- A novel water-dispersible and magnetically recyclable nickel nanoparticles for the one-pot reduction-Schiff base condensation of nitroarenes in pure water
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In this work, a heterogeneous nanocatalyst called Ni-Fe3O4@Pectin~PPA ~ Piconal was first synthesized, which was investigated as a bifunctional catalyst containing nickel functional groups. On the other hand, this Ni-Fe3O4@Pectin~PPA ~ Piconal catalyst in aqueous solvents shows a very effective performance at ambient temperature for the nitroarene reduction reaction with sodium borohydride, for which NaBH4 is considered as a reducing agent. This is a novelty magnetic catalyst that was approved by various methods, including Fourier-transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), Dynamic light scattering (DLS), Transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), Inductively coupled plasma (ICP), Energy-dispersive X-ray spectroscopy (EDX), and Field emission scanning electron microscopy (FESEM) analyses. From the satisfactory results obtained from the reduction of nitrogen, this catalytic system is used for a one-pot protocol containing a reduction-Schiff base concentration of diverse nitroarenes. It was corroborated with the heterogeneous catalytic experiments on the one-pot tandem synthesis of imines from nitroarenes and aldehydes. Finally, the novel Ni-Fe3O4@Pectin~PPA ~ Piconal catalyst could function as a more economically desirable and environmentally amicable in the catalysis field. The favorable products are acquired in good to high performance in the attendance of Ni-Fe3O4@Pectin~PPA ~ Piconal as a bifunctional catalyst. This catalyst can be recycled up to six steps without losing a sharp drop.
- Ghamari Kargar, Pouya,Ravanjamjah, Asiye,Bagherzade, Ghodsieh
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p. 1916 - 1933
(2021/07/10)
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- Influence of substituents on the structure of Schiff bases Cu(II) complexes
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The relationship between molecular conformation and substituent effects of salicylaldehyde Schiff-base Cu(II) complexes was explored. For this study, eight samples of the complexes Cu(Sal-X)2 (X = OMe, Me, H, F, Cl, Br, CF3 and CN) w
- Xiao, Yan,Cao, Chenzhong
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- Simple synthesis of the novel Cu-MOF catalysts for the selective alcohol oxidation and the oxidative cross-coupling of amines and alcohols
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A novel porous metal–organic framework {Cu2(bbda)0.5(Hbbda)1.5(OAc)1.5.8H2O} (UoB-5) was synthesized under ultrasound irradiation by employing a new Schiff base ligand H2bbda (4,4'(1,4-phenylene bis (azanylylidene)) bis (methanylylidene))dibenzoic acid) and was fully characterized. The microporous nature of UoB-5 was confirmed by gas-sorption measurements. This framework acted as a highly effective heterogeneous catalyst for the alcohol oxidation reaction with tert-butyl hydroperoxide (t-BuOOH) as an oxidant. The presence of coordinatively unsaturated metal sites in UoB-5 could be the reason for high performance in this reaction. Furthermore, using the long linker with the free -NC group and uncoordinated -N atom on the wall of the pores created UoB-5 an excellent candidate for the catalytic activities without activation of the framework. It was confirmed with the heterogeneous catalytic experiments on the one-pot tandem synthesis of imines from benzyl alcohols and anilines. Eventually, the new Cu-MOF (UoB-5) could be an alternative catalyst as a more economically favorable and environmentally friendly in the catalysis field.
- Ghamari Kargar, Pouya,Aryanejad, Sima,Bagherzade, Ghodsieh
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- Iron-Catalyzed Nitrene Transfer Reaction of 4-Hydroxystilbenes with Aryl Azides: Synthesis of Imines via C=C Bond Cleavage
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C=C bond breaking to access the C=N bond remains an underdeveloped area. A new protocol for C=C bond cleavage of alkenes under nonoxidative conditions to produce imines via an iron-catalyzed nitrene transfer reaction of 4-hydroxystilbenes with aryl azides is reported. The success of various sequential one-pot reactions reveals that the good compatibility of this method makes it very attractive for synthetic applications. On the basis of experimental observations, a plausible reaction mechanism is also proposed.
