- New protocols for the synthesis of 3,4-annulated and 4-substituted quinolines from β-bromo-α,β-unsaturated aldehydes and 1-bromo-2-nitrobenzene or 2-bromoacetanilide
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The palladium[0]-mediated Ullmann cross-coupling of readily available β-bromo-α,β-unsaturated aldehydes of the general form 2 with 1-bromo-2-nitrobenzene (3, X = Br) delivers products, 4, that undergo reductive cyclization to novel quinolines (5) upon exposure to indium in aqueous ammonium chloride or to Raney-nickel in the presence of dihydrogen. Analogous cross-coupling of 2-bromoacetanilide (6) with 2 affords products of type 7 that undergo in situ and K2CO3-mediated cyclization to give the same types of quinolines (5).
- Some, Surajit,Ray, Jayanta K.,Banwell, Martin G.,Jones, Matthew T.
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- Azulene–Naphthalene-Type Rearrangements in Benz[a]azulene and Cyclohepta[b]indole
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Flash vacuum pyrolysis (FVP) of benz[a]azulene yields phenanthrene and 2-ethynylbiphenyl. FVP of cyclohepta[b]indole similarly yields phenanthridine and 2-cyanobiphenyl. The reversibility of the reactions is demonstrated by FVP of 2-ethynylbiphenyl and 2-isocyanobiphenyl. All the observed reactions are in accord with the norcaradiene–vinylidene mechanism of the azulene–naphthalene rearrangement, whereas other proposed mechanisms are ruled out.
- Wentrup, Curt,Becker, Jürgen
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- The photochemistry of 6-phenanthridinecarbonitrile I. Product analysis [1]
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When 6-phenanthridinecarbonitrile (3) is irradiated at 2537 A in neutral 9:1 2-propanol/water, three major products are formed. These are dimethyl-(6-phenanthridinyl)methanol (4), phenanthridine (5) and 6,6'- biphenanthridine (6). When benzophenone is present in the reaction mixture, diphenyl-(6-phenanthridinyl)methanol is also formed. 6-Phenanthridinyl radical which is common to the formation of all these products, is formed by a monophotonic process involving hydrogen atom abstraction from an alcohol molecule by an excited state of 3. Unlike what is generally found with other nitrogen-heterocycles, the photochemistry of 3 appears to involve only a π,π* singlet state. The fluorescence of 3 is quenched with the triplet quencher cis/trans-piperylene as a function of the concentration of the diene without the accompaniment of an exciplex emission.
- Vittimberga, Bruno M.,Sears, Donald F.
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- Hydride-induced anionic cyclization: An efficient method for the synthesis of 6- H -phenanthridines via a transition-metal-free process
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A novel procedure for hydride-induced anionic cyclization has been developed. It includes the reduction of a biaryl bromo-nitrile with a nucleophilic aromatic substitution (SNAr). A range of polysubstituted 6-H-phenanthridines were so obtained in moderate to good yield with good substrate tolerance. This method involves a concise transition-metal-free process and was applied to synthesize natural alkaloids.
- Chen, Wei-Lin,Chen, Chun-Yuan,Chen, Yan-Fu,Hsieh, Jen-Chieh
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- Synthesis of phenanthridines and analogues via suzuki coupling and condensation
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A convenient and short methodology has been developed towards the synthesis of highly substituted phenanthridines and their analogous benzo[k] and benzo[i] derivatives in a single step via Suzuki coupling and condensation between suitably substituted aromatic ortho-bromoaldehydes and ortho-aminobenzeneboronic acids in good to excellent yields. Georg Thieme Verlag Stuttgart. New York.
- Dhara, Shubhendu,Ghosh, Munmun,Ray, Jayanta K.
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- LEWIS ACID PROMOTED PHOTOCYCLIZATION OF ARYLIMINES. STUDIES DIRECTED TOWARDS THE SYNTHESIS OF PENTACYCLIC NATURAL PRODUCTS.
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Arylimines are converted into 9-azaphenanthrene derivatives (38-46percent) when photolyzed in the presence of boron trifluoride etherate.
- Thompson, Charles M.,Docter, Stephen
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- Substituent-guided switch between C-H activation and decarboxylative cross-coupling during palladium/copper-catalyzed cascade reactions of 2-aminobenzoates with 2-haloarylaldehydes
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Cascade switch: Phenanthridines, pyrazole[4,3-c]quinolines and isocryptolepine were prepared in one step from the Pd/Cu-catalyzed reaction between potassium 2-aminobenzoates and 2-haloarylaldehydes (see scheme). Although the reactions of 2-aminobenzoates proceeded via a cascade imination/C-H functionalization, the reactions of 6-nitro-2-aminobenzoates ensued via a tandem imination/decarboxylative cross-coupling. Copyright
- Bhowmik, Subhendu,Pandey, Garima,Batra, Sanjay
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- Tert-Butyl peroxybenzoate (TBPB)-mediated 2-isocyanobiaryl insertion with 1,4-dioxane: Efficient synthesis of 6-alkyl phenanthridines via C(sp 3)-H/C(sp2)-H bond functionalization
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An efficient method for the construction of 6-alkyl phenanthridines by tert-butyl peroxybenzoate (TBPB)-mediated 2-isocyanobiaryl insertion with 1,4-dioxane was established. Two new C-C bonds were formed in this reaction via a sequential C(sp3)-H/C(sp2)-H bond functionalization under metal-free conditions. This journal is the Partner Organisations 2014.
