- A Facile Reduction Procedure for N,N′-bis[5-Substituted Salicylidene]-m/p-phenylenediamines with Sodium Borohydride-Silica Gel System
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An easy approach involving sodium borohydride/silica gel system offers a fast method of reduction for N,N′-bis[5-substituted salicylidene] m/p-phenylenediamines to the corresponding amines with excellent yield. The observed formation of boron chelates in
- Sridharan,Muthusubramanian,Sivasubramanian
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- Highly selective and sensitive simultaneous nanomolar detection of Cs(i) and Al(iii) ions using tripodal organic nanoparticles in aqueous media: The effect of the urea backbone on chemosensing
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Chemosensing plays a very important role in the detection of essential/pollutant ions in aqueous media. In this manuscript, two tripodal ligands, i.e., 1-(2-hydroxybenzyl)-3-(4-nitrophenyl)-1-phenylurea (ligand 1) and 1-(2-hydroxybenzyl)-3-(4-nitrophenyl)
- Ganguli, Ashok K.,Kaur, Manpreet,Kaur, Navneet,Mishra, Jayanti
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- Monitoring of reduction reaction of 2-((phenylimino)methyl)phenol compound with sodium borohydride in solution by infrared spectroscopy
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In this study, an imine compound 2-((phenylimino)methyl)phenol was synthesized by the reaction of salicylaldehyde and aniline for in situ monitoring of reduction with sodium borohydride. The reduction of C = N double bond to C–N in solution was continuous
- Turhan, Onur,Ya?ar, Hatice
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- BF3·Et2O as a metal-free catalyst for direct reductive amination of aldehydes with amines using formic acid as a reductant
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A versatile metal- and base-free direct reductive amination of aldehydes with amines using formic acid as a reductant under the catalysis of inexpensive BF3·Et2O has been developed. A wide range of primary and secondary amines and diversely substituted aldehydes are compatible with this transformation, allowing facile access to various secondary and tertiary amines in high yields with wide functional group tolerance. Moreover, the method is convenient for the late-stage functionalization of bioactive compounds and preparation of commercialized drug molecules and biologically relevant N-heterocycles. The procedure has the advantages of simple operation and workup and easy scale-up, and does not require dry conditions, an inert atmosphere or a water scavenger. Mechanistic studies reveal the involvement of imine activation by BF3and hydride transfer from formic acid.
- Fan, Qing-Hua,Liu, Xintong,Luo, Zhenli,Pan, Yixiao,Xu, Lijin,Yang, Ji,Yao, Zhen,Zhang, Xin
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supporting information
p. 5205 - 5211
(2021/07/29)
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- Sulfated polyborate: A dual catalyst for the reductive amination of aldehydes and ketones by NaBH4
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An efficient, quick, and environment-friendly one-pot reductive amination of aldehydes or ketones was developed. In ethanol at 70 °C, a imination catalyzed by sulfated polyborate and further reduced by sodium borohydride yields various amines. The present method has many significant benefits, including a shorter reaction time, excellent yields, and a hassle-free, straightforward experimental process. The reaction has a wide range of applications due to its flexibility, including secondary amine for reductive amination.
- Ganwir, Prerna,Chaturbhuj, Ganesh
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- Screening of simple carbohydrates as a renewable organocatalyst for the efficient construction of 1,3-benzoxazine scaffold
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A convenient protocol for the two component preparation of 1,3-benzoxazines by using several protected and unprotected carbohydrate molecules as organocatalysts have been developed which is broadly applicable to condensation reaction between variety of Ma
- Y?ld?r?m, Ayhan,Kaya, Yunus,G?ker, Mustafa
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- Chiral N-heterocyclic carbene-iridium complexes for asymmetric reduction of prochiral ketimines
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Enantioselective reduction of imines to the corresponding chiral secondary amines has been studied using a series of chiral half-sandwich iridium complexes. Chiral N-heterocyclic carbene (NHC) ligands in these complexes were synthesized from readily available, naturally occurring amino acids. Inexpensive phenylsilane was used as a convenient hydrogen donor. Under the optimized conditions, Ir-NHC complexes could reduce ketimines in good yields, albeit with moderate enantiomeric excess (ee). The phenylglycine derived chiral NHC was shown to give the best Ir catalyst and it also gave the maximum ee compared to catalysts prepared from other NHCs in this series. The opposite enantiomer of the reduction product was always obtained while using the Ir complex bearing a valine based NHC. The yields were consistently high with a variety of imine substrates having different steric and electronic demands.
- Kathuria, Lakshay,Samuelson, Ashoka G.
