- Ionic-liquid-supported synthesis of amines and derivatives
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Amine precursors such as glycines protected at nitrogen with a Boc or formyl group were grafted by esterification on the hydroxylated arms of 1-(2-hydroxyethyl)-3-methylimidazolium hexafluorophosphates or tetrafluoroborates. The cleavage of the Boc group was then realized at room temperature by successively treating acetonitrile solutions of the thus formed glycinates with methanol and acetyl chloride (two equivalents each). Interestingly, the resulting glycinate hydrochlorides were converted into the corresponding amines during the removal of the solvent. Ugi reaction of one of these ionic-liquid-grafted amines with phthalaldehydic acid and tert-butyl isocyanide, followed by cleavage, furnished a phthalimidine. Georg Thieme Verlag Stuttgart.
- Debdab, Mansour,Mongin, Florence,Bazureau, Jean Pierre
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Read Online
- Preparation and reactions of new zincated nitrogen-containing heterocycles
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A range of nitrogen-containing iodinated or in some cases brominated heterocycles were converted to the corresponding zincated heterocyclic derivatives by the direct insertion of zinc dust under mild conditions (25°C to 70°C, 1-3 h) in a solvent like THF or DMAC. This reaction was extended to the preparation of zincated nucleic acid bases and nucleosides. The reaction of these new zinc reagents toward various electrophiles with palladium (O) or copper(I) catalysis allows the preparation of a broad range of polyfunctional nitrogen-containing heterocycles.
- Prasad, A. S. Bhanu,Stevenson, Thomas M.,Citineni, Janakiram Rao,Nyzam, Valerie,Knochel, Paul
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- Photophysical properties of substituted homoleptic and heteroleptic phenylimidazolinato Ir(III) complexes as a blue phosphorescent material
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Iridium complexes are one of the most important materials for fabrication of organic light emitting diodes (OLEDs). There are difficulties in the preparation of blue phosphorescent complexes with respect to chromaticity, emission efficiency, and stability of the material, compared with green and red phosphorescent complexes. Control of the frontier orbital energy level (HOMO-LUMO) is the sole method to achieve better blue phosphorescent iridium complexes by appropriate ligand selection and the introduction of adequate substituents. Homoleptic and heteroleptic iridium(III) tris(phenylimidazolinate) complexes were synthesized, and the effect of the substituents on their nature in the excited state was examined. Density functional theory calculation showed that the imidazolinato complexes have the HOMO localized at the iridium d- and phenyl π-orbitals. The LUMO is also localized on the phenyl moiety with a much higher population than HOMO. This LUMO is quite different from other complexes, such as iridium(III) tris(phenylpyridinate) and tris(phenylpyrazolinate) complexes. Therefore, substitution with π-electron donating groups and electron withdrawing groups induces blue and red spectral shifts, respectively, which is the reverse shift exhibited by other complexes. The ancillary ligand (acetylacetone) acts as a path for nonradiative deactivation in the blue phosphorescent complexes.
- Karatsu, Takashi,Takahashi, Masatomo,Yagai, Shiki,Kitamura, Akihide
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Read Online
- Novel amide and imidazole compounds as potent hematopoietic prostaglandin D2 synthase inhibitors
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In seeking novel and potent small molecule hematopoietic prostaglandin D2 synthase (H-PGDS) inhibitors as potential therapies for PGD2-mediated diseases and conditions, we explored a series comprising multiple aryl/heteroaryl rings attached in a linear arrangement. Each compound incorporates an amide or imidazole “linker” between the pyrimidine or pyridine “core” ring and the “tail” ring system. We synthesized and screened twenty analogs by fluorescence polarization binding assay, thermal shift assay, glutathione S-transferase inhibition assay, and a cell-based assay measuring suppression of LPS-induced PGD2 stimulation. Amide analogs show ten-fold greater shift in the thermal shift assay in the presence of glutathione (GSH) versus the same assay run in the absence of GSH. The imidazole analogs did not produce a significant change in thermal shift between the two assay conditions, suggesting a possible stabilization effect of the amide linker in the synthase-GSH-inhibitor complex. Imidazole analog 23, (KMN-010034) demonstrates superior potency across the in vitro assays and good in vitro metabolic stability in both human and guinea pig liver microsomes.