- Peng, Yi,Fan, Yan-Hui,Li, Si-Yuan,Li, Bin,Xue, Jing,Deng, Qing-Hai
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supporting information
p. 8389 - 8394
(2019/10/16)
-
- Design, synthesis, and biological activity of Schiff bases bearing salicyl and 7-hydroxycoumarinyl moieties
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Abstract: 18 (11 novel) Schiff bases, derivatives of salicylaldehyde, 2-hydroxyacetophenone, and 6-acetyl-, 8-acetyl-, and 8-formyl-7-hydroxy-4-methylcoumarin were synthesized and characterized by their spectral studies. 6-Acetyl-7-hydroxy-4-methylcoumarin was prepared by novel method under microwave assistance. These Schiff bases were evaluated for antibacterial activities against 12 bacterial and six fungi strains in vitro. N-(3,5-Dichloro-2-hydroxybenzylidene)-4-aminobenzenesulfonic acid sodium salt proved to be the most active against Staphylococcus aureus and MRSA strains (MIC 0.0194?μmol/cm3). The substitution pattern, two chlorine atoms in the salicylidene ring and the SO3Na group, is probably the most beneficial for the activity against Gram-(+) bacteria strains. All Schiff bases were evaluated for cancer efficacy against CFPAC-1 and HeLa cell cultures originating from human pancreas cancer or human cervical cancer. Schiff bases derived from salicylaldehyde are highly effective in pancreas and cervical cancer cells; however, they demonstrate also substantial toxicity towards NIH3T3 cells. Derivatives of coumarin contain three highly selective compounds: 7-hydroxy-8-[(4-methoxyphenylimino)methyl]-4-methyl-2H-chromen-2-one, N-[(7-hydroxy-4-methyl-2-oxo-2H-chromen-8-yl)methylene]-4-aminobenzenesulfonic acid sodium salt, and 7-hydroxy-8-[1-(4-hydroxyphenylimino)ethyl]-4-methyl-2H-chromen-2-one suggesting more promising potential of the second group of substances.
- Hejchman, El?bieta,Kruszewska, Hanna,Maciejewska, Dorota,Sowirka-Taciak, Barbara,Tomczyk, Magdalena,Sztokfisz-Ignasiak, Alicja,Jankowski, Jan,M?ynarczuk-Bia?y, Izabela
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p. 255 - 266
(2019/01/16)
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- Improving C=N bond reductions with (Cyclopentadienone)iron complexes: Scope and limitations
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Herein, we broaden the application scope of (cyclo-pentadienone)iron complexes 1 in C=N bond reduction. The catalytic scope of pre-catalyst 1b, which is more active than the “Kn?lker complex” (1a) and other members of its family, has been expanded to the catalytic transfer hydrogenation (CTH) of a wider range of aldimines and ketimines, either pre-isolated or generated in situ. The kinetics of 1b-promoted CTH of ketimine S1 were assessed, showing a pseudo-first order profile, with TOF = 6.07 h–1 at 50 % conversion. Moreover, the chiral complex 1c and its analog 1d were employed in the enantioselective reduction of ketimines and reductive amination of ketones, giving fair to good yields and moderate enantioselectivity.
- Cettolin, Mattia,Bai, Xishan,Lübken, Dennis,Gatti, Marco,Facchini, Sofia Vailati,Piarulli, Umberto,Pignataro, Luca,Gennari, Cesare
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supporting information
p. 647 - 654
(2018/10/24)
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- Effect of substituents on the UV spectra of supermolecular system: Silver nanoparticles with bi-aryl Schiff bases containing hydroxyl
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Effect of substituents on the ultraviolet (UV) spectra of supermolecular system involving silver nanoparticles (AgNPs) and Schiff bases was investigated. AgNPs and 49 samples of model compounds (MC), bi-aryl Schiff bases containing hydroxyl (XBAY, involving 4-OHArCH?NArY, 2-OHArCH?NArY, XArCH?NAr-4′-OH, and XArCH?NAr-2′-OH), were synthesized. The size of AgNPs was characterized by transmission electron microscopy (TEM), and the UV absorption spectra of AgNPs, XBAYs, and MC-AgNPs mixed solutions were measured, respectively. The results show that (1) the size of AgNPs is larger in MC-AgNPs solutions than that in AgNPs solution due to the distribution of MC molecules on the surface of AgNPs; (2) the UV absorption wavelength of XBAYs changes in the action of AgNPs and their wavelength shift exists limitation between XBAY and MC-AgNPs solutions; and (3) the wavelength shift limit of MC-AgNPs (λWSL) is influenced by the substituents X and Y and the position of hydroxyl OH. The wavenumber ΔνWSL of λWSL can be quantified by employing the excited-state substituent constant σexCC and Hammett constant σ of substituents X and Y. Comparing with the 4-OH, the 4′-OH makes the ΔνWSL a red shift, whereas the 2′-OH, comparing with the 2-OH, makes the ΔνWSL a blue shift.
- Cao, Chao-Tun,Cheng, Shimao,Zhang, Jingyuan,Cao, Chenzhong
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- AIPE-active platinum(ii) complexes with tunable photophysical properties and their application in constructing thermosensitive probes used for intracellular temperature imaging
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Aggregation-induced phosphorescent emission (AIPE) luminogens based on phosphorescent transition metal complexes have many application advantages in bioimaging compared with fluorescent organic dyes because of their long excitation lifetime and reduced ph
- Lin, Shengheng,Pan, Honghao,Li, Lin,Liao, Rui,Yu, Shengzhen,Zhao, Qiang,Sun, Huibin,Huang, Wei
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supporting information
p. 7893 - 7899
(2019/07/10)
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- Organocatalytic synthesis of densely functionalized oxa-bridged 2,6-epoxybenzo[: B] [1,5]oxazocine heterocycles
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Metal-free addition of salicylhydrazones to electron deficient internal alkynes catalyzed by 1,4-diazabicyclo[2.2.2]octane (DABCO) to yield oxa-bridged 2,6-epoxybenzo[b][1,5]oxazocine heterocycles was achieved. The demonstrated protocol proceeds through an o-quinone methide formation, aza-Michael addition, stereoselective protonation, enamine promoted aromatization, O,O-acetalization and O,N-aminalization sequence to provide privileged heterocycles in good yields with high diastereoselectivities.