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supporting information
(2020/12/28)
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- Ruthenium N-Heterocyclic Carbene Complexes for Chemoselective Reduction of Imines and Reductive Amination of Aldehydes and Ketones
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Chemoselective reduction of imines to secondary amines is catalyzed efficiently by tethered and untethered, half-sandwich ruthenium N-heterocyclic carbene (NHC) complexes at room temperature. The untethered Ru-NHC complexes are more efficient as catalysts for the reduction of aldimines and ketimines than the tethered complexes. Using the best untethered complex as a catalyst, electronic and steric demands on the reaction was probed using a series of imines. Chemoselectivity of the catalyst towards imine reduction was tested by performing inter and intramolecular competitive reactions in a variety of ways. The catalyst exhibits a very high TON and TOF under anaerobic conditions.
- Kathuria, Lakshay,Samuelson, Ashoka G.
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- Switching the N-Alkylation of Arylamines with Benzyl Alcohols to Imine Formation Enables the One-Pot Synthesis of Enantioenriched α-N-Alkylaminophosphonates
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The selective N-alkylation of anilines with benzylic alcohols can be switched in favor of the dehydrogenative condensation process using the nitrile-ligated Kn?lker's complex by conducting the reaction either in a closed system under inert conditions, or in an open system in air. The selective formation of imines, containing reactive C=N bonds, provides an opportunity towards further functionalization. Indeed, a one-pot three-component condensation of alcohols, amines and phosphites, promoted by an iron-based Kn?lker-type complex in combination with a chiral BINOL-based phosphoric acid, provides access to enantioenriched α-N-alkylaminophosphonates.
- Hofmann, Natalie,Hultzsch, Kai C.
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supporting information
p. 3105 - 3111
(2019/06/08)
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- Multistep solid-state organic synthesis of carbamate-linked covalent organic frameworks
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Herein, we demonstrate the first example of a multistep solid-state organic synthesis, in which a new imine-linked two-dimensional covalent organic framework (COF-170, 1) was transformed through three consecutive postsynthetic modifications into porous, crystalline cyclic carbamate and thiocarbamate-linked frameworks. These linkages are previously unreported and inaccessible through de novo synthesis. While not altering the overall connectivity of the framework, these chemical transformations induce significant conformational and structural changes at each step, highlighting the key importance of noncovalent interactions and conformational flexibility to COF crystallinity and porosity. These transformations were assessed using 15N multiCP-MAS NMR spectroscopy, providing the first quantitation of yields in COF postsynthetic modification reactions, as well as of amine defect sites in imine-linked COFs. This multistep COF linkage postsynthetic modification represents a significant step toward bringing the precision of organic solution-phase synthesis to extended solid-state compounds.
- Lyle, Steven J.,Osborn Popp, Thomas M.,Waller, Peter J.,Pei, Xiaokun,Reimer, Jeffrey A.,Yaghi, Omar M.
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p. 11253 - 11258
(2019/08/07)
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- Reduction of imines catalysed by NHC substituted group 6 metal carbonyls
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The catalytic activity of a series of metal carbonyls [M(CO)6], and the corresponding NHC substituted [M(CO)5(NHC)], (M = Cr, Mo, W) complexes was examined in the reduction of N-benzylideneaniline and acetophenone using silyl hydrides and isopropanol/KOH as reductants. The use of various additives and ultraviolet irradiation to promote the reduction of imines using silyl hydrides as reductants was explored. From a comparison of the reactivity of [Mo(CO)6], [Mo(CO)5(NHC)], and [Mo(CO)4(bis NHC)] it was inferred that electron density on the metal centre plays a key role in the catalysis. Four of the best catalysts were then tested in the reduction of a variety of imines with different electronic and steric properties.
- Reshi, Noor U Din,Kathuria, Lakshay,Samuelson, Ashoka G.