- Olson, Kirk L.,Holt, Melissa C.,Ciske, Fred L.,Kramer, James B.,Heiple, Paige E.,Collins, Margaret L.,Johnson, Carrie M.,Ho, Chi S.,Morano, M. Ines,Barrett, Stephen D.
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supporting information
(2021/01/19)
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- Bimetallic Cooperative Catalysis for Decarbonylative Heteroarylation of Carboxylic Acids via C-O/C-H Coupling
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Cooperative bimetallic catalysis is a fundamental approach in modern synthetic chemistry. We report bimetallic cooperative catalysis for the direct decarbonylative heteroarylation of ubiquitous carboxylic acids via acyl C-O/C-H coupling. This novel catalytic system exploits the cooperative action of a copper catalyst and a palladium catalyst in decarbonylation, which enables highly chemoselective synthesis of important heterobiaryl motifs through the coupling of carboxylic acids with heteroarenes in the absence of prefunctionalization or directing groups. This cooperative decarbonylative method uses common carboxylic acids and shows a remarkably broad substrate scope (>70 examples), including late-stage modification of pharmaceuticals and streamlined synthesis of bioactive agents. Extensive mechanistic and computational studies were conducted to gain insight into the mechanism of the reaction. The key step involves intersection of the two catalytic cycles via transmetallation of the copper–aryl species with the palladium(II) intermediate generated by oxidative addition/decarbonylation.
- Liu, Chengwei,Ji, Chong-Lei,Zhou, Tongliang,Hong, Xin,Szostak, Michal
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supporting information
p. 10690 - 10699
(2021/04/09)
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- Method for alkylating N1-position of imidazole compound
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The present invention relates to a method for alkylating an N1-position of an imidazole compound and belongs to the technical field of organic synthesis. The method comprises the following steps: mixing an imidazole compound and carbonic ester with a molar ratio of 1:(1-2), conducting a heating reaction under a temperature of 80-140 DEG C under presence of aromatic hydrocarbons or a dipolar aprotic solvent and a strongly basic organic tertiary amine catalyst, and after reaction, directly conducting vacuum distillation or layering, and conducting vacuum distillation to obtain a N1 alkylated imidazole compound. The raw materials used in the method are non-toxic or low-toxic, the process is simple, reaction conditions are mild, and yield is high; and by-products in the reaction process are extremely few, environmental pollution is extremely small, and the preparation method is green and environmentally-friendly.
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Paragraph 0012
(2020/02/29)
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- Mild, Selective Ru-Catalyzed Deuteration Using D2O as a Deuterium Source
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A method for the selective deuteration of polyfunctional organic molecules using catalytic amounts of [RuCl2(PPh3)3] and D2O as a deuterium source is presented. Through variation of additives like CuI, KOH, and various amounts of zinc powder, orthogonal chemoselectivities in the deuteration process are observed. Mechanistic investigation indicates the presence of different, defined Ru-complexes under the given specific conditions.
- Eisele, Pascal,Ullwer, Franziska,Scholz, Sven,Plietker, Bernd
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supporting information
p. 16550 - 16554
(2019/12/11)
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- Alkylation method for nitrogen-hydrogen containing compounds and application thereof
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The invention discloses an alkylation method for nitrogen-hydrogen containing compounds and an application thereof, belonging to the technical field of synthesis of organic compounds. The invention provides a series of methods for a nitrogen alkylation reaction of N-H containing heterocyclic compounds (II) with N,N-dimethylformamide dialkyl acetal as an alkyl source under the condition of no participation of metals, and a product with a hydrogen atom on a nitrogen atom substituted by R1 is obtained. The method provided by the invention has the advantages of highly-efficient reaction, high yield, simple treatment after the reaction, simple and convenient operation, mild reaction conditions, no participation of the metals, high tolerance of functional groups of a reaction substrate, wide range and easy preparation of the substrate, high reaction efficiency after amplification of the reaction, and applicability to large-scale industrial production.
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Paragraph 0048-0051; 0059; 0060
(2018/10/04)
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- Development of a supramolecular ensemble of an AIEE active hexaphenylbenzene derivative and Ag@Cu2O core-shell NPs: An efficient photocatalytic system for C-H activation
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A supramolecular ensemble having Ag@Cu2O core-shell nanoparticles stabilized by aggregates of a hexaphenylbenzene derivative has been developed which exhibits excellent photocatalytic efficiency in reactions involving preparation of imidazole and benzimidazole derivatives via C-H activation.
