- A DFT and experimental study of the spectroscopic and hydrolytic degradation behaviour of some benzylideneanilines
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The spectroscopic and hydrolytic degradation behaviour of some N-benzylideneanilines are investigated experimentally and theoretically via high quality density function theoretical (DFT) modelling techniques. Their absorption and vibrational spectra, accurately predicted by DFT calculations, are highly dependent on the nature of the substituents on the aromatic rings, hence, though some of their spectroscopic features are similar, energetic differences exist due to differences in their electronic structures. Whereas the o-hydroxy aniline derived adducts undergo hydrolysis via two pathways, the most energetically economical of which is initiated by a fast enthalpy driven hydration, over a conservative free energy (ΔG?) barrier of 53 kJ mol?1, prior to the rate limiting entropy controlled lysis step which occurs via a conservative barrier of ca.132 kJ mol?1, all other compounds hydrolyse via a slower two-step pathway, limited by the hydration step. Barriers heights for both pathways are controlled primarily by the structure and hence, stability of the transition states, all of which are cyclic for both pathways.
- Robertson, Tahjna I.,Nelson, Peter N.
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- Electrochemical Generation of Hypervalent Bromine(III) Compounds
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In sharp contrast to hypervalent iodine(III) compounds, the isoelectronic bromine(III) counterparts have been little studied to date. This knowledge gap is mainly attributed to the difficult-to-control reactivity of λ3-bromanes as well as to their challenging preparation from the highly toxic and corrosive BrF3 precursor. In this context, we present a straightforward and scalable approach to chelation-stabilized λ3-bromanes by anodic oxidation of parent aryl bromides possessing two coordinating hexafluoro-2-hydroxypropanyl substituents. A series of para-substituted λ3-bromanes with remarkably high redox potentials spanning a range from 1.86 V to 2.60 V vs. Ag/AgNO3 was synthesized by the electrochemical method. We demonstrate that the intrinsic reactivity of the bench-stable bromine(III) species can be unlocked by addition of a Lewis or a Br?nsted acid. The synthetic utility of the λ3-bromane activation is exemplified by oxidative C?C, C?N, and C?O bond forming reactions.
- Francke, Robert,Mohebbati, Nayereh,Sokolovs, Igors,Suna, Edgars
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supporting information
p. 15832 - 15837
(2021/06/14)
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- Oxidative NHC catalysis for base-free synthesis of benzoxazinones and benzoazoles by thermal activated NHCs precursor ionic liquid catalyst using air as oxidant
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A reusable thermal activated NHC precursor ionic liquid catalyst ([BMIm]2[WO4]) has been prepared and developed for the synthesis of nitrogen-containing heterocycles such as benzoxazinones and benzoazoles through imines activation. [BMIm]2[WO4] exhibited the good activity for the base-free condensation and oxidative NHC catalysis tandem under air atmosphere. The catalyst can be recovered and reused for at least five runs in gram scale synthesis without any decrease in catalytic activity. Furthermore, the control experiments demonstrated that the reaction involved formation of aromatic aldimines, NHC-catalyzed oxidative formation of imidoyl azoliums and intramolecular cyclization to generate the product.
- Guan, Jiali,Liu, Wei,Liu, Yuchen,Song, Zhibin,Tao, Duan-Jian,Yan, Jieying,Yuan, Jian-Jun,Zhou, Youkang
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- Continuous flow/waste-minimized synthesis of benzoxazoles catalysed by heterogeneous manganese systems
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Herein, we present our results on the development of a waste minimized protocol for the synthesis of 2-arylbenzoxazoles in continuous flow. Manganese-based heterogeneous catalysts were used in combination with cyclopentylmethyl ether as an environmentally friendly and safe reaction medium. The use of oxygen promotes the oxidative process ensuring at the same time a complete regeneration of the catalyst adopting a flow configuration which does not include the use of an additional mechanical pump. These features allowed for a faster synthesis compared to batch procedures with minimal metal leaching.
- Ferlin, Francesco,Van Der Hulst, Mitchell K.,Santoro, Stefano,Lanari, Daniela,Vaccaro, Luigi
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p. 5298 - 5305
(2019/10/11)
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- Fe3O4@SiO2@Im[Cl]Mn(III)-complex as a highly efficient magnetically recoverable nanocatalyst for selective oxidation of alcohol to imine and oxime
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An efficient and environmentally friendly oxidation process for the one-pot preparation of oxime, imine and carbonyl compounds through alcohol oxidation in the presence of H2O2 and/or O2 have been developed by a melamine-Mn(III) Schiff base complex supported on Fe3O4@SiO2–Cl nanoparticles, named as Fe3O4@SiO2@Im[Cl]Mn(III)-complex nanocomposite, at room temperature. Direct oxidation of alcohol to carboxylic acid was performed using the catalyst in the presence of molecular O2 at room temperature in a different approach. The oxidation products were obtained with excellent yields and high TOFs. The properties of the catalyst were characterized by Fourier transform infrared spectroscopy (FTIR), elemental analysis (C, H, N), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), dynamic light scattering (DLS), energy dispersive X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS), inductive coupled plasma (ICP), cyclic voltammetry (CV), nuclear magnetic resonance (1H & 13C NMR), vibration sample magnetometer (VSM), Brunauer– Emmett–Teller (BET) and differential pulse voltammetry (DPV) analyses. The mechanism of the oxidation processes was investigated for the both H2O2 and O2 oxidants. The role of the imidazolium moiety in the catalyst as a secondary functionality was investigated. Chemoselectivity behavior of the catalyst was studied by some combinations. The catalyst could be recycled from the reaction mixture by a simple external magnet and reused for several times without any considerable reactivity loss.