- Cao, Jia-Jia,Zhu, Tong-Hao,Wang, Shun-Yi,Gu, Zheng-Yang,Wang, Xiang,Ji, Shun-Jun
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- Photocyclization synthesis of phenanthridine and its derivatives under direct dehydrogenation conditions
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A new method for synthesizing phenanthridines by photocyclization has been established. This method does not require inert gas protection, does not require transition metal catalysts and is environmentally friendly, efficient and convenient. It is proposed to use (E)-N,1-diphenylformimines as substrates to synthesize phenanthridine and its derivatives by ultraviolet light, which provides a new synthesis route for further research on the synthesis of phenanthridines by photocyclization. Eight new phenanthridine compounds were synthesized. The confirmation of their structures provides a material basis for further study of their properties and tapping of their potential for applications. The establishment of this method further broadens the synthetic pathways of phenanthridine compounds.
- Zhu, Wen-Qing,Zhang, Jin,Fan, Pan,Shi, Lan-Ting,Li, Hong,Yang, Min-Ge,Li, Yang
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- A ruthenium-catalyzed free amine directed (5+1) annulation of anilines with olefins: Diverse synthesis of phenanthridine derivatives
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A ruthenium(ii)-catalyzed cross-ring (5+1) annulation between 2-aminobiphenyls and activated olefins is disclosed for succinct synthesis of valuable phenanthridine scaffolds. The protocol avails a common organic functional group, free amine, as a directing group and represents a unique combination of C-H activation/annulation/C-C bond cleavage cascade that bodes well in the production of bioactive alkaloids including trisphaeridine and bicolorine.
- Chowdhury, Deepan,Dana, Suman,Mandal, Anup,Baidya, Mahiuddin
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- Design of fluorinated 5-HT4R antagonists: Influence of the basicity and lipophilicity toward the 5-HT4R binding affinities
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Analogues of potent 5-HT4R antagonists possessing a fluorinated N-alkyl chain have been synthesized in order to investigate the effect of the resulting change in basicity and lipophilicity on the affinity and selectivity profile. We demonstrate that for this series, the affinity is decreased with decreased basicity of the piperidine's nitrogen atom. In contrast, the resulting increase in lipophilicity has minimal impact on binding affinity and selectivity. 3,3,3-Trifluoropropyl and 4,4,4-trifluorobutyl derivatives 6d and 6e have shown to bind to the 5-HT4R while maintaining their pharmacological profile and selectivity toward other 5-HT receptors.
- Fontenelle, Clement Q.,Wang, Zhong,Fossey, Christine,Cailly, Thomas,Linclau, Bruno,Fabis, Frederic
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- SYNTHETIC APPLICATION OF LITHIATION REACTIONS-XIV. NOVEL SYNTHESIS OF 7,8-DIMETHOXY PHENANHRIDINE
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The difficultly accessible 7,8-dimethoxy phenenthridine has been synthesised by organolithiation reaction in simple steps and in good yield.
- Narasimhan, N. S.,Chandrachood, P. S.,Shete, N. R.
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- Covalent Organic Frameworks toward Diverse Photocatalytic Aerobic Oxidations
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Photoactive two-dimensional covalent organic frameworks (2D-COFs) have become promising heterogenous photocatalysts in visible-light-driven organic transformations. Herein, a visible-light-driven selective aerobic oxidation of various small organic molecules by using 2D-COFs as the photocatalyst was developed. In this protocol, due to the remarkable photocatalytic capability of hydrazone-based 2D-COF-1 on molecular oxygen activation, a wide range of amides, quinolones, heterocyclic compounds, and sulfoxides were obtained with high efficiency and excellent functional group tolerance under very mild reaction conditions. Furthermore, benefiting from the inherent advantage of heterogenous photocatalysis, prominent sustainability and easy photocatalyst recyclability, a drug molecule (modafinil) and an oxidized mustard gas simulant (2-chloroethyl ethyl sulfoxide) were selectively and easily obtained in scale-up reactions. Mechanistic investigations were conducted using radical quenching experiments and in situ ESR spectroscopy, all corroborating the proposed role of 2D-COF-1 in photocatalytic cycle.
- Liu, Shuyang,Tian, Miao,Bu, Xiubin,Tian, Hua,Yang, Xiaobo
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supporting information
p. 7738 - 7744
(2021/05/07)
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- Radical Borylative Cyclization of Isocyanoarenes with N-Heterocyclic Carbene Borane: Synthesis of Borylated Aza-arenes
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Borylated aza-arenes are of great importance in the area of organic synthesis. A radical borylative cyclization of isocyanoarenes with N-heterocyclic carbene borane (NHC-BH3) under metal-free conditions was developed. The reaction allows the efficient assembly of several types of borylated aza-arenes (phenanthridines, benzothiazoles, etc.), which are difficult to access using alternative methods. Mild reaction conditions, a good functional-group tolerance, and generally good efficiencies were observed. The utility of these products is demonstrated, and the mechanism is discussed.