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p. 119 - 128
(2018/11/03)
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- Well-Defined Amidate-Functionalized N-Heterocyclic Carbene -Supported Rare-Earth Metal Complexes as Catalysts for Efficient Hydroboration of Unactivated Imines and Nitriles
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Four amidate-functionalized N-heterocyclic carbene (NHC) rare-earth metal amido complexes [(κ2-N,O-κ1-L)2REN(SiMe3)2] (L = 1-(C6H5CONCH2CH2)-3-(CH3)3C6H2(N(CH)2NC)) [RE = Er (1), Y (2), Dy (3), Gd (4)] were synthesized by one-pot reactions of 2 equiv of (1-(C6H5CONHCH2CH2)-3-(CH3)3C6H2-(N(CH)2NCH))Br (H2LBr) with 5 equiv of KN(SiMe3)3 followed by treatment with 1 equiv of RECl3 in tetrahydrofuran at -40 °C. These complexes were fully characterized, and their catalytic activities toward hydroboration of unactivated imines and nitriles were investigated, and it was found that these complexes displayed excellent activities as well as remarkable functional group compatibility for imine and nitrile substrates such as halo-, alkyl-, hydroxyl-, N,N-dimethylamino-, and nitro- substituents. Among those, the chemoselectivity for this reaction among the common unsaturated functional groups was achieved in the order CO CN > C=N > CO2Et > CC in the current catalytic system, which may facilitate their further application in synthetic chemistry.
- Huang, Zeming,Wang, Shaowu,Zhu, Xiancui,Yuan, Qingbing,Wei, Yun,Zhou, Shuangliu,Mu, Xiaolong
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supporting information
p. 15069 - 15078
(2018/12/14)
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- Hydroxy Group Directed Catalytic Hydrosilylation of Amides
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Chemo- and site-selective hydrosilylation of α- or β-hydroxy amides using organocatalyst B(C6F5)3 and commercially available hydrosilanes is described. This transformation is operative under mild conditions and tolerates a wide range of functional groups. The reaction was applied for selective reduction of a specific amide group of the therapeutically important cyclic peptide cyclosporin A, demonstrating the potential usefulness of this catalytic method in late-stage structural transformations of drug lead molecules.
- Ni, Jizhi,Oguro, Tsubasa,Sawazaki, Taka,Sohma, Youhei,Kanai, Motomu
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p. 7371 - 7374
(2018/11/25)
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- (η5-Pentamethylcyclopentadienyl)iridium Complex Catalyzed Imine Reductions Utilizing the Biomimetic 1,4-NAD(P)H Cofactor and N-Benzyl-1,4-dihydronicotinamide as the Hydride-Transfer Agent
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The interaction between synthetic organometallic complexes and metabolic cofactors has proven to be a newly emerging topic in bioorganometallic chemistry. Thus, the first cationic Cp*Ir-catalyzed (Cp=η5-pentamethylcyclopentadienyl) imine reduction in neutral buffered aqueous medium was examined. The reaction was found to proceed through hydride transfer from NADH as the hydride source at room temperature in air. Cationic Cp*Ir complexes proved to be the most efficient catalysts for this transformation. We also highlighted that the choice of the proton source was essential. The method was subsequently applied to cyclic and noncyclic imines. Eventually, the concept was extended to the reductive alkylation of one amine.
- Soetens, Mathieu,Drouet, Fleur,Riant, Olivier
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p. 929 - 933
(2017/03/27)
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- Oxazine Ring-Related Vibrational Modes of Benzoxazine Monomers Using Fully Aromatically Substituted, Deuterated, 15N Isotope Exchanged, and Oxazine-Ring-Substituted Compounds and Theoretical Calculations
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Polymerization of benzoxazine resins is indicated by the disappearance of a 960-900 cm-1 band in infrared spectroscopy (IR). Historically, this band was assigned to the C-H out-of-plane bending of the benzene to which the oxazine ring is attach
- Han, Lu,Iguchi, Daniela,Gil, Phwey,Heyl, Tyler R.,Sedwick, Victoria M.,Arza, Carlos R.,Ohashi, Seishi,Lacks, Daniel J.,Ishida, Hatsuo
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p. 6269 - 6282
(2017/09/01)
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- Design, synthesis and biological evaluation of GPR55 agonists
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GPR55, a G protein-coupled receptor, is an attractive target to alleviate inflammatory and neuropathic pain and treat osteoporosis and cancer. Identifying a potent and selective ligand will aid to further establish the specific physiological roles and pharmacology of the receptor. Towards this goal, a targeted library of 22 compounds was synthesized in a modular fashion to obtain structure-activity relationship information. The general route consisted of coupling a variety of p-aminophenyl sulfonamides to isothiocyanates to form acylthioureas. For the synthesis of a known naphthyl ethyl alcohol motif, route modification led to a shorter and more efficient process. The 22 analogues were analyzed for their ability to serve as agonists at GPR55 and valuable information for both ends of the molecule was ascertained.
- Fakhouri, Lara,Cook, Christopher D.,Al-Huniti, Mohammed H.,Console-Bram, Linda M.,Hurst, Dow P.,Spano, Michael B.S.,Nasrallah, Daniel J.,Caron, Marc G.,Barak, Larry S.,Reggio, Patricia H.,Abood, Mary E.,Croatt, Mitchell P.