- Gurubrahamam, Ramani,Nagaraju, Koppanathi,Chen, Kwunmin
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supporting information
p. 6048 - 6051
(2018/06/18)
-
- Remarkable difference between five- and six- number-membered ring transition states for intramolecular proton transfer in excited state
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In this study, a range of organic dyes were prepared to investigate difference between five- and six- number-membered ring transition states for internal proton transfer in excited state. Different strength intramolecular hydrogen bond in the target dyes
- Qin, Xiaozhuan,Ding, Ge,Wang, Zhenqiang,Zhang, Shengtao,Li, Hongru,Luo, Ziping,Gao, Fang
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- A green protocol for the one-pot multicomponent Petasis boronic Mannich reaction using ball milling
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Solvent-free reactions of salicylaldehyde with various boronic acids and amines were accomplished under ball-milling conditions to achieve the corresponding alkyl- and arylaminophenols in good to excellent yields. This simple protocol offers advantages su
- Hosseinzadeh,Lasemi,Oloub,Pooryousef
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p. 347 - 355
(2017/01/10)
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- Carbocation Organocatalysis in Interrupted Povarov Reactions to cis-Fused Pyrano- and Furanobenzodihydropyrans
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Tritylium cation-catalyzed interrupted Povarov reactions afforded cis-4-aminobenzodihydropyrans in excellent yields (90 %) within 10 min by low catalyst loadings (1 mol-%). A mechanism involving Lewis acidic catalysis by a carbocation was proposed and val
- Liu, Jingjing,Xu, Jiaxi,Li, Zhenjiang,Huang, Yu,Wang, Haixin,Gao, Yu,Guo, Tianfo,Ouyang, Pingkai,Guo, Kai
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p. 3996 - 4003
(2017/07/28)
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- Catalyst-free allylation of 2-aminophenol–derived aldimines with allyltrichlorosilane under thermal conditions
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Allylation of 2-aminophenol-derived aldimines using allyltrichlorosilane under catalyst free conditions has been developed. This reaction afforded the corresponding homoallylic amines in good to excellent yields (68–94%). The salicylaldehyde-derived aldimines as well as benzoylhydrazone also found to react with allyltrichlorosilane smoothly under the same conditions, to furnish the corresponding homoallylic amine derivatives. This study suggests that the phenolic –OH group acts as an anchoring group for the transfer of allyl group from allyl silane reagent.
- Venkatanna, Kesa,Ramanathan, Chinnasamy Ramaraj
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supporting information
p. 3650 - 3653
(2017/08/22)
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- Abnormal effect of hydroxyl on the longest wavelength maximum in ultraviolet absorption spectra for bis-aryl Schiff bases
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Two sets of bis-aryl Schiff bases that contain 4(or 4′)-OH and 2(or 2′)-OH were synthesized. The first set consists of 4-HOArCH=NArY and XArCH=NArOH-4′, and the second set consists of 2-HOArCH=NArY and XArCH=NArOH-2′. Their ultraviolet absorption spectra were measured and investigated. A very interesting phenomenon was observed by analyzing their wave number νmax (cm?1) of longest wavelength maximum λmax (nm) of ultraviolet. Compared with the change regularity of the νmax of XArCH=NArY (where the X and Y excluded OH), the 4′-position hydroxyl (4′-OH) and 2′-position hydroxyl (2′-OH) have abnormal performance. The details are the following: the 4′-OH contributes an additional red shift to the νmax of XArCH=NArOH-4′ (λmax increase), whereas the 2′-OH contributes an additional blue shift to the νmax of XArCH=NArOH-2′ (λmax decrease). In addition, there are ortho steric effects of all 2-OH and 2′-OH on the νmax for 2-HOArCH=NArY and XArCH=NArOH-2′, and the ortho steric effect contributes a red shift to their νmax. These experimental facts can provide an important theoretical reference for us using aryl Schiff base compounds as optical materials and performing the molecular design.
- Cao, Chao-Tun,Zhou, Wei,Cao, Chenzhong
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- PdCl2(Ph3P)2/Salicylaldimine Catalyzed Diarylation of Anilines with Unactivated Aryl Chlorides
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Triphenylphosphine and salicylaldimine could be used as a mixed ligand system to obtain a high catalytic activity for palladium catalyzed diarylation of primary anilines with unactivated aryl chlorides by the synergistic effect of ligands. The activity and selectivity of the catalytic system could be improved by modifying the structure of salicylaldimine. In refluxing o-xylene, PdCl2(Ph3P)2 with 2,5-ditrifluoromethyl N-phenylsalicylaldimine as a coligand shows high efficiency for the diarylation of various anilines. The catalytic system shows good toleration for the steric hindrance of the substrates. The facile catalytic system works as well on the multiple arylation of 1,1′-biphenyl- 4,4′-diamine with aryl chlorides to afford N,N,N′,N′-tetraaryl-1,1′-biphenyl-4,4′-diamines which are important intermediates of organic light emitting diode (OLED) hole transport materials.