- Liu, Yao,Li, Ji-Lin,Liu, Xu-Ge,Wu, Jia-Qiang,Huang, Zhi-Shu,Li, Qingjiang,Wang, Honggen
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p. 1891 - 1897
(2021/03/08)
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- Synthesis of highly substituted fluorenones via metal-free TBHP-promoted oxidative cyclization of 2-(aminomethyl)biphenyls. Application to the total synthesis of nobilone
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Highly substituted fluorenones are readily prepared in mostly fair to good yields via metal- and additive-free TBHP-promoted cross-dehydrogenative coupling (CDC) of readily accessible N-methyl-2-(aminomethyl)biphenyls and 2-(aminomethyl)biphenyls. This methodology is compatible with numerous functional groups (methoxy, cyano, nitro, chloro, and SEM and TBS-protective groups for phenols) and was further utilized in the first total synthesis of the natural product nobilone.
- Bracher, Franz,Jourjine, Ilya A. P.,Krau?, Jürgen,Zeisel, Lukas
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p. 2668 - 2679
(2021/11/30)
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- Metal-free tandem carbene N-H insertions and C-C bond cleavages
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A metal-free C-H [5 + 1] annulation reaction of 2-arylanilines with diazo compounds has been achieved, giving rise to two types of prevalent phenanthridines via highly selective C-C cleavage. Compared to the simple N-H insertion manipulation of diazo, this method elegantly accomplishes a tandem N-H insertion/SEAr/C-C cleavage/aromatization reaction, and the synthetic utility of this new transformation is exemplified by the succinct syntheses of trisphaeridine and bicolorine alkaloids. This journal is
- Chen, Pu,Nan, Jiang,Hu, Yan,Kang, Yifan,Wang, Bo,Ma, Yangmin,Szostak, Michal
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p. 803 - 811
(2021/01/28)
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- Hydrogenation/dehydrogenation of N-heterocycles catalyzed by ruthenium complexes based on multimodal proton-responsive CNN(H) pincer ligands
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Ru complexes based on lutidine-derived pincer CNN(H) ligands having secondary amine side donors are efficient precatalysts in the hydrogenation and dehydrogenation of N-heterocycles. Reaction of a Ru-CNN(H) complex with an excess of base produces the formation of a Ru(0) derivative, which is observed under catalytic conditions.
- álvarez, Eleuterio,Hernández-Juárez, Martín,López-Serrano, Joaquín,Paneque, Margarita,Rendón, Nuria,Sánchez, Práxedes,Santos, Laura L.,Suárez, Andrés
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supporting information
p. 9583 - 9587
(2020/07/30)
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- Expeditious synthesis of phenanthridines through a Pd/MnO2-mediated C-H arylation/oxidative annulation cascade from aldehydes, aryl iodides and amino acids
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The expeditious construction of phenanthridine scaffolds via a Pd/MnO2-mediated C-H arylation/oxidative annulation cascade involving aldehydes, aryl iodides and amino acids is disclosed. This reaction proceeds smoothly involving the formation of multiple chemical bonds with the tolerance of a wide range of functional groups. The control experiments suggest a radical mechanism for C-N bond formation via MnO2-promoted oxidative annulation of imine compounds. The synthetic utility of this transformation has been demonstrated via the straightforward access to bioactive natural alkaloid trisphaeridine and its analogue.
- Fan, Jian,Li, Li,Xie, Meihua,Zhang, Jitan
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supporting information
p. 2775 - 2778
(2020/03/13)
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- Preparation of phenanthridines from N-(o-arylbenzyl)trifluoromethanesulfonamides with 1,3-diiodo-5,5-dimethylhydantoin
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Treatment of N-(o-arylbenzyl)trifluoromethanesulfonamides with 1,3-diiodo-5,5-dimethylhydantoin in 1,2-dichloroethane under irradiation with a tungsten lamp, followed by the reaction with tBuOK gave the corresponding 6-arylphenanthridines and 6-unsubstituted phenanthridines in good to moderate yields, respectively. The reaction proceeds through an oxidative cyclization onto the aromatic ring by sulfonamidyl radicals formed from the N-iodosulfonamides. The present reaction is a one-pot method for the preparation of both 6-arylphenanthridines and 6-unsubstituted phenanthridines from N-(o-arylbenzyl)trifluoromethanesulfonamides under transition-metal-free conditions.
- Yanai, Kei,Togo, Hideo
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- Synthesis of phenanthridines through iodine-supported intramolecular C-H amination and oxidation under visible light
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Herein, we report a metal-free and step-economic synthesis of phenanthridines from 2-biarylmethanamines under mild conditions. The reaction involves iodine-supported intramolecular C-H amination and oxidation of 5,6-dihydrophenanthridine under air and benign visible light. The mechanism study reveals that visible light plays a key role in both these steps.
- Chen, Xuenian,Ma, Yan-Na,Gao, Yan,Jing, Yi,Li, Lixin,Zhang, Jie
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p. 12187 - 12198
(2020/11/10)
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- One-pot Cascade Reaction for the Synthesis of Phenanthridines via Suzuki Coupling/C?H Oxidation/Aromatization
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A one-pot cascade coupling/annulation reaction for the synthesis of phenanthridines has been developed from arylboronic acids and o-bromo arylamides with DMSO as a carbon source. The desired phenanthridines were obtained in moderate to good yields by using simple procedure. (Figure presented.).