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p. 4355 - 4367
(2017/07/22)
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- Metal-Free Diaryl Etherification of Tertiary Amines by Ortho-C(sp2)-H Functionalization for Synthesis of Dibenzoxazepines and -ones
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A phenyliodine(III) diacetate mediated umpolung reactivity of the tertiary amines with suitably substituted o-hydroxybenzyl and phenyl groups is exploited to facilitate o-C(sp2)-H functionalization to afford diaryl ethers. The presence of an o-
- Jamsheena, Vellekkatt,Mahesha, Chikkagundagal K.,Joy, M. Nibin,Lankalapalli, Ravi S.
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supporting information
p. 6614 - 6617
(2017/12/26)
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- Palladium-Catalyzed Regioselective C-Benzylation via a Rearrangement Reaction: Access to Benzyl-Substituted Anilines
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An unprecedented C-benzylation rearrangement reaction, catalyzed by palladium, is reported. The reaction proceeds by rearrangement leading to the direct synthesis of para or ortho benzyl-substituted N-methylanilines. The product is obtained in high regioselectivity, without the need to use a ligand for the catalytic process.
- Amézquita-Valencia, Manuel,Alper, Howard
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p. 16774 - 16778
(2016/11/17)
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- A Highly Efficient Base-Metal Catalyst: Chemoselective Reduction of Imines to Amines Using An Abnormal-NHC-Fe(0) Complex
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A base-metal, Fe(0)-catalyzed hydrosilylation of imines to obtain amines is reported here which outperforms its noble-metal congeners with the highest TON of 17000. The catalyst, (aNHC)Fe(CO)4, works under very mild conditions, with extremely low catalyst loading (down to 0.005 mol %), and exhibits excellent chemoselectivity. The facile nature of the imine reduction under mild conditions has been further demonstrated by reducing imines towards expensive commercial amines and biologically important N-alkylated sugars, which are difficult to achieve otherwise. A mechanistic pathway and the source of chemoselectivity for imine hydrosilylation have been proposed on the basis of the well-defined catalyst and isolable intermediates along the catalytic cycle.
- Bhunia, Mrinal,Hota, Pradip Kumar,Vijaykumar, Gonela,Adhikari, Debashis,Mandal, Swadhin K.
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supporting information
p. 2930 - 2937
(2016/10/06)
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- Study on products and reaction paths for synthesis of 3,4-dihydro-2H-3-phenyl-1,3-benzoxazine from phenol, aniline and formaldehyde
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To study the synthesis of 3,4-dihydro-2H-3-phenyl-1,3-benzoxazine (benzoxazine), the reaction paths of phenol, aniline and formaldehyde were investigated by analyzing the synthesis crude products. With the aid of high-performance liquid chromatography (HP
- Zhang, Cheng-Xi,Deng, Yu-Yuan,Zhang, Yi-Yang,Yang, Po,Gu, Yi
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p. 348 - 352
(2015/04/14)
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- Programmed synthesis palladium supported on Fe3O4@C: An efficient and heterogeneous recyclable catalyst for one-pot reductive amination of aldehydes with nitroarenes in aqueous reaction medium
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A highly efficient Pd/Fe3O4@C catalytic system has been developed for direct reductive amination of carbonyl compounds with nitroarenes in aqueous reaction medium. The catalyst was characterized by TEM, XRD, XPS and VSM. It was found that the catalyst showed a high activity for the one-pot direct reductive amination of aldehydes with nitroarenes in the presence of molecular hydrogen at mild temperature. Besides, the catalyst could be recovered in a facile manner from the reaction mixture and recycled six times without obvious loss in activity.
- Zhou, Xingchun,Li, Xinzhe,Jiao, Lixin,Huo, Hongfei,Li, Rong
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p. 1591 - 1599
(2017/05/22)
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- Fe@Pd/C: An efficient magnetically separable catalyst for direct reductive amination of carbonyl compounds using environment friendly molecular hydrogen in aqueous reaction medium
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Direct reductive amination of carbonyl compounds with variety of amines has been reported by using magnetically separable Fe@Pd/C as an efficient catalyst in aqueous reaction medium. The developed methodology offers synthesis of various secondary and tertiary amines using different aldehydes and ketones with amines giving excellent yield. Moreover, the magnetically separable Fe@Pd/C catalyst was easily separated from reaction mixture and can be recycled for further reaction.
- Patil, Nilesh M.,Bhanage, Bhalchandra M.