- Tao, Xiaochun,Li, Lei,Zhou, Yu,Qian, Xuanying,Zhao, Min,Cai, Liangzhen,Xie, Xiaomin
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p. 1749 - 1754
(2017/10/06)
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- The effect of solvent on electronic absorption bands of some Benzylideneanilines
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In the present investigation the effects of solvents of varied polarities on the UV–visible spectral bands of some substituted benzylideneanilines and their o/p-hydroxy derivatives were explored. The analyses of the electronic absorption bands indicated t
- Panigrahi, Sagarika,Misra, Pramila K.
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- Lanthanum(III)-Catalyzed Three-Component Reaction of Coumarin-3-carboxylates for the Synthesis of Indolylmalonamides and Analysis of Their Photophysical Properties
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New methodology has been developed for the Lewis acid catalyzed synthesis of malonamides. First, the scandium(III)-catalyzed addition of diverse nucleophiles (e.g., indoles, N,N-dimethyl-m-anisidine, 2-ethylpyrrole, and 2-methylallylsilane) to coumarin-3-carboxylates has been developed to afford chromanone-3-carboxylates in high yields as a single diastereomer. Upon investigating a subsequent lanthanum(III)-catalyzed amidation reaction, a new multicomponent reaction was designed by bringing together coumarin-3-carboxylates with indoles and amines to afford indolylmalonamides, which were identified to exhibit fluorescent properties. The photophysical properties for selected compounds have been analyzed, including quantum yield, molar absorptivity, and Stokes shift. Synthetic studies of several reaction byproducts involved in the network of reaction equilibria for the three-component reaction provide mechanistic insight for the development of this methodology.
- Jennings, Julia J.,Bhatt, Chinmay P.,Franz, Annaliese K.
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p. 6211 - 6222
(2016/08/16)
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- Triggering effect caused by elemental sulfur as a mean to reduce the polymerization temperature of benzoxazine monomers
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Mixtures of different benzoxazine resins and elemental sulfur (S8) are prepared and then reacted at 120 °C, below the temperature for radical formation of sulfur. The progress of the reaction and the chemical structures of the main products are monitored and characterized by proton nuclear magnetic resonance spectroscopy (1H NMR) and Fourier transform infrared spectroscopy (FT-IR). Thermal analysis of all reactive systems are also performed and studied by differential scanning calorimetry (DSC). The introduction of S8 into benzoxazines generates a new structure bearing a Schiff base and a phenolic -OH within the reactive system, which then triggers the reduction of the polymerization temperature in about 15% when as low as 5 mol% of S8 is added.
- Arza, Carlos Rodriguez,Froimowicz, Pablo,Ishida, Hatsuo
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p. 35144 - 35151
(2016/05/19)
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- Synthesis and development of Chitosan anchored copper(II) Schiff base complexes as heterogeneous catalysts for N-arylation of amines
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Abstract The Chitosan anchored Cu(II) Schiff base complexes (C1-C3) have been synthesized and characterized by FTIR, UV, FE-SEM, EDAX, TGA, AAS and elemental analysis. These complexes have been found to be efficient and recyclable heterogeneous catalysts for the Chan-Lam C-N coupling reaction of various aromatic/aliphatic amines with arylboronic acid under mild reaction conditions. These complexes can be easily filtered out from the reaction medium and reused up to five times without significant loss of catalytic activity.
- Anuradha,Kumari, Shweta,Pathak, Devendra D.
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supporting information
p. 4135 - 4142
(2015/08/03)
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- Substituent effects on the absorption and vibrational spectra of some 2-hydroxy Schiff bases: DFT/TDDFT, natural bond orbital and experimental study
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The electronic structure of salicylideneaniline (SA) and some of its derivatives are investigated both experimentally and theoretically. The equilibrium geometric structures of the studied compounds are determined at the B3LYP/6-311++Glevel of theory. A set of 12 substituted SA derivatives is considered in the present work. The choice of these substituents aims to create a push-pull system on the SA basic structure which would shade light onto its photo physics. The electronic absorption spectra of SA are recorded in the UV-VIS region, in both polar and nonpolar solvents. Assignments of the observed electronic transitions are facilitated via time-dependent density functional theory (TDDFT) computations at the same level of theory. Electronic configurations contributing to each excited state are identified and the relevant MOs are characterized. The extent of delocalization and intramolecular charge transfer are estimated and discussed in terms of natural bond orbitals (NBO) analysis and second order perturbation interactions between donor and acceptor MOs. Solvent effects on the electronic absorption spectra are discussed in terms of the difference in polarizabilities of the ground and excited states. FTIR spectra of SA and its derivatives are measured in KBr platelets. Detailed vibrational assignments are given based on the calculated potential energy distributions. "IR marker bands" that characterize the SA framework are identified. The effect of substituents, the nature of the characteristic "marker bands", and intensity quenching of some bands are discussed.