- Kazemnejadi, Milad,Alavi, Seyyedeh Ameneh,Rezazadeh, Zinat,Nasseri, Mohammad Ali,Allahresani, Ali,Esmaeilpour, Mohsen
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p. 230 - 249
(2019/03/28)
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- Hemoglobin: A New Biocatalyst for the Synthesis of 2-substituted Benzoxazoles via Oxidative Cyclization
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Efficient and mild synthesis of a series of 2-substituted benzoxazoles via oxidative cyclization catalyzed by hemoglobins reported here for the first time. Satisfactory yields (84 %–97 %) and mild reaction conditions make this method highly viable for practical applications.
- Li, Fengxi,Li, Zhengqiang,Tang, Xuyong,Cao, Xinyu,Wang, Chunyu,Li, Jialin,Wang, Lei
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p. 1192 - 1195
(2019/02/07)
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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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- Enantioselective Strecker and Allylation Reactions with Aldimines Catalyzed by Chiral Oxazaborolidinium Ions
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Chiral oxazaborolidinium ion (COBI)-catalyzed enantioselective nucleophilic addition reactions of aldimines using tributyltin cyanide and allyltributylstannane have been developed. Various α-aminonitriles and homoallylic amines were synthesized in high yi
- Kang, Ki-Tae,Park, Sang Hyun,Ryu, Do Hyun
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supporting information
p. 6679 - 6683
(2019/09/12)
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- Metal-free synthesis of N-containing heterocycles from O-substituted aniline derivatives via 2,4,6-trihydroxybenzoic acid-catalyzed oxidative dehydrogenation of benzylamines under oxygen atmosphere
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A series of N-heterocycles, i.e., benzimidazoles, benzoxazoles, and benzothiazoles, can be conveniently synthesized by the oxidative cyclization of benzylamines with o-substituted aniline derivatives, i.e., o-phenylenediamines, o-aminophenols, and o-aminothiophenols, using 2,4,6-trihydroxybenzoic acid as an organocatalyst under an oxygen atmosphere. This approach provides a mild and efficient tool towards benzimidazoles and benzothiazoles with good yields and a broad substrate scope. The developed synthesis of N-heterocycles might proceed via the oxidative dehydrogenation of benzylamines (ArCH2NH2), generating the corresponding imines (ArCH=NH) as key intermediates.
- Kumazawa, Shun,Uematsu, Akinori,Dong, Chun-Ping,Kodama, Shintaro,Nomoto, Akihiro,Ueshima, Michio,Ogawa, Akiya
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p. 842 - 853
(2019/04/26)
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- Unexpected Decarboxylation-Triggered o-Hydroxyl-Controlled Redox Condensation of Phenylglycines with 2-Nitrophenols in Aqueous Media
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A decarboxylation-triggered and o-hydroxyl-controlled hydrogen-transfer strategy for the one-pot synthesis of benzoxazoles from readily available amino acids and 2-nitrophenols is reported. On the basis of this autoredox reaction, the C?N bond can be efficiently constructed to afford the desired products in moderate to good yields under transition-metal-free conditions in aqueous media. (Figure presented.).
- Tang, Lin,Yang, Zhen,Sun, Tian,Zhang, Di,Ma, Xiantao,Rao, Weihao,Zhou, Yuqiang
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supporting information
p. 3055 - 3062
(2018/08/01)
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- Synthesis, characterization and Pd(II)-coordination chemistry of the ligand tris(quinolin-8-yl)phosphite. Application in the catalytic aerobic oxidation of amines
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The synthesis and characterization of the ligand tris(quinolin-8-yl)phosphite, (P(Oquin)3), are described and its coordination chemistry toward the metal precursor [Pd(COD)Cl2] (COD = 1,5-cyclooctadiene, C8H12) is reported. A new Pd(ii)-P(Oquin)3 metal complex was isolated and fully characterized ([Pd{P(Oquin)3}Cl2]), and its X-ray diffraction analysis shows that the phosphite ligand coordinates as a bidentate P-N chelate. This complex is an efficient catalyst for the solvent-free mild oxidative coupling of primary amines to imines using air as an oxidant, obtaining moderate to good yields (up to 99%) and turnover numbers (TONs up to 230). This catalyst can be recovered from the reaction mixture and reused in a subsequent run without a significant loss of activity. Kinetic measurements of the oxidation of benzylamine suggest that the rate law is r = kapp[BnNH2][cat] ([BnNH2] = molar concentration of benzylamine, [cat] = molar concentration of [Pd{P(Oquin)3}Cl2], kapp = k[O2]c = 0.756 L mol-1 h-1 = apparent rate constant). In situ NMR tests were performed to gain some insight into the reactivity of the Pd(ii)-P(Oquin)3 complex toward benzylamine.