- Chopra, Radhika,Kumar, Manoj,Bhalla, Vandana
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supporting information
p. 10179 - 10182
(2016/08/18)
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- C-H arylation and alkenylation of imidazoles by nickel catalysis: Solvent-accelerated imidazole C-H activation
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The first nickel-catalyzed C-H arylations and alkenylations of imidazoles with phenol and enol derivatives are described. Under the influence of Ni(OTf)2/dcype/K3PO4 (dcype: 1,2-bis(dicyclohexylphosphino)ethane) in t-amyl alcohol, imidazoles can undergo C-H arylation with phenol derivatives. The C-H arylation of imidazoles with chloroarenes as well as that of thiazoles and oxazoles with phenol derivatives can also be achieved with this catalytic system. By changing the ligand to dcypt (3,4-bis(dicyclohexylphosphino)thiophene), enol derivatives could also be employed as coupling partners achieving the C-H alkenylation of imidazoles as well as thiazoles and oxazoles. Thus, a range of C2-arylated and alkenylated azoles can be synthesized using this newly developed nickel-based catalytic system. The key to the success of the C-H coupling of imidazoles is the use of a tertiary alcohol as solvent. This also allows the use of an air-stable nickel(ii) salt as the catalyst precursor.
- Muto, Kei,Hatakeyama, Taito,Yamaguchi, Junichiro,Itami, Kenichiro
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p. 6792 - 6798
(2015/11/24)
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- Iron catalyzed oxidative assembly of N-heteroaryl and aryl metal reagents using oxygen as an oxidant
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An equivalent amount of N-heteroaryl and aryl Grignard or lithium reagents, after mediation by an equivalent of titanate, was facilely coupled to furnish N-heteroaryl-aryl compounds under the catalysis of FeCl3/TMEDA at ambient temperature using oxygen as an oxidant. Most of the common N-heteroaryls were all good candidates, and thus provided a general, green and pratical protocol for the flexible construction of various N-heteroaryl-aryl structures. This journal is
- Liu, Kun Ming,Liao, Lian Yan,Duan, Xin Fang
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supporting information
p. 1124 - 1127
(2015/01/09)
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- N -heterocyclic carbene-palladium(II)-1-methylimidazole complex-catalyzed direct C-H bond arylation of (Benz)imidazoles with aryl chlorides
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(Benz)imidazoles can be efficiently functionalized by (hetero)aryl chlorides via direct C-H bond arylation in the presence of a well-defined NHC-Pd(II)-Im complex. Under the optimal conditions, various activated, unactivated, and deactivated (hetero)aryl chlorides were successfully applied as the arylating reagents to achieve the 2-(hetero)aryl (benz)imidazoles in acceptable to high yields, giving a facile and alternative methodology for the direct C-H bond arylation of (benz)imidazoles.
- Gu, Zheng-Song,Chen, Wen-Xin,Shao, Li-Xiong
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p. 5806 - 5811
(2014/07/08)
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- Direct arylation of heterocycles through C-H bond cleavage using metal-organic-framework Cu2(OBA)2(BPY) as an efficient heterogeneous catalyst
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A crystalline porous metal-organic-framework Cu2(OBA)2(BPY) was synthesized and characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR), atomic absorption spectrophotometry (AAS), and nitrogen physisorption measurements. The Cu-MOF was shown to be an efficient heterogeneous catalyst for direct C-arylation of a variety of heterocycles by iodoarenes. The optimal conditions employed tBuOLi in dioxane at elevated temperature. In addition, a leaching test was also conducted to investigate the heterogeneity. Gratifyingly, the MOF catalyst can be facilely recycled several times under identical conditions without remarkable loss in catalytic reactivity. This journal is
- Truong, Thanh,Nguyen, Vu T.,Le, Hue T. X.,Phan, Nam T. S.