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p. 182 - 189
(2015/03/30)
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- Structure-activity relationship study of E6 as a novel necroptosis inducer
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Necroptosis inducers represent a promising potential treatment for drug-resistant cancer. We herein describe the structure modification of E6, which was identified recently as a potent and selective necroptosis inducer. The studies described herein demonstrate for the first time that functionalized biphenyl derivatives possess necroptosis inducer activity. Furthermore, these studies have led to the identification of two promising compounds (5h and 5j) that can be used for further optimization studies as well as mechanism of action investigations.
- Mou, Jianfeng,Park, Ann,Cai, Yu,Yuan, Junying,Yuan, Chengye
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supporting information
p. 3057 - 3061
(2015/06/22)
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- Ruthenium(II) complexes containing lutidine-derived pincer CNC ligands: Synthesis, structure, and catalytic hydrogenation of C=N bonds
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Abstract A series of Ru complexes containing lutidine-derived pincer CNC ligands have been prepared by transmetalation with the corresponding silver-carbene derivatives. Characterization of these derivatives shows both mer and fac coordination of the CNC ligands depending on the wingtips of the N-heterocyclic carbene fragments. In the presence of tBuOK, the Ru-CNC complexes are active in the hydrogenation of a series of imines. In addition, these complexes catalyze the reversible hydrogenation of phenantridine. Detailed NMR spectroscopic studies have shown the capability of the CNC ligand to be deprotonated and get involved in ligand-assisted activation of dihydrogen. More interestingly, upon deprotonation, the Ru-CNC complex 5e(BF4) is able to add aldimines to the metal-ligand framework to yield an amido complex. Finally, investigation of the mechanism of the hydrogenation of imines has been carried out by means of DFT calculations. The calculated mechanism involves outer-sphere stepwise hydrogen transfer to the C=N bond assisted either by the pincer ligand or a second coordinated H2 molecule. The outer limits: Facially coordinated Ru-CNC complexes, in the presence of tBuOK, are active catalysts in the hydrogenation of a series of substrates containing C=N bonds (see scheme). Intermediate species in the catalytic cycle have been studied by using NMR spectroscopy; DFT calculations support a stepwise outer-sphere mechanism for the hydrogen transfer to the C=N bond assisted by either the pincer ligand or a second coordinated H2 molecule.
- Hernández-Juárez, Martín,López-Serrano, Joaquín,Lara, Patricia,Morales-Cerón, Judith P.,Vaquero, Mónica,álvarez, Eleuterio,Salazar, Verónica,Suárez, Andrés
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p. 7540 - 7555
(2015/05/13)
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- Influence of substituent on equilibrium of benzoxazine synthesis from Mannich base and formaldehyde
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N-Substituted aminomethylphenol (Mannich base) and 3,4-dihydro-2H-3- substituted 1,3-benzoxazine (benzoxazine) were synthesized from substituted phenol (p-cresol, phenol, p-chlorophenol), substituted aniline (p-toluidine, aniline, p-chloroaniline) and formaldehyde to study influence of substituent on equilibrium of benzoxazine synthesis from Mannich base and formaldehyde. 1H-NMR and charges of nitrogen and oxygen atoms illustrate effect of substituent on reactivity of Mannich base, while oxazine ring stability is characterized by differential scanning calorimetry (DSC) and C-O bond order. Equilibrium constants were tested from 50 °C to 80 °C, and the results show that substituent attached to phenol or aniline has same impact on reactivity of Mannich base; however, it has opposite influence on oxazine ring stability and equilibrium constant. Compared with the phenol-aniline system, electron-donating methyl on phenol or aniline increases the charge of nitrogen and oxygen atoms in Mannich base. When the methyl group is located at para position of phenol, oxazine ring stability increases, and the equilibrium constant climbs, whereas when the methyl group is located at the para position of aniline, oxazine ring stability decreases, the benzoxazine hydrolysis tends to happen and equilibrium constant is significantly low. the Partner Organisations 2014.
- Deng, Yuyuan,Zhang, Qin,Zhou, Qianhao,Zhang, Chengxi,Zhu, Rongqi,Gu, Yi
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p. 18341 - 18348
(2014/09/30)
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- Palladium supported on hollow magnetic mesoporous spheres as recoverable catalyst for one-pot reductive amination of aldehydes with nitroarenes under mild conditions
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We described here a method to stabilize Pd(0) on the surface of hollow magnetic mesoporous spheres (HMMS), with Fe3O4 nanoparticles embedded in the mesoporous shell. The catalyst was characterized by TEM, XRD and VSM. It was found that the catalyst showed a high activity for the one-pot direct reductive amination of aldehydes with nitroarenes in the presence of molecular hydrogen in ethanol, even at room temperature. Besides, the catalyst could be recovered in a facile manner from the reaction mixture and recycled six times without loss in activity.