- Elroby,Aboud,Aziz,Hilal
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p. 414 - 427
(2015/08/06)
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- Synthesis of Chemically and Configurationally Stable Monofluoro Acylboronates: Effect of Ligand Structure on their Formation, Properties, and Reactivities
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The recent disclosures of two classes of acylborons, potassium acyltrifluoroborates (KATs) and N-methyliminodiacetyl (MIDA) acylboronates, demonstrated that certain acylboron species can be both remarkably stable and uniquely reactive. Here we report new classes of ligands for acylboronates that have a significant influence on the formation, properties, and reactivities of acylboronates. Our systematic investigations identified a class of neutral, monofluoroboronates that can be prepared in a one step, gram-scale fashion from readily accessible KATs. These monofluoroboronates are stable to air, moisture, and silica gel chromatography and can be easily handled without any special precautions. X-ray crystallography, NMR spectroscopy, and HPLC studies showed that they are tetravalent, configurationally stable B-chiral acylboronates. Significantly, the ligands on the boronate allow for fine-tuning of the properties and reactivity of acylboronates. In amide-forming ligation with hydroxylamines under aqueous conditions, a considerable difference in reactivity was observed as a function of ligand structure. The solid-state structures suggested that subtle steric and conformational factors modulate the reactivities of the acylboronates.
- Noda, Hidetoshi,Bode, Jeffrey W.
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supporting information
p. 3958 - 3966
(2015/04/14)
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- Iodine(III)-mediated C-H alkoxylation of aniline derivatives with alcohols under metal-free conditions
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The development of a novel intermolecular oxidative C-H alkoxylation of aniline derivatives is described under metalfree conditions with high reaction rates at ambient temperature. In the presence of an I(III) oxidant, a range of aldehydes, anilines, and alcohol substrates undergo three-component coupling to produce synthetically useful alkoxyl-substituted N-arylimines. The preliminary mechanism investigations revealed that the transformation proceeds via imines as intermediates.
- Jiang, Qing,Wang, Jing-Yu,Guo, Cancheng
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p. 8768 - 8773
(2014/12/12)
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- Solvent-free synthesis, spectral correlations and antimicrobial activities of some aryl imines
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A series of aryl imines have been synthesized by Fly-ash: H 2SO4 catalyzed microwave assisted process under solvent-free conditions. The yields of the imines have been found to be more than 87%. The purity of all imines has been checked using their physical constants and spectral data as published earlier in literature. The UV λmaxCN(nm), infrared νCN(cm-1), NMR δ(ppm) of CH and CN spectral data have been correlated with Hammett substituent constants and F and R parameters using single and multi-linear regression analysis. From the results of statistical analysis, the effect of substituents on the above spectral data has been studied. The antimicrobial activities of All synthesised imines have been studied using Bauer-Kirby method.
- Suresh,Kamalakkannan,Ranganathan,Arulkumaran,Sundararajan,Sakthinathan,Vijayakumar,Sathiyamoorthi,Mala,Vanangamudi,Thirumurthy,Mayavel,Thirunarayanan
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p. 239 - 248
(2013/02/22)
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- Efficient synthesis of 2,3-disubstituted-1,3-benzoxazines by chlorotrimethylsilane-mediated aza-acetalizations of aromatic aldehydes
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A series of novel substituted 3,4-dihydro-2H-1,3-benzoxazines were prepared in moderate to good yields by aza-acetalizations of aromatic aldehydes with 2-(N-substituted aminomethyl)phenols in the presence of chlorotrimethylsilane or SnCl4. It w
- Tang, Zilong,Zhu, Zhonghua,Yan, Lin,Chang, Shuhong,Liu, Hanwen
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p. 1116 - 1120
(2013/10/21)
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- Triphenylphosphine as a ligand for the Pd-catalyzed amination of unactivated aryl chlorides with anilines promoted by salicylaldimine
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An efficient and selective amination of unactivated aryl chlorides with anilines catalyzed by mixed ligand Pd catalytic system of Ph3P- salicylaldimine has been developed for the preparation of diarylamines. The benzyne mechanism was ruled out based on experimental results. Georg Thieme Verlag Stuttgart · New York.
