis[μ3‐4‐(3,2′:6′,3′′‐terpyridin‐4′‐yl)benzoato]cadmium(II)], [Cd(C22H14N3O2)2]n or [Cd(3‐cptpy)2]n, (I), has been synthesized solvothermally and characterized by IR spectroscopy, thermogravimetric analysis, and single‐crystal and powder X‐ray diffraction. The structure is composed of 3‐cptpy? ligands bridging Cd atoms, with each Cd atom coordinated by six ligands and each ligand coordinating to three Cd atoms. Each Cd atom is in a slightly distorted trans‐N2O4 octahedral environment, forming a two‐dimensional layer structure with a (3,6)‐connected topology. Layers are linked to each other by π–π stacking, resulting in a three‐dimensional supramolecular framework. The strong luminescence and good thermal stability of (I) indicate that it can potentially be used as a luminescence sensor. The compound also shows a highly selective and sensitive response to 2,4,6‐trinitrophenol through the luminescence quenching effect. 相似文献
9.
Cigdem Hopa Ismail Cokay 《Acta Crystallographica. Section C, Structural Chemistry》2016,72(2):149-154
The design and synthesis of polymeric coordination compounds of 3d transition metals are of great interest in the search for functional materials. The coordination chemistry of the copper(II) ion is of interest currently due to potential applications in the areas of molecular biology and magnetochemistry. A novel coordination polymer of CuII with bridging N,N′‐bis(2‐hydroxyphenyl)‐2,2‐dimethylpropane‐1,3‐diamine (H2L‐DM) and dicyanamide (dca) ligands, catena‐poly[[[μ2‐2,2‐dimethyl‐N,N′‐bis(2‐oxidobenzylidene)propane‐1,3‐diamine‐1:2κ6O,N,N′,O′:O,O′]dicopper(II)]‐di‐μ‐dicyanamido‐1:2′κ2N1:N5;2:1′κ2N1:N5], [Cu2(C19H20N2O2)(C2N3)2]n, has been synthesized and characterized by CHN elemental analysis, IR spectroscopy, thermal analysis and X‐ray single‐crystal diffraction analysis. Structural studies show that the CuII centres in the dimeric asymmetric unit adopt distorted square‐pyramidal geometries, as confirmed by the Addison parameter (τ) values. The chelating characteristics of the L‐DM2− ligand results in the formation of a CuII dimer with a double phenolate bridge in the asymmetric unit. In the crystal, the dimeric units are further linked to adjacent dimeric units through μ1,5‐dca bridges to produce one‐dimensional polymeric chains. 相似文献
10.
Bismuth‐Based Coordination Polymers with Efficient Aggregation‐Induced Phosphorescence and Reversible Mechanochromic Luminescence
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Dr. Oksana Toma Magali Allain Dr. Francesco Meinardi Dr. Alessandra Forni Dr. Chiara Botta Prof. Nicolas Mercier 《Angewandte Chemie (International ed. in English)》2016,55(28):7998-8002
Two bismuth coordination polymers (CPs), (TBA)[BiBr4(bp4mo)] (TBA=tetrabutylammonium) and [BiBr3(bp4mo)2], which are based on the rarely used simple ditopic ligand N‐oxide‐4,4′‐bipyridine (bp4mo), show mechanochromic luminescence (MCL). High solid‐state phosphorescence quantum yields of up to 85 % were determined for (TBA)[BiBr4(bp4mo)] (λem=540 nm). Thorough investigations of the luminescence properties combined with DFT and TDDFT calculations revealed that the emission is due to aggregation‐induced phosphorescence (AIP). Upon grinding, both samples became amorphous, and their luminescence changed from yellow to orange and red, respectively. Heating or exposure to water vapor led to the recovery of the initial luminescence. These materials are the first examples of mechanochromic phosphors based on bismuth(III). 相似文献
11.