- Rodríguez-Lugo,Chacón-Terán,De León,Vogt,Rosenthal,Landaeta
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supporting information
p. 2061 - 2072
(2018/02/17)
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- Benzoxazole-Linked Ultrastable Covalent Organic Frameworks for Photocatalysis
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The structural uniqueness of covalent organic frameworks (COFs) has brought these new materials great potential for advanced applications. One of the key aspects yet to be developed is how to improve the robustness of covalently linked reticular frameworks. In order to make the best use of π-conjugated structures, we develop herein a ";killing two birds with one stone" strategy and construct a series of ultrastable benzoxazole-based COFs (denoted as LZU-190, LZU-191, and LZU-192) as metal-free photocatalysts. Benefiting from the formation of benzoxazole rings through reversible/irreversible cascade reactions, the synthesized COFs exhibit permanent stability in the presence of strong acid (9 M HCl), strong base (9 M NaOH), and sunlight. Meanwhile, reticulation of the benzoxazole moiety into the π-conjugated COF frameworks decreases the optical band gap and therefore increases the capability for visible-light absorption. As a result, the excellent photoactivity and unprecedented recyclability of LZU-190 (for at least 20 catalytic runs, each with a product yield of 99%) have been illustrated in the visible-light-driven oxidative hydroxylation of arylboronic acids to phenols. This contribution represents the first report on the photocatalytic application of benzoxazole-based structures, which not only sheds new light on the exploration of robust organophotocatalysts from small molecules to extended frameworks but also offers in-depth understanding of the structure-activity relationship toward practical applications of COF materials.
- Wei, Pi-Feng,Qi, Ming-Zhu,Wang, Zhi-Peng,Ding, San-Yuan,Yu, Wei,Liu, Qiang,Wang, Li-Ke,Wang, Huai-Zhen,An, Wan-Kai,Wang, Wei
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supporting information
p. 4623 - 4631
(2018/04/10)
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- PROCESS FOR MONO N-ALKYLATION OF AMINOPHENOL
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The invention relates to a process for the preparation of a compound represented by formula (I) wherein X is selected from the group consisting of -H, -halogen, linear or branched C1-C7 alkyl group, linear or branched C1-C5 alkoxy group, - NO2
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Page/Page column 5
(2019/01/07)
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- Design, Synthesis, and Biological Activity of New N -(Phenylmethyl)-benzoxazol-2-thiones as Macrophage Migration Inhibitory Factor (MIF) Antagonists: Efficacies in Experimental Pulmonary Hypertension
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Macrophage migration inhibitory factor (MIF) is a key pleiotropic mediator and a promising therapeutic target in cancer as well as in several inflammatory and cardiovascular diseases including pulmonary arterial hypertension (PAH). Here, a novel series of N-(phenylmethyl)-benzoxazol-2-thiones 5-32 designed to target the MIF tautomerase active site was synthesized and evaluated for its effects on cell survival. Investigation of structure-activity relationship (SAR) particularly at the 5-position of the benzoxazole core led to the identification of 31 that potently inhibits cell survival in DU-145 prostate cancer cells and pulmonary endothelial cells derived from patients with idiopathic PAH (iPAH-ECs), two cell lines for which survival is MIF-dependent. Molecular docking studies helped to interpret initial SAR related to MIF tautomerase inhibition and propose preferred binding mode for 31 within the MIF tautomerase active site. Interestingly, daily treatment with 31 started 2 weeks after a subcutaneous monocrotaline injection regressed established pulmonary hypertension in rats.
- Le Hiress, Morane,Akagah, Bernardin,Bernadat, Guillaume,Tu, Ly,Thuillet, Rapha?l,Huertas, Alice,Phan, Carole,Fadel, Elie,Simonneau, Gérald,Humbert, Marc,Jalce, Ga?l,Guignabert, Christophe
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p. 2725 - 2736
(2018/04/23)
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- Improvement in aluminum complexes bearing a Schiff base in ring-opening polymerization of ε-caprolactone: the synergy of the N,S-Schiff base in a five-membered ring aluminum system
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A series of five-membered ring aluminum complexes bearing thiol-Schiff base ligands were synthesized, and their application in the ring-opening polymerization of ε-caprolactone (CL) was investigated. The complexes exhibited dramatically higher catalytic a
- Huang, Ting-Wei,Su, Rou-Rong,Lin, Yi-Chen,Lai, Hsin-Yu,Yang, Chien-Yi,Senadi, Gopal Chandru,Lai, Yi-Chun,Chiang, Michael Y.,Chen, Hsuan-Ying
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p. 15565 - 15573
(2018/11/20)
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- Conversion of Imine to Oxazole and Thiazole Linkages in Covalent Organic Frameworks
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Imine-linked ILCOF-1 based on 1,4-phenylenediamine and 1,3,6,8-tetrakis(4-formylphenyl)pyrene was converted through consecutive linker substitution and oxidative cyclization to two isostructural covalent organic frameworks (COFs), having thiazole and oxazole linkages. The completeness of the conversion was assessed by infrared and solid-state NMR spectroscopies, and the crystallinity of the COFs was confirmed by powder X-ray diffraction. Furthermore, the azole-linked COFs remain porous, as shown by nitrogen sorption experiments. The materials derived in this way demonstrate increased chemical stability, relative to the imine-linked starting material. This constitutes a facile method for accessing COFs and linkages that are otherwise difficult to crystallize due to their inherently limited microscopic reversibility.