- Chen, Rener,Ding, Yuxin,Ma, Yongmin,Zhang, Yi
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p. 5697 - 5707
(2020/12/01)
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- Rhodium(I)-Catalyzed Aryl C-H Carboxylation of 2-Arylanilines with CO2
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An unprecedented Rh(I)-catalyzed, amino-group-assisted C-H carboxylation of 2-arylanilines with CO2 under redox-neutral conditions has been developed. This reaction was promoted by a phosphine ligand with t-BuOK as the base and did not require the use of additional strong organometallic reagent. It enabled an efficient direct conversion of a broad range of 2-(hetero)arylanilines including electron-deficient heteroarenes to various phenanthridinones. Possible intermediates of the reaction were also evaluated in the preliminary mechanistic studies.
- Gao, Yuzhen,Cai, Zhihua,Li, Shangda,Li, Gang
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p. 3663 - 3669
(2019/05/17)
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- Application of phenanthridine compounds to pesticides
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The invention relates to an application of phenanthridine compounds shown in general formula (1) to pesticides. Part of the compounds is used as a plant virus agent and can well inhibit the tobacco mosaic virus; when used as a bactericide, the compounds have good inhibitory activity on tomato early blight, wheat scab, potato late blight, phytophthora capsici, rape sclerotinia rot, cucumber gray mould, rice sheath blight disease, cucumber fusarium wilt, cercospora brown spot of peanut, apple ring rot, wheat sharp eyespot, corn southern leaf blight, watermelon anthracnose and rice bakanae disease; when used as an insecticide, the compounds have poisonous activity on armyworms, mosquito larvae, cotton bollworms, ostrinia nubilalis, aphids, adult mites and plutella xylostella. In the formula,when molecular nitrogen is not imine, R can represent hydrogen atoms, methyl, acetyl and benzoyl; R and R represent a hydrogen atom or an oxygen atom simultaneously; R and R can represent hydroxyl, acetoxyl, methoxyl, methyleneoxy, a fluorine atom and the hydrogen atom; R is a bromine atom or the fluorine atom; R is the hydrogen atom or vinyl. When nitrogen is imine, R doesnot represent any group; one of R and R does not represent any group, and the other can represent the hydrogen atom, methoxyl, ethyoxyl, benzyloxy and a chlorine atom; R, R, R and Rrepresent the hydrogen atom.
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- Electrochemical Deoxygenation of N-Heteroaromatic N -Oxides
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An electrochemical method for the deoxygenation of N-heteroaromatic N -oxide to give the corresponding N-heteroaromatics has been developed. Several classes of N-heterocycles such as pyridine, quinoline, isoquinoline, and phenanthridine are tolerated. The electrochemical reactions proceed efficiently in aqueous solution without the need for transition-metal catalysts and waste-generating reducing reagents.
- Xu, H.-C.,Xu, P.
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supporting information
p. 1219 - 1221
(2019/06/08)
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- Dehydrogenation of N-Heterocycles by Superoxide Ion Generated through Single-Electron Transfer
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Nitrogen-containing heteroarene motifs are found in numerous pharmaceuticals, natural products, and synthetic materials. Although several elegant methods for synthesis of these compounds through dehydrogenation of the corresponding saturated heterocycles have been reported, some of the methods are hampered by long reaction times, harsh conditions, and the need for catalysts that are not readily available. This work reports a novel method for dehydrogenation of N-heterocycles. Specifically, O2.? generated in situ acts as the oxidant for N-heterocycle substrates that are susceptible to oxidation through a hydrogen atom transfer mechanism. This method provides a general, green route to N-heteroarenes.
- Huang, Yuan-Qiong,Song, Hong-Jian,Liu, Yu-Xiu,Wang, Qing-Min
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p. 2065 - 2069
(2018/01/27)
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- CO2-Catalyzed Efficient Dehydrogenation of Amines with Detailed Mechanistic and Kinetic Studies
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CO2-catalyzed dehydrogenation of amines has been achieved under photocatalytic conditions. With this concept, various amines have been selectively dehydrogenated to the corresponding imines in the presence of different functional groups such as nitrile, nitro, ester, halogen, ether, thioether, and carbonyl or carboxylic acid moieties. At the end, the CO2-catalyzed synthesis of pharmaceutical drugs has been achieved. The CO2 radical has been detected by EPR spectroscopy using DMPO, and the mechanism of this reaction is proposed on the basis of DFT calculations and experimental evidence.
- Riemer, Daniel,Schilling, Waldemar,Goetz, Anne,Zhang, Yu,Gehrke, Sascha,Tkach, Igor,Hollóczki, Oldamur,Das, Shoubhik
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p. 11679 - 11687
(2018/11/23)
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- Visible-Light Photocatalyzed Deoxygenation of N-Heterocyclic N-Oxides
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A scalable and operationally simple method is described that allows for the chemoselective deoxygenation of a wide range of N-heterocyclic N-oxides (a total of 36 examples). This visible-light-induced protocol features the use of only commercially available reagents, room-temperature conditions, and unprecedented chemoselective removal of the oxygen atom in a quinoline N-oxide in the presence of a pyridine N-oxide in the same molecule through the judicious selection of a photocatalyst.
- Kim, Kyu Dong,Lee, Jun Hee
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supporting information
p. 7712 - 7716
(2019/01/03)
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- Palladium-Catalyzed α-Arylation of Silylenol Ethers in the Synthesis of Isoquinolines and Phenanthridines
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A diverse array of isoquinolines and phenanthridines have been accessed by developing a two-step, one-pot method constituting regioselective palladium-catalyzed Kuwajima-Urabe α-arylation of silylenol ethers and acid-mediated deprotection, annulation, and aromatization. Structural diversity in the silylenol ethers leads to three different classes of isoquinolines and phenanthridines from which related natural products can be derived. The synthetic utility of this method by the quick assembly of the natural product trispheridine is also demonstrated.