- Liu, Tao-Ping,Cheng, Qiang,Song, Wen-Jing,Cai, Liang-Zhen,Tao, Xiao-Chun
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p. 2333 - 2336
(2013/07/19)
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- SnCl4-catalyzed aza-acetalization of aromatic aldehydes: Synthesis of aryl substituted 3,4-dihydro-2H-1,3-benzoxazines
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Stannic tetrachloride was an efficient Lewis acid catalyst for the aza-acetalization of aromatic aldehydes with o-arylaminomethyl phenols, and a series of novel aryl substituted 3,4-dihydro-2H-1,3-benzoxazines were prepared in good yields under mild condi
- Tang, Zilong,Chen, Weiwen,Zhu, Zhonghua,Liu, Hanwen
-
scheme or table
p. 1372 - 1383
(2012/04/04)
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- Synthesis and fungicidal activity of novel 2,3-disubstituted-1,3- benzoxazines
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A series of new 2,3-disubstituted-3,4-dihydro-2H-1,3-benzoxazines were prepared in moderate to excellent yields by aza-acetalizations of aromatic aldehydes with 2-(N-substituted aminomethyl)phenols in the presence of TMSCl. Their structures were confirmed
- Tang, Zilong,Zhu, Zhonghua,Xia, Zanwen,Liu, Hanwen,Chen, Jinwen,Xiao, Wenjing,Ou, Xiaoming
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scheme or table
p. 8174 - 8185
(2012/09/25)
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- The substituent effects on the 13C chemical shifts of the azomethine carbon atom of N-(substituted phenyl)salicylaldimines
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Hammett correlations between the 13C-NMR chemical shifts of the azomethine carbon atom and the corresponding substituent constants were established for thirteen Schiff bases. The successful correlation of the chemical shifts with the electrophilic substituent constants σ+ indicate a significant resonance interaction of the substituents on the aniline ring with the azomethine carbon atom in the examined series of imines. The demand for electrons in the investigated compounds was compared to that of the N-benzylideneanilines and N-(substituted phenyl)pyridinealdimines. The manner of transmission of the substituent effects is discussed and they were separated into resonance and inductive effects. The inductive effects prevail over the resonance effects.
- Drmanic, Sasa Z.,Marinkovic, Aleksandar D.,Nikolic, Jasmina B.,Jovanovic, Bratislav Z.
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p. 993 - 1001
(2012/10/29)
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- GREEN SYNTHESIS OF ARYL ALDIMINES USING ETHYL LACTATE
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The present invention relates to a method for preparing aryl aldimines. In particular, the present invention relates to methods of preparing aryl aldimines that uses environmentally friendly solvent systems.
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-
Page/Page column 5-6
(2011/08/22)
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- Facile synthesis of highly fluorescent Boranil complexes
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Complexation of a large variety of Anils (aniline-imines) with boron(III) precursors provides stable Boranils, some of which have been structurally characterized. Analysis of their optical properties reveals that the fluorescence stems from an intraligand
- Frath, Denis,Azizi, Sebastien,Ulrich, Gilles,Retailleau, Pascal,Ziessel, Raymond
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supporting information; experimental part
p. 3414 - 3417
(2011/08/22)
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- Antihyperglycemic, α-glucosidase inhibitory and DPPH free radical scavenging activity of 5-bromosalicylaldehyde and schiff bases
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α-Glucosidase inhibition and DPPH free radical scavenging by 5-bromosalicylaldehyde and some Schiff bases have been measured. 5-Bromosalicylaldehyde shows lowest IC50 value (8.80 μM) for α-glucosidase inhibition and also shows good results in in vivo experiments for antihyperglycemic potential. Springer Science+Business Media, LLC 2010.
- Misra, Sristicheta,Pandeya, Krishna Bihari,Tiwari, Ashok Kumar,Ali, Amtul Zehra,Saradamani, Thimmapatruni,Agawane, Sachin Bharat,Madhusudana, Kuncha
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experimental part
p. 1431 - 1437
(2012/05/20)
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- Synthesis of 2,3-diaryl-3,4-dihydro-2H-1,3-benzoxazines and their fungicidal activities
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A series of novel 2,3-diaryl-3,4-dihydro-2H-1,3-benzoxazines have been prepared in high yields from o-arylaminomethylphenols and aromatic aldehydes in the presence of SnCl4 for the first time, and their fungicidal activities were investigated t
- Tang, Zilong,Chen, Weiwen,Zhu, Zhonghua,Liu, Hanwen
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scheme or table
p. 255 - 260
(2011/06/19)
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- Antileishmanial, antimicrobial and antifungal activities of some new aryl azomethines
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A series of eighteen azomethines has been synthesized by the reaction of appropriate primary aromatic amines with aryl and/or heteroaryl carboxaldehydes. The synthesized azomethines have been evaluated for their in vitro antileishmanial, antibacterial and antifungal activities. The results revealed some antifungal activity of most of the synthesized compounds, whereas the antileishmaniasis activity results highlighted that all synthesized azomethines inhibited parasite growth and most of them showed highly potent action towards Leishmania major promastigotes. No remarkable bactericidal activities were observed.