- Waller, Peter J.,Alfaraj, Yasmeen S.,Diercks, Christian S.,Jarenwattananon, Nanette N.,Yaghi, Omar M.
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supporting information
p. 9099 - 9103
(2018/08/03)
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- Oxidative NHC Catalysis for the Generation of Imidoyl Azoliums: Synthesis of Benzoxazoles
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N-Heterocyclic carbene (NHC)-catalyzed intramolecular cyclization of aldimines generated from 2-amino phenols and aromatic aldehydes leading to the synthesis of 2-arylbenzoxazoles under mild conditions is presented. The reaction proceeds via the generation of the aza-Breslow intermediates from imines and NHC, which under oxidative conditions form the key imidoyl azoliums and a subsequent intramolecular cyclization furnishes the product. The reaction tolerates a broad range of functional groups, and the products are formed in generally good yields.
- Patra, Atanu,James, Anjima,Das, Tamal Kanti,Biju, Akkattu T.
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p. 14820 - 14826
(2019/01/03)
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- One-pot green synthesis of benzoxazole derivatives through molecular sieve-catalyzed oxidative cyclization reaction
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An one-pot approach to benzoxazole ring from 2-aminophenol and aldehydes utilizing molecular sieve as the catalyst have been developed. The new oxidative cyclization reaction excluded the usage of hazardous chemical reagents, transition-metal catalysts, chemical oxidants, or strong acids, and, therefore, reduced the production of toxic chemical waste. This offers an environmentally friendly pathway for the synthesis of various benzoxazole derivatives.
- Chang, Weichieh,Sun, Yukai,Huang, Yungtzung
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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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- OMS-2/H2O2/Dimethyl Carbonate: An Environmentally-Friendly Heterogeneous Catalytic System for the Oxidative Synthesis of Benzoxazoles at Room Temperature
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A manganese octahedral molecular sieve (OMS-2) was found to be an efficient and recyclable heterogeneous catalyst for the oxidative synthesis of benzoxazoles in the gram-scale from phenolic imines at room temperature. H2O2 and biobased reagent dimethyl carbonate (DMC) were successfully employed as the environmentally friendly oxidant and solvent, respectively, in an OMS-2-catalysted redox reaction for the first time. Benzoxazoles could also be obtained from N-substituted 2-aminophenols via Cu(OH)x/OMS-2-catalyzed sequential oxidative transformation at elevated temperatures.
- Meng, Xu,Wang, Yuanguang,Chen, Baohua,Chen, Gexin,Jing, Zhenqiang,Zhao, Peiqing
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supporting information
p. 2018 - 2024
(2017/12/26)
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- 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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- Synthesis of Benzoxazoles Using Electrochemically Generated Hypervalent Iodine
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The indirect ("ex-cell") electrochemical synthesis of benzoxazoles from imines using a redox mediator based on the iodine(I)/iodine(III) redox couple is reported. Tethering the redox-active iodophenyl subunit to a tetra-alkylammonium moiety allowed for anodic oxidation to be performed without supporting electrolyte. The mediator salt can be easily recovered and reused. Our "ex-cell" approach toward the electrosynthesis of benzoxazoles is compatible with a range of redox-sensitive functional groups. An unprecedented concerted reductive elimination mechanism for benzoxazole formation is proposed on the basis of control experiments and DFT calculations.
- Koleda, Olesja,Broese, Timo,Noetzel, Jan,Roemelt, Michael,Suna, Edgars,Francke, Robert
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p. 11669 - 11681
(2017/11/24)
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- Base-Free and Catalyst-Free Synthesis of Functionalized Dihydrobenzoxazoles via Vinylogous Carbonate to Carbamate Rearrangement
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An unexpected, catalyst-free, and base-free intramolecular cyclization of N-aryloxyacrylate aldimines, under thermal conditions leading to the synthesis of functionalized dihydrobenzoxazoles, is reported. The reaction features a unique rearrangement of vi
- Das, Tamal Kanti,Mondal, Santigopal,Gonnade, Rajesh G.,Biju, Akkattu T.