- Saini, Gaurav,Kumar, Pravin,Kumar, Gangam Srikanth,Mangadan, Arun Raj Kizhakkayil,Kapur, Manmohan
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supporting information
p. 441 - 444
(2018/01/28)
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- Synthesis method of phenanthridine and derivative of phenanthridine
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The invention discloses a synthesis method of phenanthridine as shown in a formula (I) and a derivative of the phenanthridine. In the synthesis method, o-arylphenylsulfimide shown as a formula (II) isused as a raw material and reacts in an organic solvent under the action of a [Cu]/Selectfluor catalyst to obtain a corresponding target product (I). The synthesis method disclosed by the invention has the advantages of cheap and easily available and low-toxicity catalyst, environmental friendliness, mild reaction conditions, high universality of functional group and easiness and convenience in operation. The formulas (I) and (II) are shown in the description.
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Paragraph 0023-0025
(2018/03/24)
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- Synthesis of Phenanthridines through Palladium-Catalyzed Cascade Reaction of 2-Halo-N-Ms-arylamines with Benzyl Halides/Sulfonates
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An efficient palladium-catalyzed nucleophilic substitution/C–H activation/aromatization cascade reaction between readily available 2-halo-N-Ms-arylamines (Ms = methanesulfonyl) and benzyl halides/sulfonates has been described. A wide variety of phenanthridines were synthesized in a one-pot fashion in moderate to high yields (37–86 %). Notably, this method provides a straightforward, facile approach for the synthesis of phenanthridines. The practicality was further substantiated by successfully carrying out a gram-scale preparation.
- Yang, Si-Yi,Han, Wen-Yong,Zhang, Ding-Lei,Zhou, Xiao-Jian,Bai, Mei,Cui, Bao-Dong,Wan, Nan-Wei,Yuan, Wei-Cheng,Chen, Yong-Zheng
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p. 996 - 1003
(2017/02/15)
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- A preparation method of compound phenanthridine apperception (by machine translation)
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The invention discloses a method for preparing phenanthridine apperception composition, comprising: adding the reactant in the solvent 2 - halogenated -N- Protection of the aromatic amine and benzylic or benzyl sulfonic acid ester compound, then adding metal palladium catalyst, a ligand and an alkali, in heating and inert gas protection under the conditions of the chemical reaction, the reaction is complete after treatment to obtain the compound of the present invention pure product. Preparation method of this invention adopts the simple and easily obtained 2 - halogenated -N- Protection of the aromatic amine and benzylic or benzyl sulfonic acid ester compound as a raw material, by nucleophilic substitution/C - H activation/aromatization series reaction to obtain the phenanthridine compound, with raw materials are easy, simple operation, after treatment is simple, and high yield. (by machine translation)
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Paragraph 0028; 0038
(2017/05/12)
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- Coupling N-H Deprotonation, C-H Activation, and Oxidation: Metal-Free C(sp3)-H Aminations with Unprotected Anilines
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An intramolecular oxidative C(sp3)-H amination from unprotected anilines and C(sp3)-H bonds readily occurs under mild conditions using t-BuOK, molecular oxygen and N,N-dimethylformamide (DMF). Success of this process, which requires mildly acidic N-H bonds and an activated C(sp3)-H bond (BDE 85 kcal/mol), stems from synergy between basic, radical, and oxidizing species working together to promote a coordinated sequence of deprotonation: H atom transfer and oxidation that forges a new C-N bond. This process is applicable for the synthesis of a wide variety of N-heterocycles, ranging from small molecules to extended aromatics without the need for transition metals or strong oxidants. Computational results reveal the mechanistic details and energy landscape for the sequence of individual steps that comprise this reaction cascade. The importance of base in this process stems from the much greater acidity of transition state and product for the 2c,3e C-N bond formation relative to the reactant. In this scenario, selective deprotonation provides the driving force for the process.
- Evoniuk, Christopher J.,Gomes, Gabriel Dos Passos,Hill, Sean P.,Fujita, Satoshi,Hanson, Kenneth,Alabugin, Igor V.
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p. 16210 - 16221
(2017/11/22)
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- A radical addition/cyclization of diverse ethers to 2-isocyanobiaryls under mildly basic aqueous conditions
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Mildly basic aqueous conditions facilitated the tert-butyl peroxybenzoate (TBPB) mediated dehydrogenative addition of a range of ethers, including acetals, to diverse substituted 2-isocyanobiaryls. Mechanistic studies suggest that this radical cascade is an example of base promoted homolytic aromatic substitution (BHAS).
- Anton-Torrecillas, Cintia,Felipe-Blanco, Diego,Gonzalez-Gomez, Jose C.
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p. 10620 - 10629
(2016/11/30)
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- Double C-H amination by consecutive SET oxidations
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A new method for intramolecular C-H oxidative amination is based on a FeCl3-mediated oxidative reaction of anilines with activated sp3 C-H bonds. The amino group plays multiple roles in the reaction cascade: (1) as the activating group in single-electron-transfer (SET) oxidation process, (2) as a directing group in benzylic/allylic C-H activation at a remote position, and (3) internal nucleophile trapping reactive intermediates formed from the C-H activation steps. These multielectron oxidation reactions proceed with catalytic amounts of Fe(iii) and inexpensive reagents.