- Zhou, Jinghui,Dong, Zhengping,Wang, Peng,Shi, Zhiqiang,Zhou, Xingchun,Li, Rong
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- A quick route for the synthesis of 3-Aryl-3,4-dihydro-2H-benz[e]-1,3- oxazin-2-ones
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N-(2-Hydroxy)-benzyl-arylamines (1) gave substantially pure 3-aryl-3,4-dihydro-2H-benz[e]-1,3-oxazin-2-one 2 on cyclization with carbonyldiimidazole in DMSO in 20-30 min at 20-25 °C in excellent yields.
- Shukla, Davender Kumar,Rani, Manju,Khan, Arif Ali
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p. 4537 - 4540
(2013/06/27)
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- Synthesis and biological activity of some 3-aryl-3,4-dihydro-2h-benz[e]-1, 3-oxazines/6-bromo-3-aryl-3,4-dihydro-2h-benz[e]-1,3-oxazines
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N-(2-Hydroxy)-benzyl-arylamine (1) gives substantially pure 3-aryl-3,4-dihydro-2H-benz[e]-1,3-oxazines/6-bromo-3-aryl-3,4-dihydro-2H-benz[e] -1,3-oxazines (2) on cyclization with formaldehyde in methanol within 0.5-1.0 h at 65-68 C in excellent yields. Th
- Shukla, Davender Kumar,Rani, Manju,Khan, Arif Ali,Tiwari, Kavita,Gupta, Rajinder K.
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p. 5921 - 5924
(2013/07/26)
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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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- 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
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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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p. 8174 - 8185
(2012/09/25)
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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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p. 255 - 260
(2011/06/19)
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- Synthesis and structure-antibacterial activity relationship studies of 4-substituted phenyl-4,5-dihydrobenzo[f][1,4]oxazepin-3(2H)-thiones
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The synthesis and characterization of a series of 4-substituted phenyl-4,5-dihydrobenzo[f][1,4]oxazepin- 3(2H)-thiones were presented. Preliminary in vitro antimicrobial activity of the compounds was assessed against a panel of microorganisms including S.
- Agirbas, Hikmet,Kemal, Berat,Budak, Fatma
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experimental part
p. 1170 - 1180
(2012/05/05)
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- Diastereospecific coupling of imines by low-valent titanium: An experimental and Computational study
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The reaction of phenylsilane (PhSiH3) and titanium(IV) isopropoxide [Ti(OiPr)4] generates low-valent titanium alkoxides that reduce and reductively couple imines. The C-C coupling reaction is diastereospecific, with exclusive formati
- Kumar, Akshai,Samuelson, Ashoka G.
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supporting information; experimental part
p. 951 - 959
(2011/04/15)
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- An efficient, recoverable fluorous organocatalyst for direct reductive amination of aldehydes
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A commercially available perfluorooctyl aniline and phenyl isothiocyanate were reacted under mild conditions to give 1-[4-(perfluorooctyl)phenyl]-3- phenylthiourea as an analogue of thiourea-based organocatalyst. This fluorous organocatalyst was successfully employed to direct reductive amination of aldehydes. It could be readily separated from reaction product by fluorous solid phase extraction for direct use.
- Huang, Yi-Bo,Yi, Wen-Bin,Cai, Chun
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experimental part
p. 879 - 882
(2010/10/01)
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- Direct reductive amination of aldehydes and ketones mediated by a thiourea derivative as an organocatalyst
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The direct reductive arylamination of arylaldehydes and ketones has been achieved using a selective imine activation by a hydrogen bond of a thiourea derivative. This mild, acid- and metal-free process requires a catalytic amount of N N′-bis[3,5-bis(trifluoromethyl)phenyl]thiourea, the Hantzsch 1,4-dihydropydine diethyl 1,4-dihydro-2,6-dimethyl-3,5-pyridinedicarboxylate as hydride source and activated 5A-molecule sieve as dehydrant. The method is adaptable for the synthesis of various amines.