- Al-Kahraman, Yasser M.S.A.,Madkour, Hassan M.F.,Ali, Dildar,Yasinzai, Masoom
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experimental part
p. 660 - 671
(2010/06/16)
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- Catalytic asymmetric mannich-ketalization reaction: Highly enantioselective synthesis of aminobenzopyrans
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"Chemical Equation Present" Domino catalysis: We have developed the first enantioselective domino Mannich-ketalization reaction of o-hydroxy benzaldimines with electron-rich alkenes (see scheme). The new reaction sequence provides an easy and direct acces
- Rueping, Magnus,Lin, Ming-Yuan
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supporting information; experimental part
p. 4169 - 4172
(2010/07/05)
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- Catalytic asymmetric inverse-electron-demand (IED) [4+2] cycloaddition of salicylaldimines: Preparation of optically active 4-aminobenzopyran derivatives
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The catalytic asymmetric inverse-electron-demand (IED) [4+2] cycloaddition of various salicylaldehyde-derived N-arylimines with electron-rich alkenes in the presence of chiral BINOL-derived phosphoric acid catalysts has been studied with the aim of obtaining optically active 4-aminobenzopyran derivatives. Dienophiles such as 2,3-dihydro-2H-furan, benzyl N-vinylcarbamate and 2-vinylindole have been employed. Copyright
- Bernardi, Luca,Comes-Franchini, Mauro,Fochi, Mariafrancesca,Leo, Virginia,Mazzanti, Andrea,Ricci, Alfredo
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supporting information; experimental part
p. 3399 - 3406
(2011/02/23)
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- Insight into the steric and electronic effects of ancillary ligands: Synthesis and structure-reactivity relationship of well-defined, air- and moisture-stable (NHC)Pd(sal)Cl complexes (sal = salicylaldimine)
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Synthesis of a series of (NHC)Pd(sal)Cl complexes, 1-5, bearing a salicylaldimine (sal) unit was described. The structure-reactivity relationship, especially the steric and electronic effects of the salicylaldimine ligands on their catalytic activities, was investigated intensively in the Buchwald-Hartwig coupling reaction. Our study demonstrated that the sterically encumbered N-aryl groups in the salicylaldimine unit give rise to an obviously negative effect in the aryl amination reaction. Additionally, incorporating a steric substituent into the ortho-position of the phenoxide oxygen atom does not appear to be beneficial to their catalytic activity. Notably, the electronic nature of N-substituted aryl groups in the salicylaldimine ligands plays a significant role in their catalytic activities. An electron-rich N-aryl group causes an obviously decreasing yield, while an electron-deficient one, such as complex 5b, leads to enhanced reactivity. The aryl amination reaction with complex 5b was also found to be remarkably tolerant to both air and moisture. Under optimized reaction conditions, a range of aryl chlorides and amines could be coupled smoothly under aerobic conditions.
- Jin, Zhong,Qiu, Ling-Ling,Li, Yan-Qing,Song, Hai-Bin,Fang, Jian-Xin
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scheme or table
p. 6578 - 6586
(2011/02/16)
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- Reversible-irreversible approach to schiff base macrocycles: Access to isomeric macrocycles with multiple salphen pockets
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We have developed methodology for the formation of a new family of metal-free Schiff base macrocycles utilizing the differential exchange rates of aldimines and ketimines. The more robust ketimine bond Is kinetically Inert under the milder conditions used for aldimine bond formation. In particular, this route enables access to the first conjugated macrocycles with four unsymmetrical N2O2 salphen-like pockets.
- Frischmann, Peter D.,Jiang, Jian,Hui, Joseph K.-H.,Grzybowski, Joseph J.,MacLachlan, Mark J.
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supporting information; body text
p. 1255 - 1258
(2009/04/06)
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- Cu(OTf)2 or Et3N-catalyzed three-component condensation of aldehydes, amines and cyanides: a high yielding synthesis of α-aminonitriles
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Copper(II) triflate or Et3N have been found to catalyze, under ambient conditions, the addition of a cyanide anion, such as trimethylsilyl cyanide or acetone cyanohydrin, onto in situ generated imines, furnishing α-aminonitriles in excellent yi
- Paraskar, Abhimanyu S.,Sudalai, Arumugam
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p. 5759 - 5762
(2007/10/03)
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- A study of the tautomers of N-salicylidene-p-X-aniline compounds in methanol
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We have studied the enol-imine→keto-amine tautomeric equilibrium of N-salicylidene-p-X-aniline compounds with X = Me, OMe, NMe2 as electron donor substituents and X = COMe, CN and NO2 as electron acceptor substituents. The equilibrium constants (Ktauo) and standard thermodynamic properties ΔGtauo, ΔHtauo and ΔStauo were measured and calculated in methanol solution at various temperatures, by means of excitation fluorescence spectroscopy. We have analyzed the p-phenylaniline substitution effect on Ktauo and the thermodynamic properties through the Hammett parameters σ. We have performed molecular orbital calculations at the semiempirical AM1 and ab initio HF/3-21G levels to interpret the experimental results, explicitly including the solute-solvent interaction through the formation of an intermolecular hydrogen bond between the salicylidene and methanol molecules. These computational results show a good correlation with the experimental values. An interpretation of the experimental values of TΔSo, based on changes in the molecular structure produced in the enol-imine→keto-amine tautomeric reaction, is proposed.