Surface Functionalization of g‐C3N4: Molecular‐Level Design of Noble‐Metal‐Free Hydrogen Evolution Photocatalysts
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Dr. Yin Chen Dr. Bin Lin Dr. Weili Yu Prof. Yong Yang Shahid M. Bashir Dr. Hong Wang Prof. Kazuhiro Takanabe Prof. Hicham Idriss Prof. Jean‐Marie Basset 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(29):10290-10295
A stable noble‐metal‐free hydrogen evolution photocatalyst based on graphite carbon nitride (g‐C3N4) was developed by a molecular‐level design strategy. Surface functionalization was successfully conducted to introduce a single nickel active site onto the surface of the semiconducting g‐C3N4. This catalyst family (with less than 0.1 wt % of Ni) has been found to produce hydrogen with a rate near to the value obtained by using 3 wt % platinum as co‐catalyst. This new catalyst also exhibits very good stability under hydrogen evolution conditions, without any evidence of deactivation after 24 h. 相似文献
12.
Dr. Hao Wei Prof. Dr. Haixiang Gao Prof. Dr. Jean'ne M. Shreeve 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(51):16943-16952
One route to high density and high performance energetic materials based on 1,2,4,5‐tetrazine is the introduction of 2,4‐di‐N‐oxide functionalities. Based on several examples and through theoretical analysis, the strategy of regioselective introduction of these moieties into 1,2,4,5‐tetrazines has been developed. Using this methodology, various new tetrazine structures containing the N‐oxide functionality were synthesized and fully characterized using IR, NMR, and mass spectroscopy, elemental analysis, and single‐crystal X‐ray analysis. Hydrogen peroxide (50 %) was used very effectively in lieu of the usual 90 % peroxide in this system to generate N‐oxide tetrazine compounds successfully. Comparison of the experimental densities of N‐oxide 1,2,4,5‐tetrazine compounds with their 1,2,4,5‐tetrazine precursors shows that introducing the N‐oxide functionality is a highly effective and feasible method to enhance the density of these materials. The heats of formation for all compounds were calculated with Gaussian 03 (revision D.01) and these values were combined with measured densities to calculate detonation pressures (P) and velocities (νD) of these energetic materials (Explo 5.0 v. 6.01). The new oxygen‐containing tetrazines exhibit high density, good thermal stability, acceptable oxygen balance, positive heat of formation, and excellent detonation properties, which, in some cases, are superior to those of 1,3,5‐tritnitrotoluene (TNT), 1,3,5‐trinitrotriazacyclohexane (RDX), and octahydro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine (HMX). 相似文献
13.
Ultrasound‐Assisted Synthesis of 6‐Methyl‐1,2,3,4‐tetrahydro‐N‐aryl‐2‐oxo/thio‐4‐arylpyrimidine‐5‐carboxamides Catalyzed by Uranyl Nitrate Hexahydrate
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An efficient and simple method developed for the synthesis of 6‐methyl‐1,2,3,4‐tetrahydro‐N‐aryl‐2‐oxo/thio‐4‐arylpyrimidine‐5‐carboxamide derivatives ( 4a‐o ) using UO2(NO3)2.6H2O catalyst under conventional and ultrasonic conditions. The ultrasound irradiation synthesis had shown several advantages such as milder conditions, shorter reaction times and higher yields. The structures of all the newly synthesized compounds have been confirmed by FT‐IR, 1H NMR, 13C NMR and mass spectra. 相似文献
14.
Surendra Kumar Nayak Vikramdeep Monga Navneet Kaur Rahul Jain 《Journal of heterocyclic chemistry》2007,44(6):1265-1269
15.