- Evoniuk, Christopher J.,Hill, Sean P.,Hanson, Kenneth,Alabugin, Igor V.
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p. 7138 - 7141
(2016/06/09)
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- Metal-free photoredox catalyzed cyclization of O-(2,4-dinitrophenyl)oximes to phenanthridines
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A metal-free visible-light photoredox-catalyzed intermolecular cyclization reaction of O-2,4-dinitrophenyl oximes to phenanthridines was developed. In this study, the organic dye eosin Y and i-Pr2NEt were used as photocatalyst and terminal reductant, respectively. The oxime substrates were transformed into iminyl radical intermediates by single-electron reduction, which then underwent intermolecular homolytic aromatic substitution (HAS) reactions to give phenanthridine derivatives.
- Liu, Xiubin,Qing, Zhixing,Cheng, Pi,Zheng, Xinyu,Zeng, Jianguo,Xie, Hongqi
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- Assembly of substituted phenanthridines via a cascade palladium-catalyzed coupling reaction, deprotection and intramolecular cyclization
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The discovery and development of a general method for the one-pot synthesis of substituted phenanthridines is presented. In the presence of Pd(PPh3)4, accessible precursors undergo a Suzuki cross-coupling reaction with 2-(Boc-amino)benzeneboronic acid pinacol ester and then spontaneously undergo deprotection and intramolecular condensation to form the corresponding phenanthridines in one step. This reaction has a wide range of substrates with various functional groups, and the corresponding products have been obtained in good yields.
- Ge, Jun,Wang, Xiaojian,Liu, Tianqi,Shi, Zeyu,Xiao, Qiong,Yin, Dali
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p. 19571 - 19575
(2016/03/01)
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- Cascade C-C and C-N Bond Formation: A Straightforward Synthesis of Phenanthridines and Fused Quinolines
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A Pd-catalyzed cascade process has been developed for the synthesis of quinoline and phenanthridine derivatives from various β-chloro α,β-unsaturated aldehydes and 2-chloroaryl aldehydes, respectively, in good to high yields. The reaction proceeds through Pd-catalyzed cascade carbon-carbon and carbon-nitrogen bond formation in a single reaction vessel. The requisite β-chloro α,β-unsaturated aldehydes were efficiently synthesized from their corresponding carbonyl compounds. The use of the ligand Sphos with Pd(OAc)2 is crucial for the successful implementation of the present cascade process. This synthetic protocol is also applied for the gram-scale synthesis of a trispheridine alkaloid.
- Borah, Ashwini,Gogoi, Pranjal
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supporting information
p. 2200 - 2206
(2016/05/09)
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- Domino Suzuki coupling and condensation reaction: An efficient strategy towards synthesis of phenanthridines
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A short and convenient hetero-annulation protocol has been developed for the synthesis of substituted phenanthridines via domino Suzuki coupling and condensation between N-(2-iodo-aryl)-formamide derivatives and 2-formylphenylboronic acid in the presence of Pd(OAc)2, Cs2CO3 and PPh3 as catalytic system in dry DMF at 85-90 °C for 6-7 h. The intermediate after Suzuki coupling and deprotection of nitrogen under the same catalytic system, furnishes the corresponding phenanthridines in good yields after immediate condensation and dehydration.
- Ghosh, Munmun,Ahmed, Atiur,Singha, Raju,Ray, Jayanta K.
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p. 353 - 355
(2015/03/05)
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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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- Catalytic oxidative cyclization of 2′-arylbenzaldehyde oxime ethers under photoinduced electron transfer conditions
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A series of 2′-arylbenzaldehyde oxime ethers were synthesized and shown to generate the corresponding phenanthridines upon irradiation in the presence of 9,10-dicyanoanthracene in acetonitrile. Mechanistic studies suggest that the oxidative cyclization reaction sequence is initiated by an electron transfer step followed by nucleophilic attack of the aryl ring onto the nitrogen of the oxime ether. A concave downward Hammett plot is presumably the result of a change in charge distribution in the radical cation species with strongly electron-donating substituents that yields a less electrophilic nitrogen atom and a decreased amount of cyclized product. The reaction is selective (no nitrile byproduct is formed unlike other photochemical reactions involving aldoxime ethers) as well as regiospecific when using 2′-aryl groups with metasubstituents, making this reaction a useful alternative for preparing substituted phenanthridines.
- Hofstra, Julie L.,Grassbaugh, Brittany R.,Tran, Quan M.,Armada, Nicholas R.,De Lijser, H. J. Peter
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p. 256 - 265
(2016/09/09)
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- Visible-light-promoted iminyl-radical formation from Acyl oximes: A unified approach to pyridines, quinolines, and phenanthridines
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A unified strategy involving visible-light-induced iminyl-radical formation has been established for the construction of pyridines, quinolines, and phenanthridines from acyl oximes. With fac-[Ir(ppy)3] as a photoredox catalyst, the acyl oximes were converted by 1 e- reduction into iminyl radical intermediates, which then underwent intramolecular homolytic aromatic substitution (HAS) to give the N-containing arenes. These reactions proceeded with a broad range of substrates at room temperature in high yield. This strategy of visible-light-induced iminyl-radical formation was successfully applied to a five-step concise synthesis of benzo[c]phenanthridine alkaloids.