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p. 52307 - 52315
(2014/12/10)
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- Nano CuO-catalyzed C-H functionalization of 1,3-azoles with bromoarenes and bromoalkenes
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Copper oxide catalyzed direct C-H arylation and alkenylation of aromatic heterocycles using aryl and alkenyl bromides have been developed and have been applied to the C-H functionalization of a variety of 1,3-azoles like benzoxazole, benzothiazole, 1-methylbenzimidazole, and 1-methylimidazole, with moderate to excellent yields. The best performance has been achieved in the presence of PPh3 when average size of CuO nanoparticles is 6.5 nm. This catalyst can be recovered and reused without significant decrease in its catalytic activity.
- Zhang, Wu,Tian, Yujie,Zhao, Na,Wang, Yuanyuan,Li, Jia,Wang, Zhenghua
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p. 6120 - 6126
(2015/03/30)
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- Cyclometalated 2-phenylimidazole palladium carbene complexes in the catalytic Suzuki-Miyaura cross-coupling reaction
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We present the syntheses of 12 cyclometalated palladium C-N 2-phenylimidazole carbene complexes with different N-1 groups as well as different substituents at the C-2 phenyl group of the cyclometalating imidazole. We investigated the influence of these substituents by comparing the catalytic performance of the complexes in the Suzuki-Miyaura cross-coupling reaction of aryl chlorides. We can show a strong dependence between the steric demand of the N-1 substituent of the cyclometalating imidazole and the catalytic activity in the cross-coupling reaction. The most active complex shows a wide substrate scope, where several aryl as well as benzyl chlorides could be coupled with different boronic acids in excellent yields using very low catalyst concentrations of 0.05 mol %.
- Micksch, Maik,Tenne, Mario,Strassner, Thomas
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p. 3966 - 3976
(2014/09/30)
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- Visible light-mediated direct arylation of arenes and heteroarenes using diaryliodonium salts in the presence and absence of a photocatalyst
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Diaryliodonium salts have been used as aryl radical sources under visible light-mediated photoredox catalysis. Benzene and a range of heteroarenes are arylated with Ar2I+ in the presence of [Ir(ppy)2(bpy)] PF6 upon irradiation with visible light. When pyrroles are used, the arylation proceeds in the absence of a photoredox catalyst. Both processes are initiated by photoinduced single-electron-transfer to Ar2I+, generating aryl radicals.
- Tobisu, Mamoru,Furukawa, Takayuki,Chatani, Naoto
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supporting information
p. 1203 - 1205
(2013/10/22)
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- Alkaline stable C2-substituted imidazolium-based anion-exchange membranes
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The alkaline stability of imidazolium salts and imidazolium-based alkaline anion-exchange membranes (AEMs) was investigated in this work. C2-substituted (with methyl, isopropyl or phenyl groups) imidazolium salts, 3-ethyl-1,2-dimethyl imidazolium bromine ([EDMIm][Br]), 3-ethyl-2-isopropyl-1- methylimidazolium bromine ([EIMIm][Br]), and 3-ethyl-1-methyl-2-phenyl- imidazolium bromine ([EMPhIm][Br]), were synthesized and characterized. The effect of the C2-substitution on the alkaline stability of imidazolium salts was investigated by 1H and 13C NMR spectroscopy. Compared with the C2-unsubstituted imidazolium salt, 3-ethyl-1-methylimidazolium bromine ([EMIm][Br]), the alkaline stability of C2-substituted imidazolium salts is significantly enhanced at elevated temperatures, probably due to the steric hindrance of the substituents, which protected the imidazolium cations against the hydroxide attack. Moreover, the higher LUMO energies may also improve the alkaline stability of imidazolium salts. The alkaline stability of C2-substituted imidazolium salts was found to be in the order [EDMIm][Br] > [EIMIm][Br] > [EMPhIm][Br]. This work provides a feasible approach for enhancing the chemical stability of C2-substituted imidazolium salts, which has potential applications for alkaline anion-exchange membranes.
- Lin, Bencai,Dong, Huilong,Li, Youyong,Si, Zhihong,Gu, Fenglou,Yan, Feng
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p. 1858 - 1867
(2013/07/28)
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- Base-mediated intermolecular sp2 C-H bond arylation via benzyne intermediates
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A transition-metal-free method for arylation of heterocycle and arene carbon-hydrogen bonds by aryl chlorides and fluorides has been developed. The reactions proceed via aryne intermediates and are highly regioselective with respect to the C-H bond coupling component.