- Huang, Yi-Bo,Cai, Chun
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experimental part
p. 686 - 688
(2010/03/24)
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- Salt/ligand-activated low-valent titanium formulations: the 'salt effect' on diastereoselective carbon-carbon bond forming SET reactions
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A comprehensive study on the influence of exogenously added electropositive metal salts as promoters/secondary activators on preformed LVT species has resulted in the construction of highly efficient low-valent titanium (LVT) reagents. These salt-activated LVT reagents while exhibiting enhanced chemoselectivity and diastereoselectivity accelerated the reductive olefination rates of aromatic and aliphatic carbonyls under ambient temperature conditions and in much reduced reaction times. The versatility of the salted reagent was further explored in other single electron transfer reactions, namely, imino-pinacol couplings and one-pot synthesis of phenanthrenes from o-alkoxy aromatic carbonyls. We envisage that, in contrast to multiphase heterogeneous colloidal slurries, salt-activated LVT reagents afforded uniformly viscous homogeneous slurries generating a highly reactive monomeric intermetallic LVT complex. Continued judicious exploration of the emerging paradigms by studying the influence of external ligands/auxiliaries/redox agents on LVT reagents, and organometallics in general, will be critical to widen the scope and utility of the classical McMurry reaction and other SET reactions.
- Rele, Shyam M.,Nayak, Sandip K.,Chattopadhyay, Subrata
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p. 7225 - 7233
(2008/12/20)
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- Synthesis, infrared spectral studies and theoretical calculations of 4-phenyl-4,5-dihydrobenzo[f][1,4]oxazepin-3(2H)-one (thione)
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Salicylaldehyde (1) was reacted with aniline to afford 2-[(E)-(phenylimino)methyl]phenol (2). The reduction of (2) by NaBH4 gave 2-((phenylamino)methyl)phenol (3) which was reacted with chloroacetyl chloride to give 2-chloro-N-(2-hydroxybenzyl)
- Agirbas, Hikmet,Sagdinc, Seda,Kandemirli, Fatma,Kemal, Berat
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scheme or table
p. 132 - 139
(2009/03/12)
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- Synthesis of 3,4-dihydro-2H-1,3-benzoxazines by condensation of 2-hydroxyaldehydes and primary amines: Application to the synthesis of hydroxy-substituted and deuterium-labeled compounds
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We report the synthesis of several substituted 3,4-dihydro-2H-1,3- benzoxazines by simple ring closure of 2-hydroxybenzylamines with paraformaldehyde. The facile synthesis of the benzylamine precursors from commercially available salicylaldehyde derivativ
- Andreu,Ronda
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p. 2316 - 2329
(2008/09/21)
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- Generation and application of o-Quinone methides bearing various substituents on the benzene ring
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o-Quinone methides (o-QMs) are highly reactive, short-lived intermediates, which have potential synthetic applicability. However, few studies on the generation of o-QMs bearing an electron-withdrawing group have been reported. Herein we present a general method for the generation of o-QMs, particularly those substituted with an 0lectrophilic substituent, from new precursors, 4H-1,2-benzoxazines 2. We have also studied systematically the Diels-Alder reactions of o-QMs with various dienophiles, such as vinyl ethers, enamines and imines. The reactions provide a versatile route to substituted chromans, phenols and 3,4-dihydro-2H-benzo[e]-[1,3]oxazines (3,4-dihydro-1,3-benzoxazines). Furthermore, we applied the new method to the derivatization of some natural products.
- Sugimoto, Hiromichi,Nakamura, Satoshi,Ohwada, Tomohiko
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p. 669 - 679
(2008/02/09)
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- Influence of the nature of the metal ion on the rate of reduction of coordinated azomethine group
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The kinetics of reduction of the azomethine bond in various Schiff bases and their transition metal complexes with sodium borohydride in dimethylformamide and ethanol solutions was studied. The reduction rate depends on both the structure of the starting
- Medzhidov,Mamedova,Aydin,Yalcin,Tascioglu,Kaki
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p. 1761 - 1765
(2008/09/16)
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- Reductive amination of aldehydes and ketones with sodium borohydride supported onto HZSM-5 zeolite under microwave irradiation in a solvent free system
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Sodium borohydride supported onto a HZSM-5 zeolite is presented as a general reducing agent for the reductive amination of aldehydes and ketones under microwave irradiation in solventless system. Copyright Taylor & Francis Inc.
- Oskooie, Hossein A.,Amiri, Somaih Solemani,Heravi, Majid M.,Ghassemzadeh, Mitra
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p. 2047 - 2050
(2007/10/03)
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- Highly active salted low-valent titanium reagents for various SET induced reactions
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External addition of inorganic salts (Group I and II metal halides) to the preformed low-valent titanium reagent A (TiCl3-Li-THF) dramatically enhanced its activity. The new reagents were used to carry out various SET reactions including McMurry's olefination at a faster rate even at ambient temperature.