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supporting information
p. 5597 - 5600
(2017/10/25)
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- ELECTROLUMINESCENT DEVICE USING AZOMETHINE-LITHIUM-COMPLEX AS ELECTRON INJECTION LAYER
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In OLEDs, improved efficiency is obtained by compounds which can form inter alia electron injection layers of the formula (I) wherein R1 is a 1-5 ring aryl (including polycyclic), aralkyl or heteroaryl group which is optionally substituted with one or mor
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Paragraph 0192 - 0194
(2016/10/07)
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- The evaluation of the role of C-H?F hydrogen bonds in crystal altering the packing modes in the presence of strong hydrogen bond
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Interactions involving fluorine is an area of contemporary research. To unravel the importance of weak C-H?F hydrogen bonds and C-H?π interactions in organic compounds in the presence of strong hydrogen bond, a series of N-benzylideneanilines with simultaneously hydroxyl (-OH) and fluorine substitutions were synthesized for structural analysis. These compounds have been studied through experimental single crystal X-ray diffraction analysis and computational methods (Gaussian09 and AIM2000). The hydroxyl group present in all the molecules were found to form strong O-H?N hydrogen bond, but the spatial arrangement of the molecules connected by this hydrogen bond have been found to be controlled by the weak C-H?F and C-H?O hydrogen bonds, weak C-H?π and π?π interactions. This manuscript illustrates the importance of several weaker interactions in altering the packing modes in the presence of strong hydrogen bonds.
- Kaur, Gurpreet,Singh, Sandhya,Sreekumar, Amritha,Choudhury, Angshuman Roy
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p. 154 - 169
(2015/11/18)
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- Sustainable Synthesis of 2-Arylbenzoxazoles over a cobalt-based nanocomposite catalyst
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A new cobalt-based heterogeneous catalyst was prepared by adsorbing in situ produced nitrogen-ligated cobalt(II) acetate complexes on commercially available SiO2 and subsequent pyrolysis at 800 °C for 2 h under N2 atmosphere. By applying this catalyst under the O2 balloon, the aerobic oxidation of phenolic imines proceeded smoothly and gave various 2-arylbenzoxazoles in good yields. Meanwhile, on the basis of the experimental results, a plausible reaction pathway was described to elucidate the reaction mechanism.
- He, Jian,Lin, Fu,Yang, Xufang,Wang, Di,Tan, Xiaohua,Zhang, Shujun
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supporting information
p. 1093 - 1096
(2017/01/16)
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- Copper-catalyzed synthesis of 2-arylbenzoxazoles from o-aminophenol derivatives with arylmethyl chlorides
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A facile and efficient synthesis of 2-arylbenzoxazoles via copper-catalyzed tandem condensation/oxidative reaction of o-aminophenol derivatives with arylmethyl chlorides was developed. Note that this reaction utilized arylmethyl chlorides as a new type of simple and cheap acyl sources and KNO3 as a readily available and low-cost benign oxidant.
- Zhang, Guodong,Wang, Peng,Yang, Fan,Wu, Yangjie
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supporting information
p. 57 - 63
(2015/02/02)
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- Metal-free reductive amination of aldehydes for the synthesis of secondary and tertiary amines
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Reductive amination of aldehydes to produce secondary amines at room-temperature by in situ generated benzimidazoline is discussed. The bonus of the reaction is the formation of pharmaceutically important benzimidazole as a by-product in good yield, which can be recovered from the reaction mixture by simple filtration. The product, secondary amine, is transformed to tertiary amine in the same pot.
- Ambica,Khajuria, Rajni,Saini, Yeshwinder,Kapoor, Kamal K
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p. 1252 - 1259
(2015/11/25)
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- Ruthenium-catalyzed synthesis of benzoxazoles using acceptorless dehydrogenative coupling reaction of primary alcohols with 2-aminophenol under heterogeneous conditions
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An efficient ruthenium-catalyzed acceptorless dehydrogenative coupling reaction of primary alcohols with 2-aminophenol for one-pot synthesis of benzoxazoles is introduced. The phosphine-functionalized magnetic nanoparticles (PFMNPs; Fe3O4@SiO2@PPh2) as a magnetic recyclable phosphorus ligand in the presence of Ru2Cl 4(CO)6 was found to be an efficient heterogeneous catalytic system for promotion of the designed protocol. The reaction was carried out efficiently with a variety of substrates to give the corresponding products in moderate to good yields.
- Khalafi-Nezhad, Ali,Panahi, Farhad
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p. 1686 - 1692
(2014/06/24)
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- Gold nanoparticles supported on titanium dioxide: An efficient catalyst for highly selective synthesis of benzoxazoles and benzimidazoles
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A highly efficient and selective reaction for the synthesis of 2-substituted benzoxazoles and benzimidazoles catalyzed by Au/TiO2 has been developed via two hydrogen-transfer processes. This reaction has a good tolerance to air and water, a wide substrate scope, and represents a new avenue for practical C-N and C-O bond formation. More importantly, no additional additives, oxidants and reductants are required for the reaction and the catalyst can be recovered and reused readily. This journal is the Partner Organisations 2014.