Two novel five‐coordinate zinc(II) complexes with the tripod ligand tris(N‐methylbenzimidazol‐2‐ylmethyl)amine (Mentb) and two different α,β‐unsaturated carboxylates, with the composition [Zn(Mentb)(acrylate)] (ClO4)·DMF·1.5CH3OH ( 1 ) and [Zn(Mentb)(cinnamate)](ClO4)·2DMF·0.5CH3OH ( 2 ), were synthesized and characterized by means of elemental analyses, electrical conductivity measurements, IR, UV, and 1H NMR spectra. The crystal structure of two complexes have been determined by a single‐crystal X‐ray diffraction method, and show that the ZnII atom is bonded to a Mentb ligand and a α,β‐unsaturated carboxylate molecule through four N atoms and one O atom, resulting in a distorted trigonal‐bipyramidal coordination [τ( 1 ) = 0.853, τ( 2 ) = 0.855], with approximate C3 symmetry. 相似文献
16.
Steffen Treiling Cui Wang Christoph Frster Florian Reichenauer Jens Kalmbach Pit Boden Joe P. Harris Luca M. Carrella Eva Rentschler Ute Resch‐Genger Christian Reber Michael Seitz Markus Gerhards Katja Heinze 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(50):18243-18253
Photoactive metal complexes employing Earth‐abundant metal ions are a key to sustainable photophysical and photochemical applications. We exploit the effects of an inversion center and ligand non‐innocence to tune the luminescence and photochemistry of the excited state of the [CrN6] chromophore [Cr(tpe)2]3+ with close to octahedral symmetry (tpe=1,1,1‐tris(pyrid‐2‐yl)ethane). [Cr(tpe)2]3+ exhibits the longest luminescence lifetime (τ=4500 μs) reported up to date for a molecular polypyridyl chromium(III) complex together with a very high luminescence quantum yield of Φ=8.2 % at room temperature in fluid solution. Furthermore, the tpe ligands in [Cr(tpe)2]3+ are redox non‐innocent, leading to reversible reductive chemistry. The excited state redox potential and lifetime of [Cr(tpe)2]3+ surpass those of the classical photosensitizer [Ru(bpy)3]2+ (bpy=2,2′‐bipyridine) enabling energy transfer (to oxygen) and photoredox processes (with azulene and tri(n‐butyl)amine). 相似文献
17.
A series of N‐substituted 1,4‐dihydro‐4‐oxo‐1,8‐naphthyridine‐3‐carboxylate esters has been prepared in two steps from ethyl 2‐(2‐chloronicotinoyl)acetate. Treatment of the β‐ketoester with N,N‐dimethylformamide dimethyl acetal in N,N‐dimethylformamide (DMF) gave a 95% yield of the 2‐dimethylaminomethylene derivative. Subsequent reaction of this β‐enaminone with primary amines in DMF at 120oC for 24 h then afforded the target compounds in 47–82% yields by a tandem SNAr‐addition‐elimination reaction. Synthetic and procedural details as well as a mechanistic rationale are presented. 相似文献
18.
One‐Pot Synthesis of 2‐Oxazolines from Ethyl α‐Cyanocinnamate Derivatives with N‐Bromoacetamide
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Zhanguo Chen Hua Wen Wenli Li Jimei Zhou Junli Hu Wei Xia 《Journal of heterocyclic chemistry》2014,51(3):794-802
An efficient method for the one‐pot synthesis of 2‐oxazolines from ethyl α‐cyanocinnamate derivatives with N‐bromoacetamide in the presence of K3PO4 has been developed. The reaction performed smoothly and cleanly to give 2‐oxazolines in good to excellent yields (up to 98%) within 4.5 h in acetone at room temperature without protection of inert gases. A total of 13 examples have been investigated. A possible nucleophilic addition reaction mechanism is proposed. 相似文献
19.