- Truong, Thanh,Daugulis, Olafs
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supporting information; experimental part
p. 4243 - 4245
(2011/06/21)
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- Palladium-catalyzed desulfitative C-H arylation of heteroarenes with sodium sulfinates
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Desulfitative C-H arylation: Palladium-catalyzed desulfitative C-H arylation of heteroarenes with sodium sulfinates has been disclosed to construct aryl-heteroaryl bonds without the need for any extra ligands (see scheme). Copyright
- Liu, Bo,Guo, Qiang,Cheng, Yangyang,Lan, Jingbo,You, Jingsong
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supporting information; experimental part
p. 13415 - 13419
(2012/01/03)
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- N-phosphorylated imidazolium salts as precursors to 2- and 5-phosphorylated imidazoles and new imidazol-2-ylidenes featuring the PNCN unit
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It has been experimentally proven that the reaction of 1- or 1,2-disubstituted imidazoles with diorganylphosphorus(III) halides proceeds via initial formation of N-phosporylated imidazolium salts. Treatment of these salts with strong bases results in phosphorylation of the parent imidazoles at the 2- or 5-positions, correspondingly. In a previous case, imidazol-2-ylidenes are formed as intermediates. With both N1 and N3 atoms bearing sterically demanding or/and π-donating groups, deprotonation of 1,3-disubstituted imidazolium salts with NaN(SiMe3)2 afforded new stable N-phosphorus-substituted Arduengo-type carbenes.
- Marchenko, Anatolii P.,Koidan, Heorgii N.,Huryeva, Anastasiya N.,Zarudnitskii, Evgeniy V.,Yurchenko, Aleksandr A.,Kostyuk, Aleksandr N.
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supporting information; experimental part
p. 7141 - 7145
(2010/12/29)
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- Light-emitting material
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This invention pertains to light emitting materials comprising novel ortho-metalated transition metal complexes [C?N]2ML comprising two orthometalated ligands having imidazole moieties and an ancillary ligand of β-diketonate type. It has been surprisingly found that when the metal has bound thereto both ortho-metalated ligands comprising imidazole moieties and an ancillary ligand of β-diketonate type, said ligands advantageously participate in the emission process, significantly broadening emission in the visible region and enabling appreciable improvement of the white emission efficiency of complexes [C?N]2ML. Still objects of the invention are the use of said light emitting materials and organic light emitting device comprising said light emitting material.
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- COPPER-CATALYZED C-H BOND ARYLATION
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The present invention is a one-step method for efficiently converting carbon-hydrogen bonds into carbon-carbon bonds using a combination of aryl halides, a substrate, and a copper salt as catalyst. This method allows faster introduction of complex molecular entities, a process that would otherwise require many more steps. This invention is particularly relevant for the organic synthesis of complex molecules such as, but not limited to, pharmacophores and explosives.
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Page/Page column 22
(2009/04/24)
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- A general method for copper-catalyzed arylation of arene C-H bonds
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A general method for copper-catalyzed arylation of sp2 C-H bonds with pKa's below 35 has been developed. The method employs aryl halide as the coupling partner, lithium alkoxide or K3PO4 base, and DMF, DMPU, or mixed DMF/xylenes solvent. A variety of electron-rich and electron-poor heterocycles such as azoles, caffeine, thiophenes, benzofuran, pyridine oxides, pyridazine, and pyrimidine can be arylated. Furthermore, electron-poor arenes possessing at least two electron-withdrawing groups on a benzene ring can also be arylated. Two arylcopper-phenanthroline complex intermediates were independently synthesized.
- Do, Hien-Quang,Khan, Rana M. Kashif,Daugulis, Olafs
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supporting information; experimental part
p. 15185 - 15192
(2009/03/12)
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- Manganese-catalyzed insertion of aldehydes into a C-H bond
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(Chemical Equation Presented) Mn gets in the game: In the presence of a manganese catalyst and a stoichiometric amount of hydrosilane, aldehydes insert into C-H bonds of aromatic rings of compounds with directing groups (see scheme). This first example of a manganese-catalyzed chemical transformation through C-H bond activation gives silyl ethers in good to excellent yields and can also be applied to asymmetric transformation.