- Tang, Lin,Guo, Xuefeng,Yang, Yu,Zha, Zhenggen,Wang, Zhiyong
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p. 6145 - 6148
(2014/06/09)
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- One-pot synthesis of 2-substituted benzoxazoles promoted by copper acetate monohydrate
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An efficient synthesis of 2-substituted benzoxazoles via copper acetate monohydrate oxidative coupling of aldehydes with o-aminophenol is described. This synthetic strategy has some advantages as simple procedure, inexpensive and easily available catalyst, and facile isolation of the products in moderate to good yields.
- Chen, Guo-Feng,Shen, Hai-Dong,Zhang, Li-Yan,Li, Hong-Yang,Lan, Rui-Jia,Chen, Bao-Hua,Li, Ji-Tai,Hu, Qing-Hui
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p. 180 - 187
(2014/05/20)
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- Metal-free TEMPO-promoted C(sp3)-H amination to afford multisubstituted benzimidazoles
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An efficient TEMPO-air/cat. TEMPO-O2 oxidative protocol was developed to synthesize multisubstituted or fused tetracyclic benzimidazoles via a metal-free oxidative C-N coupling between the sp3 C-H and free N-H of readily available N1-benzyl/alkyl-1,2-phenylenediamines.
- Xue, Ding,Long, Ya-Qiu
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p. 4727 - 4734
(2014/06/09)
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- Synthesis of New C2-Symmetric Chiral Bisamides from (1S,2S)-Cyclohexane-1,2-dicarboxylic Acid
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A series of new C2-symmetric (1S,2S)-cyclohexane-1,2-dicarboxamides was synthesized from (1S,2S)-cyclohexane-1,2-dicarbonyl dichloride and N-benzyl-substituted aromatic amines, which were prepared from 2-aminopyridine, 2-chloroaniline, and 2-aminophenol via imine formation with benzaldehyde and subsequent reduction with NaBH4. (1S,2S)-N,N′-Dibenzyl-N,N′-bis[2-(benzyloxy)phenyl]cyclohexane-1,2-dicarboxamide was converted to (1S,2S)-N,N′-dibenzyl-N,N′-bis(2-hydroxyphenyl)cyclohexane-1,2-dicarboxamide via hydrogenolysis in the presence of Pd(OH)2 on active carbon powder.
- Zhou, Chan,Xu, Jiaxi
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p. 1396 - 1405
(2015/08/25)
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- Synthesis of 2-substituted pyrimidines and benzoxazoles via a visible-light-driven organocatalytic aerobic oxidation: Enhancement of the reaction rate and selectivity by a base
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An efficient visible-light-driven photocatalytic oxidation of various 2-substituted dihydropyrimidines and phenolic imines has been achieved using an organic photocatalyst eosin Y bis(tetrabutyl ammonium salt) (TBA-eosin Y) and inexpensive oxidant molecular oxygen. With the aid of a base, significantly enhanced photoinduced electron transfer from substrates dihydropyrimidines or phenolic imines to the excited state of TBA-eosin Y has enabled the aerobic oxidation to yield 2-(methylthio)pyrimidines or 2-arylbenzoxazoles selectively. This journal is the Partner Organisations 2014.
- Wang, Lin,Ma, Zhi-Gang,Wei, Xiao-Jing,Meng, Qing-Yuan,Yang, Deng-Tao,Du, Shao-Fu,Chen, Zi-Fei,Wu, Li-Zhu,Liu, Qiang
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supporting information
p. 3752 - 3757
(2014/08/05)
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- Design, synthesis and biological evaluation of imine resveratrol derivatives as multi-targeted agents against Alzheimer's disease
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A series of imine resveratrol derivatives (1-20) have been designed, synthesized, and evaluated as multi-targeted compounds for the treatment of Alzheimer's disease (AD). In vitro studies show that most of the molecules exhibit a significant ability to in
- Li, Su-Yi,Wang, Xiao-Bing,Kong, Ling-Yi
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- Transition-metal catalyst free C=N coupling with phenol/phenoxide: A green synthesis of a benzoxazole scaffold by an anodic oxidation reaction
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By utilizing an anodic oxidative reaction and consuming 2.2 F mol -1 of electricity, C=N coupling with phenol/phenoxide to obtain the five-membered N,O-heteroatom ring of a benzoxazole has been achieved at room temperature. Transition-metal catalysts, chemical oxidants, strong acids, reactive chemical reagents and refluxing are not required. Studies of the electrode, solvent, electrolyte and additive effects to promote the anodic cyclization are included. From the CV studies, the reaction mechanisms of the anodic cyclization are proposed. The Royal Society of Chemistry 2013.
- Shih, Yachen,Ke, Chengyi,Pan, Chinghao,Huang, Yungtzung
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p. 7330 - 7336
(2013/07/05)
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- Photoprotective activity of resveratrol analogues
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Resveratrol is a promising agent for protecting human skin from UV radiation and to reduce the occurrence of cutaneous malignancies. We describe the photoprotective activity of six resveratrol analogues using the diffuse transmittance technique to determine the SPF and the protection against UVA radiation. The analogues presented a varied profile of photoprotection, the SPF ranging from 2 to 10 and the UVAPF from 0 to 9. Among the six compounds tested, the protection against UVB sunrays provided by compound B was more significant than the protection provided by resveratrol; compounds C, D, E and F show photoprotection similar to resveratrol.