- Jiang, Heng,An, Xiaode,Tong, Kun,Zheng, Tianyi,Zhang, Yan,Yu, Shouyun
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supporting information
p. 4055 - 4059
(2015/03/30)
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- Palladium-Catalyzed Nucleophilic Substitution/C-H Activation/Aromatization Cascade Reaction: One Approach to Construct 6-Unsubstituted Phenanthridines
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A facile and practical palladium-catalyzed nucleophilic substitution/C-H activation/aromatization cascade reaction has been developed. A range of 6-unsubstituted phenanthridines could be obtained in moderate to good yields (31-85%) with readily prepared N-Ms arylamines and commercially available 2-bromobenzyl bromide derivatives as starting materials. The potential application of the protocol was also demonstrated by the expeditious synthesis of the natural alkaloid trisphaeridine.
- Han, Wenyong,Zhou, Xiaojian,Yang, Siyi,Xiang, Guangyan,Cui, Baodong,Chen, Yongzheng
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p. 11580 - 11587
(2015/12/01)
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- Metal-free nitrogenation of 2-acetylbiphenyls: Expeditious synthesis of phenanthridines
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An intermolecular nitrogenation reaction toward the synthesis of phenanthridines has been developed. This metal-free protocol provides a novel nitrogen-incorporation transformation using azides as the nitrogen source. Phenanthridines, which are of great interest in pharmaceutical and medicinal chemistry, are synthesized efficiently in one step. Moreover, the byproducts derived from the Schmidt reaction are inhibited, which further demonstrated the high chemoselectivity of this transformation.
- Tang, Conghui,Yuan, Yizhi,Jiao, Ning
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supporting information
p. 2206 - 2209
(2015/05/13)
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- Visible-light-promoted and one-pot synthesis of phenanthridines and quinolines from aldehydes and o -Acyl hydroxylamine
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A one-pot synthesis of phenanthridines and quinolines from commercially available or easily prepared aldehydes has been reported. O-(4-Cyanobenzoyl)hydroxylamine was utilized as the nitrogen source to generate O-acyl oximes in situ with aldehydes catalyzed by Bronsted acid. O-Acyl oximes were then subjected to visible light photoredox catalyzed cyclization via iminyl radicals to furnish aza-arenes. A variety of phenanthridines and quinolines have been prepared assisted by Bronsted acid and photocatalyst under visible light at room temperature with satisfactory yields.
- An, Xiao-De,Yu, Shouyun
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supporting information
p. 2692 - 2695
(2015/06/16)
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- Di-tert butyl peroxide-promoted sequential methylation and intramolecular aromatization of isonitriles
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The di-tert butyl peroxide (DTBP)-promoted sequential reaction of isonitriles is developed, leading to 6-methylphenanthridine derivatives in moderate to excellent yields. DTBP served as both promoter and methyl source. The procedure proceeds through the addition of a methyl radical derived from the peroxide to the isonitrile followed by aromatic homolytic cyclization. It tolerates a series of functional groups, such as fluoro, chloro, acetyl, methoxycarbonyl, cyano and trifluoromethyl.
- Dai, Qiang,Yu, Jin-Tao,Feng, Xiaomei,Jiang, Yan,Yang, Haitao,Cheng, Jiang
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supporting information
p. 3341 - 3346
(2015/01/09)
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- A new synthetic approach to 6-unsubstituted phenanthridine and phenanthridine-like compounds under mild and metal-free conditions
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A new and mild synthetic approach for the synthesis of 6-unsubstituted phenanthridine and phenanthridine-like compounds under metal-free conditions at room temperature has been developed. The strategy involved a tandem azide rearrangement/intramolecular annulation and oxidation reactions of biarylmethyl azide precursors to obtain the desired products in up to 99% yields with high regioselectivity.
- Tummatorn, Jumreang,Krajangsri, Suppachai,Norseeda, Krissada,Thongsornkleeb, Charnsak,Ruchirawat, Somsak
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p. 5077 - 5081
(2014/07/08)
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- Bronsted acid-mediated reactions of aldehydes with 2-vinylaniline and biphenyl-2-amine
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Herein we report simple Bronsted acid-mediated reactions of aldehydes with 2-vinylaniline and biphenyl-2-amine. Ultimately, the useful nitrogen-containing heterocycle derivatives are obtained. The electronic properties of the substituents on the aldehydes and 2-vinylaniline were investigated. It was found that molecules with both electron-donating and -withdrawing substituents were perfectly suitable substrates for this transformation, and the expected products were obtained in moderate to excellent yields.
- Zhang, Xu,Xu, Xuefeng,Yu, Lintao,Zhao, Qiang
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supporting information
p. 2280 - 2282
(2014/04/17)
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- Synthesis of 6-Substituted Phenanthridine Derivatives by Palladium-Catalysed Domino Suzuki-Miyaura/Aza-Michael Reactions
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An efficient method for the synthesis of 6-substituted phenanthridine derivatives has been developed through a one-pot process involving a sequence of palladium-catalysed Suzuki-Miyaura reaction followed by intramolecular aza-Michael addition. This method is applicable to the synthesis of a wide range of substituted phenanthridines from simple substrates.