- Kuninobu, Yoichiro,Nishina, Yuta,Takeuchi, Takahiro,Takai, Kazuhiko
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p. 6518 - 6520
(2008/09/16)
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- METAL COMPLEX COMPOUND AND ORGANIC ELECTROLUMINESCENT DEVICE USING SAME
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A metal complex compound having a special structure containing metals such as iridium. An organic electroluminescence device which comprises at least one organic thin film layer sandwiched between a pair of electrode consisting of an anode and a cathode, wherein the organic thin film layer comprises the above metal complex compound, which emits light by applying an electric voltage between the pair of electrode. An organic EL device employing the novel metal complex compound emits various phosphorous lights including blue light having an enhanced current efficiency and prolonged lifetime.
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Page/Page column 372-373
(2010/11/08)
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- Expedient synthesis of substituted imidazoles from nitriles
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Expedient and practical new methodology for the synthesis of substituted imidazoles was developed to provide a rapid access to a variety of 2-substituted, 1,2-disubstituted and 1,2,4-trisubstituted imidazoles by the direct CuCl-mediated reaction of nitriles with α-amino acetals in an intermolecular as well as intramolecular fashion.
- Frutos, Rogelio P.,Gallou, Isabelle,Reeves, Diana,Xu, Yibo,Krishnamurthy, Dhileepkumar,Senanayake, Chris H.
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p. 8369 - 8372
(2007/10/03)
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- Mild, efficient, and chemoselective dehydrogenation of 2-imidazolines, bis-imidazolines, and N-substituted-2-imidazolines with potassium permanganate supported on montmorillonite K-10
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Different types of 2-imidazolines, bis-imidazolines, and N-substituted-2-imidazolines are efficiently oxidized to their corresponding imidazoles with potassium permanganate (KMnO4) supported on montmorillonite K-10 under very mild conditions. The procedure is very simple and no strict conditions were required. Selective dehydrogenation of 2-alkyl-2-imidazolines in the presence of 2-aryl-2-imidazolines is a noteworthy advantage of this method and can be considered as a useful practical achievement in these reactions.
- Mohammadpoor-Baltork, Iraj,Abdollahi-Alibeik, Mohammad
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p. 110 - 114
(2007/10/03)
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- Certain 4-aminomethyl-2-substituted imidazole derivatives and 2-aminomethyl-4-substituted imidazole derivatives: new classes of dopamine receptor subtype specific ligands
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Disclosed are compounds of the formula: wherein R1 represents optionally substituted aryl, heteroaryl, arylalkyl, or cycloalkyl groups; X, Z, and Y are optionally substituted nitrogen or carbon atoms; R3 and R4 are organic or inorganic substitutents which may togther form ring structutes; m is zero, one or two; and R5 and R6 are are organic or inorganic substituents; and the pharmaceutically acceptable addition salts thereof, which compounds are highly selective partial agonists or antagonists at brain dopamine receptor subtypes or prodrugs thereof and are useful in the diagnosis and treatment of affective disorders such as schizophrenia and depression as well as certain movement disorders such as Parkinsonism.
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- Synthesis and chemistry of 4,5-dimagnesioimidazole dianions
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An experimentally convenient procedure for the generation of 4,5-dimagnesioimidazoles is described. N-Protected 2-substituted 4,5-diiodoimidazoles were treated with i-PrMgC1 (2.4 equiv) in THF at 0-5 °C. The resulting vicinal dianions reacted with electro
- Butz, Ralf H.-J.,Lindell, Stephen D.
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p. 2699 - 2701
(2007/10/03)
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- Palladium-Catalyzed Arylation of Azole Compounds with Aryl Halides in the Presence of Alkali Metal Carbonates and the Use of Copper Iodide in the Reaction
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The reactions of iodobenzene with azole compounds, 1,2-disubstituted imidazoles and 2-substituted oxazoles and thiazoles, were examined in the presence of catalytic amounts of Pd(OAc)2 and PPh3 in DMF using alkali metal carbonates as bases. It was found that the coupling products, 5-arylazoles, could be selectively produced in good yields by using CS2CO3. In the case that their 2-position is unsubstituted, the site could also be arylated. In reactions using bromobenzene in place of iodobenzene, K2CO3 was also as effective as Cs2CO3- The addition of a stoichiometric amount of Cul appeared to specifically promote the reactions of thiazoles as well as those of thiophene derivatives. The reactions of 2-unsubstituted azole compounds with aryl iodides could be mediated by Cul to some extent without using the palladium species to give 2-arylazoles.