- Polonini, Hudson Caetano,Lima, Larissa Lavorato,Goncalves, Karla Mara,Do Carmo, Antonio Marcio Resende,Da Silva, Adilson David,Raposo, Nadia Rezende Barbosa
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p. 964 - 968
(2013/04/10)
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- Telluroxane-supported coordination ligands: Synthetic and structural aspects
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The reactions of (4-MeOC6H4)2TeO with selected carboxylic acids and phenols afforded the formation of mononuclear organotelluroxanes. The utilization of functional carboxylic acids/phenols, such as 2,2-bis(3,5-dimethylpyra
- Chandrasekhar, Vadapalli,Kumar, Arun,Pandey, Mrituanjay D.,Metre, Ramesh K.
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supporting information
p. 1362 - 1368
(2013/05/22)
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- Cyanide as a powerful catalyst for facile synthesis of benzofused heteroaromatic compounds via aerobic oxidation
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Highly efficient synthesis of benzofused heteroaromatic compounds via aerobic oxidation catalyzed by cyanide anion has been developed. The Schiff bases derived from 2-aminophenol and aldehydes provided the corresponding benzoxazoles in high yields in the presence of a catalytic amount of cyanide in an open flask under ambient conditions without the use of any external metal co-oxidants and bases. Furthermore, we have developed a catalytic sequential one-step protocol for the synthesis of benzoxazoles by adding a catalytic amount of NaCN to Schiff bases generated in situ from 2-aminophenol and aldehydes without the isolation of imine intermediates. This one-pot protocol was further extended to the synthesis of benzothiazoles from 2-aminothiophenol and aldehydes. A variety of aldehydes could be applied to this sequential one-pot protocol and the desired benzofused azole products were obtained in high yields.
- Cho, Yeon-Ho,Lee, Chun-Young,Cheon, Cheol-Hong
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p. 6565 - 6573
(2013/07/26)
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- Efficient indirect electrochemical synthesis of 2-substituted benzoxazoles using sodium iodide as mediator
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An electrochemical strategy for the effi-cient synthesis of 2-substituted benzoxazoles was de-veloped using a catalytic amount of sodium iodide (Nal) as a redox catalyst in a two-phase buffer system.
- Li, Wei-Cui,Zeng, Cheng-Chu,Hu, Li-Ming,Tian, Hong-Yu,Little, R. Daniel
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p. 2884 - 2890
(2014/03/21)
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- Ni nanoparticles: Mild and efficient catalyst for the chemoselective synthesis of 2-arylbenzimidazoles, 2-arylbenzothiazoles, and azomethines
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(Chemical Equation Presented) A new and efficient method has been developed for the synthesis of biologically significant 2-arylbenzimidazoles, 2-arylbenzothiazoles, and azomethines using recyclable and inexpensive polyvinyl pyrrolidone (PVP)-stabilized Ni nanoparticles in ethylene glycol at room temperature in excellent yields. Copyright Taylor & Francis Group, LLC.
- Khurana, Jitender M.,Sneha,Vij, Kanika
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experimental part
p. 2606 - 2616
(2012/08/08)
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- Synthesis, characterization and catalytic activity of three palladium(II) complexes containing Schiff base ligands
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Three new Pd(II) complexes of Schiff base ligands, namely, [Pd4(L 1)4] (1), [Pd2(L2)2Cl2] (2) and [Pd(L3)2 Cl2] (3) [HL1 = N-(benzylidene)-2- aminophenol; L2 = N-(2,4-dichlorobenzylidene)-2,6-diethylbenzenamine, L3 = 4-(2,4-dichlorobenzylide-neamino)phenol] have been synthesized using solvothermal methods and characterized by elemental analysis, spectroscopy and single crystal X-ray diffraction. The crystal structures of the free ligands were also determined. The l-oxygen-bridged tetranuclear cyclometallated Pd(II) complex (1) contains four nearly planar units, in which PdII is four-coordinate. Complex 2 is a l-chloro-bridged dinuclear cyclometallated Pd(II) complex, whereas complex 3 is mononuclear. The Heck reactions of bromobenzene with acrylic acid catalyzed by complexes 1-3 have also been studied. Springer Science+Business Media B.V. 2012.
- Guo, Hai-Fu,Pan, Yong,Ma, De-Yun,Lu, Kuan,Qin, Liang
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p. 661 - 669
(2013/01/15)
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- Catalytic asymmetric synthesis of dihydroquinazolinones from imines and 2-aminobenzamides
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An unprecedented catalytic asymmetric synthesis of aminal-containing heterocyclic compounds has been developed from imines and tethered nitrogen/nitrogen nucleophiles. In the presence of 10mol% of a commercially available chiral phosphoric acid, a range of aromatic, α,β- unsaturated, and aliphatic imines react with 2-aminobenzamides to give dihydroquinazolinones in good to excellent yields and ee. The enantioselectivity is significantly affected by the imine N-substituent through non-bonding interactions with the chiral phosphoric acid and the 2-aminobenzamide. Copyright
- Cheng, Dao-Juan,Tian, Yu,Tian, Shi-Kai
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supporting information; experimental part
p. 995 - 999
(2012/06/01)
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- Water-promoted one-pot vinylogous Mannich-type reaction of trimethylsilyloxyfuran
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Water, produced in situ during the formation of imines from aldehydes 1 and amines 2, is employed to promote the one-pot Mannich reaction of trimethylsilyloxyfuran 3a without addition of extra solvent or catalyst. This clean and quick reaction allows the obtention of a series of 5-substituted γ-butenolides 4 with good yields and modest diastereomeric ratio. A large panel of substituents is tolerated ranging from aliphatic chains to aromatic or heteroaromatic rings.