- Bao, Xiaobo,Yao, Wei,Zhu, Qihua,Xu, Yungen
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supporting information
p. 7443 - 7450
(2016/02/19)
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- Synthesis of phenanthridine derivatives by microwave-mediated cyclization of o-furyl(allylamino)arenes
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A novel and efficient synthesis of phenanthridines and aza analogues is reported. The key step is a microwave-mediated intramolecular Diels-Alder cyclization of o-furyl(allylamino)arenes. In the presence of a catalytic amount of acid, the DA-adduct reacts further to give the dihydrophenanthridines, which easily can be oxidized to fully aromatic compounds by air in the presence of UV light or by DDQ.
- Read, Matthew Lovell,Gundersen, Lise-Lotte
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p. 1311 - 1316
(2013/03/29)
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- Iron-catalyzed hydrogenation for the in situ regeneration of an NAD(P)H model: Biomimetic reduction of α-Keto-/α-iminoesters
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Two irons for a smoother finish: An NAD(P)H model was regenerated readily in situ by iron-catalyzed reduction with molecular hydrogen. The subsequent biomimetic reduction of α-keto-/ α-iminoesters proceeded smoothly in the presence of an iron-based Lewis acid (LA) to provide α-hydroxyesters and amino acid esters in good to excellent yields (see scheme; NAD(P) +=nicotinamide adenine dinucleotide (phosphate), TM=transition metal). Copyright
- Lu, Liang-Qiu,Li, Yuehui,Junge, Kathrin,Beller, Matthias
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supporting information
p. 8382 - 8386
(2013/09/02)
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- Synthesis of phenanthridine and its analogues via aerobic ligand-free domino Suzuki coupling-Michael addition reaction catalyzed by in situ generated palladium-nanoparticles in water
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A convenient methodology has been developed towards the synthesis of substituted phenanthridines and analogous benzo[k] and benzo[i] derivatives via aerobic ligand-free domino Suzuki coupling-Michael addition reaction in the presence of Pd(OAc)2 and K3PO4 as a catalytic system in H2O at 90 C in good yields. Reaction was believed to be catalyzed by in situ generated palladium nanoparticles in water with the elimination of acetone.
- Ghosh, Munmun,Ahmed, Atiur,Dhara, Shubhendu,Ray, Jayanta K.
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supporting information
p. 4837 - 4840
(2013/08/28)
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- Mixed oxides as highly selective catalysts for the flash pyrolysis of phenacyl benzotriazole: One-pot synthesis of dibenzazepin-7-one
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The one-pot synthesis of dibenzo[b,d]azepin-7-one (3) was selectively achieved from 1-phenacyl-1,2,3-benzotriazole (1) using the catalytic flash vacuum pyrolysis (cfvp) methodology. Catalysts with the scheelite structure ABO4 (A = Ca2+, Sr2+, Ba2+ and B = Mo6+, W6+) and fergusonite BiVO4 were explored in this new catalytic reaction. These oxides promoted high conversion of starting material at lower temperatures than those observed for noncatalytic reactions. The chemical nature of A and B cations in the scheelite structure showed a strong influence on the formation toward the desired azepinone. In addition, the catalyst's morphology had a significant influence on the course of the cfvp reaction.
- Lener, German,Carbonio, Raul E.,Moyano, E. Laura
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p. 1020 - 1025
(2013/07/25)
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- Expeditious approach to pyrrolophenanthridones, phenanthridines, and benzo[ c ]phenanthridines via organocatalytic direct biaryl-coupling promoted by potassium tert -butoxide
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A methodology involving a "transition metal-free" intramolecular biaryl-coupling of o-halo-N-arylbenzylamines has been developed in the presence of potassium tert-butoxide and an organic molecule as catalyst. The reaction appears to proceed through KOtBu-promoted intramolecular homolytic aromatic substitution (HAS). Interestingly, this biaryl coupling also works in the presence of potassium tert-butoxide as sole promoter. On extending our approach further, we found that N-acyl 2-bromo-N-arylbenzylamines undergo a one-pot N-deprotection/biaryl coupling followed by oxidation, thus offering an expeditious route to the phenanthridine and benzo[c]phenanthridine skeletons. The strategy has been applied to a concise synthesis of Amaryllidaceae alkaloids viz. oxoassoanine (1b), anhydrolycorinone (1d), 5,6-dihydrobicolorine (2d), trispheridine (2b), and benzo[c]phenanthridines alkaloids dihydronitidine (3b), dihydrochelerythidine (3d), dihydroavicine (3f), nornitidine (3h), and norchelerythrine (3j).
- De, Subhadip,Mishra, Sourabh,Kakde, Badrinath N.,Dey, Dhananjay,Bisai, Alakesh
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p. 7823 - 7844
(2013/09/12)
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- [Ru(TPP)CO]-catalysed intramolecular benzylic C-H bond amination, affording phenanthridine and dihydrophenanthridine derivatives
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Shedding light on azides: [Ru(TPP)CO] (TPP=tetraphenyl porphyrin dianion), white light and O2 were found to be a suitable catalyst combination to perform the annulation of several biaryl azides (see scheme). The high chemoselectivity of the process allows the synthesis of phenanthridines and dihydrophenanthridines in good yield and purity. Copyright
- Intrieri, Daniela,Mariani, Matteo,Caselli, Alessandro,Ragaini, Fabio,Gallo, Emma
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p. 10487 - 10490,4
(2012/12/12)
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