- Pivsa-Art, Sommai,Satoh, Tetsuya,Kawamura, Yoshiki,Miura, Masahiro,Nomura, Masakatsu
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p. 467 - 473
(2007/10/03)
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- Photochemistry of Phenyl-Substituted 1-Methylpyrazoles
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Direct irradiation of 1-methyl-4-phenylpyrazole (2) in methanol results in regiospecific phototransposition to 1-methyl-4-phenylimidazole (4) and in photocleavage to (E)/(Z)-3-(N-methylamino)-2-phenylpropenenitrile (5) and (E)/(Z)-2-(N-methylaimno)-1-phenylethenyl isocyanide (6). Deuterium labeling confirms that the phototransposition occurs via the P4 permutation pathway. Separate experiments show that 5 and 6 undergo (Z) → (E) isomerization and photocyclization to imidazole 4. Quantum yields for these reactions show that the sequence 2 → 6 → 4 is a major pathway for the P4 phototransposition of 2 → 4. Isocyanides were also detected as intermediates in the P4 phototransposition of a variety of other pyrazoles confirming the generality of this pathway in pyrazole photochemistry. Direct irradiation of 1-methyl-5-phenylpyrazole (3) resulted in the formation of 1-methyl-5-phenylimidazole (7), 1-methyl-2-phenylimidazole (8), and 1-methyl-4-phenylimidazole (4). Deuterium labeling revealed that these products were formed by P4, P6, and P7 permutation pathways, respectively. (E)/(Z)-3-(N-methylamino)-3-phenylpropenenitrile (9) and (E)/(Z)-2-(N-methylamino)-2-phenylethenyl isocyanide (10) photocleavage products were also formed in this reaction. Irradiation of 3 in furan solvent did not result in phototransposition but led to the formation of endo and exo adducts formed by Diels-Alder reaction of furan with 4-phenyl-5-methyl-1,5-diazabicyclo[2.1.0]pent-2-ene. This constitutes the first direct evidence for the formation of a 1,5-diazabicyclo[2.1.0]hex-2-ene from photolysis of a pyrazole and is consistent with the electrocyclic ring closure - heteroatom migration mechanism suggested for the P6 and P7 phototranspositions.
- Pavlik, James W.,Kebede, Naod
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p. 8325 - 8334
(2007/10/03)
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- INVESTIGATIONS OF 2-SUBSTITUTED IMIDAZOLES. 2. SYNTHESIS AND ELECTROPHILIC SUBSTITUTION OF 1-METHYL-2-(THIENYL-2)IMIDAZOLE. A CONVENIENT METHOD OF METHYLATION OF 2-R-IMIDAZOLES
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We have synthesized 2-(thienyl-2)imidazole and its N-methyl derivative.The latter product was obtained by nitration, bromination, acylation, and formylation, occurring as a rule on the thiophene ring.A general method for methylating 2-R-imidazoles with methyl iodide KOH-dimethoxy ethane is proposed.
- Stoyanov, V. M.,El'chaninov, M. M.,Pozharskii, A. F.
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p. 1140 - 1144
(2007/10/02)
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- Reactions with Dimethyl Carbonate, 2. - N-Methylation of Imidazole and Derivatives
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The use of dimethyl carbonate as methylating agent for imidazole derivatives is demonstrated by selected examples.The comparison of the toxicological values of dimethyl carbonate and dimethyl sulfate should inspire to replace the highly toxic dimethyl sulfate by dimethyl carbonate.
- Lissel, Manfred
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- Palladium-Catalyzed Coupling between Organic Halides and Organotin Compounds Involving C-N Unsaturated Bonds at the Reaction Centers
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Imidoyl chlorides were good substrates which can react with a variety of organotin compounds to give ketimines in the presence of a catalytic amount of palladium complex.Under similar conditions, C-tributylstannyl imines did not give the products except with 2-(tributylstannyl)benzothiazole, -benzoxazole, and 1-methyl-2-(tributylstannyl)imidazole.And N-tributylstannyl imines could not be utilized.
- Kosugi, Masanori,Koshiba, Mamoru,Atoh, Akira,Sano, Hiroshi,Migita, Toshihiko
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p. 677 - 679
(2007/10/02)
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