- Vargas,Amigo
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p. 1124 - 1129
(2007/10/03)
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- LiBF4-catalyzed formation of fused pyrano- and furanobenzopyrans
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Lithium tetrafluoroborate efficiently catalyzes an unusual cyclization of o-hydroxybenzaldimines with 2,3-dihydrofuran and 3,4-dihydro-2H-pyran at ambient temperature to afford a class of new pyrano- and furanobenzopyran derivatives in excellent yields with high diastereoselectivity.
- Yadav,Reddy,Madhuri, Ch,Sabitha, G,Jagannadh, B,Kumar,Kunwar
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p. 6381 - 6384
(2007/10/03)
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- GROUND- AND EXCITED-STATE PROTOTROPIC TAUTOMERISM IN ANILS OF AROMATIC α-HYDROXYALDEHYDES STUDIED BY ELECTRONIC ABSORPTION, FLUORESCENCE AND 1H AND 13C NMR SPECTROSCOPIES AND SEMI-EMPIRICAL CALCULATIONS
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Proton transfer processes in both the ground and excited states in anils of aromatic α-hydroxyaldehydes (salicylaldehyde, 2-hydroxynaphthalene-1-carbaldehyde and the novel 10-hydroxyphenanthrene-9-carbaldehyde) have been studied by a combination of spectroscopic techniques.Solution 1H and 13C NMR is used to establish the position of the tautomeric equilibria.UV-visible absorption and fluorescence spectral data help to characterize the existence, in all cases, of excited-state intramolecular proton transfer (ESIPT) phenomena.Semi-empirical calculations involving full geometry optimization and calculation of heats of formation for the ground state (AM1) and vertical excitation energies and oscillator strengths (INDO/S) are in agreement with the experimental observations.
- Alarcon, Sergio H.,Olivieri, Alejandro C.,Cravero, Raquel M.,Labadie, Guillermo,Gonzalez-Sierra, Manuel
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p. 713 - 720
(2007/10/02)
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- Qualitative analysis of the stability of the oxazine ring of various benzoxazine and pyridooxazine derivatives with proton nuclear magnetic resonance spectroscopy
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A series of 3,4-dihydro-1,3-benzoxazine and 3,4-dihydro-1,3-pyridooxazine derivatives was synthesized, and the hydrolysis of the derivatives was studied with proton nuclear magnetic resonance spectroscopy. The oxazine derivatives underwent various degrees of hydrolysis when H2O was added to dimethyl sulfoxide solutions of the compounds. The rates and extents of decomposition of the oxazine ring systems depended on the electronic effects of substituents within the molecules. Examination of the proton nuclear magnetic resonance spectra that were generated during decomposition of the oxazines and trends in stability of the oxazine derivatives suggest the formation of an intermediate in the hydrolysis mechanism.
- Moloney,Craik,Iskander
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p. 692 - 697
(2007/10/02)
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- New Route for the Preparation of 2H-3-Aryl-3,4-dihydro-1,3-benzoxazines and 2H-3-Aryl-3,4-dihydro-4-methyl-1,3-benzoxazines
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2-Hydroxybenzaldehyde (1) and 1-(2-hydroxyphenyl)ethanone (2) on reaction with different primary aromatic amines gave 2-(arylimino)methylphenols (3) and 2-phenols (4), respectively. 3 and 4 on reduction with sodium borohydride gave 2-(arylamino)methylphenols (5) and 2-phenols (6), which underwent cyclisation with formaldehyde to form 2H-3-aryl-3,4-dihydro-1,3-benzoxazines (7) and 2H-3-aryl-3,4-dihydro-4-methyl-1,3-benzoxazines (8), respectively.
- Joglekar, S. J.,Samant, S. D.
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p. 110 - 111
(2007/10/02)
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- Substituent Effect and Mechanism of the Thermal Retautomerization of Flashed Salicylidene Anilines
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V-shaped Hammett plots are obtained with a series of p-substituted salicylidene anilines for the relaxation rate of their phototautomers.This is interpreted by a change-over in the mechanism from O-protonation (donor substituents) to NH-deprotonation (acc
- Grummt, U.-W.
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p. 227 - 234
(2007/10/02)
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- REACTIONS OF DICHLOROBIS(CYCLOPENTADIENYL)ZIRCONIUM(IV) WITH BIDENTATE SCHIFF BASES DERIVED FROM SALICYLALDEHYDE AND 4-SUBSTITUTED ANILINES
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Dichloro bis(cyclopentadienyl)zirconium(IV), Cp2ZrCl2, reacts with bidentate Schiff bases such as salicylidene-4-anisidine, salicylidene-4-phenetidine, salicylidene-4-chloroaniline, salicylidene-4-bromoaniline, salicylidene-4-iodoaniline and salicylidene-4-nitroaniline in a 1:1 molar ratio in refluxing tetrahydrofuran in the presence of triethylamine to yield Cp2Zr(SB)Cl, where (SB)- is the anion of the corresponding Schiff base, SBH.The new derivatives have been characterized on the basis of elemental analysis, molecular weight determination, conductance measurement and spectral (IR, 1H NMR) and electronic studies.
- Sharma, A. K.,Khera, B.,Kaushik, N. K.
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p. 123 - 130
(2007/10/02)
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