- Landelle, Grégory,Claraz, Aurélie,Oudeyer, Sylvain,Levacher, Vincent
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supporting information; experimental part
p. 2414 - 2416
(2012/06/01)
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- Cyanide as a powerful catalyst for facile preparation of 2-substituted benzoxazoles via aerobic oxidation
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A cyanide-catalyzed synthesis of 2-substituted benzoxazoles from Schiff bases via aerobic oxidation has been developed. The products from various Schiff bases were obtained in high yields in an open flask under ambient conditions without other external oxidants. We have also developed a simple one-step protocol for the synthesis of benzoxazoles from aminophenol and the corresponding aldehydes in the presence of cyanide without isolation of imine intermediates. Copyright
- Cho, Yeon Ho,Lee, Chun-Young,Ha, Deok-Chan,Cheon, Cheol-Hong
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supporting information
p. 2992 - 2996
(2013/01/15)
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- An efficient synthesis of 2-substituted benzoxazoles using cerium(III) chloride/sodium iodide as catalyst
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An efficient and environmentally benign method for the synthesis of 2-substituted benzoxazoles is reported. The condensation of 2-aminophenol with an aldehyde gave an imine intermediate, which was cyclized and dehydrogenated to 2-substituted benzoxazole with good yield in the presence of CeCl 3 /NaI as catalyst. The one-pot synthesis was carried out in toluene at 100 ° C using O 2 as the oxidant.
- Zhu, Xun,Wei, Yunyang
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p. 211 - 214
(2013/01/16)
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- The efficient o-benzenedisulfonimide catalysed synthesis of benzothiazoles, benzoxazoles and benzimidazoles
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O-Benzenedisulfonimide has been used to efficiently catalyse the reaction between 2-aminothiophenol, 2-aminophenol, o-phenylenediamine and various ortho esters (28 examples; average yield 90%) or aldehydes (17 examples; average yield 72%) giving the corresponding benzofused azoles in excellent yields. Reaction conditions were very simple. In addition, other carboxylic acid derivatives have been tested and gave good results. The catalyst was easily recovered and reused. ARKAT-USA, Inc.
- Barbero, Margherita,Cadamuro, Silvano,Dughera, Stefano
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p. 262 - 279
(2013/02/25)
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- The antioxidant effect of imine resveratrol analogues
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Twenty five Imine resveratrol analogues (IRAs) were synthesized, replacing the CC bond in resveratrol with CN bond, as well as substitution modifications on aromatic rings. Radical scavenging activities against DPPH, along with singlet oxygen quenching capacities were evaluated, and further confirmed using density functional theory calculations (DFT). It was found that IRAs bearing ortho-OH on B ring have better radical scavenging activities against DPPH than resveratrol, these compounds were also found to be effective 1O 2 quenchers. Theoretical studies on the reaction mechanism of these compounds with 1O2 suggest that the 1,3-addition to a double bond with a -OH group with the formation of allylic hydroperoxide is the most probable reaction route.
- Lu, Jing,Li, Chang,Chai, Yun-Feng,Yang, De-Yu,Sun, Cui-Rong
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supporting information; experimental part
p. 5744 - 5747
(2012/09/22)
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- Synthesis of aryl aldimines and their activity against fungi of clinical interest
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Aldimines are aldehyde-derived compounds that contain a C=N group. Besides its broad industrial applications, this class of non-naturally occurring compounds are found to possess antibacterial, antifungal, antimalarial, antiproliferative, anti-inflammatory, antiviral, and antipyretic properties. Based on this, six aryl aldimines were synthesized from the condensation of aromatic amines with benzaldehydes. The antifungal activities of synthesized compounds were evaluated against nineteen fungal strains that included Candida and Aspergillus species, Cryptococcus neoformans. The aryl aldimines 2-(benzylideneamino)phenol (3) and 4-(benzylideneamino)phenol (8) were the most active compounds against the fungi studied. Compounds 3 and 8 efficiently inhibited the metabolism of C. neoformans mature biofilm.
- da Silva, Cleiton M.,da Silva, Danielle L.,Martins, Cleide V.B.,de Resende, Maria A.,Dias, Esther S.,Magalhaes, Thais F.F.,Rodrigues, Leticia P.,Sabino, Adao A.,Alves, Rosemeire B.,de Fatima, Angelo
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scheme or table
p. 810 - 815
(2012/06/30)
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