Analysis of the Role of Peripheral Ligands Coordinated to ZnII in Enhancing the Energy Barrier in Luminescent Linear Trinuclear Zn‐Dy‐Zn Single‐Molecule Magnets
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Dr. Jean Pierre Costes Dr. Silvia Titos‐Padilla Itziar Oyarzabal Tulika Gupta Dr. Carine Duhayon Prof. Gopalan Rajaraman Prof. Enrique Colacio 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(44):15785-15796
Three new Dy complexes have been prepared according to a complex‐as‐ligand strategy. Structural determinations indicate that the central Dy ion is surrounded by two LZn units (L2? is the di‐deprotonated form of the N2O2 compartmental N,N′‐2,2‐dimethylpropylenedi(3‐methoxysalicylideneiminato) Schiff base. The Dy ions are nonacoordinate to eight oxygen atoms from the two L ligands and to a water molecule. The Zn ions are pentacoordinate in all cases, linked to the N2O2 atoms from L, and the apical position of the Zn coordination sphere is occupied by a water molecule or bromide or chloride ions. These resulting complexes, formulated (LZnX)‐Dy‐(LZnX), are tricationic with X=H2O and monocationic with X=Br or Cl. They behave as field‐free single‐molecule magnets (SMMs) with effective energy barriers (Ueff) for the reversal of the magnetization of 96.9(6) K with τ0=2.4×10?7 s, 146.8(5) K with τ0=9.2×10?8 s, and 146.1(10) K with τ0=9.9×10?8 s for compounds with Zn?OH2, Zn?Br, and Zn?Cl motifs, respectively. The Cole–Cole plots exhibit semicircular shapes with α parameters in the range of 0.19 to 0.29, which suggests multiple relaxation processes. Under a dc applied magnetic field of 1000 Oe, the quantum tunneling of magnetization (QTM) is partly or fully suppressed and the energy barriers increase to Ueff=128.6(5) K and τ0=1.8×10?8 s for 1 , Ueff=214.7 K and τ0=9.8×10?9 s for 2 , and Ueff=202.4 K and τ0=1.5×10?8 s for 3 . The two pairs of largely negatively charged phenoxido oxygen atoms with short Dy?O bonds are positioned at opposite sides of the Dy3+ ion, which thus creates a strong crystal field that stabilizes the axial MJ=±15/2 doublet as the ground Kramers doublet. Although the compound with the Zn?OH2 motifs possesses the larger negative charges on the phenolate oxygen atoms, as confirmed by using DFT calculations, it exhibits the larger distortions of the DyO9 coordination polyhedron from ideal geometries and a smaller Ueff value. Ab initio calculations support the easy‐axis anisotropy of the ground Kramers doublet and predict zero‐field SMM behavior through Orbach and TA‐QTM relaxations via the first excited Kramers doublet, which leads to large energy barriers. In accordance with the experimental results, ab initio calculations have also shown that, compared with water, the peripheral halide ligands coordinated to the Zn2+ ions increase the barrier height when the distortions of the DyO9 have a negative effect. All the complexes exhibit metal‐centered luminescence after excitation into the UV π–π* absorption band of ligand L2? at λ=335 nm, which results in the appearance of the characteristic DyIII (4F9/2→6HJ/2; J=15/2, 13/2) emission bands in the visible region. 相似文献
20.
The preparation of three new N‐Fmoc‐protected (Fmoc=[(9H‐fluoren‐9‐yl)methoxy]carbonyl) β2‐homoamino acids with proteinogenic side chains (from Ile, Tyr, and Met) is described, the key step being a diastereoselective amidomethylation of the corresponding Ti‐enolates of 3‐acyl‐4‐isopropyl‐5,5‐diphenyloxazolidin‐2‐ones with CbzNHCH2OMe/TiCl4 (Cbz=(benzyloxy)carbonyl) in yields of 60–70% and with diastereoselectivities of >90%. Removal of the chiral auxiliary with LiOH or NaOH gives the N‐Cbz‐protected β‐amino acids, which were subjected to an N‐Cbz/N‐Fmoc (Fmoc=[(9H‐fluoren‐9‐yl)methoxy]carbonyl) protective‐group exchange. The method is suitable for large‐scale preparation of Fmoc‐β2hXaa‐OH for solid‐phase syntheses of β‐peptides. The Fmoc‐amino acids and all compounds leading to them have been fully characterized by melting points, optical rotations, IR, 1H‐ and 13C‐NMR, and mass spectra, as well as by elemental analyses. 相似文献