- Rele, Shyam,Chattopadhyay, Subrata,Nayak, Sandip K.
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p. 9093 - 9095
(2007/10/03)
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- Generation of reactive low-valent titanium species using metal-arenes as efficient organic reductants for TiCl3: Applications to organic synthesis
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A comprehensive study on the use of metal-arene systems as organic reductants for TiCl3 has resulted in an efficient method for the generation of highly reactive low-valent titanium (LVT) reagents. The activated titanium species could be prepared by refluxing a mixture of substoichiometric amounts of arenes, TiCl3, and Li/Mg in THF or DME. Among the LVT reagents screened, TiCl3 - Li-naphthalene - THF (reagent I) was the best for coupling of carbonyls to olefins. The reagent could carry out the McMurry olefination of both aromatic and aliphatic substrates at a lower temperature and in a much reduced time as compared to the conventional procedures. Subtle changes in the method of preparation of the LVT reagents influenced the stereoisomeric ratio of the olefins. The reagent was also useful for the synthesis of O- and N- heterocycles and vicinal diamines via intramolecular carbonyl coupling and reductive duplication of imines, respectively.
- Rele,Talukdar,Banerji,Chattopadhyay
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p. 2990 - 2994
(2007/10/03)
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- Indium-mediated tandem dimerization and cyclization of nitrqones and aldimines to 3-arylaminodihydrobenzofurans under aqueous conditions
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Nitrones undergo deoxygenative reductive coupling and subsequent cyclization to 3-arylamino-2,3-dihydrobenzofuran derivatives in the presence of indium under aqueous conditions at ambient temperature in good yields.
- Jeevanandam, Arumugasamy,Ling, Yong-Chien
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p. 4361 - 4362
(2007/10/03)
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- Alkylation of amino acids and glutathione in water by o-Quinone methide. Reactivity and selectivity
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o-Quinone methide (1) has been produced in water both thermally and photochemically from (2-hydroxybenzyl)trimethylammonium iodide (2). Michael addition reactions of 1 to various amines, and sulfides, including amino acids and glutathione have been carried out, obtaining alkylated adducts (3-16) in fairly good to quantitative yields. The reaction rate and selectivity of 1 toward nitrogen and sulfur nucleophiles, in competition with the hydration reaction, have been investigated at different pH by laser flash photolysis technique. The observed reactivity spans 7 orders of magnitude on passing from water (kNu = 5.8 M-1 s-1) to the most reactive nucleophile (2.8 × 108 M-1 s-1, 2-mercaptoethanol under alkaline conditions). These are the first direct reaction rate measurements of nucleophilic addition to the parent o-quinone methide (1). Competition experiments provided strong kinetic support to the involvement of free 1 as an intermediate in both thermal and photochemical reactions. Furthermore, several alkylation adducts regenerate 1 either by heating (9, 10, 13, and 14) or by irradiation (9, 11-13, 16). Such a thermal and photochemical reversibility of the alkylation process opens a new perspective for the use and application of such adducts as o-QM molecular carriers.
- Modica,Zanaletti,Freccero,Mella
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- Chemoselective reductive amination of aldehydes and ketones by dibutylchlorotin hydride-HMPA complex
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Reductive amination of various aldehydes and ketones has been performed effectively by pentacoordinate chloro-substituted tin hydride complex, Bu2SnClH-HMPA. The tin reagent worked particularly well for the case using weakly basic aromatic amines as starting substrates. Stoichiometric amounts of a substrate and a reducing agent were adequate for the reaction. The Sn-Cl bond in the complex plays an important role for both steps of imine formation and subsequent reduction. Highly chemoselective reduction of carbonyls could be achieved regardless of other functionalities such as halogen, carbon- carbon double bond and hydroxyl groups in the starting carbonyls and amines.
- Suwa, Toshihiro,Sugiyama, Erika,Shibata, Ikuya,Baba, Akio
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p. 789 - 800
(2007/10/03)
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- A facile radical induced selective removal of N-propargyl protecting groups using low valent titanium reagents
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Low valent titanium mediated cleavage of N-propargyl bonds offers a facile, mild, and high yielding method for the deprotection of amines under neutral conditions. The methodology could be used for the chemoselective removal of propargyl groups from amines in preference to the allyl/benzyl counterparts and can be performed chemoselectively in the presence of methoxy, methylenedioxy, and chloro functionalities.
- Rele, Shyam,Talukdar, Sanjay,Banerji, Asoke
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p. 767 - 770
(2007/10/03)
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